Test Data AC1-05: Difference between revisions

From KBwiki
Jump to navigation Jump to search
No edit summary
No edit summary
 
(32 intermediate revisions by 4 users not shown)
Line 1: Line 1:
{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}
='''Ahmed body'''=
='''Ahmed body'''=


Line 7: Line 9:
=='''Overview of Tests'''==
=='''Overview of Tests'''==


The first experiment (Exp1) deals with conventional average values such as oil flow patterns, static pressure measured on large times. Thus no information about unsteadiness will be included in the data. In Exp1, conventional wake surveys are performed with 10 hole probes. Drag is measured by strain gauge balance. The contribution of the drag is estimated for each part of the model. (front, slant rear, vertical rear base). The Reynolds number based on the model total length is 4.29 x 106.
The first experiment (Exp1) deals with conventional average values such as oil flow patterns, static pressure measured on large times. Thus no information about unsteadiness will be included in the data. In Exp1, conventional wake surveys are performed with 10 hole probes. Drag is measured by strain gauge balance. The contribution of the drag is estimated for each part of the model. (front, slant rear, vertical rear base). The Reynolds number based on the model total length is 4.29 x 10<sup>6</sup>.
 
The second experiment (Exp2) uses a two-components LDV system. Averages are performed on a high number of samples (40,000) on long time durations, typically 5 minutes.
 
 
NAME
 
GNDPs
 
PDPs
 
(problem definition parameters)
 
MPs (measured parameters)
 
 
Re
 
External velocity
 
External turbulence level
 
 
Slant angle


detailed data
The second experiment (Exp2) uses a two-components LDV system. Averages are performed on a high number of samples (40000) for long time durations, typically 5 minutes.
 
DOAPs
 
EXP 1 Ahmed original (1984)
 
4.29 106
 
60m/s
 
0.5%
 
5, 12.5, 25, 30
 
Pw, Ui
 
Cx, Flow structure


   
   
{| border="1" align="center"
 
|+ Table EXP-A Summary Description of All Test Cases
Re
! align="center" | NAME
! align="center" | [[DOAPs#GNDPs:_Governing_Non-Dimensional_Parameters|GNDPs]]
 
! align="center" colspan="3" | [[DOAPs#PDPs:_Problem_Definition_Parameters|PDPs]]
! align="center" colspan="2" | [[DOAPs#MPs:_Measured_Parameters|MPs]]
|-
 
!
! align="center" | Re
! align="center" | External velocity
 
! align="center" | External turbulence level
! align="center" | Slant angle
! align="center" | Detailed Data
 
! align="center" | [[DOAPs#DOAPs:_Design_or_Assessment_Parameters|DOAPs]]
detailed data
|-
| align="center" | EXP 1 Ahmed original (1984)
 
| align="center" | 4.29x10<sup>6</sup>
DOAPs
| align="center" | 60ms<sup>-1</sup>
 
| align="center" | 0.5%
EXP2 Lienhart et al. (2000)
| align="center" | 5&deg;, 12.5&deg;, 25&deg;, 30&deg;
| align="center" | P<sub>w</sub>, U<sub>i</sub>
 
| align="center" | C<sub>x</sub>, Flow structure
2.78 106
|-
!
 
! align="center" | Re
40m/s
!
!
 
!
0.25%
! align="center" | Detailed Data
! align="center" | [[DOAPs#DOAPs:_Design_or_Assessment_Parameters|DOAPs]]
 
|-
25, 35
| align="center" | EXP2 Lienhart et al. (2000)
| align="center" | 2.78x10<sup>6</sup>
 
| align="center" | 40ms<sup>-1</sup>
First, second and third moments
| align="center" | 0.25%
| align="center" | 25&deg;, 35&deg;
 
| align="center" | First, second and third moments
Pw, Flow structure
| align="center" | P<sub>w</sub>, Flow structure
 
|}
Table EXP-A Summary description of all test cases
 


=='''Test Case EXP-1'''==
=='''Test Case EXP-1'''==
Line 119: Line 62:
==='''Boundary Data'''===
==='''Boundary Data'''===


==='''The test section is a ¾ open test section. Only the floor is a solid boundary. The homogeneity and far field conditions are not given.'''===
'''The test section is a ¾ open test section. Only the floor is a solid boundary. The homogeneity and far field conditions are not given.'''


