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How Ansys Flunet Calculte the Wall Heat Flux? |
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Hi all, I am currently working on a simulatoin case of "crossflow over a tube", the shematic geometry and boundary conditions are shown in following figure
https://www.dropbox.com/scl/fi/c0082...lcznbc3jp&dl=0 - Introduction - I've develpoed a mathematical model ( in-house code ) to simulate the heat transfer of the tube solid region including external flow ( see above figure ) and aim to couple it with Ansys Fluent. The in-house code require the outer wall heat flux from Ansys Fluent as the boundary conditions. - How I calculate the outer wall heat flux using UDF - The whole process is control by DEFINE_ON_DEMAND ( a macro in UDF ) which is a general-purpose macro in Ansys Fluent. I calculate the outer wall heat flux as below: https://www.dropbox.com/scl/fi/mhli8...71jx2s6zw&dl=0 Using right hand side of Eq. (1) in above figure, the snippet of code see Code:
// Phase domain Domain *domain = Get_Domain(1) ; // The ID of the BC created in ANSYS Fluent const int wall_ID = 21 ; // Get the thread from the domain, the thread is partitioned Thread *f_thread = Lookup_Thread( domain, wall_ID ) ; // Create face ID face_t f_ID ; /* Adjacent cell information */ // adjacent cell index of the boundary face cell_t c0 ; // thread index of adjacent cell Thread *t0 ; // xf represents facets location array and xc is cell center locatoin array real xf[ND_ND] ; real xc[ND_ND] ; begin_f_loop( f_ID, f_thread ) { /* Get the cell center F_CENTROID( xf, f_ID, f_thread ) ; /* Get the cell id of the cell adjacent to the face*/ c0 = F_C0( f_ID, f_thread ) ; /* Get the Thread id of the cells adjacent to the face*/ t0 = F_C0_THREAD( f_ID, f_thread ) ; C_CENTROID( xc, c0, t0 ) ; /* dx is ignored because the cell center and face center are align in radial direction double dy = abs(xc[1] - xf[1]) ; double dz = abs(xc[2] - xf[2]) ; double dr = sqrt(dy*dy+dz*dz) ; // Calculate the surface heat flux, k_f * (T_cell - T_face ) / dr q_array[ f_ID ] = C_K_L(c0, t0) * (C_T(c0, t0) - F_T(f_ID, f_thread)) / dr ; // C_K_L(c0, t0) is the UDF macro return fluid thermal conductivity } end_f_loop( f_ID, f_thread ) The difference between the outer wall heat flux calcuted by UDF and from Ansys ( using built-in function on GUI, File->export->solution data->Total Surface Heat Flux ) are shown below https://www.dropbox.com/scl/fi/yva9r...xpomlujum&dl=0 The outer wall heat flux is represented in 2D and θ=180° is bottom region of the tube. Refer to the figure, most of the error occurs at θ=120°~240° and the maximum error of 5.33%. Does anyone have any experience with this? I would appreciate your advice and suggestions. ![]() ![]() Last edited by eddie4160; October 25, 2023 at 13:42. |
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fluent, heat flux udf |
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