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-   -   wind turbines (http://www.cfd-online.com/Forums/fluent/37276-wind-turbines.html)

sharuk July 14, 2005 17:01

wind turbines
 
i'm running wind turbines rotor simulations in FLUENT, i meshed one blade with periodic boundary conditions, inlet, outflow and on the tope i've given wall condition, my solution is diverging, i've used coupled solver and K-epsilon turbulence model, can any one tell me which solver i've to use and which turbulence model i've to use, my rotor dia is 2 mts thanks in advance sharuk

antonio July 23, 2005 06:50

Re: wind turbines
 
Hi,i'm modelling a wind turbine too,but there are a lot of particular you should not neglect.. as first,i don't think that wall boundary condition should be the best choice, because they reflect pressure waves so it is not the thrut. if you are running a steady simulation,rotational periodic are well posed and it gives you quite good results,but if you want to study unsteady phenomenas,as my case,with sliding mesh,i tried to mesh just a portion of the domain but it doesn't work well,so you have to mesh all the rotor(360 degrees). because of the mach number is quite low (i think it should not be bigger than 0.15 at least),you should use the segregated solver with k-e model of turbulence.. please let me know what are your results and tell me some yours suggestions..bye Antonio

sharuk July 23, 2005 11:35

Re: wind turbines
 
yeah, i guess the wall conditions r not appropriate for me, but prior to that i need to consider many more factors, i've modelled only one blade, but tell me about the rotating reference, if suppose my rotor is moving in anti-clock wise direction, then for my moving reference frame which direction of rotation i've to consider, do i keep the blade stationary or let it rotate at relative velocity to the reference frame in the same/opposite direction(sugest me this, i'll b very thankful if u answer me. regarding ur problem,do u need to take the mach no till 0.15 i guess it should b in the range of 0.03 to 0.07(i'm not sure), i'm using S-A turbulence model, since it is suggested for aerodynamic problems(Fluent user manual),the moment i'm getting for 2m dia rotor at 10m/s is around 130 N-m. let me know some improvements sharuk

antonio July 25, 2005 11:08

Re: wind turbines
 
you have to create two different volumes one rotating with respect to the other and then put rotating reference frame condition on the internal volume(solidal with the blade wall).put z axis rotation and put just the z component of the angular velocity vector in the rotational velocity specification. should you tell me what are the condition of the wind at the inlet? turbulence intensity,lenght scale,turb viscosity ratio..please..bye Antonio

sharuk July 26, 2005 03:38

Re: wind turbines
 
when u know the wind velocity u can give velocity inlet condition, incase if u dont 've idea about inlet velocity then give pressure inlet(this is used in case of propellers and fans rotating in still ambient).u can know the inlet pressure conditions from actuator disk theory. In my case, i created two volumes, later i subtracted the blade from the large volume and had jst the walls of the blade, since there is only one volume, i've given rotating reference to that and i kept blade walls as stationary, am i approaching in wrong way. regards sharuk

antonio July 26, 2005 07:45

Re: wind turbines
 
you must create two volumes and two fluid zones,so you have to put one in motion with resect to the other.you cannot tell to just a volume to be in motion,in motion with respect to what?do you understand me? i ask you if you know common values of the intensity and the lenght scale of the turbulence ay the inlet..Antonio

sharuk July 26, 2005 13:46

Re: wind turbines
 
turbulence intensity I=SQRT(2/3k)/Vref. k-turbulence kinectic energy, Vref-reference velocity apologise if u knew this. I dont know about length scale. Thanks for ur suggetion sharuk

abolfazl April 20, 2009 07:32

wind turbine MRF
 
hi to all
I have a problem to implement the MRF, exaclty to bulid two volumes in Gambit.
i dont know the size of the volume(which is moved in MRF) around the wind turbine blade?
furthermore, in a computational domain, where is the volume ( moving reference frame zone) must be placed?is it near to the blade or far from the blade?
Thanks for replay.

yochule April 22, 2009 09:44

rotating speed?
 
1 Attachment(s)
antonio, sharuk, hi to all. i was reading your post and it look interesting for me. i am developing a fan. but i have a question. how can I define the rotating velocity of the rotors and the mass flow? I am using MRF and set the flow rate as boundary condition, but I donít know if this set is corresponding with a RPM that I set. may I set the RPM and goal the mass flow rate? how? I asked you because I suppose you are doing something similar. you have a velocity inlet and you want to know the RPM of the rotor, no? thanks you chule


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