Solver Settings in Star CCM+

Aim

To model a cube of side 10 mm and construct a domain around it for external aero simulations.

Procedure

Stage 1 Modelling : Cube

We model the geometry using the 3D CAD modeler in STAR CCM+

1) Open the simulation, Expand Geometry, right click on the 3D CAD Modeler and select New

2) The modeling window will open, select the XY plane and select Create Sketch.

3) Draw a square whose length is 10 mm & exit.

2D sketch of the Cube

4) Right click on the 3D model which is on the CAD tree and select Extrude and give the thickness as 1 cm

Extruded view (Cube)

5) Close the 3D cad modeller and save.

6) Expand geometry >3D CAD model > Right click on the 3D model created and select New Geometry Part.

Block (Wind Tunnel)

1) Right click on Parts > New shape part > Block.

2) 6 balls corresponding to the vertices of the rectangle block will appear, enlarge them in such a way that the cube is inside the block.

3) Click create and close.

4) To give boundary conditions split the block by patches by right clicking on it and clicking split by patches.

5) Select the Front & rename it as inlet and the back face as outlet and the side faces as walls.

Wind tunnel

Combine the wind tunnel and cube by selecting the mentioned and right clicking on any of the selected one and click combine.

Stage 2 Surface Repair

Checked for surface errors & 8 face proximity errors were found, this can be rectified by remeshesing the surface.

Stage 3 Surface Wrapper

Since there were no surface errors, a surface wrap wasn't needed.

Assigning to regions

Right click on the wind tunnel and click on the Assign to regions, a dialog box will appear in that change the boundary setting as Create a boundary each part surface, & click ok.

Regions dialog box

Applying BC

1) Expand Regions > Regions > Boundaries.

2) The boundaries are listed for inlet select Velocity Inlet, for outlet select Pressure outlet & for the rest select wall.

Stage 4 Surface remecher and Volume Mesher.

1) Select Operations > New > Mesh > Automated Mesh.

2) A dialog box will appear Select the following

• Surface remesher
• Automatic surface repair
• Trimmed Mesher (Core mesher)
• Prism layer Mesher

and click ok

3) Expand Default Controls, and select Base size and give the value as 1 mm(less than the length of the cube 10 mm).

4) Right click Custom control > New > Surface control and select inlet & outlet of the wind tunnel and increase the target & minimum surface size by 4 times the base value(1 mm) and click ok

5) Right click Custom control > New > Surface control and select the walls of the wind tunnel and increase the target & minimum surface size by 8 times the base value(1 mm) and click ok

6) Right click Custom control > New > Surface control and select cube & expand controls > Trimmer Wake refinement & check the box in the property window and give the spread angle as 10 deg.

7) Go to values & give 100 % of base and default growth rate as slow and click ok

Block (to capture near the cube)

1) Right click on Parts > New shape part > Block.

2) 6 balls corresponding to the vertices of the rectangle block will appear, enlarge them in such a way that the cube is inside the block.

3) Click create and close.

Block inside the wind tunnel

Cube inside the block

This is set to capture the flow over the cube perfectly.

8) Right click Custom control > New > Volume control & select the block( mentioned above) which was created click Controls > Trimmer, in property window check the Customize isotropic size & in the values gice 200% of base.

9) Right click on the Automated mesh and select Execute.

10) After the volume mesh is complete we need to generate the mesh scene to do that, go to title bar and click Create/Open scene & select Mesh scene.

Mesh Scene

11) To see the quality of the volume mesh a cut section of the modeled can be viewed, for that right click on derived parts > New parts > Section > Plane.

12) A new window will open and orient the plane in such a way it is perpendicular to X axis, and click ok.

13) To view the cut section, go to Scenes and select the Mesh Scene 1, then go to Scenes/Plots window, and Expand Displayers > Mesh 1 > Parts > Wind tunnel.

14) Right click on Wind tunnel and select Hide and the plane section can be viewed

Cross-sectional view of the volume mesh

For setting BC's for inlet & outlet,

1) Goto Continua > Physics 1 > Select Models.

2) A dialog box will appear and select > Steady > Laminar > Segregated flow > Constant Density & click close.

3) Go to Regions & expand it and click Regions > Boundaries.

4) Select wind tunnel inlet >Physics Values > Velocity Magnitude in that give the value as 50 m/s

5) Select wind tunnel outlet and check whether the value is 0 pa.

Mesh Quality

To check the mesh quality go to the Mesh icon in the title bar and click diagnostic

Mesh Report for the model