https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC4-01&feed=atom&action=history Evaluation AC4-01 - Revision history 2024-03-28T15:24:27Z Revision history for this page on the wiki MediaWiki 1.39.2 https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC4-01&diff=32738&oldid=prev Dave.Ellacott: Dave.Ellacott moved page SilverP:Evaluation AC4-01 to Evaluation AC4-01 over redirect 2017-02-11T16:35:51Z <p>Dave.Ellacott moved page <a href="/w/index.php/SilverP:Evaluation_AC4-01" class="mw-redirect" title="SilverP:Evaluation AC4-01">SilverP:Evaluation AC4-01</a> to <a href="/w/index.php/Evaluation_AC4-01" title="Evaluation AC4-01">Evaluation AC4-01</a> over redirect</p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <tr class="diff-title" lang="en"> <td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 16:35, 11 February 2017</td> </tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div> </td></tr></table> Dave.Ellacott https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC4-01&diff=8920&oldid=prev Tonyh at 15:24, 14 April 2009 2009-04-14T15:24:04Z <p></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 15:24, 14 April 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l9">Line 9:</td> <td colspan="2" class="diff-lineno">Line 9:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>=='''Comparison of Test data and CFD'''==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>=='''Comparison of Test data and CFD'''==</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The results of the simulation CFD2 and its comparison to the wind tunnel data was discussed previously in the results sections for [[CFD_Simulations_AC4-01#CFD2|CFD2]]. The main conclusions emerging from the results of these simulations are summarized below.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The results of the simulation CFD2 and its comparison to the wind tunnel data was discussed previously in the results sections for [[CFD_Simulations_AC4-01#<ins style="font-weight: bold; text-decoration: none;">Simulation Case </ins>CFD2|CFD2]]. The main conclusions emerging from the results of these simulations are summarized below.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In CFD2 it was possible to produce incident wind profiles in the CFD calculations to match the velocity profile in the wind tunnel, however the corresponding turbulence kinetic energy k values were significantly lower than those measured in the wind tunnel for all CFD profiles. A reason for this discrepancy may be a deficiency in the boundary layer in the wind tunnel, i.e. it is possible that the profile was not fully developed at the location of the building and was not in equilibrium with the tunnel ground roughness. In CFD2, two different sets of inlet profiles were considered: one based on the established method of Castro and Apsley (BL2), and another of profiles (BL1) calculated using a 2D empty tunnel simulation based on a plausible modification of the value of Cμ to match the wind tunnel value of k at the wall. The BL1 mean velocity profile was similar to the experimental, and its k profile values were closer to those measured than the corresponding BL2 profile; nonetheless, using BL1 as input caused subsequent calculations of the flow around the building to diverge. Therefore the incident wind profiles for a CFD simulation should be selected with care; a converged solution was obtained using the profiles by Castro and Apsley (BL2), though further work is recommended to fully resolve this issue of selecting appropriate and self-consistent profiles, to match conditions in an atmospheric boundary layer.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In CFD2 it was possible to produce incident wind profiles in the CFD calculations to match the velocity profile in the wind tunnel, however the corresponding turbulence kinetic energy k values were significantly lower than those measured in the wind tunnel for all CFD profiles. A reason for this discrepancy may be a deficiency in the boundary layer in the wind tunnel, i.e. it is possible that the profile was not fully developed at the location of the building and was not in equilibrium with the tunnel ground roughness. In CFD2, two different sets of inlet profiles were considered: one based on the established method of Castro and Apsley (BL2), and another of profiles (BL1) calculated using a 2D empty tunnel simulation based on a plausible modification of the value of Cμ to match the wind tunnel value of k at the wall. The BL1 mean velocity profile was similar to the experimental, and its k profile values were closer to those measured than the corresponding BL2 profile; nonetheless, using BL1 as input caused subsequent calculations of the flow around the building to diverge. Therefore the incident wind profiles for a CFD simulation should be selected with care; a converged solution was obtained using the profiles by Castro and Apsley (BL2), though further work is recommended to fully resolve this issue of selecting appropriate and self-consistent profiles, to match conditions in an atmospheric boundary layer.