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You may have noticed in previous sections, that the pipe looks extremely long and thin on the screen. In fact, due to the symmetry condition of the experimentaxisymmetric assumption, we have only modeled half of a 2D section through the pipe in our analysis. To be able to make full use of the results, we must:

1) Generate the results for the parameter investigated (e.g. temperature, pressure, velocity).

2) Mirror the result to reflect the result of the full pipe section.

3) Adjust the scaling of the resulting graphs so that the variation of the Stretch the pipe in y direction is more pronounced. the radial direction to better view contours.

Temperature Contour

Our first challenge is the temperature contour. On the top menu, click on contour . We will be calling this contour "Temperature Contour", OK when done. On the left hand side, Details of Temperature Contour will allow you to select parameters relevant to the results we're looking for. In this example, the Locations is periodic 1, the Variable is Temperature. The number of contours is a personal preference, in this example, we have selected 100. This step tells CFD-Post we are looking to plot contours of temperature.

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The next step is to mirror the image, this will make the results more intuitive and easier to understand. From the previous screen, select the View tab. This tab will allow us to adjust the appearance of the contour plot we have just generated. Check Apply Reflection/Mirroring. Select ZX Plane for Method. Choosing this option reflects the current model in the ZX plane and allows us to view the "full" pipe section.

Finally, we want to view the variation of parameters along the y axis of the pipe. This means we will need to "stretch out" the plotstretch the pipe in the radial direction. Select Apply Scale. Enter 30 for y-axis. This will stretch our model in the y (radial) direction by a factor of 30. Click Apply. 

After you click Apply, you will see that under Outline > User Locations and Plots, Temperature Contour is created. You will also see that the Temperature Contour is plotted in the Graphics window on the right. Under Outline > User Locations and Plots, uncheck Wireframe to see just the Temperature Contour in the Graphics window.

https://confluence.cornell.edu/download/attachments/111221576/temperature%20contour.png

 
Note if you see the image below instead:

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Our next challenge is to produce velocity vectors. This is a very similar process to creating the temperature contours above. On the top menu, click on vector . Please name Name it "Velocity Vector" and click OK. Under Details of Velocity Vector, select periodic 1 for Locations. Select Velocity for Variable. This tells CFD-post we are looking for vector plots of velocity.

In the next step, we will specify the appearance of vector arrows. Select the Symbol tab. Enter 0.05 for Symbol Size. This again is dependent on personal preference.

Finally click Apply. You will see that under Outline > User Locations and Plots, Velocity Vector is created. Un-check Temperature Contour so that Graphics window shows just the Velocity Vector plot.

It would be beneficial to repeat the previous steps involved with mirroring and stretching the plot

Image Removed

You can mirror the plot about the axis as before. You can translate the model to look at flow development near the entrance. There is a toolbar option at top that puts you in translate mode. You can click on the z-axis to restore our original view.

Does the flow become fully developed at the end of the first sectionPlease focus on the first section of the pipe as it shows flow development. Can you see at which point the flow becomes fully developed?

Centerline Temperature Plot

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In the experiment, we are only able to measure the temperature at two points. First, at the inlet of the pipe and second, after the adiabatic mixing stage. The simulation can show us the variation of temperate temperature in between these two points.

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Insert > Chart 
Please name this chart "Centerline Temperature". You will see Details of Centerline Temperature appear on the lower left panel. Select the General tab and name the chart "Temperature Variation along Pipe Axis".

Moving on, please select the Data Series tab. This tab will help us specify the source of the chart data. Create a new data series .  Change the name from Series 1 to FLUENT. Under Data Source, specify Centerline as Location. Click Apply. On top of this would would also like to plot the experimental data, which can be downloaded here. Download it to a directory of your choice. Now, click a new data series . Name it "Experiment". Under Data Source, select File and browse for the downloaded experimental data.

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Now the y axis: Click on Y Axis tab. Next to Variable, choose Temperature.

