value of Wmax

wilson · December 9, 2009, 17:30

I've been looking at Tutorial 9 on CFX, flow through a butterfly valve. I ran the computation first with Wmax=5m/s and then =20m/s and calculated the loss coefficient which came out to be equal for both values of Wmax. In the literature I've been given, it says not to increase Wmax by a factor of more than 5, why does the increase to Wmax have to be limited?

Thanks

Tristan · December 10, 2009, 15:24

Perhaps you can't obtain steady-state convergence at higher velocities?

Tristan

wilson · December 10, 2009, 16:38

This might sound ridiculous, but what does steady-state convergence mean?

Thanks

Tristan · December 10, 2009, 17:01

The code is able to find a converged solution to the steady state equations i.e. there's no time variation in the solution. As you increase the flow velocities, the code may not be able to find a steady state solution and you have to perform an unsteady analysis which takes a lot longer to run and would therefore not be desirable for a tutorial.

December 9, 2009, 17:30	value of Wmax	#1
wilson New Member Mike Join Date: Dec 2009 Posts: 14 Rep Power: 16	I've been looking at Tutorial 9 on CFX, flow through a butterfly valve. I ran the computation first with Wmax=5m/s and then =20m/s and calculated the loss coefficient which came out to be equal for both values of Wmax. In the literature I've been given, it says not to increase Wmax by a factor of more than 5, why does the increase to Wmax have to be limited? Thanks

December 10, 2009, 15:24		#2
Tristan Member Tristan Burton Join Date: Mar 2009 Posts: 43 Rep Power: 17	Perhaps you can't obtain steady-state convergence at higher velocities? Tristan

December 10, 2009, 16:38		#3
wilson New Member Mike Join Date: Dec 2009 Posts: 14 Rep Power: 16	This might sound ridiculous, but what does steady-state convergence mean? Thanks

December 10, 2009, 17:01		#4
Tristan Member Tristan Burton Join Date: Mar 2009 Posts: 43 Rep Power: 17	The code is able to find a converged solution to the steady state equations i.e. there's no time variation in the solution. As you increase the flow velocities, the code may not be able to find a steady state solution and you have to perform an unsteady analysis which takes a lot longer to run and would therefore not be desirable for a tutorial.