Flow over a cylinder

Flow over a cylinder

Aim: To examine the air flow over a cylinder.

Objective:

• Create a cylinder with specified dimensions.
• Study the velocity and pressure change of air acting on the surface of cylinder.
• Compare the velocity and pressure change occurred.
• Create animations for each parametric study.
• Explain the results.

Theory:

SOLIDWORKS Flow Simulation is a tool used for studying the flow over and within the solids. Within SOLIDWORKS Flow Simulation users have the ability to solve either external flow or internal flow studies. In this project, External flow simulation is used. External flow studies concerns flows not bounded by outer surfaces, but rather only by the fluid domain boundaries. In this case, the solid part is surrounded by the flow, this type of analysis is most commonly associated with aerodynamic studies. The project includes the flow of air over a cylinder at different velocities.

Flow of procedure while conducting the project

Note: In this project MKS system is used.

Create a solid cylinder of required dimension on which the study is to be taken place.

Here, the dimensions of cylinder consists a diameter of 0.02m and length of 0.05m.

After creating the cylinder, a new flow simulation project is created by selecting the ‘wizard’ option.

Steps followed while setting up wizard

1. Enter the name of flow simulation project as ‘Flow over a cylinder’ and click next.
2. All the value in the window is kept constant and click next.
3. Select the analysis type as external and click on Time-dependent feature and enter the value for Total analysis time as 1 sec and Output time step as 0.01 sec and then click next.

Here, the Total time analysis means the time taken to flow the fluid from inlet to outlet which is specified as 1 sec. Output time step refers to the interval of time at which the output is taken which is specified as 0.01 sec. That means the fluid will take 1sec to travel through inlet to outlet and as the output time step is 0.01, 100 values of output are obtained.

4. Select the Fluids as Air located inside Gases and click next.
5. In the next window keep everything as it is and click next.
6. Next is to specify the value of Velocity in X direction as 1.507 m/s and click finish.

The velocity specified is calculated on the basis of Reynolds number which is initially assumed as 2000. The Reynolds number increases by 20%, 40% and 100% in further cases.

The pressure is kept constant at 101325 Pa.

Formula to calculate the velocity.

Case 1:

At velocity V1 = 1.507 m/s (@Re = 2000)

Flow simulation of change in Velocity

Flow simulation of change in Pressure

Case 2:

At velocity V2 = 1.8084 m/s (@ Re = 2400)

Flow simulation of change in Velocity

Flow simulation of change in Pressure

Case 3:

At velocity V3 = 2.1098 m/s (@ Re = 2800)

Flow simulation of change in Velocity

Flow simulation of change in Pressure

Case 4:

At velocity V4 = 3.014 m/s (@ Re = 4000)

Flow simulation of change in Velocity

Flow simulation of change in Pressure

RESULT

From above animations, it is seen that the change in velocity affect the change in pressure slightly. In the above flow simulations pressure, there is not much difference in between in the change in pressure after changing the velocity. The velocity majorly depends upon the Reynolds number but pressure change does not depend on it. The change in pressure depends upon velocity. In this project, the velocity difference is very less approximately 0.3014 m/s in first three cases. As a result the pressure change is very less while the difference between case 3 and case 4 is more i.e. 0.9042 m/s due to which the pressure change is slightly more than the previous cases.

Reference:

https://www.cati.com/blog/2018/06/solidworks-flow-simulation-tutorial-fluid-flow-problems/