COMPUTATIONAL INVESTIGATION OF UNSTEADY FLOWS ACROSS BLUFF BODIES AT

HIGH REYNOLDS NUMBERS

ByRajesh Kancheti

(0928024)

Project Guide Mr. Surendra Bogadi

Assistant Professor

Dept. of Aeronautical Engg.

OBJECTIVE

• Flow over Bluff Body.

• Flow at different angle of attacks.

• Flow over the bodies when they are kept in tandem configuration and in

v-configuration .

• To view the vortex shedding behind the wake of the body.

• Computational work is being carried out using FLUENT for coefficient of

pressures, and to see the effect of flow turbulence on the wake bodies.

PROCEDURE

• The model here is the circular cross-section bluff body composed using GAMBIT with structured mesh.

• For each angle of attach we need to determine the following coefficients

LiftDragPressure

PROCEDURE

• The values determined needs to be validated with the pre defined data and the best results are plotted .

• Observe the vortices behind the body to analyze on how it is going to effect the other body which would be in the wake region.

CONFIGURATIONS

• This is an example photograph of circular cross-section bluff body

PLAN OF WORK

2D structured grid

Single cylinder with different diameter ‘s

Three cylinders in tandem position with different

diameter’s

Three cylinders in v-configuration with different

diameter’s

Solution Settings: CFD code: Fluent 6.3.26

• Finite Volume Method based Navier-Stokes Solver

Solver: Pressure BasedViscous Model: K-epsilon

• Standard K-epsilon modelDiscretization schemes:

• Time: 2ndorder implicit• Momentum: 2ndorder upwind• Pressure-Velocity Coupling: SIMPLE

Boundary conditions:Default Interior: InteriorFluid : Fluid Inlet: velocity-inlet Outlet: Pressure outletCylinder: wallLower & upper extent : Wall

Inlet conditions:Velocity inletSpecification method = k and OmegaVelocity magnitude = 4.39m/sTurbulent kinetic energy(m2/s2) = 0.0145Specific dissipation rate(1/s) = 0.0569Velocity magnitude = 4.39m/sTurbulent kinetic energy(m2/s2) = 0.0145Specific dissipation rate(1/s) = 0.0569

Transient Solution:Time step size: 1.701 secondTotal time steps: 800Run time: 9 hoursHardware: Intel(R)core(TM)i3 processors, 3 GB RAM, 2.39 GHz,

Windows 7 64-bit operating system

Boundary conditions created for single cylinder for both Re=1.5 x 103 & 5.3 x 107

Cp vs Angle for single cylinder

The vortex shedding is visualized for single cylinder with respect to time by means of the Velocity Vorticity Magnitude Contour for Re = 5.2 x 107 at 00 AOA

Domain created for three cylinder in Tandem configuration

Grid created for three cylinder in Tandem configuration

Cp vs θ for three cylinders in Tandem at 00 of AOA

Re=1.5 x 103 Re=5.2 x 107

0 50 100 150 200 250 300 350

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

Cp

Angle (deg)

C1 C2 C3

0 50 100 150 200 250 300 350

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Cp

Angle (deg)

c1 c2 c3

The vortex shedding is visualized for Tandem with respect to time by means of the Velocity Vorticity Magnitude Contour for

Re = 5.2 x 107 at 00 AOA

t=680sect=1190sec

Cp vs θ for three cylinders in Tandem at 300 of AOA

Re=1.5 x 103Re=5.2 x 107

0 50 100 150 200 250 300 350

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

c1 c2 c3

Cp

Angle (deg)0 50 100 150 200 250 300 350

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

c1 c2 c3

Cp

Angle (deg)

The vortex shedding is visualized for Tandem with respect to time by means of the Velocity Vorticity Magnitude Contour for

Re = 5.2 x 107 at 300 AOA

t=680sect=1190sec

Cp vs θ for three cylinders in Tandem at 450 of AOA

Re=1.5 x 103 Re=5.2 x 107

0 50 100 150 200 250 300 350

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

c1 c2 c3

Cp

Angle (deg)0 50 100 150 200 250 300 350

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

c1 c2 c3

Cp

Angle (deg)

The vortex shedding is visualized for Tandem with respect to time by means of the Velocity Vorticity Magnitude Contour for

