Flow over a cylinder

Aim : To simulate flow over a cylinder at different Reynolds number. Run a baseline simulation and then calculate the Reynolds number.

Introduction : The present study to analyse the fluid flow over a cylinder and calculate Reynold's number for baseline simulation and increase the calculated Reynolds number to a factor of 20%, 40%, & 100% and perform the simulation for all the three values of Reynold's number and create an animation file for velocity-pressure.

Parameters :

Cylinder Diameter : 0.06m

Cylinder Length : 0.120m

Baseline Velocity : 10 m/s

Working Fluid : Air

Density of Working Fluid : 1.225 kg/m3

Dynamic Viscosity of Working Fluid : 1.81 × 10^-5 kg/(m.s)

Length of Domain : 0.21 + 1.29 = 1.5m

Flow Through Time : Length of Domain / Inlet Velocity of Fluid

End Time = 2 * Flow Through Time (Recommended)

Equation for Reynold's Number :

Calculation :

Flow through time = length of domain / inlet velocity

= 1.5 / 10

= 0.15 sec

End time = 0.3 sec

When the Velocity is 10 m/s for Re = 40518.19

At Baseline For V = 10 m/s , Re = 40518.19 , Simulation end time = 0.3 sec

At 20% For V = 11.99 m/s , Re = 48621.83 , Simulation end time = 0.250 sec

At 40% For V = 13.99 m/s , Re = 56725.46 , Simulation end time = 0.214 sec

At 100% For V = 19.99 m/s , Re = 81036.38 , Simulation end time = 0.150 sec

Results :

For V = 10 m/s , Re = 40518.19 , Simulation end time = 0.3 sec

At 20% For V = 11.99 m/s , Re = 48621.83 , Simulation end time = 0.250 sec

At 40% For V = 13.99 m/s , Re = 56725.46 , Simulation end time = 0.214 sec

At 100% For V = 19.99 m/s , Re = 81036.38 , Simulation end time = 0.150 sec

CONCLUSION(OBSERVATION)

• As Reynold's number increases the Velocity increases and the flow through time decreases.
• As the velocity or Reynold’s number increase the flow over the cylinder becomes steady and the velocity plot at 20% and 40% exhibit slight unsteady plot whereas at 100% the flow is steady and we can draw a clear understanding of the flow when velocity is increased.
• There is no significant change in the pressure plot and pressure is mainly acting of the frontal area of the cylinder.