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-   -   NASA Rotor 37 Boundary Condition Problems (http://www.cfd-online.com/Forums/fluent/50747-nasa-rotor-37-boundary-condition-problems.html)

Dom March 3, 2009 07:41

NASA Rotor 37 Boundary Condition Problems
 
Hi everone,

I'm having some troubles with getting a model of NASA Rotor 37 to run in Fluent and output some realistic results.

I think the problem lies with the boundary conditions I am specifying. I have a pressure inlet using a pressure profile (average gauge pressure is about 540Pa), and temperature profile (~288K). I have a pressure outlet with a gauge static back pressure (17975Pa) with radial equilibrium and backflow temp 288.15K. I have my fluid rotating (1800 rad/s), my case is static (relative to adjacent cell, so should be moving with the fluid), I have defined the hub and blade as having zero rotation and have rotationally periodic boundary conditions also. I'm not sure that the inlet and outlet are rotating with the flow correctly, however, so specifying the direction at the inlet and outlet is I think what is causing the solution to be unrealistic. I have to start solving with low rpm and back pressure, and gradually increase these to the final values, otherwise Fluent just diverges.

If you could possibly give me some advice on my boundary conditions, or another method of solving that you know to work, I'd be very grateful indeed.

I have tried my current setup with pressure and desity based solvers and various solution methods (as many combinations as I can think of!), and am now at a loss as to what is wrong, so any help at all will be happily received!

Thanks very much,

Dom


mm.abdollahzadeh March 27, 2012 07:00

Quote:

Originally Posted by Dom
;157081
Hi everone,

I'm having some troubles with getting a model of NASA Rotor 37 to run in Fluent and output some realistic results.

I think the problem lies with the boundary conditions I am specifying. I have a pressure inlet using a pressure profile (average gauge pressure is about 540Pa), and temperature profile (~288K). I have a pressure outlet with a gauge static back pressure (17975Pa) with radial equilibrium and backflow temp 288.15K. I have my fluid rotating (1800 rad/s), my case is static (relative to adjacent cell, so should be moving with the fluid), I have defined the hub and blade as having zero rotation and have rotationally periodic boundary conditions also. I'm not sure that the inlet and outlet are rotating with the flow correctly, however, so specifying the direction at the inlet and outlet is I think what is causing the solution to be unrealistic. I have to start solving with low rpm and back pressure, and gradually increase these to the final values, otherwise Fluent just diverges.

If you could possibly give me some advice on my boundary conditions, or another method of solving that you know to work, I'd be very grateful indeed.

I have tried my current setup with pressure and desity based solvers and various solution methods (as many combinations as I can think of!), and am now at a loss as to what is wrong, so any help at all will be happily received!

Thanks very much,

Dom

Dear Dom

I am trying to solve the same problem. have you been able to solve your problem? according to what you have said... i think the value of pressure and temperature that you are using may be wrong. i have checked the values in NASA report but they were quite diffrent. secondly if you are using a profile and if you are using the same values from that report your inlet and outlet should be ( i think) at the same place the staions that they used for measureing.
I am using the pressure inlet and pressure outlet boundary with the extended geomtry so i think it is correct to use constant boundary condition. however i was not able to validate the case yet ( i can not obtain the same pressure ratio for the design mass flow rate near peak efficiny). i have tried using targeting mass flow rate at outlet and even replacing the inlet boundary with mass flow inlet.

Regards


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