Week 2 - Flow over a Cylinder.

Aim:

To simulate the flow over a cylinder and explain the phenomenon of Karman vortex street.

Objective:

PART-I

1. Simulate the flow with the steady and unsteady case and calculate the Strouhal Number for Re= 100.

PART-II

1. Calculate the coefficient of drag and lift over a cylinder by setting the Reynolds number to 10,100,1000,10000 & 100000. (Run with steady solver)
2. Discuss the effect of Reynolds number on the coefficient of drag. [ Results should be validated with any standard literature and error should be within 5 %]

Procedure:

Geometry:

• Make a Circle of 2 meters diameter and make a rectangle with 5m and 10m length and breadth.

• Take the pull tool, click on the middle of the circle, delete it, and delete all the other geometric lines.
• Now we can close the module and go for meshing.

Meshing:

• Opening the model in the meshing module and generating the mesh to see how the mesh is generating.
• Now clearing the model and going to give some parameters to the meshing.
• Using inflation and given some inflation layer around the circle.
• Now going for 100mm meshing which we'll get fine mesh.
• Now zooming to see if our inflation layer is good enough.
• we have generated a fine mesh.

Creating Mesh:

Setup:

• Open the Ansys setup to set up the fluid flow on the cylinder.
• Setting up the viscous to laminar flow.
• Creating the fluid and flow setting up the inlet and outlet flow. With appropriate vlaues and temperature.
• Now generating the viscous flow over the cylinder with some different level of iterations. As follows.

Creating Result setup module:

100 iteration:

150 iteration:

200 iteration:

Result Explanation:

• In the first, there is zero vortex in the velocity magnitude due to less no iteration.
• As we start increasing the mesh size we will get fine mesh with the inflation layers we can have more vortex in the high iteration.
• In the second figure, we can see we used 150 iterations so the flow started some vortex toward the outlet.
• As we increase the no of iterations up to 200 iterations then we can see more vortex in the 3rd figure of velocity magnitude.
• And we can see the velocity magnitude of the graph having a jumping texture which represents the vortex is maximum at those points.

Conclusion:

Hence we have simulated the flow over the cylinder with a steady and unsteady flow.

AS we increase the iteration we can more vortex in the outlet of the cylinder laminar flow.