Learning Forum

[wayne.rumsey]

I am attempting to learning Discovery AIM by replicate a wind tunnel with the ASMO vehicle.  In the AIM tutorials or App (ie Wind Tunnel) I have reviewed the enclosure domain is small compaired to what I have used in other CFD software.

• Is there a recommended distance from inlet to vehicle and vehicle to outlet?
• Is there a recommended blockage factor for the x-sectional area of the enclosure?
  • I have used 3X vehicle length for inlet and 8X for outlet.
  • With 5% x-sectional area blockage factor.
  • Intel velocity magnitude of 50 m s^-1
  • Outlet gauge static pressure of 0 Pa
  • For the walls and top of the tunnel a flow specification of: Free Slip
  • For the floor of the tunnel a flow specification of: No Slip, moving at a magnitude of 50 m s^-1
  • K-Omega SST for RANS Model
• I am monitoring Force.x and have run the analysis up to 2,000 iterations.

---

Medium solution fidelity:

 

High solution fidelity:

 

I am finding as I increase the solution fidelity the drag (Force.x) as shown above in the chart increases in variation, appearing less stable.

• I am attempting to find a converged solution but not sure what else to try?

[Naresh Patre]

Hello WRumsey

I will contact you separately for requesting the file.

[Naresh Patre]

Hello WRumsey

I tried changing some solver settings and mesh settings but though the convergence plot and drag values are stable, the model is still not converging. I will continue working on it and will update you.

[wayne.rumsey]

Naresh,

Thank you for the status update, I have continued working as well, without success.

Any general guidelines on:

• Recommended distance from inlet to vehicle and vehicle to outlet?
• Recommended blockage factor for the x-sectional area of the enclosure?
• Is there a way to define mesh refinement zones around the vehicle or in the wake behind the vehicle?

Best regards,

WRumsey

[Naresh Patre]

Hello WRumsey

I have passed on the model to development team and will let you know their suggestions.

Regarding your questions:

• Recommended distance from inlet to vehicle: 3X vehicle length
• Recommended distance from outlet to vehicle: 5X vehicle length
• Recommended blockage factor: I am not sure about the factor but generally the width and height of tunnel can be considered as 2 times the vehicle length.
• Currently, there is no option to define mesh refinement zones. One workaround here is to split the fluid body into appropriate sections which resemble refinement zones and specify body sizings.