</div></td></tr> </table> Tonyh https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC4-01&diff=8919&oldid=prev Tonyh at 15:23, 14 April 2009 2009-04-14T15:23:06Z <p></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 15:23, 14 April 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l9">Line 9:</td> <td colspan="2" class="diff-lineno">Line 9:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>=='''Comparison of Test data and CFD'''==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>=='''Comparison of Test data and CFD'''==</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The results of the simulation CFD2 and its comparison to the wind tunnel data was discussed previously in the results sections for [<del style="font-weight: bold; text-decoration: none;">http://qnet.cfms.org.uk/data/TA4/AC4</del>-01<del style="font-weight: bold; text-decoration: none;">/A4-01cfd </del>CFD2]. The main conclusions emerging from the results of these simulations are summarized below.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The results of the simulation CFD2 and its comparison to the wind tunnel data was discussed previously in the results sections for [<ins style="font-weight: bold; text-decoration: none;">[CFD_Simulations_AC4</ins>-01<ins style="font-weight: bold; text-decoration: none;">#CFD2|</ins>CFD2<ins style="font-weight: bold; text-decoration: none;">]</ins>]. The main conclusions emerging from the results of these simulations are summarized below.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In CFD2 it was possible to produce incident wind profiles in the CFD calculations to match the velocity profile in the wind tunnel, however the corresponding turbulence kinetic energy k values were significantly lower than those measured in the wind tunnel for all CFD profiles. A reason for this discrepancy may be a deficiency in the boundary layer in the wind tunnel, i.e. it is possible that the profile was not fully developed at the location of the building and was not in equilibrium with the tunnel ground roughness. In CFD2, two different sets of inlet profiles were considered: one based on the established method of Castro and Apsley (BL2), and another of profiles (BL1) calculated using a 2D empty tunnel simulation based on a plausible modification of the value of Cμ to match the wind tunnel value of k at the wall. The BL1 mean velocity profile was similar to the experimental, and its k profile values were closer to those measured than the corresponding BL2 profile; nonetheless, using BL1 as input caused subsequent calculations of the flow around the building to diverge. Therefore the incident wind profiles for a CFD simulation should be selected with care; a converged solution was obtained using the profiles by Castro and Apsley (BL2), though further work is recommended to fully resolve this issue of selecting appropriate and self-consistent profiles, to match conditions in an atmospheric boundary layer.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In CFD2 it was possible to produce incident wind profiles in the CFD calculations to match the velocity profile in the wind tunnel, however the corresponding turbulence kinetic energy k values were significantly lower than those measured in the wind tunnel for all CFD profiles. A reason for this discrepancy may be a deficiency in the boundary layer in the wind tunnel, i.e. it is possible that the profile was not fully developed at the location of the building and was not in equilibrium with the tunnel ground roughness. In CFD2, two different sets of inlet profiles were considered: one based on the established method of Castro and Apsley (BL2), and another of profiles (BL1) calculated using a 2D empty tunnel simulation based on a plausible modification of the value of Cμ to match the wind tunnel value of k at the wall. The BL1 mean velocity profile was similar to the experimental, and its k profile values were closer to those measured than the corresponding BL2 profile; nonetheless, using BL1 as input caused subsequent calculations of the flow around the building to diverge. Therefore the incident wind profiles for a CFD simulation should be selected with care; a converged solution was obtained using the profiles by Castro and Apsley (BL2), though further work is recommended to fully resolve this issue of selecting appropriate and self-consistent profiles, to match conditions in an atmospheric boundary layer.</div></td></tr> </table> Tonyh https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC4-01&diff=7513&oldid=prev Daveg: Evaluation AC4-01 moved to SilverP:Evaluation AC4-01 2009-04-03T13:46:02Z <p><a href="/w/index.php/Evaluation_AC4-01" title="Evaluation AC4-01">Evaluation AC4-01</a> moved to <a href="/w/index.php/SilverP:Evaluation_AC4-01" class="mw-redirect" title="SilverP:Evaluation AC4-01">SilverP:Evaluation AC4-01</a></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <tr class="diff-title" lang="en"> <td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 13:46, 3 April 2009</td> </tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div> </td></tr></table> Daveg https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC4-01&diff=6780&oldid=prev Daveg: /* Comparison of Test data and CFD */ 2009-03-27T10:57:07Z <p><span dir="auto"><span class="autocomment">Comparison of Test data and CFD</span></span></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 