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This page of this tutorial is currently under construction. Please check back soon. |
Step 6: Results
Velocity Vectors
One can plot vectors in the entire domain, or on selected surfaces. Here, the vectors will be plotted for the entire domain. First, click on Graphics & Animations . Next, double click on Vectors which is located under Graphics. Then, click on Display in the Vectors menu. You should obtain, the following output.
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https://confluence.cornell.edu/download/attachments/118771111/VectPlot_Full.png |
You can use the wheel button of the mouse to zoom into the region that closely surrounds the plate, to get a better view of the boundary layer velocities.
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https://confluence.cornell.edu/download/attachments/118771111/VectPlot2_Full.png |
Outlet Velocity Profile
In this section we will first plot the variation of the x component of the velocity along the outlet. Then we will plot the Blasius solution and to see how the numerical solution compares. In order to start the process (Click) Results > Plots > XY Plot... > Set Up.. as shown below.
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https://confluence.cornell.edu/download/attachments/118771111/xyplotsetup_Full.png |
In the
Solution XY Plot menu make sure that
Position on Y Axis is selected , and
X is set to
0
and
Y is set to
1
. This tells FLUENT to plot the y-coordinate value on the ordinate of the graph. Next, select
Velocity... for the first box underneath
X Axis Function and select
X Velocity for the second box. Please note that
X Axis Function and
Y Axis Function describe the
x and
y axes of the
graph, which should not be confused with the
x and
y directions of the geometry. Finally, select
outlet under
Surfaces since we are plotting the x component of the velocity along the
outlet. This finishes setting up the plotting parameters. Your
Solution XY Plot menu should look exactly the same as the following image.
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https://confluence.cornell.edu/download/attachments/118771111/SolXY1_Full.png |
Now, click
Plot. The plot of the x component of the velocity as a function of distance along the
outlet now appears.
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https://confluence.cornell.edu/download/attachments/118771111/XVelPlot1_Full.png |
In order to increase the legibility of the graph, we will plot the data as a line rather than points. To turn on the line feature, click on
Curves... in the
Solution XY Plot menu. Then, set
Pattern to
Center, set the
Weight to
2
and select nothing for
Symbol, as shown below.
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https://confluence.cornell.edu/download/attachments/118771111/CurveMen_Full.png |
Next, click
Apply in the
Curves - Solution XY Plot menu. Next, close the
Curves - Solution XY Plot menu.
Now, the range of the y axis will be truncated, as we are not interested in far field velocity. Furthermore, the grid lines will be turned on. In order to implement these two changes. First click
Axes in the
Solution XY Plot menu. Next, select
Y for
Axis, deselect
Auto Range, select
Major Rules, select
Minor Rules. Then, set
Minimum to
0
and set
Maximum to 1.2. Your
Axes - Solution XY Plot menu, should look exactly like the image below.
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https://confluence.cornell.edu/download/attachments/118771111/AxesMen1_Full.png |
Then, click
Apply in the
Axes - Solution XY Plot menu. Now, select
X for
Axis and select
Major Rules and
Minor Rules, as shown below.
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https://confluence.cornell.edu/download/attachments/118771111/Axes2_Full.png |
Next, click
Apply in the
Axes - Solution XY Plot menu. Close the
Axes - Solution XY Plot menu. Now, click
Plot menu in the
Solution XY Plot menu. You should obtain the following output.
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https://confluence.cornell.edu/download/attachments/118771111/Plot5_Full.png |
It is of interest to compare the numerical velocity profile to the velocity profile obtained from the Blasius solution. In order to plot the theoretical results, first click
here to download the necessary file. Save the file to your working directory. Next, go to the
Solution XY Plot menu and click
Load File... and select the file that you just downloaded,
BlasiusU.xy. Lastly, click
Plot in the
Solution XY Plot menu. You should then obtain the following figure.
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https://confluence.cornell.edu/download/attachments/118771111/Plot6_Full.png |
Pressure Coefficients
In this section we will create contour plots for the pressure coefficients. Before we begin, we must first set the reference values for velocity. In order to do so, first click on Reference Values then set Compute from to inlet, as shown below.
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https://confluence.cornell.edu/download/attachments/118771111/CompInlet_Full.png |
Next, click on Graphics and Animations, then double click on Contours, as shown below.
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https://confluence.cornell.edu/download/attachments/118771111/ContPlot_Full.png |
In the
Contours menu, set
Contours of to
Pressure... and set the box below to
Pressure Coefficient. Next, select
Filled and set
Levels to 90. Your
Contours menu should look exactly like the following image.
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https://confluence.cornell.edu/download/attachments/118771111/Contou_Full.png |
Lastly, click
Display in the
Contours menu to generate the contour plot. You should obtain the following output.
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https://confluence.cornell.edu/download/attachments/118771111/ContP1_Full.png |
You can zoom then zoom in to the leading edge of the plate with the wheel mouse button as shown below.
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https://confluence.cornell.edu/download/attachments/118771111/ContZoom_Full.png |
Plot Skin Friction Coefficient
Now we will plot the skin friction coefficient along the flat plate.
Results > Plots > XY Plot
Change Pressure to Wall Fluxes. Then, change Wall Shear Stress to Skin Friction Coefficient. Under Surfaces, select plate.
Click Plot.
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https://confluence.cornell.edu/download/attachments/118771111/step6_005.png?version=1 |
Now, compare your solution to the with the Blasius solution's skin friction by loading the file and then plotting it with your solution. (Download file here)
Also, you can change the symbol into lines by going to Curves... and click on the corresponding pattern that you like. Increase the Weight to 3 for readability. Both results should be fairly similar.
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https://confluence.cornell.edu/download/attachments/118771111/step6_007.png?version=1 |
Plot Velocity Profiles
Results > Plots > XY Plot
Uncheck Position on X Axis and check Position on Y Axis under Options. Under Plot Direction, set X to 0 and Y to 1. Under X Axis Function, select Velocity...Then, change Velocity Magnitude to X Velocity. Finally under surface, select outlet. Before we are ready to plot, click on the Axes... button and rescale the y-axis from 0 to 0.12. Also, check the Major Rules and Minor Rules for both axes. Remember that you must click the Apply button when performing changes in each axis.
Click Plot.
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https://confluence.cornell.edu/download/attachments/118771111/step6_008.png?version=1 |
To compare with the Blasius solution, download the solution here. Click Load File...and select the file you just downloaded. Then plot the solutions again to display both lines on the same graph.
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https://confluence.cornell.edu/download/attachments/118771111/step6_009.png?version=1 |
What is the noticeably different between two solutions? Why is the velocity overshoot 1 for FLUENT's solution?
Now we will compare the velocity profile at two sections. Create another section in the middle of the plate.
Again, in the XY Plot window under New Surface > Line/Rake
Check the line tool checkbox under Options and set the initial coordinate to (0.5,0) and final coordinate to (0.5,0.5). Under the New Surface Name field, type in x_0.5 and then click the Create button to create the line.
We can now plot and compare the velocity profile at the mid point and the outlet of the flow.
Under Surfaces, select outlet and {}x_0.5 and Plot.
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https://confluence.cornell.edu/download/attachments/118771111/step6_010.png?version=1 |
Go to Step 7: Refine Mesh