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Flow in a channel with changing cross section
Posted Jun 20, 2012, 4:53 a.m. EDT Computational Fluid Dynamics (CFD), Studies & Solvers Version 4.2a 1 Reply
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Hi,
I want to simulate a simple flow through a channel with changing cross section. If I have just a rectangle there is no problem and I get the expected parabola velocity field. Then I want to change the cross section somewhere so that the velocity raises. If I change it only a little bit, there is no problem. But if I change it about 50% or I get always errors like this:
Failed to find a Solution for all parameters
even when using the minimum parameter step
So what is the problem here? Do I have to change some parameters in the solver settings that Comsol can solve this one? Because this problem shouldn't be that complicated to solve.
I want to simulate a simple flow through a channel with changing cross section. If I have just a rectangle there is no problem and I get the expected parabola velocity field. Then I want to change the cross section somewhere so that the velocity raises. If I change it only a little bit, there is no problem. But if I change it about 50% or I get always errors like this:
Failed to find a Solution for all parameters
even when using the minimum parameter step
So what is the problem here? Do I have to change some parameters in the solver settings that Comsol can solve this one? Because this problem shouldn't be that complicated to solve.
1 Reply Last Post Jun 20, 2012, 3:45 p.m. EDT
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Posted:
1 decade ago
Hi
how do your define your initial conditions ? all "0" ?
If so perhaps you can add some initial velocity and pressure drop
some models propose too many bifurcations, and COMSOl has no way to decide clearly left or right, but with some initial effects, the biffurcation decision is already done, and the convergence is ieasier (but not alsways, if its a time series, transient effects might occure and give solver issues
--
Good luck
Ivar
how do your define your initial conditions ? all "0" ?
If so perhaps you can add some initial velocity and pressure drop
some models propose too many bifurcations, and COMSOl has no way to decide clearly left or right, but with some initial effects, the biffurcation decision is already done, and the convergence is ieasier (but not alsways, if its a time series, transient effects might occure and give solver issues
--
Good luck
Ivar