10:57, 27 March 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l9">Line 9:</td> <td colspan="2" class="diff-lineno">Line 9:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>=='''Comparison of Test data and CFD'''==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>=='''Comparison of Test data and CFD'''==</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The results of the <del style="font-weight: bold; text-decoration: none;">simulations CFD1 and </del>CFD2 and <del style="font-weight: bold; text-decoration: none;">their </del>comparison to the wind tunnel data was discussed previously in the results sections for <del style="font-weight: bold; text-decoration: none;">[http://qnet.cfms.org.uk/data/TA4/AC4-01/A4-01cfd CFD1] and </del>[http://qnet.cfms.org.uk/data/TA4/AC4-01/A4-01cfd CFD2]. The main conclusions emerging from the results of these simulations are summarized below.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The results of the <ins style="font-weight: bold; text-decoration: none;">simulation </ins>CFD2 and <ins style="font-weight: bold; text-decoration: none;">its </ins>comparison to the wind tunnel data was discussed previously in the results sections for [http://qnet.cfms.org.uk/data/TA4/AC4-01/A4-01cfd CFD2]. The main conclusions emerging from the results of these simulations are summarized below.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>In <del style="font-weight: bold; text-decoration: none;">both CFD1 and </del>CFD2 it was possible to produce incident wind profiles in the CFD calculations to match the velocity profile in the wind tunnel, however the corresponding turbulence kinetic energy k values were significantly lower than those measured in the wind tunnel for all CFD profiles. A reason for this discrepancy may be a deficiency in the boundary layer in the wind tunnel, i.e. it is possible that the profile was not fully developed at the location of the building and was not in equilibrium with the tunnel ground roughness. In CFD2, two different sets of inlet profiles were considered: one based on the established method of Castro and Apsley (BL2), and another of profiles (BL1) calculated using a 2D empty tunnel simulation based on a plausible modification of the value of Cμ to match the wind tunnel value of k at the wall. The BL1 mean velocity profile was similar to the experimental, and its k profile values were closer to those measured than the corresponding BL2 profile; nonetheless, using BL1 as input caused subsequent calculations of the flow around the building to diverge. Therefore the incident wind profiles for a CFD simulation should be selected with care; a converged solution was obtained using the profiles by Castro and Apsley (BL2), though further work is recommended to fully resolve this issue of selecting appropriate and self-consistent profiles, to match conditions in an atmospheric boundary layer.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>In CFD2 it was possible to produce incident wind profiles in the CFD calculations to match the velocity profile in the wind tunnel, however the corresponding turbulence kinetic energy k values were significantly lower than those measured in the wind tunnel for all CFD profiles. A reason for this discrepancy may be a deficiency in the boundary layer in the wind tunnel, i.e. it is possible that the profile was not fully developed at the location of the building and was not in equilibrium with the tunnel ground roughness. In CFD2, two different sets of inlet profiles were considered: one based on the established method of Castro and Apsley (BL2), and another of profiles (BL1) calculated using a 2D empty tunnel simulation based on a plausible modification of the value of Cμ to match the wind tunnel value of k at the wall. The BL1 mean velocity profile was similar to the experimental, and its k profile values were closer to those measured than the corresponding BL2 profile; nonetheless, using BL1 as input caused subsequent calculations of the flow around the building to diverge. Therefore the incident wind profiles for a CFD simulation should be selected with care; a converged solution was obtained using the profiles by Castro and Apsley (BL2), though further work is recommended to fully resolve this issue of selecting appropriate and self-consistent profiles, to match conditions in an atmospheric boundary layer.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">Both the </del>3D simulations in <del style="font-weight: bold; text-decoration: none;">CFD1 and </del>CFD2 gave mean velocity profiles in the wake of the building that were in overall agreement with experimental data at the location of the runway, for a incident wind normal to the building (180°)<del style="font-weight: bold; text-decoration: none;">. CFD1 results under-predicted the velocity deficit at the runway slightly, but results for wind directions 30° either side of the normal wind direction showed a closer agreement with experimental data</del>. Thus, the predictions for the velocity deficit ([[DOAP]]1) were relatively close to experimental data and are thus considered satisfactory for the purpose of assessing the wind environment over the runway.