## Fluids

#### Modelling multiphase heat transfer coefficient in UDF with DEFINE_PROFILE

• senthilathiban
Subscriber
Hi, nI am doing a multiphase simulation ( Euler-Euler )with gas and solid. nI have two heat transfer coefficients. h(wall-gas) and h(wall-solid). nThe simplified equations arenh(gas-wall) = 1.54*Re_g*k_g/Dnandnh(solid-wall) = D/k_s + [2 * sqrt(k_s * rho_s * cp_s / pi)]^(-1)nFirst, I tried to code only the h(gas-wall) as follows.n#include udf.hnDEFINE_PROFILE(heat_test,t,i)n{n face_t f;nThread *ti = THREAD_SUB_THREAD(t,0);nreal D = 1;nreal beta = 90;nreal v_x=0., v_y=0., v_z=0.;nreal vel;nreal De = 0.5*D*(2*M_PI-beta+sin(beta*M_PI/180))/(M_PI-beta/2-sin((beta*M_PI/180)/2));nnbegin_f_loop(f,t)n{nv_x = F_U(f,ti);nv_y = F_V(f,ti);nv_z = F_W(f,ti);nvel = sqrt(v_x*v_x + v_y*v_y + v_z*v_z);nreal Re = vel;nF_PROFILE(f,t,i) = 1.54*Re/De;nnend_f_loop(f,t)nnnThe above code works when I use v_x = F_U(f,t) and produces a SIGSEGV error when I use F_U(f,ti).nIs this the correct way to code this type of UDF?.Looking forward to your response.Thanks,nSenthiln
• DrAmine
Ansys Employee
Because the wall has only one temperature and that is the mixture level.n
• senthilathiban
Subscriber
I am not using temperature field. I am using only velocity field.n
• DrAmine
Ansys Employee
What is the thread ti in your UDF? Where are you hooking the UDF?n
• senthilathiban
Subscriber
Thread ti is the phase thread of primary phase in the multiphase simulation. I am hooking the UDF in the boundary conditions for wall as convection heat transfer coefficient.n
• DrAmine
Ansys Employee
Okay that will explain the issue: There is no phase velocity associated with wall boundary. You can however access the near wall cell velocity values of each phase.n
• senthilathiban
Subscriber
• DrAmine
Ansys Employee
Yes because it is wrong: you are no doing any loops. Check the documentation to know how things are working.n
• senthilathiban
Subscriber
The loops are below. I didn't post the full code. The full code is lengthy. I kept three dots in the bottom..!!n
• DrAmine
Ansys Employee
I cannot forecast what you are telling with your 3 dots.n
• YasserSelima
Subscriber
If you are still facing the same error, trynbegin_f_loop(f,ti)n