Challenge

Week 2 - Flow over a Cylinder.

Aim :

Simulate the flow over a cylinder through Ansys software.

Objective:

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

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)
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:

Open Ansys fluent software
Set the Spaceclaims units to change millimetres to meters.
Then start the geometry.
First, select the axis set the mid point draw the circle 2 m.
Draw the left-hand side 20 m of the circle and the right side 40 m.
Then start drawing the rectangle height is 20 m.
Open Ansys fluent software .
Finally 2D geometry change to 3D geometry.

Meshing

After drawing the geometry then start meshing the geometry
Right-click the mesh option insert and body selection and Quad dominant to a triangle.
Finally, generate a mesh element size of 2.0m and click generate the mesh option.
Mesh right click insert and sizing method click geometry click the edge and option type number of division and number of dimensions (36).
Mesh insert option inflation and select face and inflation option.
This improves mesh quality. Perfect mesh is created.

Setup

To view te model and Meshed flow over the cylinder
Click the on "Double Precision" and set the Solver process to 4.
After that, you can select the viscous model and choose laminar flow.
To modify the fluid flow poroperties,select "User Defined Material" and adjust the values for air density and viscosity
Finally ,make sure to change the inlet velocity values for the boundary condition based on the Reynolds number.
To compute the referernce values,please provide the inlet condition.
Finally initialize the boundry condition above 300 iteration
We get the results Residual plots,Drag coefficient,Lift coefficient.
This same process will the multiple Reynolds Number.

Results

Reynolds number=10

Drag plot

Lift plot

Reynolds number=100 (Steady Flow)

Lift Plot

Vertex velocity

Drag Plot

Reynolds number =100 (Unsteady Flow)

Drag Plot

Lift Plot

Vertex velocity Transient Stage

Reynolds number =1000

Lift Plot

Drag Plot

Vertex Average Velocity

Reynolds number=10000

Lift Plot

Drag Plot

Vertex Average velocity Plot

Reynolds number =100000

Lift Plot

Drag Plot

Vertex Average Velocity Plot

Part (B)

Von Vertex Karman Street
In fluid dynamics, a Karman vortex street (or a von Karman 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 flow of a fluid around blunt bodies.
Analysis
A vortex street will form only at a certain range of flow velocities, specified by a range of Reynolds numbers (Re), typically above a limiting Re value of about 90. The (global) Reynolds number for a flow is a measure of the ratio of inertial to viscous forces in the flow of a fluid around a body or in a channel, and may be defined as a nondimensional parameter of the global speed of the whole fluid flow:

Swirling Cloud

Ship work like this
in your own course.