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">The </ins>3D simulations in CFD2 gave mean velocity profiles in the wake of the building that were in overall agreement with experimental data at the location of the runway, for a incident wind normal to the building (180°). Thus, the predictions for the velocity deficit ([[DOAP]]1) were relatively close to experimental data and are thus considered satisfactory for the purpose of assessing the wind environment over the runway.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Although the predictions for the mean velocity are acceptable <del style="font-weight: bold; text-decoration: none;">for both CFD1 and CFD2</del>, the prediction of the turbulence kinetic energy is considered less successful<del style="font-weight: bold; text-decoration: none;">. CFD1 results predicted turbulence kinetic energy levels that are significantly higher than the experimental measurements</del>. CFD2 showed clear evidence of a large increase in the turbulence kinetic energy in the wake of the building (by a factor of 5 compared to the empty tunnel) which is larger than the turbulence increase in the wind tunnel measurements. The inadequacy of the k-ε turbulence model with regards to excessive k production is well-documented; in areas of high streamwise strain rates which occur around bluff bodies the k-ε model is known to fail to model the turbulence dissipation adequately and therefore over-predicts the turbulence kinetic energy in those areas. The roof protrusion and the roof leading edge are such areas, so one would expect excessively high quantities of turbulence to be generated there. As these unphysically high levels of turbulence are transported downstream, then these can cause an increase in the mean velocity as momentum is transferred from these high k areas to parts of the boundary layer that have been retarded by the building.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Although the predictions for the mean velocity are acceptable, the prediction of the turbulence kinetic energy is considered less successful. CFD2 showed clear evidence of a large increase in the turbulence kinetic energy in the wake of the building (by a factor of 5 compared to the empty tunnel) which is larger than the turbulence increase in the wind tunnel measurements. The inadequacy of the k-ε turbulence model with regards to excessive k production is well-documented; in areas of high streamwise strain rates which occur around bluff bodies the k-ε model is known to fail to model the turbulence dissipation adequately and therefore over-predicts the turbulence kinetic energy in those areas. The roof protrusion and the roof leading edge are such areas, so one would expect excessively high quantities of turbulence to be generated there. As these unphysically high levels of turbulence are transported downstream, then these can cause an increase in the mean velocity as momentum is transferred from these high k areas to parts of the boundary layer that have been retarded by the building.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>It is therefore interesting that the mean velocity predictions for both <del style="font-weight: bold; text-decoration: none;">CFD1 and </del>CFD2 should be close to experimental data despite the strong over-prediction of the turbulence in the wake. As indicated in CFD2 however, the actual levels of turbulence simulated in the wake (rather than the turbulence increase) did match the experimental results, but this is likely to be the result of the much lower levels of turbulence prescribed at the inlet balancing the over-generation of turbulence downstream of the building. This coincidence may have contributed to the simulations reproducing the flow re-attachment and recovery correctly, leading to a correct prediction of the velocity deficit at the runway.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>It is therefore interesting that the mean velocity predictions for both CFD2 should be close to experimental data despite the strong over-prediction of the turbulence in the wake. As indicated in CFD2 however, the actual levels of turbulence simulated in the wake (rather than the turbulence increase) did match the experimental results, but this is likely to be the result of the much lower levels of turbulence prescribed at the inlet balancing the over-generation of turbulence downstream of the building. This coincidence may have contributed to the simulations reproducing the flow re-attachment and recovery correctly, leading to a correct prediction of the velocity deficit at the runway.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>As the building is roughly symmetrical and is much longer than it is wide, it may appear that a 2D simulation could be used instead of a full 3D calculation. In CFD2 a 2D simulation was carried out to illustrate why such a simplification is inappropriate; in contrast to the 3D simulation, the 2D simulation failed to predict any velocity deficit at the runway, since the flow had re-attached and recovered too soon, well before reaching the runway.