Discussion Forum

Hello all,

I am a new COMSOL user trying to model a 2D compressible gas flow at low Reynolds numbers. I am only interested in and solving for fluid velocity (u in x-direction), thus the model is quite simple and consists only of an inlet, outlet and walls or symmetry boundaries.

The model itself produces reasonable values, but I am looking for pointers on doing two things:

(1) I would like to be able to find the boundary layer thickness above a surface in the model defined by 99% of the maximum velocity at that position. Is there a way to define stream(s) so that I can quickly evaluate the points (x,y) having 0.99*maximum(x-velocity)? I could easily convert this to boundary layer thickness knowing the surface height.

(2) I would like to perform a parametric sweep by varying the inlet velocity. I have defined a global parameter (u_inlet) and written the parameter name in place of numeric values in defining the inlet velocity and initial value for the laminar flow module. I have also added a parametric sweep step to the solver that varies this parameter in a range of values. However, I get an error that "Parameter names must not be empty" and that it "failed to evaluate the variable". Have I gone astray somewhere in properly initializing this parameter?

I realize these are probably rudimentary questions, but I've had little luck finding these things addressed explicitly in the help files thusfar.

Thanks!
--Dave