Flow over a cylinder

AIM : To perform transient flow simulation over a cylinder.

OBJECTIVE OF THE PROJECT:

Our main objective is to run a transient simulation over a cylinder with a baseline simulation and then calculate the Reynolds number. Then increase the Reynolds number by a factor of 20%, 40%, and 100% then run the transient flow simulation also Create animations for pressure-velocity for all the three Reynolds number.

REYNOLDS NUMBER:

The Reynolds number is an dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow.

Reynolds number is the ratio of intertial force to the viscous force.

`Re = (rhoVD)/(mu)`

Where,

ρ = fluid density in kg/m^3`.

V = Velocity of the fluid in m/s.

D = Diameter of the cylinder in meters.

μ = Viscosity of the fluid in Pa-s.

PROCEDURE FOR THIS PROJECT:

1. Creating a solid cylinder.
2. Saving it and using wizard option selecting external flow, air as our medium.
3. Creating global mesh.
4. Running the solver.
5. After obtaining result using cut plot , inserting cut plot for velocity and pressure.
6. Running animation for the velocity and pressure.

Baseline calculation of Reynolds number:

Length of pipe = 1m.

Density of air = 1.274 kg`/m^3` .

Dynamic viscosity of air = `1.81 xx10^(-5)` .

.Inlet velocity = 10.22 m/s.

Renolds number = 36000.

Simulation for velocity:

Simulation for Pressure :

Increasing Reynolds no. by 20%:

By increasing Reynolds number by 20% we get inlet velocity = 12.27 m/s.

Simulation for velocity:

Simulation for Pressure :

Increasing Reynolds no. by 40%:

By increasing Reynolds number by 40% we get inlet velocity = 14.3 m/s.

Simulation for velocity:

Simulation for Pressure :

Increasing Reynolds no. by 100%:

By increasing Reynolds number by 100% we get inlet velocity = 20.45 m/s.

Simulation for velocity:

Simulation for Pressure :

RESULTS:

From the animation we see that by increasing the Reynolds number flow velocity around the cylinder also increases. As the velocity increases the pressure difference also increases due to which suction occurs at the back of cylinder.

CONCLUSION :

1. I have done the flow simulation over the cylinder successfully.