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>As the building is roughly symmetrical and is much longer than it is wide, it may appear that a 2D simulation could be used instead of a full 3D calculation. In CFD2 a 2D simulation was carried out to illustrate why such a simplification is inappropriate; in contrast to the 3D simulation, the 2D simulation failed to predict any velocity deficit at the runway, since the flow had re-attached and recovered too soon, well before reaching the runway.</div></td></tr> </table> Daveg https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC4-01&diff=5852&oldid=prev David.Fowler at 16:12, 18 March 2009 2009-03-18T16:12:42Z <p></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 16:12, 18 March 2009</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1">Line 1:</td> <td colspan="2" class="diff-lineno">Line 1:</td></tr> <tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">{{AC|front=AC 4-01|description=Description_AC4-01|testdata=Test Data_AC4-01|cfdsimulations=CFD Simulations_AC4-01|evaluation=Evaluation_AC4-01|qualityreview=Quality Review_AC4-01|bestpractice=Best Practice Advice_AC4-01|relatedUFRs=Related UFRs_AC4-01}}</ins></div></td></tr> <tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>='''Wind environment around an airport terminal building'''=</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>='''Wind environment around an airport terminal building'''=</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l29">Line 29:</td> <td colspan="2" class="diff-lineno">Line 31:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Site Design and Implementation: [[Atkins]] and [[UniS]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Site Design and Implementation: [[Atkins]] and [[UniS]]</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">        Top              Next</del></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">{{AC|front=AC 4-01|description=Description_AC4-01|testdata=Test Data_AC4-01|cfdsimulations=CFD Simulations_AC4-01|evaluation=Evaluation_AC4-01|qualityreview=Quality Review_AC4-01|bestpractice=Best Practice Advice_AC4-01|relatedUFRs=Related UFRs_AC4-01}}</ins></div></td></tr> </table> David.Fowler https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC4-01&diff=1699&oldid=prev Tonyh at 14:10, 19 September 2008 2008-09-19T14:10:19Z <p></p> <table style="background-color: #fff; color: #202122;" data-mw="interface"> <col class="diff-marker" /> <col class="diff-content" /> <col class="diff-marker" /> <col class="diff-content" /> <tr class="diff-title" lang="en"> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td> <td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 14:10, 19 September 2008</td> </tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l11">Line 11:</td> <td colspan="2" class="diff-lineno">Line 11:</td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In both CFD1 and CFD2 it was possible to produce incident wind profiles in the CFD calculations to match the velocity profile in the wind tunnel, however the corresponding turbulence kinetic energy k values were significantly lower than those measured in the wind tunnel for all CFD profiles. A reason for this discrepancy may be a deficiency in the boundary layer in the wind tunnel, i.e. it is possible that the profile was not fully developed at the location of the building and was not in equilibrium with the tunnel ground roughness. In CFD2, two different sets of inlet profiles were considered: one based on the established method of Castro and Apsley (BL2), and another of profiles (BL1) calculated using a 2D empty tunnel simulation based on a plausible modification of the value of Cμ to match the wind tunnel value of k at the wall. The BL1 mean velocity profile was similar to the experimental, and its k profile values were closer to those measured than the corresponding BL2 profile; nonetheless, using BL1 as input caused subsequent calculations of the flow around the building to diverge. Therefore the incident wind profiles for a CFD simulation should be selected with care; a converged solution was obtained using the profiles by Castro and Apsley (BL2), though further work is recommended to fully resolve this issue of selecting appropriate and self-consistent profiles, to match conditions in an atmospheric boundary layer.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In both CFD1 and CFD2 it was possible to produce incident wind profiles in the CFD calculations to match the velocity profile in the wind tunnel, however the corresponding turbulence kinetic energy k values were significantly lower than those measured in the wind tunnel for all CFD profiles. A reason for this discrepancy may be a deficiency in the boundary layer in the wind tunnel, i.e. it is possible that the profile was not fully developed at the location of the building and was not in equilibrium with the tunnel ground roughness. In CFD2, two different sets of inlet profiles were considered: one based on the established method of Castro and Apsley (BL2), and another of profiles (BL1) calculated using a 2D empty tunnel simulation based on a plausible modification of the value of Cμ to match the wind tunnel value of k at the wall. The BL1 mean velocity profile was similar to the experimental, and its k profile values were closer to those measured than the corresponding BL2 profile; nonetheless, using BL1 as input caused subsequent calculations of the flow around the building to diverge. Therefore the incident wind profiles for a CFD simulation should be selected with care; a converged solution was obtained using the profiles by Castro and Apsley (BL2), though further work is recommended to fully resolve this issue of selecting appropriate and self-consistent profiles, to match conditions in an atmospheric boundary layer.