Flow over a Cylinder using SolidWorks

Aim: To study the flow over cylinder using SolidWorks Flow Simulation

Objective:

• Calculate Reynold's number for the baseline simulation
• Run the baseline simulation
• Run the transient simulation for an increasing Reynold’s number by a factor of 20%, 40%, and 100% of the baseline Reynold’s number.
• Create an animation for Pressure-velocity for all three conditions of Reynold’s number.

Theory: Prepare the cylinder for simulation of the following dimensions-

Cylinder diameter = 0.04m

Length of cylinder = 0.05m

The characteristics of fluid flowing inside the pipe are as follows:

Fluid - Air

Dynamic viscosity - 0.00001825 N.S/m^2

Density - 1.225kg/m^3

Assumptions:

• The surface of the cylinder is smooth and roughness is taken as zero.
• The effect of temperature is not considered in the study.
• The computational domain of velocity in the x-direction is changed as per the speed calculated by Reynold's number.

Calculations:

Let us assume the velocity of air over the cylinder is 10m/s.

The formula for Reynold’s number:

`R_e = (rho*V*D)/mu`

Where,

Re = Reynold’s number

V = Flow Velocity

D = Diameter of the cylinder

rho = density

mu = dynamic viscosity

Substituting the values for D, V, rho, and mu, Reynold’s number is calculated as mentioned below:

For baseline simulation, Re = 27012.13, Simulation end time = 0.1 sec

For 20% increment, Re = 32414.55, Simulation end time = 0.0833 sec

For 40% increment, Re = 37817, Simulation end time = 0.0714 sec

For 100% increment, Re = 54024.26, Simulation end time = 0.05 sec

Procedure:

1. The cylinder of the above-mentioned dimensions is designed and extruded.
2. Set the external flow analysis wizard with air as the fluid and create a transient simulation, i.e., time-dependent.
3. The calculated simulation end time is taken analysis time.
4. Velocity in the x-direction is taken as calculated from Reynold’s number.
5. Run the project and then obtain the cut plots for velocity and pressure.
6. Save the plots and animate them separately and save those animations as well.

Results:

• Baseline Simulation

Velocity Distribution over the cylinder

Pressure Distribution over the cylinder

• For Reynold’s number = 32414.55 and velocity = 12m/s

Velocity Distribution over the cylinder

Pressure Distribution over the cylinder

• For Reynold’s number = 37817 and velocity = 14m/s

Velocity Distribution over the cylinder

Pressure Distribution over the cylinder

• For Reynold’s number = 54024.26 and velocity = 20m/s

Velocity Distribution over the cylinder

Pressure Distribution over the cylinder

Find animations for all the three cases on this link - https://drive.google.com/drive/folders/1mDeLUWVLyX-fTSxE9hz92tWBdszh2Zyg?usp=sharing

Conclusion:

• Inlet velocity in x-direction increases with an increase in Reynold’s number, thereby increasing the flow over the cylinder.
• The relative pressure does not vary to a large extent for Reynold's number.
• It is observed that high pressure is created on the surface facing the inlet velocity.
• The velocity variation in the above animations has a different velocity profile, velocity is maximum at the surface of the cylinder contact with inlet velocity, and it approximately zeroes close to the surface which is not in contact with the inlet velocity.