==='''The incoming turbulence intensity is less than 0.5% for 60 m/s. No details on the incoming turbulence are available.'''===
'''The incoming turbulence intensity is less than 0.5% for 60 ms<sup>-1</sup>. No details on the incoming turbulence are available.'''


The size of the nozzle at the entrance of the test section is 3x3 .
The size of the nozzle at the entrance of the test section is 3x3 m<sup>2</sup>.


The model is supposed to be smooth. No info is available on the turbulent/laminar nature of the boundary layers on the model. The influence of possible transition can be tested by CFD;
The model is supposed to be smooth. No info is available on the turbulent/laminar nature of the boundary layers on the model. The influence of possible transition can be tested by CFD;
Line 132: Line 75:


No details on the typical time scales are provided. The influence of the unsteadiness of the wake on the averaging process can be estimated through URANS or LES.
No details on the typical time scales are provided. The influence of the unsteadiness of the wake on the averaging process can be estimated through URANS or LES.


==='''Measurement Errors'''===
==='''Measurement Errors'''===
Line 163: Line 105:
   
   


All these data are provided for slant angles j = 5, 12.5, 25 and 30 °.
All these data are provided for slant angles j = 5&deg;, 12.5&deg;, 25&deg; and 30&deg;.


An additional test is performed by fixing a splitter plate vertically in the wake of the body, in the plane of symmetry.
An additional test is performed by fixing a splitter plate vertically in the wake of the body, in the plane of symmetry.


=='''References'''==
=='''References'''==
Line 181: Line 122:
==='''Boundary Data'''===
==='''Boundary Data'''===


==='''The test section is a ¾ open test section. Only the floor is a solid boundary. The homogeneity and far field conditions are not given. However the blockage is assumed to be less than 4%.'''===
'''The test section is a ¾ open test section. Only the floor is a solid boundary. The homogeneity and far field conditions are not given. However the blockage is assumed to be less than 4%.'''


==='''The incoming turbulence intensity is less than 0.25% for 40 m/s measured by hot wire anemometry 400 mm upstream of the model. The viscosity ratio is about 10.'''===
'''The incoming turbulence intensity is less than 0.25% for 40 ms<sup>-1</sup> measured by hot wire anemometry 400 mm upstream of the model. The viscosity ratio is about 10.'''


The models are supposed to be smooth. Transition to turbulence of the boundary layer on the front part is triggered.
The models are supposed to be smooth. Transition to turbulence of the boundary layer on the front part is triggered.
Line 190: Line 131:


No detail on the typical time scales are provided. The influence of the unsteadiness of the wake on the averaging process can be estimated through URANS or LES.
No detail on the typical time scales are provided. The influence of the unsteadiness of the wake on the averaging process can be estimated through URANS or LES.


==='''Measurement Errors'''===
==='''Measurement Errors'''===
Line 199: Line 139:
==='''Measured Data'''===
==='''Measured Data'''===


LDA measurements of mean velocities: U, V, W, Reynolds stresses [[Image:Image23.gif]] [[Image:Image24.gif]] [[Image:Image25.gif]] [[Image:Image26.gif]] [[Image:Image27.gif]]    and third order moments , , , , , , in some planes for 2 slant angles:
LDA measurements of mean velocities: U, V, W, Reynolds stresses <math>\overline{u'u'},  \overline{v'v'}, \overline{w'w'}, \overline{u'v'}, \overline{u'w'}</math> and third order moments <math>\overline{u'u'u'}, \overline{v'v'v'}, \overline{w'w'w'}, \overline{u'u'v'}, \overline{u'u'w'}, \overline{u'v'v'}, \overline{u'w'w'}</math> in some planes for 2 slant angles:


