According to the Fluent 6.3 UDF manual, section 3.2.3 "Cell Macros", quantities are defined as:

C_MU_L(c,t)->laminar viscosity

C_MU_T(c,t)->turbulent viscosity

C_MU_EFF(c,t)->effective viscosity

In my case (which involves vortices shedding, computed using k-w SST), I store 10 udms which use C_MU_L(c,t) and C_MU_T(c,t) during post-processing. From the definitions above, I inferred that for all (c,t), C_MU_L(c,t) would have been equal to 1.78e-5, for air is the fluid modeled in my case. To my surprise, a small test computing C_UDMI(c,t,13)=C_MU_L(c,t) led to an inhomogeneous distribution of C_MU_L(c,t), which average value is 0.006 in one of my sampling plane, for example. The topology of the distribution of C_MU_L(c,t) is very similar to the topology of k, which is strange given that is should be constant.

This could be a minor problem in my case, as I could replace C_MU_L(c,t) by 1.78e-5 in my UDF. However, I have no way to know beforehand the value of C_MU_T(c,t), and I fear it is not giving me what I expect it to, just like C_MU_L(c,t).

If anybody knows why I am not retreiving the values I am expecting and how to get them, I would really appreciate the help.

It is fixed, I messed with my various .C files and was not looking at the right UDM.

[hitzhwan]

Originally Posted by John Deas
;156717

According to the Fluent 6.3 UDF manual, section 3.2.3 "Cell Macros", quantities are defined as:

C_MU_L(c,t)->laminar viscosity

C_MU_T(c,t)->turbulent viscosity

C_MU_EFF(c,t)->effective viscosity

In my case (which involves vortices shedding, computed using k-w SST), I store 10 udms which use C_MU_L(c,t) and C_MU_T(c,t) during post-processing. From the definitions above, I inferred that for all (c,t), C_MU_L(c,t) would have been equal to 1.78e-5, for air is the fluid modeled in my case. To my surprise, a small test computing C_UDMI(c,t,13)=C_MU_L(c,t) led to an inhomogeneous distribution of C_MU_L(c,t), which average value is 0.006 in one of my sampling plane, for example. The topology of the distribution of C_MU_L(c,t) is very similar to the topology of k, which is strange given that is should be constant.

This could be a minor problem in my case, as I could replace C_MU_L(c,t) by 1.78e-5 in my UDF. However, I have no way to know beforehand the value of C_MU_T(c,t), and I fear it is not giving me what I expect it to, just like C_MU_L(c,t).

If anybody knows why I am not retreiving the values I am expecting and how to get them, I would really appreciate the help.

what is the difference for the below three variable, which should be choose when I simulate ? is the dynamic viscosity or kinematic viscosity ?

C_MU_L(c,t)->laminar viscosity

C_MU_T(c,t)->turbulent viscosity

C_MU_EFF(c,t)->effective viscosity