Turbulent Flow in Diffuser: Exercise 7—Analyzing Results
This exercise describes how the results are analyzed during and after the simulation. To hide CAD surfaces (not the fluid domain), switch between CAD Bodies and Flow Analysis Bodies in the Show group. Clear any variable display by selecting No Selection in the Legend drop-down. Click XYPlot Panel to view the XY Plot.
* 
1. To show/hide selected geometric entities, click Show in View Panel.
2. To change the color scheme, click on More in the Legend and select between Blue Red and Blue Purple.
Viewing the Pressure Contours on a Section
Pressure
Pa
1. In the Post-processing group, click Section View and create a section. Section 02 appears under Derived Surfaces.
2. Select Section 02.
3. In the Properties panel, Model tab, set values for the options as listed below:
TypePlane Y
Position — 0
4. In the Properties panel, View tab, for Surface, set values for the options as listed below:
GridNo
OutlineYes
VariablePressure [Pa] : Flow
Viewing the Velocity Magnitude on a Section
Velocity Magnitude
m/s
1. In the Post-processing group, click Section View and create a section. Section 03 appears under Derived Surfaces.
2. Select Section 03.
3. In the Properties panel, Model tab, set values for the options as listed below:
TypePlane Y
Position — 0
4. In the Properties panel, View tab, for Surface, set values for the options as listed below:
GridNo
OutlineYes
VariableVelocity Magnitude [m/s] : Flow
Plotting the Temperature at the Monitoring Point
1. In the Flow Analysis Tree, under Results, click Monitoring Points..
2. Select Point01 to Point10.
3. Click XYPlot. A new entity xyplot1 appears in the Flow Analysis Tree under Results > XY Plots
4. Click xyplot1.
5. In the Properties panel, View tab, for Surface, set Variable to Pressure [Pa] : Flow.
Plotting the Temperature at the Monitoring Point
1. In the Flow Analysis Tree, under Results, click Monitoring Points..
2. Select Point10.
3. Click XYPlot. A new entity xyplot2 appears in the Flow Analysis Tree under Results > XY Plots
4. The monitoring point Point10 is added to xyplot2.
Validation
The coefficient of pressure at diffuser wall is calculated as follows:
where,
P
Pressure at the diffuser walls (Pa): From monitoring points
ρ
Density (kg/m3): 1.15758
Pdiffuser
Pressure at the diffuser outlet (Pa): -2.6066
u
Inlet velocity m/s: 18.06
The monitoring points in the simulation are used to measure the pressure close to the diffuser wall:
Points
X
X/D
Static Pressure (Pa)
Pressure at Diffuser Outlet (Pa)
Coefficient of Pressure Cp
Point01
3.500
0.000
-170.453
-2.293
-0.891
Point02
3.575
0.738
-106.429
-2.293
-0.552
Point03
3.650
1.476
-72.543
-2.293
-0.372
Point04
3.725
2.215
-51.002
-2.293
-0.258
Point05
3.800
2.953
-36.504
-2.293
-0.181
Point06
3.875
3.691
-26.172
-2.293
-0.126
Point07
3.950
4.429
-18.522
-2.293
-0.086
Point08
4.025
5.167
-12.885
-2.293
-0.056
Point09
4.100
5.906
-8.056
-2.293
-0.031
Point10
4.218
7.067
-2.293
-2.293
0.000
where,
X/D= (X-3.5)/D and D (m) = 0.1016
The comparison of the coefficient of pressure from experiments and Creo Flow Analysis are as follows:
Reference: Azad, R. S., & Kassab, S. Z. (1989). Turbulent flow in a conical diffuser: Overview and implications. Physics of Fluids A: Fluid Dynamics, 1(3), 564–573.
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