NUMERICAL INSTABILITY OVER THE SWIRLING VANES

February 8, 2005, 14:34

Hi!

Has anyone observed the numerical instability over the swirling vanes. What we have is the flow over a set of vanes. We have pressure inlets and one pressure outlet. What we are observing is the mass flow rate through the pressure outlet is oscillating in a sinusoidal fashion.

Has anyone come across this kind of situation and has any comments/suggestions. We have tried with lowering the under relaxation factors. Even to a small number like 0.001, the mass flow rate is still sinusoidal.

February 8, 2005, 16:48

Are you doing a transient or steady state calculation. By that I mean, are you solving

dq/dt = RHS

or

RHS = 0?

Asked another way: are you sure that your problem doesn't actually have a periodic (shedding) solution?

February 9, 2005, 09:12

I am using RHS=0

It is solved in steady state

February 8, 2005, 14:34	NUMERICAL INSTABILITY OVER THE SWIRLING VANES	#1
Dan Guest Posts: n/a	Hi! Has anyone observed the numerical instability over the swirling vanes. What we have is the flow over a set of vanes. We have pressure inlets and one pressure outlet. What we are observing is the mass flow rate through the pressure outlet is oscillating in a sinusoidal fashion. Has anyone come across this kind of situation and has any comments/suggestions. We have tried with lowering the under relaxation factors. Even to a small number like 0.001, the mass flow rate is still sinusoidal.

February 8, 2005, 16:48	Re: NUMERICAL INSTABILITY OVER THE SWIRLING VANES	#2
Jim_Park Guest Posts: n/a	Are you doing a transient or steady state calculation. By that I mean, are you solving dq/dt = RHS or RHS = 0? Asked another way: are you sure that your problem doesn't actually have a periodic (shedding) solution?

February 9, 2005, 09:12	Re: NUMERICAL INSTABILITY OVER THE SWIRLING VANES	#3
Dan Guest Posts: n/a	I am using RHS=0 It is solved in steady state

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