25° slant angle:
25° slant angle:


planes: Ahmed_25_y=0_global.dat (whole flow); Ahmed_25_y=0_focus.dat (focus on the slant part); y=100; y=180;
planes: <span class="plainlinks">[{{filepath:Ahmed_25_y=0_global.dat}} Ahmed_25_y=0_global.dat]</span>  (whole flow);
<span class="plainlinks">[{{filepath:Ahmed_25_y=0_focus.dat}} Ahmed_25_y=0_focus.dat]</span>  (focus on the slant part);
<span class="plainlinks">[{{filepath:Ahmed_25_y=100.dat}} y=100]</span>;  
<span class="plainlinks">[{{filepath:Ahmed_25_y=180.dat}} y=180]</span>;
<span class="plainlinks">[{{filepath:Ahmed_25_y=195.dat}} y=195]</span>;
<span class="plainlinks">[{{filepath:Ahmed_25_y=-195.dat}} y=-195.dat]</span>
<span class="plainlinks">[{{filepath:Ahmed_25_x=-178.dat}} x=-178]</span>;
<span class="plainlinks">[{{filepath:Ahmed_25_x=-138.dat}} x=-138]</span>;


y=195; Ahmed_25_y=-195.dat
<span class="plainlinks">[{{filepath:Ahmed_25_x=-88.dat}} x=-88]</span>;
<span class="plainlinks">[{{filepath:Ahmed_25_x=-38.dat}} x=-38]</span>;
<span class="plainlinks">[{{filepath:Ahmed_25_x=0.dat}} x=0]</span>;
<span class="plainlinks">[{{filepath:Ahmed_25_x=80.dat}} x=80]</span>;
<span class="plainlinks">[{{filepath:Ahmed_25_x=200.dat}} x=200]</span>;
<span class="plainlinks">[{{filepath:Ahmed_25_x=500.dat}} x=500]</span>


x=-178; x=-138; x=-88; x=-38; x=0; x=80; x=200; x=500


35° slant angle:
35° slant angle:


planes: Ahmed_35_y=0_global.dat (whole flow); Ahmed_35_y=0_focus.dat (focus on the slant part); y=100; y=180
planes: <span class="plainlinks">[{{filepath:Ahmed_35_y=0_global.dat}} Ahmed_35_y=0_global.dat]</span>  (whole flow);
<span class="plainlinks">[{{filepath:Ahmed_35_y=0_focus.dat}} Ahmed_35_y=0_focus.dat]</span> (focus on the slant part);
<span class="plainlinks">[{{filepath:Ahmed_35_y=100.dat}} y=100]</span>;
<span class="plainlinks">[{{filepath:Ahmed_35_y=180.dat}} y=180]</span>
 
<span class="plainlinks">[{{filepath:Ahmed_35_x=-88.dat}} x=-88]</span>;
<span class="plainlinks">[{{filepath:Ahmed_35_x=0.dat}} x=0]</span>;
<span class="plainlinks">[{{filepath:Ahmed_35_x=80.dat}} x=80]</span>;
<span class="plainlinks">[{{filepath:Ahmed_35_x=200.dat}} x=200]</span>;
<span class="plainlinks">[{{filepath:Ahmed_35_x=500.dat}} x=500]</span>


x=-88; x=0; x=80; x=200; x=500


   
   
Hot wire measurements in the boundary layer in the symmetry plane at different x-location: mean velocities, Reynolds stresses and third moments (only u-w components):
Hot wire measurements in the boundary layer in the symmetry plane at different x-location: mean velocities, Reynolds stresses and third moments (only u-w components):


25° slant angle:x=-243, -223, -203, -183, -163, -143, -123, -103,
25° slant angle:x=
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-243.dat}} -243]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-223.dat}} -223]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-203.dat}} -203]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-183.dat}} -183]</span>,  
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-163.dat}} -163]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-143.dat}} -143]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-123.dat}} -123]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-103.dat}} -103]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-83.dat}} -83]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-63.dat}} -63]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-43.dat}} -43]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-23.dat}} -23]</span>,
<span class="plainlinks">[{{filepath:Ahmed_25_BL_x=-3.dat}} -3]</span>


