Week 2 - Flow over a Cylinder.

Aim:

Simulate the flow over a cylinder and explanation of the phenomenon of the Karman vortex street

Karman vortex: In fluid dynamics, a Karman vortex street (or a von Kármán vortex street) is a repeating pattern of swirling vortices, caused by a process known as vortex shedding, which is responsible for the unsteady separation of the flow of a fluid around blunt bodies.

Set up conditons:

The geometry to be imported for running Ansys workbench simulation and from this geometry, we redefine and get required entities, which means removing unwanted surfaces and edges and finally we have the required volume to be solved CFD

Set up condition:

1. Take the geometry file and import into the Ansys workbench and edit it through Spaceclime and get the required volume.

2. Mesh the geometry until the quality parameters reach out

3. After the mesh go to the set up for initializing the condition like boundary condition, initial conditions, material properties

and run the calculations until the equations are converged

4. And post-process the simulations and check the results and compare which are suitable for better experiments.

PART-I:

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

Steady-state condition:

Transient case:

Part-II

Calculate the coefficient of drag and lift over a cylinder by setting the Reynolds number to 10,100,1000,10000 & 100000.

Drag coefficients:

Re=10

Re=100

Re=1000

Re=10000

Re=100000

Lift coefficient

Re=10

Re=100

Re=1000

Re=10000

Re=100000

Impressions:

From the above results we say, the Reynault number gets increased the drag coefficient is decreased subsequently