Flow over a cylinder using Solidworks

Aim: To simulate the flow over a cylinder

Introduction :

The flow over a cylinder is one of the most studied of aerodynamics. It is relevant to many engineering applications. The drag and the flow pattern on a cylinder are functions of the Reynolds number Re_D = rho*U*D/mu, based on the cylinder diameter D and the undisturbed free-stream velocity U. Reynolds number represents the ratio of inertial to viscous forces in the flow. The drag is usually expressed as a coefficient C _d = d/(½rU²D), where d is the drag force per unit span.

Calculations :

Density of air (rho) = 1.184 kg/m^3

Characteristic Length (D) = 0.2 m

Diameter of Cylinder (D) = 0.2 m

Dynamic Viscosity = 1.849*10^-5 kg/(m-s)

Note : The Density and Dynamic Viscosity are considered assuming abient temperature to be 25 deg. Celsius

1). Baseline calculation:

U = 10 m/s

Re = rho*U*D/mu.

Re = 1.184*10*0.2/(1.849*10^-5)

Re = 128069.2266

Flow-through time= Length of domain/Velocity

FTT= 0.4/10= 0.04 sec.

End time= FTT*2= 0.08 sec.

2) When Reynold's number is increased by 20% :

Re = 153683.0719

So,

U = 12 m/s

Flow through time= Length of domain/Velocity

FTT= 0.4/12= 0.033 sec.

End time= FTT*2= 0.0667 sec.

3) When Reynold's number is increased by 40% :

Re = 179296.9172

So,

U = 14 m/s

Flow through time= Length of domain/Velocity

FTT= 0.4/14= 0.02857 sec.

End time= FTT*2= 0.05714 sec.

4) When Reynold's number is increased by 100% :

Re = 256138.40

So,

U = 20 m/s

Flow through time= Length of domain/Velocity

FTT= 0.4/20= 0.02 sec.

End time= FTT*2= 0.04 sec.

Procedure :

• Create the cylinder of the prescribed dimensions.
• Now, create a wizard and set up the required conditions in it such as external flow, Time-dependent, Unit system, type of flow, Velocity in x-direction, etc.

• Setup global mesh,

• Then run the active project.
• Next, create the required cut-plots by setting up the required output parameters such as velocity and pressure and animations.
• 

RESULTS :

Baseline Simulation :

• Velocity Distribution :

• Pressure Distribution :

Reynold’s number increased by 20% :

• Velocity Distribution :

• Pressure Distribution :

Reynold’s number increased by 40% :

• Velocity Distribution :

• Pressure Distribution :

Reynold’s number increased by 100% :

• Velocity Distribution :

• Pressure Distribution :

Animation: The link contains animation videos for the mentioned cases.

https://drive.google.com/drive/folders/1RD6LPmDhrzkikV8QDryDvxIE8srixNe6?usp=sharing

Inference :

• From the above plots, it can be seen that as Reynold's number increases the flow of air over the cylinder.
• There is no significant change in the pressure distribution for all conditions.
• With the increase in the Reynolds number, the velocity distribution portion (dark blue colored) increases.
• Similarly, higher velocity regions are increased (red-colored) with an increased Reynold's number.