# Fluent UDS boundary conditions in INTERFACE

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 November 29, 2023, 10:56 Fluent UDS boundary conditions in INTERFACE #1 New Member   MrXuxu Join Date: Sep 2019 Posts: 19 Rep Power: 6 Hello everyone, I'm using the UDS for my equation, which is make up of three terms： unsteady term and diffusity term on LHS while the explicit term on RHS. And its TEX can be written as : $$\frac{1}{c^2}\frac{\partial^2 p}{\partial t^2} - \nabla^2 p =0$$ In two domains, there is one pair of interface connected with each other. Actually, the two domain is one-domain, which is separeted by ME with the aim to check the correct behaviour of UDS boundary condition. The model is shown as below.[geoPic] Now, if I want to make the two interface as "virtual BC", which means that they doesn't physically exist. As the result, the quantity A(the parameter that solved in my UDS equation) can be transfered like the situation that interface does not exist. geoPic.jpg Here are some problems needed to be clear. 1) In order to obtain it, what kind of BC should be applied? In my theory, the benefit of FVM in Fluid solving, the flux should be "equal". SO, I think, it can be done if the flux of the two interfaces are the same. As the result, the BC of "specified Flux" should be used instead of specificed value. flux_CFD.jpg 2)By refering to Help.Doc of Fluent, in the chapter 3.2.5 Connectivity Macros, eqaution3.1 and equation 3.3 are displayed for the calculation of "scalar on face" and "diffusive flux across a face". In my code using DEFINE_PROFILE with specified flux, real A[ND_ND], dG[ND_ND], dr0[ND_ND],dr1[ND_ND], es[ND_ND], dr, A_by_es; begin_f_loop(){ INTERIOR_FACE_GEOMETRY(f, thread, A, dr, es, A_by_es, dr0, dr1); F_PROFILE(f, thread, nv) = ( C_UDSI(c1, t1, 0) - C_UDSI(c0, t0, 0) ) * (gamma * A_by_es / dr )+ beta0; } But it is wrong and result shows the evident reflection wave near the inteface. If anyone know the relative information of interface boundar condition on UDS, plz give me a hand and I'll be very grateful for you help. Best wishes Memorise

 Tags fluent, interface, uds