-83, -63, -43, -23, -3
35° slant angle:x=
 
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-243.dat}} -243]</span>,
35° slant angle:x=-243, -223, -203, -183, -163, -143, -123, -103,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-223.dat}} -223]</span>,
 
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-203.dat}} -203]</span>,
-83, -63, -43, -23, -3
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-183.dat}} -183]</span>,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-163.dat}} -163]</span>,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-143.dat}} -143]</span>,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-123.dat}} -123]</span>,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-103.dat}} -103]</span>,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-83.dat}} -83]</span>,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-63.dat}} -63]</span>,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-43.dat}} -43]</span>,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-23.dat}} -23]</span>,
<span class="plainlinks">[{{filepath:Ahmed_35_BL_x=-3.dat}} -3]</span>


   
   
Line 231: Line 211:
Pressure coefficients on the rear of the body:
Pressure coefficients on the rear of the body:


25° slant angle
<span class="plainlinks">[{{filepath:Ahmed_25_Cp.dat}} 25° slant angle]</span>


35° slant angle
<span class="plainlinks">[{{filepath:Ahmed_35_Cp.dat}} 35° slant angle]</span>


   
   


Inlet.dat
<span class="plainlinks">[{{filepath:Inlet.dat}} Inlet.dat]</span>
© ERCOFTAC 2004
 
References
=='''References'''==


Flow and Turbulence Structures in the Wake of a Simplified Car Model (Ahmed model),
Flow and Turbulence Structures in the Wake of a Simplified Car Model (Ahmed model),
Line 246: Line 226:


H. Lienhart and S. Becker, Flow and turbulence structures in the wake of a simplified car model, SAE Paper 2003-01-0656, 2003.
H. Lienhart and S. Becker, Flow and turbulence structures in the wake of a simplified car model, SAE Paper 2003-01-0656, 2003.
© copyright ERCOFTAC 2004
© copyright ERCOFTAC 2004


Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers
----
 
 
''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &mdash; Update (2024) F.R.Menter, ANSYS Germany '',


Site Design and Implementation: Atkins and UniS
Site Design and Implementation: [[Atkins]] and [[UniS]]
        Top              Next
{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}

Latest revision as of 09:46, 14 February 2024

Front Page

Description

Test Data

CFD Simulations

Evaluation

Best Practice Advice

Ahmed body

Application Challenge 1-05 © copyright ERCOFTAC 2004


Overview of Tests

The first experiment (Exp1) deals with conventional average values such as oil flow patterns, static pressure measured on large times. Thus no information about unsteadiness will be included in the data. In Exp1, conventional wake surveys are performed with 10 hole probes. Drag is measured by strain gauge balance. The contribution of the drag is estimated for each part of the model. (front, slant rear, vertical rear base). The Reynolds number based on the model total length is 4.29 x 106.

The second experiment (Exp2) uses a two-components LDV system. Averages are performed on a high number of samples (40000) for long time durations, typically 5 minutes.


Table EXP-A Summary Description of All Test Cases
NAME GNDPs PDPs MPs
Re External velocity External turbulence level Slant angle Detailed Data DOAPs
EXP 1 Ahmed original (1984) 4.29x106 60ms-1 0.5% 5°, 12.5°, 25°, 30° Pw, Ui Cx, Flow structure
Re Detailed Data DOAPs
EXP2 Lienhart et al. (2000) 2.78x106 40ms-1 0.25% 25°, 35° First, second and third moments Pw, Flow structure

Test Case EXP-1

Description of Experiment

See table

Boundary Data

The test section is a ¾ open test section. Only the floor is a solid boundary. The homogeneity and far field conditions are not given.

The incoming turbulence intensity is less than 0.5% for 60 ms-1. No details on the incoming turbulence are available.

