Define_Uds_Flux and mass flow rate
 

I am confused about the way in which the DEFINE_UDS_FLUX should be written in UDF. I would like to change a mass flow rate from window: Define-User Defined-Scalars in option Flux Function. I have read Fluent help (10-2 and 4-87) but still I am not sure if the NV_DOT(psi_vec, A) is a full term of the mass flow rate which will be calculate or it is only the source term of the scalar transport equation?

Re: Define_Uds_Flux and mass flow rate
 

hi this is used to customurise your flux function. yes ofcourse NV_DOT(psi_vec, A) is theoritically correct and returns mass flow rate. Did u try this example. I think you should get errror with overloading of arguments in thread ,i guess u r using fluent 6.1. Any way if it works out wrire me bye kethireddy

Re: Define_Uds_Flux and mass flow rate
 

Hello Kethireddy,

Yes, as you suspected I have used the Fluent 6.1.

Unfortunately, I have received an error when I tried to use the example of the procedure from Fluent instruction.

The error suggested that something has been made incorrect, but the message in the window wasn't precise.

I have made some changes in that procedure in spite of them, the procedure did not allow me to run the calculation.

The main goal of my work is modification the term of mass flow rate for the mixture. I have use the Mixture model.

I would like to be able to multiple the original term of the mass flow rate for the mixture model by some constant correction factor.

So, if you have more experience in writing such a procedure, I will be very grateful for any kind of help.

Paulina

Re: Define_Uds_Flux and mass flow rate
 

hi how do you want to custumurised the flux term. Is it rho*v*constant or what. let me knoe clearly bye kamesh

Re: Define_Uds_Flux and mass flow rate
 

Hello Kamesh,

Thank you for your interesting.

I am not sure in which way I should define the flux term. First, I have tried to add the original procedure from Fluent, but without any success. I have got an error message like: "Error: fluent 6.1.22 received a fatal signal (SEGMENTATION VIOLATION). Error Object: #f".

Them I have tried just to define the F_FLUX(f,t)=F_R(f,t)*F_W(F,t)*F_AREA(A,f,t), where F_W(f,t) is the velocity in Z-direction. In addition, in that case I cannot run the calculation. I suspect that the original code of the Fluent knows the term of the F_FLUX(f,t) for the mixture, which is the mass flow rate in the window Define- User-Define-Scalars-Flux Function.

I just want to multiple that term for some correction factor. Do you know how it could be done?

Re: Define_Uds_Flux and mass flow rate
 

hi fluent solver will have the value of F_FLUX(f,t). I think u have not understood how udf flux function works. In general uds eqation is solved as in equation 10.2 ( iguess). the complete advective term is present there.If u want fluent have some other different term like only (V instead of V*rho) we divide by rho so that fluent solves the equation with custumorised function. Any way i am very sorry that i coulnot understand your problem exactly. u be very specific and simple.I will try to solve this.. bye kamesh

Re: Define_Uds_Flux and mass flow rate
 

Hi Kamesh,

Thanks for your commentary. Paulina

Re: Define_Uds_Flux and mass flow rate
 

what!!

Re: Define_Uds_Flux and mass flow rate
 

Hi again,

What does it mean: "what"!!I just want to be polite. Paulina

Re: Define_Uds_Flux and mass flow rate
 

hi thanks i will continue bye kamesh

Re: Define_Uds_Flux and mass flow rate
 

Hi,

Probably now I understood what you have told me before.

I think that I have made some progress with the procedure. Now I am able to start calculation using the mass flow rate from my User Define Functions. But still I am not sure how should I declare the vector of the velocity for the mixture. When I have defined inside the procedure a constant value of the mixture velocity, everything is all right. However, when I have tried to do it by using the definition - it means: F_U(f,t), F_V(f,t) and F_W(f,t) is does not work.

If you have any suggestions, I will be very grateful.

Paulina

Re: Define_Uds_Flux and mass flow rate
 

Hi PAULINA.. try using F_V(t),it will work out however take care at boundaries otherwise u will end up up with segmentation error. kethireddy

Re: Define_Uds_Flux and mass flow rate
 

Hi Kethireddy,

Thank you for your answer. I will try to do it in that way and then I will say if it works.

Regards Paulina

Re: Define_Uds_Flux and mass flow rate
 

Do you thiunk this is used to customurise your flux function. yes ofcourse NV_DOT(psi_vec, A) is theoritically correct and returns mass flow rate. Did u try this example. I think you should get errror with overloading of arguments in thread ,i guess u r using fluent 6.1. Any way if it works out wrire me bye kethireddy. If you are check http://www.handymate.co.uk

Re: Define_Uds_Flux and mass flow rate
 

hi Haulio i guess overloading is not NV_DOT(psi_vec, A),but it is with the thread(t,f).I guess thread(t)is right one.I think it works out. regards kethireddy