Re = 5.2 x 107 at 450 AOA

t=680sec t=1190sec

Cp vs θ for three cylinders in Tandem at 900 of AOA

Re=1.5 x 103 Re=5.2 x 107

0 50 100 150 200 250 300 350

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Cp

Angle (deg)

c1 c2 c3

0 50 100 150 200 250 300 350

-4

-3

-2

-1

0

1

Cp

Angle (deg)

c1 c2 c3

The vortex shedding is visualized for Tandem with respect to time by means of the Velocity Vorticity Magnitude Contour for

Re = 5.2 x 107 at 900 AOA

t=680sec t=1190sec

Domain created for three cylinder in V-configuration position

Grid created for three cylinder in V-configuration

Cp vs θ for three cylinders in V-confiuration at 00 of AOA

Re=1.5 x 103

Re=5.2 x 107

0 50 100 150 200 250 300 350

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Cp

Angle (deg)

c1 c2 c3

0 50 100 150 200 250 300 350

-3.0-2.5

-2.0

-1.5-1.0

-0.5

0.0

0.51.01.5

C p

Angle (deg)

c1 c2 c3

The vortex shedding is visualized for V-configuration with respect to time by means of the Velocity Vorticity Magnitude

Contour for Re = 5.2 x 107 at 00 AOA

t=680sec t=1190sec

Cp vs θ for three cylinders in V-confiuration at 300 of AOA

Re=1.5 x 103 Re=5.2 x 107

0 50 100 150 200 250 300 350

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Cp

Angle (deg)

C1 C2 C3

0 50 100 150

200

250 300 350

-3.5-3.0-2.5

-2.0-1.5

-1.0

-0.50.0

0.5

1.01.5

c1 c2 c3

Cp

Angle (deg)

The vortex shedding is visualized for V-configuration with respect to time by means of the Velocity Vorticity Magnitude

Contour for Re = 5.2 x 107 at 300 AOA

t=680sec t=1190sec

Cp vs θ for three cylinders in V-confiuration at 450 of AOA

Re=5.2 x 107 Re=5.2 x 107

0 50 100 150 200 250 300 350

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Cp

Angle (deg)

C1 C2 C3

0 50 100 150 200 250 300 350

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

c1 c2 c3

Cp

Angle (deg)

The vortex shedding is visualized for V-configuration with respect to time by means of the Velocity Vorticity Magnitude

Contour for Re = 5.2 x 107 at 450 AOA

t=680sec t=1190sec

Cp vs θ for three cylinders in V-confiuration at 700 of AOA

Re=5.2 x 107 Re=5.2 x 107

0 50 100 150 200 250 300 350

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Cp

Angle (deg)

C1 C2 C3

0 50 100 150 200 250 300 350

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

c1 c2 c3

Cp

Angle (deg)

The vortex shedding is visualized for V-configuration with respect to time by means of the Velocity Vorticity Magnitude

Contour for Re = 5.2 x 107 at 700 AOA

t=680sec t=1190sec

Cp vs θ for three cylinders in V-confiuration at 900 of AOA

Re=5.2 x 107 Re=5.2 x 107

0 50 100 150 200 250 300 350

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

c1 c2 c3

Cp

Angle (deg)

0 50 100 150 200 250 300 350

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Cp

Angle (deg)

C1 C2 C3

The vortex shedding is visualized for V-configuration with respect to time by means of the Velocity Vorticity Magnitude

Contour for Re = 5.2 x 107 at 900 AOA

t=680sec t=1190sec

CONCLUSIONS• The flows around the circular cylinders with

different configuration were investigated. The results obtained are in good agreement with previous literature results.

• It has been observed that V-configuration is better suitable for situations where high pressures are expected on the wake bodies and tandem configuration is suitable for situating where pressure expected not to change considerably .

• In the three cylinders in v-configuration flow effect is more on the upstream bodies this is visualized by capturing the velocity vorticity magnitude contours with respect to the time.

• Frequency is not possible to calculate or capture in the wake of the bodies.

• In Tandem configuration at 90° AOA the three cylinders will become as a individual bodies.

• in V-configuration at 90° AOA the first cylinder acts as a individual body.

SCOPE OF FUTURE WORK

It is worth to carry out further studies for better

understanding some of them are listed below;

Can be extended to 3-D

Different orientation can be adopted.

Different shapes can be used.

Experimental work can be done.

THANK YOU