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Both the 3D simulations in CFD1 and CFD2 gave mean velocity profiles in the wake of the building that were in overall agreement with experimental data at the location of the runway, for a incident wind normal to the building (180°). CFD1 results under-predicted the velocity deficit at the runway slightly, but results for wind directions 30° either side of the normal wind direction showed a closer agreement with experimental data. Thus, the predictions for the velocity deficit ([[<del style="font-weight: bold; text-decoration: none;">DOAP1</del>]]) were relatively close to experimental data and are thus considered satisfactory for the purpose of assessing the wind environment over the runway.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Both the 3D simulations in CFD1 and CFD2 gave mean velocity profiles in the wake of the building that were in overall agreement with experimental data at the location of the runway, for a incident wind normal to the building (180°). CFD1 results under-predicted the velocity deficit at the runway slightly, but results for wind directions 30° either side of the normal wind direction showed a closer agreement with experimental data. Thus, the predictions for the velocity deficit ([[<ins style="font-weight: bold; text-decoration: none;">DOAP</ins>]]<ins style="font-weight: bold; text-decoration: none;">1</ins>) were relatively close to experimental data and are thus considered satisfactory for the purpose of assessing the wind environment over the runway.</div></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr> <tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although the predictions for the mean velocity are acceptable for both CFD1 and CFD2, the prediction of the turbulence kinetic energy is considered less successful. CFD1 results predicted turbulence kinetic energy levels that are significantly higher than the experimental measurements. CFD2 showed clear evidence of a large increase in the turbulence kinetic energy in the wake of the building (by a factor of 5 compared to the empty tunnel) which is larger than the turbulence increase in the wind tunnel measurements. The inadequacy of the k-ε turbulence model with regards to excessive k production is well-documented; in areas of high streamwise strain rates which occur around bluff bodies the k-ε model is known to fail to model the turbulence dissipation adequately and therefore over-predicts the turbulence kinetic energy in those areas. The roof protrusion and the roof leading edge are such areas, so one would expect excessively high quantities of turbulence to be generated there. As these unphysically high levels of turbulence are transported downstream, then these can cause an increase in the mean velocity as momentum is transferred from these high k areas to parts of the boundary layer that have been retarded by the building.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although the predictions for the mean velocity are acceptable for both CFD1 and CFD2, the prediction of the turbulence kinetic energy is considered less successful. CFD1 results predicted turbulence kinetic energy levels that are significantly higher than the experimental measurements. CFD2 showed clear evidence of a large increase in the turbulence kinetic energy in the wake of the building (by a factor of 5 compared to the empty tunnel) which is larger than the turbulence increase in the wind tunnel measurements. The inadequacy of the k-ε turbulence model with regards to excessive k production is well-documented; in areas of high streamwise strain rates which occur around bluff bodies the k-ε model is known to fail to model the turbulence dissipation adequately and therefore over-predicts the turbulence kinetic energy in those areas. The roof protrusion and the roof leading edge are such areas, so one would expect excessively high quantities of turbulence to be generated there. As these unphysically high levels of turbulence are transported downstream, then these can cause an increase in the mean velocity as momentum is transferred from these high k areas to parts of the boundary layer that have been retarded by the building.</div></td></tr> </table> Tonyh https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC4-01&diff=1698&oldid=prev Tonyh: New page: ='''Wind environment around an airport terminal building'''= '''Application Challenge 4-01''' © copyright ERCOFTAC 2004 =='''Comparison of Test data and CFD'''== The re... 2008-09-19T14:02:01Z <p>New page: =&#039;&#039;&#039;Wind environment around an airport terminal building&#039;&#039;&#039;= &#039;&#039;&#039;Application Challenge 4-01&#039;&#039;&#039; © copyright ERCOFTAC 2004 ==&#039;&#039;&#039;Comparison of Test data and CFD&#039;&#039;&#039;== The re...