# Mrf-turbine blade with mrf

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 March 23, 2013, 21:40 Mrf-turbine blade with mrf #1 New Member   Sai Join Date: Feb 2013 Posts: 7 Rep Power: 4 I am a Master's students in solid mechanics, conducting FSI on turbine blade.I am new to FLUENT. I know the pressure at inlet (607428.1 pa) and pressure at outlet (249970.4 pa).The temperature at inlet is 1010K. 1)I used an arbitrary static pressure to initialise the solution.It was slightly lower that the total pressure. Is it ok? 2)I have used pressure inlet and outlet, periodic boundary zones, coupled the fluid and solid zones with a shadow wall to enable conjugate heat transfer, used ideal gas equations for air and got results for a stationary blade.I have also set proper interfaces between inlet passage and rotor, rotor and outlet passage. The blade is rotating at 8000rpm. Can such high velocities be simulated, assuming I gradually increase the speed? I am guessing that I should set the cellzone velocity in absolute +830rpm,wall shadow ( which has fluid as adjacent zone) as moving wall with a relative zero velocity and axis as rotation as +X. I guess I neednt care about the solid turbine zone at all in rotation. 3)Also, the flow suddenly accelerates to high velocities new outlet, I just need the pressure distribution and velocities near the turbine wall.So doesnt really matter.But if I am to avoid it, how ? Kindly let me know if I am correct, attached are few pictures. Thanks a ton in advance Last edited by battersai; March 23, 2013 at 21:41. Reason: Image wasnt posted

 March 25, 2013, 06:08 Reply to Sai #2 New Member   Gowrav Shenoy Join Date: Feb 2013 Posts: 20 Rep Power: 4 Hi, i will try to answer few.. Mayn't correct too. asked 8000 rpm high or not.. Numerical Values doesn't make diff in simltn.. It may be high when considern yur design. Since yu ve mentioned FSI- i hope yur talking about 1 way FSI, you are taking pressure and temperature on blades for the evaluation of stresses along with centrifugal. If thats the case i feel solid body is not required in fluent.. (Just reduce no of elements). Also coupled wall BC is also not required. Yu can directly take temp/pressure on wall(blade) - to import into structural one. Since its transient hope yur using sliding mesh, if steady state MRF,MPM will do.. Along with cell zones.. Motion to the mesh/reference need to be mentioned. There s compressor example given in tutorial much relevant with yur case .. Have a look Regards Gowrav

 March 25, 2013, 08:29 #3 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,909 Blog Entries: 6 Rep Power: 38 Use 0 static pressure at oulet and see what happens? what is the operating pressure? I know there is option of average static pressure in newer version, use that option.

 March 25, 2013, 14:28 #4 Senior Member   Join Date: Apr 2009 Posts: 511 Rep Power: 12 Need to know more about the FSI before suggestion a solution approach. 1-way? 2-way using System Coupling? Steady or transient? Thermal coupling or force/displacement coupling? Are you planning on a sliding mesh approach in Fluent (do you care about transient interactions between the blade and stators) or is a mixing plane or frozen rotor approach suitable.

March 25, 2013, 17:37
#5
New Member

Sai
Join Date: Feb 2013
Posts: 7
Rep Power: 4
Quote:
 Originally Posted by Gowrav Hi, i will try to answer few.. Mayn't correct too. asked 8000 rpm high or not.. Numerical Values doesn't make diff in simltn.. It may be high when considern yur design. Since yu ve mentioned FSI- i hope yur talking about 1 way FSI, you are taking pressure and temperature on blades for the evaluation of stresses along with centrifugal. If thats the case i feel solid body is not required in fluent.. (Just reduce no of elements). Also coupled wall BC is also not required. Yu can directly take temp/pressure on wall(blade) - to import into structural one. Since its transient hope yur using sliding mesh, if steady state MRF,MPM will do.. Along with cell zones.. Motion to the mesh/reference need to be mentioned. There s compressor example given in tutorial much relevant with yur case .. Have a look Regards Gowrav
8000rpm is the design speed of the JT8D jet engine, I took the geometry of the blade from JT8D, so took their operating conditions too.
The solid body is required since ANSYS does not allow surface temperature import, only volume temperature import is allowed, so am forced to simulate conjugate heat transfer. Yes, it is 1 way FSI
Its a steady state simulation, not taking transience into account.
I am just concerned about the rotation direction of the fluid. If +x is the axis, is -837 rpm the speed of moving fluid cell zone?

March 25, 2013, 17:38
#6
New Member

Sai
Join Date: Feb 2013
Posts: 7
Rep Power: 4
Quote:
 Originally Posted by Far Use 0 static pressure at oulet and see what happens? what is the operating pressure? I know there is option of average static pressure in newer version, use that option.
Am using 0 operating pressure ( as in the tutorial) so I assume I should try 101325pa at the outlet?

March 25, 2013, 17:41
#7
New Member

Sai
Join Date: Feb 2013
Posts: 7
Rep Power: 4
Quote:
 Originally Posted by stumpy Need to know more about the FSI before suggestion a solution approach. 1-way? 2-way using System Coupling? Steady or transient? Thermal coupling or force/displacement coupling? Are you planning on a sliding mesh approach in Fluent (do you care about transient interactions between the blade and stators) or is a mixing plane or frozen rotor approach suitable.
Its a steady state, one way FSI, just need the temperature and pressure data for structural simulations. I am not worried about the stator-rotor interactions. I have aligned the inlet to give the flow a tangential velocity to avoid the presence of a stator. hope it is ok.

I am using force and thermal coupling. I am not using a sliding mesh, just MRF. If mixing planes are the interfaces which are created between stator and rotor, yes, I have created them as said in the tutorial.

 March 26, 2013, 02:10 #8 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,909 Blog Entries: 6 Rep Power: 38 Use zero pressure at outlet and start with lower rpm. The procedure would be : 1. use 0 static pressure at outlet and 2000 RPM 2. Iterate few hundred iterations and increase RPM = 4000 3. Repeat step 4 and increase RPM to 6000 and finally 8000 4. Calculate outlet total pressure if it is lower then increase outlet static pressure. PS: Use average static pressure if outlet boundary is placed less than 1.5 C downstream

March 26, 2013, 17:52
#9
New Member

Sai
Join Date: Feb 2013
Posts: 7
Rep Power: 4
Quote:
 Originally Posted by Far Use zero pressure at outlet and start with lower rpm. The procedure would be : 1. use 0 static pressure at outlet and 2000 RPM 2. Iterate few hundred iterations and increase RPM = 4000 3. Repeat step 4 and increase RPM to 6000 and finally 8000 4. Calculate outlet total pressure if it is lower then increase outlet static pressure. PS: Use average static pressure if outlet boundary is placed less than 1.5 C downstream
Thanks far.
I completed that part already. Could you please tell me which is the sign of rotation I should give( positive or negative). The axis is +X and blade is rotating in the anti-clockwise direction in front view.
Also , in fluent tutorial for fan, the top wall has been specified as non-moving wall, do you know why ?

 Tags conjugate heat transfer, mrfzones, rotor blade, turbine

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