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Search took 0.00 seconds. Search: Posts Made By: ghorrocks
Forum: CFX April 28, 2013, 21:56
Replies: 36
Views: 7,604
Posted By ghorrocks
The reference pressure changes the magnitude of...

The reference pressure changes the magnitude of the pressure difference in the momentum equation. For instance, if the pressure range in the air is 1Pa, then with a reference pressure of 0 bar it is...
Forum: CFX April 28, 2013, 18:42
Replies: 36
Views: 7,604
Posted By ghorrocks
With such a large range in pressures in the water...

With such a large range in pressures in the water - but a small range of pressure in air - this is always going to be a tricky model for the numerics. So double precision is recommended. But if you...
Forum: CFX April 28, 2013, 06:45
Replies: 36
Views: 7,604
Posted By ghorrocks
Glad to help. OK, it you are confident the...

Glad to help.

OK, it you are confident the air does not change much from atmospheric pressure then incompressible air is good and will considerably simplify the simulation.

Sorry - another...
Forum: CFX April 27, 2013, 07:56
Replies: 36
Views: 7,604
Posted By ghorrocks
I can make a key suggestions from your CCL: You...

I can make a key suggestions from your CCL: You are using incompressible air at room density, yet the inlet pressure is MPa. This does not sound very appropriate to me. Sounds like you need a...
Forum: CFX April 27, 2013, 07:16
Replies: 36
Views: 7,604
Posted By ghorrocks
The glitches are the weird spots on post #19. ...

The glitches are the weird spots on post #19.

It might help if you drew a picture of what you expect the flow to do. The images you have posted do not clearly show what is happening.
Forum: CFX April 27, 2013, 07:03
Replies: 36
Views: 7,604
Posted By ghorrocks
You are modelling a spray atomiser are you not?...

You are modelling a spray atomiser are you not? Then isn't surface tension critical to this process? If you do not understand a flow then you have no hope of modelling it.

I suggest you do some...
Forum: CFX April 21, 2013, 07:37
Replies: 36
Views: 7,604
Posted By ghorrocks
Rather than just arbitrarily reducing the tiem...

Rather than just arbitrarily reducing the tiem step, how about doing a time step sensitivity study so you work out what time step size you actually need. Or even better, use adaptive timestepping,...
Forum: CFX April 20, 2013, 07:26
Replies: 36
Views: 7,604
Posted By ghorrocks
That is very unwise. Your graphs seem to...

That is very unwise.

Your graphs seem to show that the flow is in fact not periodic for a few configurations modelled. This may well be real. There is a transition from periodic to non-periodic at...
Forum: CFX April 18, 2013, 06:14
Replies: 36
Views: 7,604
Posted By ghorrocks
Yes, that is correct.

Yes, that is correct.
Forum: CFX April 17, 2013, 18:45
Replies: 36
Views: 7,604
Posted By ghorrocks
It is up to your judgement as to whether the mesh...

It is up to your judgement as to whether the mesh sensitivity done on steady state is applicable to a transient run. It probably is, but you need to think through what has changed and if it makes a...
Forum: CFX April 17, 2013, 07:43
Replies: 36
Views: 7,604
Posted By ghorrocks
Yes, the initial conditions will affect...

Yes, the initial conditions will affect convergence. The closer the initial condition is to the real condition, and the smoother it is the better the convergence.

And yes, starting with a small...
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