Week 2 - Flow over a Cylinder.

Flow over a Cylinder

Reynold's Number Vs Coefficient of Drag

Predominantly when the drag is made up of pressure drag and form drag

Here in case of flow over cylinder ,the pressure distribution over the front of cylinder is the same as that over the rear. This leads to the theoretical

result that pressure drag is zero - d'Alembert's paradox

For a viscous, incompressible flow the drag coeffiecient is a function of Reynolds Number

Cd = f(Re)

Re = (`rho`* V* D)/ μ

Cd is large for for extremely small values of Re < 1, but decreases monotonically until Re ≈ 300,000

At this reynolds number ,there is aprecipitous drop of Cd from a value near 1 to about 0.3, then a slight recovery to about 0.6 for Re = 10^7

Part 1 - Steady State - Re 100

Geometry

Mesh

The simulation was done using steady state solver , pressure based

The density was assigned as 1 kg/m3 and Dynamic viscosity as 1 kg/ms

The inlet velocity was assigned as 50 m/s

Reference value

Compute from Inlet was given with projected area as 2m - Diameter of cylinder is 2 m

Density 1 kg/m3

Dynamic viscosity 1 kg/ms

Inlet velocity 50 m/s

Results

The following results were obtained

Cl - 0.10409036

Cd - 1.3207827

Cd plot

Cl Plot

Velocity Contour

Pressure Contour

Scaled Residual

Vertex Average -Velocity

Vertex Average - Pressure

Part 1 - Transient Re 100

The simulation was done using steady state solver , pressure based

The density was assigned as 1 kg/m3 and Dynamic viscosity as 0.02 kg/ms

The inlet velocity was assigned as 1 m/s

Reference value

Compute from Inlet was given with projected area as 2m - Diameter of cylinder is 2 m

Density 1 kg/m3

Dynamic viscosity 0.02 kg/ms

Inlet velocity 1 m/s

Results

The following results were obtained

Cl - 0.18673

Cd - 1.34711

Strouhal Number - 0.2

Cd plot

Cl plot

Strouhal Number

Contour Velocity

Contour Pressure

Scaled Residual

Vertex vel average

Vertex pressure average

Part 2 - Steady State - Re 10

The simulation was done using steady state solver , pressure based

The density was assigned as 1 kg/m3 and Dynamic viscosity as 1 kg/ms

The inlet velocity was assigned as 5 m/s

Reference value

Compute from Inlet was given with projected area as 2m - Diameter of cylinder is 2 m

Density 1 kg/m3

Dynamic viscosity 1 kg/ms

Inlet velocity 5 m/s

Results

The following results were obtained

Cl - 0.006495

Cd - 3.31937

Cd Plot

Cl plot

Velocity Contour

Pressure Contour

Scaled Residuals

Vertex average velocity

Vertex average pressure

Part 2 - Re 1000

The simulation was done using steady state solver , pressure based

The density was assigned as 1 kg/m3 and Dynamic viscosity as 1 kg/ms

The inlet velocity was assigned as 500 m/s

Reference value

Compute from Inlet was given with projected area as 2m - Diameter of cylinder is 2 m

Density 1 kg/m3

Dynamic viscosity 1 kg/ms

Inlet velocity 500 m/s

Results

The following results were obtained

Cl - 0.226549

Cd - 1.0562864

Cl Plot

Cd Plot

Velocity Contour

Pressure Contour

Scaled Residuals

Vertex average velocity

Vertex average pressure

Part 2 - Re 10000

The simulation was done using steady state solver , pressure based

The density was assigned as 1 kg/m3 and Dynamic viscosity as 1 kg/ms

The inlet velocity was assigned as 5000 m/s

Reference value

Compute from Inlet was given with projected area as 2m - Diameter of cylinder is 2 m

Density 1 kg/m3

Dynamic viscosity 1 kg/ms

Inlet velocity 5000 m/s

Results

The following results were obtained

Cl - 0.73963048

Cd - 1.1869223

Cl plot

Cd plot

Velocity contour

pressure Contour

Scaled Residual

Vertex average velocity

Vertex average pressure

Part 2 - Re 100000

The simulation was done using steady state solver , pressure based

The density was assigned as 1 kg/m3 and Dynamic viscosity as 1 kg/ms

The inlet velocity was assigned as 50000 m/s

Reference value

Compute from Inlet was given with projected area as 2m - Diameter of cylinder is 2 m

Density 1 kg/m3

Dynamic viscosity 1 kg/ms

Inlet velocity 50000 m/s

Results

The following results were obtained

Cl - (-0.1227576)

Cd - 0.85407836

Cl plot

Cd plot

Velocity contour

Pressure Contour

Scaled Residual

Vertex average velocity

Vertex average pressure