</p> <p><b>New page</b></p><div>='''Wind environment around an airport terminal building'''=<br /> <br /> '''Application Challenge 4-01''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Comparison of Test data and CFD'''==<br /> <br /> The results of the simulations CFD1 and CFD2 and their comparison to the wind tunnel data was discussed previously in the results sections for [http://qnet.cfms.org.uk/data/TA4/AC4-01/A4-01cfd CFD1] and [http://qnet.cfms.org.uk/data/TA4/AC4-01/A4-01cfd CFD2]. The main conclusions emerging from the results of these simulations are summarized below.<br /> <br /> In both CFD1 and CFD2 it was possible to produce incident wind profiles in the CFD calculations to match the velocity profile in the wind tunnel, however the corresponding turbulence kinetic energy k values were significantly lower than those measured in the wind tunnel for all CFD profiles. A reason for this discrepancy may be a deficiency in the boundary layer in the wind tunnel, i.e. it is possible that the profile was not fully developed at the location of the building and was not in equilibrium with the tunnel ground roughness. In CFD2, two different sets of inlet profiles were considered: one based on the established method of Castro and Apsley (BL2), and another of profiles (BL1) calculated using a 2D empty tunnel simulation based on a plausible modification of the value of Cμ to match the wind tunnel value of k at the wall. The BL1 mean velocity profile was similar to the experimental, and its k profile values were closer to those measured than the corresponding BL2 profile; nonetheless, using BL1 as input caused subsequent calculations of the flow around the building to diverge. Therefore the incident wind profiles for a CFD simulation should be selected with care; a converged solution was obtained using the profiles by Castro and Apsley (BL2), though further work is recommended to fully resolve this issue of selecting appropriate and self-consistent profiles, to match conditions in an atmospheric boundary layer.<br /> <br /> Both the 3D simulations in CFD1 and CFD2 gave mean velocity profiles in the wake of the building that were in overall agreement with experimental data at the location of the runway, for a incident wind normal to the building (180°). CFD1 results under-predicted the velocity deficit at the runway slightly, but results for wind directions 30° either side of the normal wind direction showed a closer agreement with experimental data. Thus, the predictions for the velocity deficit ([[DOAP1]]) were relatively close to experimental data and are thus considered satisfactory for the purpose of assessing the wind environment over the runway.<br /> <br /> Although the predictions for the mean velocity are acceptable for both CFD1 and CFD2, the prediction of the turbulence kinetic energy is considered less successful. CFD1 results predicted turbulence kinetic energy levels that are significantly higher than the experimental measurements. CFD2 showed clear evidence of a large increase in the turbulence kinetic energy in the wake of the building (by a factor of 5 compared to the empty tunnel) which is larger than the turbulence increase in the wind tunnel measurements. The inadequacy of the k-ε turbulence model with regards to excessive k production is well-documented; in areas of high streamwise strain rates which occur around bluff bodies the k-ε model is known to fail to model the turbulence dissipation adequately and therefore over-predicts the turbulence kinetic energy in those areas. The roof protrusion and the roof leading edge are such areas, so one would expect excessively high quantities of turbulence to be generated there. As these unphysically high levels of turbulence are transported downstream, then these can cause an increase in the mean velocity as momentum is transferred from these high k areas to parts of the boundary layer that have been retarded by the building.<br /> <br /> It is therefore interesting that the mean velocity predictions for both CFD1 and CFD2 should be close to experimental data despite the strong over-prediction of the turbulence in the wake. As indicated in CFD2 however, the actual levels of turbulence simulated in the wake (rather than the turbulence increase) did match the experimental results, but this is likely to be the result of the much lower levels of turbulence prescribed at the inlet balancing the over-generation of turbulence downstream of the building. This coincidence may have contributed to the simulations reproducing the flow re-attachment and recovery correctly, leading to a correct prediction of the velocity deficit at the runway.<br /> <br /> As the building is roughly symmetrical and is much longer than it is wide, it may appear that a 2D simulation could be used instead of a full 3D calculation. In CFD2 a 2D simulation was carried out to illustrate why such a simplification is inappropriate; in contrast to the 3D simulation, the 2D simulation failed to predict any velocity deficit at the runway, since the flow had re-attached and recovered too soon, well before reaching the runway.<br /> <br /> <br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> Contributors: Athena Scaperdas; Steve Gilham - Atkins<br /> <br /> Site Design and Implementation: [[Atkins]] and [[UniS]]<br /> <br /> Top Next</div> Tonyh