FLUENT - How to model viscosity (or other material property) as a function of the fluid residence time
It is sometimes desireable to have a material property such as viscosity which varies as a known function of residence time of the fluid in the system. A user-defined scalar (UDS) is used to compute the fluid residence time. The UDS value is substituted for time in the material property equation. The steps are as follows: 1. Edit and compile the material property udf 2. Read case.... set # UDS > 0 3. At inlet, set UDS (value) = 0 4. Set diffusivity of UDS to a small value 5. Set source term of UDS to "rt_source" in the appropriate fluid zones 6. Hook the UDF for viscosity (or other property) in the material properties panel 7. Iterate. -------------- UDFs follow -------------------------------------- #include "udf.h" /* * UDF to compute fluid residence time */ DEFINE_SOURCE(rt_source,c,t,dS,eqn) { real source = C_R(c,t); dS[eqn] = 0.0; return source; } /* * UDF to calculate the material property value. The example shown here sets the * material property value equal to the residence time, please edit as appropriate. */ DEFINE_PROPERTY(mat_prop,c,t) { real res_time, mat_prop; Thread *st = THREAD_SUPER_THREAD(t); res_time = C_UDSI(c,st,0); mat_prop = res_time; return mat_prop; } |
||
|