# (Solved) Automotive Aerodynamic_Wind Tunnel

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Hello everyone,

I am studying for an automotive aerodynamic simulation on AcuSolve and VWT.

I am having trouble with building Windtunnel, it's about the tunnel's dimensions.

Does anyone know about the general rules to build the tunnel?

*for example:

-the ratio between tunnel's and car's dimensions?
-where to place the car (distance from the inlet)?

Greatly apprecitate every help!

thank you!

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The virtual wind tunnel you show in your screenshot if very small for any reasonable aerodynamics results. You might get colorful picture, but probably no useful interpretation.

Wind tunnel dimensions:
o 5 car lengths ahead of the car
o 10 car lengths behind the car
o 5 car widths on each side of the car
o 10 car heights above the car
o i.e., wind tunnel dimensions LWT x WWT x HWT = 16Lc x 11Wc x 11Hc.
o The mesh farther away from the car will be coarse and increasing the wind tunnel domain would not affect the element count too much but it would still affect the B.Cs if they are too close to the car.

 Boundary Layer details
o First layer height will depend on the freestream velocity to obtain a maximum y+<100. A first guess would be 0.2mm<y<0.5mm. Ideally y+max<30.
o For some applications y+max<100 should still give good results
o growth rate of 1.3
o number of layers 5
o all tets in boundary layers

Duc_Hoang and Livil Lyle like this

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19 hours ago, ydigit said:

The virtual wind tunnel you show in your screenshot if very small for any reasonable aerodynamics results. You might get colorful picture, but probably no useful interpretation.

Wind tunnel dimensions:
o 5 car lengths ahead of the car
o 10 car lengths behind the car
o 5 car widths on each side of the car
o 10 car heights above the car
o i.e., wind tunnel dimensions LWT x WW﻿T x HWT = 16Lc x 11Wc x 11Hc.
o The mesh farther away from th﻿e car will be coarse and increasing the wind tunnel domain would not aff﻿ect the element count too much but it would still affect the B.Cs if they are too close to the car.

 Boundary Layer details
o First layer height will depend on the freestream velocity to obtain a maximum y+<100. A first guess would be 0.2mm<y<0.5mm. Ideally y+max<30.
o For some applications y+max<100 should still give good results
o growth rate of 1.3
o number of layers 5
o all tets in boundary layers

Thank you very much.

The picture i attached is just an example that i took on the internet.

Beside, i also found some information in an Altair's E-book: Learn external dynamic with VWT.
It mentioned about the tunnel size but all the dimension ratios are based on the  car's length.
You can take a look in the E-book, page 22.

Thank you again!

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