Calculate net species/ UDS flux
I am new to Fluent. I am using the software to model electrochemical analyses with advective effects. I have found in Fluent the capability to solve for the net flux of energy through a surface which has a specified temperature. Is there an easily available analogous capability for calculating the net flux of an electroactive species to a solid surface? Or the surface integral of normal gradient of the species concentration at a surface? Thanks!

Re: Calculate net species/ UDS flux
Figured it out  a UDF to do this is based on Fluent 6.1 UDF Guide section 5.2.2 Connectivity Variables. Here's the UDF for UDS0 : note that because Execute_at_end does not have threads available to be passed, the zone ID and index must be hard coded. Also, prior to linking to a case file, type "solve/set/expert" and then answer "yes" to the question "keep temporary solver memory from being freed? Finally, use as a compliled not interpreted UDF.
 #include "udf.h" #include "sg.h" DEFINE_EXECUTE_AT_END(uds_flux) { Domain *dom= Get_Domain(1); int ID=5; int index=0; Thread *f_thread = Lookup_Thread(dom,ID); Thread *tc0; face_t f; cell_t c0; real grad[ND_ND]; real A[ND_ND]; real es[ND_ND]; real dr0[ND_ND]; real A_by_es; real ds; real flux; real scalar_c; real scalar_f; real grad_p; real grad_x; real D;/* scalar diffusion coefficient*/ real rho;/* mixture density*/ flux = 0.0; begin_f_loop(f, f_thread); { c0 = F_C0(f,f_thread); tc0 = THREAD_T0(f_thread); BOUNDARY_FACE_GEOMETRY(f,f_thread,A,ds,es,A_by_es, dr0) grad[0]=C_UDSI_G(c0,tc0,index)[0]; grad[1]=C_UDSI_G(c0,tc0,index)[1]; scalar_c=C_UDSI(c0,tc0,index); scalar_f=F_UDSI(f,f_thread,index); rho = C_R(c0,tc0); D=C_UDSI_DIFF(c0,tc0,index)/rho; /* for my applications expect D to be constant therefore OK, also, my D is FLUENTs gamma/rho*/ grad_p=(scalar_fscalar_c)/ds*A_by_es; grad_x=NV_DOT(grad,A)NV_DOT(grad,es)*A_by_es; flux+=D*(grad_p+grad_x); } end_f_loop(f, f_thread); flux=flux*2.*M_PI; /* for 2D axisymetric calculation */ Message("Surface integral of boundary flux of normal gradient of scalar: %g\n", flux); 
Re: Calculate net species/ UDS flux
Slight correction to the above  for general 2 or 3  D problem replace lines such as "grad[0]=C_UDSI_G(c0,tc0,index)[0];" with ND_SET commands

Re: VOF
How can I calculate the Flux of Vof species at the cell face. Please let me know

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