UNDER CONSTRUCTION

{panel}

Author: Daniel Kantor and Andrew Einstein, Cornell University

{color:#ff0000}{*}Problem Specification{*}{color}
[1. Create Geometry in GAMBIT|FLUENT - Turbulent Flow Past a Sphere - Step 1]
[2. Mesh Geometry in GAMBIT|FLUENT - Turbulent Flow Past a Sphere - Step 2]
[3. Specify Boundary Types in GAMBIT|FLUENT - Turbulent Flow Past a Sphere - Step 3]
[4. Set Up Problem in FLUENT|FLUENT - Turbulent Flow Past a Sphere - Step 4]
[5. Solve\!|FLUENT - Turbulent Flow Past a Sphere - Step 5]
[6. Analyze Results|FLUENT - Turbulent Flow Past a Sphere - Step 6]
[7. Refine Mesh|FLUENT - Turbulent Flow Past a Sphere - Step 7]
[Problem 1|FLUENT - Turbulent Flow Past a Sphere - Problem 1]

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h2. Step 6: Analyze Results

For all of our analysis we will be looking at the {color:#660099}{*}{_}Sphere{_}{*}{color} surface under {color:#660099}{*}{_}Surfaces{_}{*}{color}, unless otherwise noted.


h4. Plot Velocity Vectors

Let's plot the velocity vectors obtained from the FLUENT solution.

*Display > Vectors*

Set the {color:#660099}{*}{_}Scale{_}{*}{color} to 14 and {color:#660099}{*}{_}Skip{_}{*}{color} to 4. Click {color:#660099}{*}{_}Display{_}{*}{color}.

\\  [!step6_velocity_vectorsm.jpg!|^step6_velocity_vector.jpg]
{newwindow:Higher Resolution Image}https://confluence.cornell.edu/download/attachments/104400192/step6_velocity_vector.jpg?version=1{newwindow}

********From this figure, we see that there is a region of low velocity and recirculation at the back of cylinder.***************
{info:title=Zoom in the cylinder using the middle mouse button.}
{info}

Now, let's take a look at the Contour of Pressure Coefficient variation around the cylinder.

*Display > Contours*

Under {color:#660099}{*}{_}Contours of{_}{*}{color}, choose {color:#660099}{*}{_}Pressure.._{*}{color} and {color:#660099}{*}{_}Pressure Coefficient{_}{*}{color}. Select the {color:#660099}{*}{_}Filled{_}{*}{color} option. Increase the number of contour levels plotted: set {color:#660099}{*}{_}Levels{_}{*}{color} to {{100}}.

!step6_Cphowto.jpg!

Click {color:#660099}{*}{_}Display{_}{*}{color}.
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[!step6_Cp_contoursm.jpg!|^step6_Cp_contour.jpg]

**********Because the cylinder is symmetry in shape, we see that the pressure coefficient profile is symmetry between the top and bottom of cylinder.*********
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h4. Plot Stream Function

Now, let's take a look at the Stream Function.

*Display > Contours*

Under {color:#660099}{*}{_}Contours of{_}{*}{color}, choose {color:#660099}{*}{_}Velocity.._{*}{color} and {color:#660099}{*}{_}Stream Function{_}{*}{color}. Deselect the {color:#660099}{*}{_}Filled{_}{*}{color} option. Click {color:#660099}{*}{_}Display{_}{*}{color}.
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[!step6_streamlinesm.jpg!|^step6_streamline.jpg]

***********Enclosed streamlines at the back of cylinder clearly shows the recirculation region.*************

h4. Plot Vorticity Magnitude

Let's take a look at the Pressure Coefficient variation around the Sphere. Vorticity is a measure of the rate of rotation in a fluid.

*Display > Contours*

Under {color:#660099}{*}{_}Contours of{_}{*}{color}, choose {color:#660099}{*}{_}Velocity.._{*}{color} and {color:#660099}{*}{_}Vorticity Magnitude{_}{*}{color}. Deselect the {color:#660099}{*}{_}Filled{_}{*}{color} option. Click {color:#660099}{*}{_}Display{_}{*}{color}.

[!step6_vorticitysm.jpg!|^step6_vorticity.jpg]

h4. Pressure Coefficient

 
Pressure coefficient is a dimensionless parameter defined by the equation !step6_cp_equation.gif! where _p_ is the static pressure, _p_ ~ref~ is the reference pressure, and _q_ ~ref~ is the reference dynamic pressure defined by
{latex}\large $$ q_{ref} = {1 \over 2}{\rho_{ref}v_{ref}^2}$${latex}
The reference pressure, density, and velocity are defined in the *Reference Values* panel in Step 5.

Let's plot pressure coefficient vs x-direction along the cylinder.

*Plot > XY Plot...*

Change the {color:#660099}{*}{_}Y Axis Function{_}{*}{color} to {color:#660099}{*}{_}Pressure{_}{*}{color}{color:#660099}...{color}, followed by {color:#660099}{*}{_}Pressure Coefficient{_}{*}{color}. Then, select {color:#660099}{*}{_}Sphere{_}{*}{color} under {color:#660099}{*}{_}Surfaces{_}{*}{color}.

\\  !Step6_CpPanel.png!

Click {color:#660099}{*}{_}Plot{_}{*}{color}.

\\  [!step6_Cpplotsm.jpg!|^step6_Cpplot.jpg]

We see that there is a lot of scatter in our data, so we will be creating a line along the sphere to try and get a better picture of the pressure coefficient.

 
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*[*Go to Step 7: Refine Mesh*|FLUENT - Steady Flow Past a Cylinder - Step 7]*

[See and rate the complete Learning Module|FLUENT - Steady Flow Past a Cylinder]

[Go to all FLUENT Learning Modules|FLUENT Learning Modules]