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Numerical Results
We can use either FLUENT or CFD-Post as post-processing tool. CFD-Post is preferable as it is more user friendly and gives you more freedom. The first check, however, will be made in FLUENT
Check mass flow
It's always good to check the mass flow rate after CFD simulation. The solver tries to keep it satisfied, but sometimes a representative imbalance is obtain, showing that something has to be done in order to get more accurate results.
To do this, we will use FLUENT.
Highlight "Reports" in the left box. Then select "Fluxes" and click "Set Up...".
FIGURE 1
Note that "Mass flow rate" is already selected.
Here you can play around to see the mass balance through each boundaries. Since most of our boundaries are single circular element, it is expected that the imbalance at each boundary alone be zero. We will check the mass flow rate though two boundaries.
First, the external boundaries. In the "Flux Reports" window, locate and highlight "farfield1" and "farfield2" and hit "Compute". The mass flow rate though that boundary is now printed in the command window.
FIGURE 2
Note that 73.5kg/s get into out domain and virtually everything leaves. The imbalance is 7.4e-9kg/s which is negligible considering the total amount of flux in the system. Nice!
Now, let's check the imbalance inside the hub. For that we only have one boundary completely circling the zone, hub_inner (note that hub_outer is essentially the same boundary).
Proceed similarly as before and check the mass flow through the hub_inner boundary. You could also select hub_outer and the result would be almost identical.
FIGURE 3
Remember to deselect farfield1 and farfield2 before hitting compute! You should get an imbalance of 3.42e-10kg/s which is essentially zero. Cool!
Velocity Contours
To plot the velocity contours we will use CFD-Post. You can now close FLUENT.
In Workbench, under Project Schematic, double click Results. This will launch CFD-Post
FIGURE 4
Check mass flow
Velocity contours
(save image)
Blade velocity (TSR)?
Pressure contours
Torque
Vorticity?
When extracting the Torque, explain that the Moving Frame of Reference is used to calculate (FOR FEA) omega squared times the radius times the mas of each element to compute the force exerted by the fluid on the blades. (check Wind Blade 2 tutorial, under Physics Setup, second video, around 3:30. It is for FEA, we should get the analogy to fluid before).
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