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Crosswind Simulations

Crosswind Simulations

I’m going to start this off with just some equations that are useful for variables that are important to us.

 

A = Reference Area (usually frontal projected area)

L = Reference Length (vehicle length)

V = Reference Velocity (V in zero yaw)

Additionally, here is a picture of yaw, pitch and roll since its easy to confuse the 3. Here are also some more equations that shows how you calculate the coefficients of them.

image-20250731-225231.png
Screenshot 2025-07-31 175504.png

To calculate the total wind velocity of the wind with crosswind, you do Vmag = sqrt(Vcw^2+Vx^2) where Vx acts as the velocity in the inlet and Vcw is the crosswind velocity.

To find the angle of attack of this type of wind, you do B = arctan(Vcw/Vx).

 

This is a picture of my general setup for a crosswind simulation.

Screenshot 2025-07-31 175956.png
Screenshot 2025-07-31 180134.png

Alright, that's everything setup-wise.

Here are the general steps now.

Workbench 

  1. Geometry 

  2. Import file 

  3. Edit in space claim 

 

Space claim 

  1. Repair 

    1. Stitch 

    2. Gaps 

    3. Missing faces 

    4. Split edges 

    5. Extra edges 

    6. Duplicates 

    7. Small faces 

  2. Design → Planes 

    1. 100.95 mm below car (or make plane on origin)

    2. Down middle 

  3. Prepare → enclosure (length:190in, width:61in, height:44in)

    1. Uncheck symmetric dimensions 

    2. Front: 4 x length 

    3. Back: 12 x length 

    4. top / bottom: 5 x height 

    5. Inlet 2 side: 6 x width

    6. Outlet 2 side: 18 x width

    7. Check mark 

  4. Structure tab (left)

    1. Suppress for physics (car file)

  5. Hide enclosure

Your goal is to make 3 bodies of influence that will look like this. The first body of influence will have the dimensions above, and then each boimedfine and boinearfine will have dimensions that increase in 50 mm increments for length and width, and the distance from the origin to a point will increase by 25 mm.

image-20250801-223300.png

 

  1. Sketch 

    1. boinearfine:

    2. Rectangle around car (positive axis)

    3. No merge 

    4. Pull from both sides 

    5. Width +250 mm

    6. boinearmedfine:

    7. Rectangle around car (positive axis)

    8. No merge

    9. Pull from both sides

    10. Width + 300 mm

    11. boinearcoarse:

    12. Rectangle around car (positive axis)

    13. No merge

    14. Pull from both sides

    15. Width + 350 mm

    16. a7e896d7-6610-4def-af44-f8aeeb6a0a32.png

    17. boifarmedfine:

    18. Taller Rectangle Behind

    19. No merge

    20. Pull from both sides

    21. Width + 350 mm

    22. boifarcoarse:

    23. Another rectangle same size

    24. No merge

    25. Pull from both sides

    26. Width + 350 mm

  2. Select face of back boi, extend up to back face of enclosure 

  3. Click on xz plane in top view and sketch

    1. Length: 3.5 x length

    2. Width: 6 x width

    3. 3000 mm in front of front line of boinearcoarse

    4. Pull no merge and height: 2 x height

      image-20250802-000513.png

  4. Create a new plane in the middle of this solid by control clicking on the left and right face and make a plane

    1. Design → split body

    2. Split along middle plane and then click escape, now it is 2 solids

  5. Design → split body

    1. Split along bottom plane so the bottom plane is the ground

  6. Groups → create ns (ORDER MATTERS)

    1. inletmain

    2. inletside

    3. sky

    4. outletmain

    5. outletside

    6. ground

    7. boinearcoarse

    8. boinearmedfine

    9. boinearfine

    10. boifarmedfine

    11. boicwmedfine

    12. boicwcoarse

    13. bulk

  7. Hide groups 

  8. Save file (ctrl+s)

  9. Close space claim

Workbench 

  1. Duplicate geometry 

  2. Edit in design modeler 

Design Modeler 

  1. Right click import  

  2. Generate 

  3. Change all body types to fluid 

  4. Change name → boinearfine for example 

  5. Save and close

Workbench 

  1. Fluent with fluent meshing 

  2. Drag duplicate geometry to mesh 

  3. Properties → m to mm 

  4. Mesh → edit 

  5. Double precision 

  6. 8 

  7. Start

 

Fluent meshing 

  1. Import geometry 

  2. Add local sizing

    1. Body of influence x 2 

      1. Rename 

      2. Select option 

      3. Target mesh 

        1. boinearfine 24mm

        2. boinearmedfine 32mm 

        3. boinearcoarse 50mm

        4. boifarmedfine 60mm

        5. boicwmedfine 60mm

        6. boifarcoarse 70mm

        7. boicwcoarse 70mm

  3. Curvature  

    1. Rename 

    2. Select option 

      1. bulk

        1. Local 1

        2. Max 8 

        3. Angle 14

  4. Generate surface mesh 

    1. Min 0.5

    2. Max 250

    3. Cells per gap 3 

    4. Generate mesh 

  5. Geometry types 

    1. Consist of only fluid regions with no voids

    2. Describe geometry

    3. sky → symmetry

  6. Add boundary layers 

    1. Offset → last-ratio

    2. Layers 8 

    3. https://plnkr.co/edit/IWnRIQ8HCvnD4if901F9?preview 

      1. Target y+ 1

      2. Velocity 9 

      3. Length of car (check units)

      4. Calculate 

      5. Copy mm number 

    4. First height: calculated (0.0861902 mm)

    5. Add boundary layers

  7. Generate volume mesh 

    1. Fill with: poly-hexcore

    2. Generate volume mesh 

  8. Right click volume mesh and click improve mesh

    1. Improve mesh

  9. Save and quit

 

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