UFR 1-05 Best Practice Advice: Difference between revisions

From KBwiki
Jump to navigation Jump to search
(New page: {{UFR|front=UFR 1-05|description=UFR 1-05 Description|references=UFR 1-05 References|testcase=UFR 1-05 Test Case|evaluation=UFR 1-05 Evaluation|qualityreview=UFR 1-05 Quality Review|bestp...)
 
m (Dave.Ellacott moved page Silver:UFR 1-05 Best Practice Advice to UFR 1-05 Best Practice Advice over redirect)
 
(4 intermediate revisions by 3 users not shown)
Line 1: Line 1:
{{UFR|front=UFR 1-05|description=UFR 1-05 Description|references=UFR 1-05 References|testcase=UFR 1-05 Test Case|evaluation=UFR 1-05 Evaluation|qualityreview=UFR 1-05 Quality Review|bestpractice=UFR 1-05 Best Practice Advice|relatedACs=UFR 1-05 Related ACs}}
{{UFR|front=UFR 1-05|description=UFR 1-05 Description|references=UFR 1-05 References|testcase=UFR 1-05 Test Case|evaluation=UFR 1-05 Evaluation|qualityreview=UFR 1-05 Quality Review|bestpractice=UFR 1-05 Best Practice Advice|relatedACs=UFR 1-05 Related ACs}}


Line 17: Line 16:
== Best Practice Advice for the UFR ==
== Best Practice Advice for the UFR ==


•Distortions of the grid should be avoided in the immediate vicinity of the jet exit.
* Distortions of the grid should be avoided in the immediate vicinity of the jet exit.
 
•For large eddy simulations, dimensions should be around <span lang="EN-US"><font face="Symbol">D</font></span>x=0.004D and <span lang="EN-US"><font face="Symbol">D</font></span>z=0.006D. Scaled up by the shear velocity of the turbulent pipe flow, the dimensions should be around <span lang="EN-US"><font face="Symbol">D</font></span>x<sup>+</sup><nowiki>=1.4 and </nowiki><span lang="EN-US"><font face="Symbol">D</font></span>z<sup>+</sup><nowiki>=2.2.</nowiki>
 
•With LES, the following boundary conditions should be used:
 
<span lang="EN-US"><font face="Wingdings">Ø<span style="font: 7.0pt &quot;Times New Roman&quot;">      </span></font></span>Free slip on the lateral and top surfaces
 
<span lang="EN-US"><font face="Wingdings">Ø<span style="font: 7.0pt &quot;Times New Roman&quot;">      </span></font></span>No slip on the bottom
 
<span lang="EN-US"><font face="Wingdings">Ø<span style="font: 7.0pt &quot;Times New Roman&quot;">      </span></font></span>Laminar boundary layer velocity profile at inlet


<span lang="EN-US"><font face="Wingdings">Ø<span style="font: 7.0pt &quot;Times New Roman&quot;">      </span></font></span>Zero gradient for all variables at outlet
* For large eddy simulations, dimensions should be around &Delta;x=0.004D and &Delta;z=0.006D. Scaled up by the shear velocity of the turbulent pipe flow, the dimensions should be around &Delta;x<sup>+</sup><nowiki>=1.4 and </nowiki>&Delta;z<sup>+</sup><nowiki>=2.2.</nowiki>


<span lang="EN-US"><font face="Wingdings">Ø<span style="font: 7.0pt &quot;Times New Roman&quot;">      </span></font></span>Instantaneous velocity profiles given by a temporal pipe flow simulation, at the pipe flow exit.
* With LES, the following boundary conditions should be used:
** Free slip on the lateral and top surfaces
** No slip on the bottom
** Laminar boundary layer velocity profile at inlet
** Zero gradient for all variables at outlet
** Instantaneous velocity profiles given by a temporal pipe flow simulation, at the pipe flow exit.


•With high velocity ratios, turbulence modelling is not critical, particularly with respect to the region near the jet, where inviscid flow conditions dominate.
* With high velocity ratios, turbulence modelling is not critical, particularly with respect to the region near the jet, where inviscid flow conditions dominate.


•Particularly with low velocity ratios, where turbulence is important near the jet exit, eddy viscosity models should be avoided. However a clearly winner turbulence model has not been found yet for JICF and Baldwin-Lomax may be used with reservations.
* Particularly with low velocity ratios, where turbulence is important near the jet exit, eddy viscosity models should be avoided. However a clearly winner turbulence model has not been found yet for JICF and Baldwin-Lomax may be used with reservations.


<u>Recommendations for future work</u>
<u>Recommendations for future work</u>


•The Baldwin-Lomax turbulence model should be tested with a very well designed, undistorted grid at the immediate vicinity of the jet exit.
* The Baldwin-Lomax turbulence model should be tested with a very well designed, undistorted grid at the immediate vicinity of the jet exit.