The size of the nozzle at the entrance of the test section is 3x3 m2.

The model is supposed to be smooth. No info is available on the turbulent/laminar nature of the boundary layers on the model. The influence of possible transition can be tested by CFD;

No information is available on the precision of the alignment of the model in the flow, although the symmetry on the visualizations give some confidence on this point. This sensitivity can also be checked by CFD.


No details on the typical time scales are provided. The influence of the unsteadiness of the wake on the averaging process can be estimated through URANS or LES.

Measurement Errors

Flow angle precision ± 0.4°.

Free stream dynamic pressure 1%.

Forces and moments are measured with balances with uncertainty of

± 0.2 N and ± 0.1Nm.


Measured Data

The test data include measurements of:

- Wall pressure

- Visualization of flow patterns on rear (slant) surface

- Wake survey (velocity vector plots, average values) :

- Mean velocity distribution in wake central plane

- Cross flow velocity for several downstream locations

- Drag coefficient: contributions of the pressure and friction drags to the total drag are estimated, as well as the repartition of the pressure drag among the front, slant part and vertical base.


All these data are provided for slant angles j = 5°, 12.5°, 25° and 30°.

An additional test is performed by fixing a splitter plate vertically in the wake of the body, in the plane of symmetry.

References

Some salient features of the time-averaged ground vehicle wake, S.R. Ahmed, G. Ramm and G. Faltin, SAE paper series Technical paper 840300, Detroit, 1984


Test Case EXP-2

Description of Experiment

See table

Boundary Data

The test section is a ¾ open test section. Only the floor is a solid boundary. The homogeneity and far field conditions are not given. However the blockage is assumed to be less than 4%.

The incoming turbulence intensity is less than 0.25% for 40 ms-1 measured by hot wire anemometry 400 mm upstream of the model. The viscosity ratio is about 10.

The models are supposed to be smooth. Transition to turbulence of the boundary layer on the front part is triggered.

No information is available on the accuracy of the alignment of the model in the flow, although the symmetry on the visualizations give some confidence on this point. This sensitivity can also be checked by CFD.

No detail on the typical time scales are provided. The influence of the unsteadiness of the wake on the averaging process can be estimated through URANS or LES.

Measurement Errors

Error on mean velocities is less than 0.005% of local mean in the outer flow. In the wake region the accuracy is assumed to be 1% for mean values and 1.5% for RMS.


Measured Data

LDA measurements of mean velocities: U, V, W, Reynolds stresses and third order moments in some planes for 2 slant angles:

25° slant angle:

planes: Ahmed_25_y=0_global.dat (whole flow); Ahmed_25_y=0_focus.dat (focus on the slant part); y=100; y=180; y=195; y=-195.dat x=-178; x=-138;

x=-88; x=-38; x=0; x=80; x=200; x=500


35° slant angle:

planes: Ahmed_35_y=0_global.dat (whole flow); Ahmed_35_y=0_focus.dat (focus on the slant part); y=100; y=180

x=-88; x=0; x=80; x=200; x=500


Hot wire measurements in the boundary layer in the symmetry plane at different x-location: mean velocities, Reynolds stresses and third moments (only u-w components):

25° slant angle:x= -243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3

35° slant angle:x= -243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3


Pressure coefficients on the rear of the body:

25° slant angle

35° slant angle


Inlet.dat

References

Flow and Turbulence Structures in the Wake of a Simplified Car Model (Ahmed model),

H. Lienhart, C. Stoots and S. Becker, DGLR Fach Symp. Der AG STAB, Stuttgart University, 15-17 nov. 2000

H. Lienhart and S. Becker, Flow and turbulence structures in the wake of a simplified car model, SAE Paper 2003-01-0656, 2003.


© copyright ERCOFTAC 2004



Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. — Update (2024) F.R.Menter, ANSYS Germany ,

Site Design and Implementation: Atkins and UniS


Front Page

Description

Test Data

CFD Simulations

Evaluation

Best Practice Advice