Now that the chart specifications are defined, we want to customize the display. The default setting is to display all data series using line charts, but since we only have very few experimental points, it would be more logical to display the experimental data using data points: Click on Line Display tab.  Select "Experimental" . Next to Line Style, change Automatic to None. Next to Symbols, change None to Diamond. Change the color to red. Click Apply.We have are now displaying experimental data using data points denoted by red diamonds.

You will see Centerline Temperature created under Report in the Outline tab.
This is what you should see in the Graphics window.

https://confluence.cornell.edu/download/attachments/111221576/Centerline%20Temperature.png

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We will now investigate the temperature variation along the wall. To do this we need to create a new line on the simulation. It needs to be a horizontal line very close correponding to the wall.

Insert > Location > Line

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You will see wall created under User Locations and Plots.

Next, we will repeat the previous process, but using this new line as source data. 
Insert > Chart

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Again in this case, the x-axis is the x-position along the pipe and the y-axis denotes temperature.
 
As previously showneshown, we will specify how the chart should be displayed. The default setting is to display the data series in lines. Since we only have a few experimental points, we want them to be displayed in data points. Click on Line Display. Then click on experimental tab. Next to Line Style, change Automatic to None. Next to Symbols, change None to Diamond. Change the color to red. Click Apply.

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https://confluence.cornell.edu/download/attachments/111221576/Wall%20Temperature.png

Although the The experimental data are a fairly good match for what the simulation has predicted, the . The wall temperature in the experiment seems to be consistently higher than the simulation in the heated section. This may be explained by the different locations of the temperature measurement. That is,the experimental data is measured from the outside of the wall, while the simulation is measured from a layer of air very close to the wall on the inside of the pipe We will later check if refining the mesh improves this agreement.

Pressure Plot

Now let's us look at the pressure variation at the centerline. We can use the center-line we created earlier.

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In this case, our x-axis variable is x and our y-axis variable is pressure. 
We want to the chart to be displayed exactly the same way as for wall temperatue temperature and centerline temperature plots.

This is what you should see in the Graphics window.

https://confluence.cornell.edu/download/attachments/111221576/centerline%20pressure.png

The simulation results follow the experimental data quite closely, the general trend is that pressure decreases (almost linearly) as we move from the inlet towards the outlet of the pipe.

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Notice preheat 2 and preheat 3 lines yield almost the same velocity profile. This tells us that after preheat 2, the flow has become mostly developed. So we can assume that the flow is developed after 1.2 meters.his almost fully developed.

Axial Velocity Profile before and after Heated Section

To make things more interesting, let's now compare the velocity profiles of before and after the heated section. To do this, we need to first create lines after heated section

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Continue the same step for creating line Outlet (x=6.096m).

 
Now we will have enough interval to look at the flow development before and after the heating.  Let's create a chart to investigate this.

Insert > Chart 
Enter "Second Section Axial Velocity Profile" as Name. You will see Details of Second Section Axial Velocity Profile appear on the lower left panel. Under General, give the chart Title as "Axial Velocity Profile".
 
Now click on Data Series tap to specify the location of the chart data. Create a new data series.  Under Data Source, specify Preheat 3 as Location. Change the name to x=1.8m. Continue adding Data Source until we added all Preheat 3, Postheat 1, Postheat 2, and Outlet. Name them according to the figure shown below.

 
Now we will specify the X Axis parameter. Click on X Axis tab. Next to Variable, choose Velocity u. Next we will specify the Y Axis parameter. Click on Y Axis tab. Next to Variable, choose Y. Click Apply. You will see First Section Axial Velocity Profile created under Report in the Outline tab.
This is what you should see in the Graphics window.

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What we notice when comparing fully developed flow before and after heated section is that the flow increases in velocity after the heated section. As air particle is heated, the density is reduced and therefore the mass is decreased. However, momentum of the air particle is conserved therefore to compensate for the smaller mass, the velocity must increasedecreases. So the velocity has to increase to maintain the same mass flow rate.

Temperature Profile

Now let's us look at the temperature profile before and after the heating section.

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