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SA October 3, 2008 16:02

Turbomachinery oulet
 
Dear CFX users,

I have long been the user of Fluent and I like it very much for its user frendlyness, easiness and accuracy.

For some time I have started to use CFX in parallel for Turbomachinery applications.

Now my questions is that

how to set the radial equilibrium for compressor rotor at outlet boundary condition. (In fluent it is very easy by just clicking on respective check box).

Any idea, I would be grateful.

Thanks in advance

SA

CycLone October 3, 2008 17:21

Re: Turbomachinery oulet
 
Hi SA,

The default Mass Flow and Average Pressure boundary conditions give a radial equilibrium condition at the outlet.

When you use the Mass Flow (with default "scale mass flows" option) and Average Pressure options in CFX, the solver allows the mass flow rate to vary over the boundary to achieve a natural static pressure profile (i.e. it does not cause unphysical conditions upstream).

Radial equilibrium is only achieved this if your outlet is a long way downstream. A radial equilibrium boundary condition is really an attempt to explicitly achieve the profile that the CFX conditions return implicitly.

Use the above conditions and you should get good results.

-CycLone

SA October 5, 2008 05:47

Re: Turbomachinery oulet
 
Thanks Cyclone for your very informative reply.

I have something more to ask regarding CFX 11.0:

1. How to make the fuction of pressure ratio (i.e new variable by diving the outlet total pessuere with inlet total pressre ).

2.plot the xy plot of any variable on outlet plane. (i.e radial profile which is circumentially averaged at each radial location).

3. how to make the nealy axial planes normal to blade chord.

Best Regards SA


CycLone October 6, 2008 11:39

Re: Turbomachinery oulet
 
Hi SA,

Q1. How to make the fuction of pressure ratio (i.e new variable by diving the outlet total pessuere with inlet total pressre ). A1: Create a CEL function Pout = areaAve(Pressure)@inlet/PR where PR = Pout/Pin and set your outlet boundary pressure to Pout.

Q2.plot the xy plot of any variable on outlet plane. (i.e radial profile which is circumentially averaged at each radial location). A2: Use the Turbo-Post tools in CFX-Post. There is a function that does exactly this.

Q3. how to make the nealy axial planes normal to blade chord. A3: Use the Turbo-Post tools in CFX-Post. Turbo-post parametrizes the geometry to allow you to create surfaces aligned with the blade leading and trailing edges.

I highly recommend reviewing the turbo-post features in the documentation.

Regards, Robin


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