•New experimental and computational work should be undertaken with velocity ratios R=1 or &lt; 1, as these values are closer to those encountered in blade cooling.
* New experimental and computational work should be undertaken with velocity ratios R=1 or &lt; 1, as these values are closer to those encountered in blade cooling.


•In general terms, the thin layer approximation of the Navier Stokes equations seems to produce good quality results, as even the more complicated behaviour of the jet with swirl was reasonably predicted. However, more work is necessary to define the best choice of turbulence model.
* In general terms, the thin layer approximation of the Navier Stokes equations seems to produce good quality results, as even the more complicated behaviour of the jet with swirl was reasonably predicted. However, more work is necessary to define the best choice of turbulence model.


•The semi-elliptic scheme applied by Bergeles et al. worked well for velocity ratio up to 0.1 with injection angle of 90 degrees and for velocity ratio up to 0.5 with injection angle of 30 degrees. They have used a k-ε turbulence model, but recommend an algebraic stress treatment to be tried in future work, including all the secondary production terms associated with the three-dimensional flow field.
* The semi-elliptic scheme applied by Bergeles et al. worked well for velocity ratio up to 0.1 with injection angle of 90 degrees and for velocity ratio up to 0.5 with injection angle of 30 degrees. They have used a k-ε turbulence model, but recommend an algebraic stress treatment to be tried in future work, including all the secondary production terms associated with the three-dimensional flow field.


<font size="-2" color="#888888">© copyright ERCOFTAC 2004</font><br />
<font size="-2" color="#888888">© copyright ERCOFTAC 2004</font><br />
Line 55: Line 49:


{{UFR|front=UFR 1-05|description=UFR 1-05 Description|references=UFR 1-05 References|testcase=UFR 1-05 Test Case|evaluation=UFR 1-05 Evaluation|qualityreview=UFR 1-05 Quality Review|bestpractice=UFR 1-05 Best Practice Advice|relatedACs=UFR 1-05 Related ACs}}
{{UFR|front=UFR 1-05|description=UFR 1-05 Description|references=UFR 1-05 References|testcase=UFR 1-05 Test Case|evaluation=UFR 1-05 Evaluation|qualityreview=UFR 1-05 Quality Review|bestpractice=UFR 1-05 Best Practice Advice|relatedACs=UFR 1-05 Related ACs}}
[[Category:Underlying Flow Regime]]

Latest revision as of 19:08, 11 February 2017

Front Page

Description

Test Case Studies

Evaluation

Best Practice Advice

References




Jet in a cross flow 

Underlying Flow Regime 1-05               © copyright ERCOFTAC 2004


Best Practice Advice

Best Practice Advice for the UFR

  • Distortions of the grid should be avoided in the immediate vicinity of the jet exit.
  • For large eddy simulations, dimensions should be around Δx=0.004D and Δz=0.006D. Scaled up by the shear velocity of the turbulent pipe flow, the dimensions should be around Δx+=1.4 and Δz+=2.2.
  • With LES, the following boundary conditions should be used:
    • Free slip on the lateral and top surfaces
    • No slip on the bottom
    • Laminar boundary layer velocity profile at inlet
    • Zero gradient for all variables at outlet
    • Instantaneous velocity profiles given by a temporal pipe flow simulation, at the pipe flow exit.
  • With high velocity ratios, turbulence modelling is not critical, particularly with respect to the region near the jet, where inviscid flow conditions dominate.
  • Particularly with low velocity ratios, where turbulence is important near the jet exit, eddy viscosity models should be avoided. However a clearly winner turbulence model has not been found yet for JICF and Baldwin-Lomax may be used with reservations.

Recommendations for future work

  • The Baldwin-Lomax turbulence model should be tested with a very well designed, undistorted grid at the immediate vicinity of the jet exit.
  • New experimental and computational work should be undertaken with velocity ratios R=1 or < 1, as these values are closer to those encountered in blade cooling.
  • In general terms, the thin layer approximation of the Navier Stokes equations seems to produce good quality results, as even the more complicated behaviour of the jet with swirl was reasonably predicted. However, more work is necessary to define the best choice of turbulence model.
  • The semi-elliptic scheme applied by Bergeles et al. worked well for velocity ratio up to 0.1 with injection angle of 90 degrees and for velocity ratio up to 0.5 with injection angle of 30 degrees. They have used a k-ε turbulence model, but recommend an algebraic stress treatment to be tried in future work, including all the secondary production terms associated with the three-dimensional flow field.

© copyright ERCOFTAC 2004


Contributors: Flavio Franco - ABB ALSTOM Power UK Ltd


Front Page

Description

Test Case Studies

Evaluation

Best Practice Advice

References

Retrieved from "http://kbwiki.ercoftac.org/w/index.php?title=UFR_1-05_Best_Practice_Advice&oldid=33048"