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Search took 0.00 seconds. Search: Posts Made By: ghorrocks
Forum: CFX August 19, 2018, 06:06
Replies: 75
Views: 18,833
Posted By ghorrocks
Specified location and Specified displacement:...

Specified location and Specified displacement: Let's say you have a mesh at x=1m and you want it to move right 0.1m at 1m/s. This can be defined by:

Specified Displacement = 0.1[m]*t

or
...
Forum: CFX August 16, 2018, 20:55
Replies: 75
Views: 18,833
Posted By ghorrocks
As you are new to moving mesh I would suggest you...

As you are new to moving mesh I would suggest you do a simpler model first to get started. As you know the motion of the actuator, that means you know the flow rate it generates. So remove the...
Forum: CFX August 14, 2018, 08:36
Replies: 75
Views: 18,833
Posted By ghorrocks
It is possible to have flow driven by a moving...

It is possible to have flow driven by a moving mesh and an inlet. I have done it many times. There is some problem with your simulation.

Your images show some pressure variation and some velocity....
Forum: CFX August 14, 2018, 07:36
Replies: 75
Views: 18,833
Posted By ghorrocks
It appears the inlet does not have motion normal...

It appears the inlet does not have motion normal to the boundary, so that is OK. mesh motion tangential to an inlet boundary is OK.

On your question about convergence: Have you done the normal...
Forum: CFX August 13, 2018, 19:23
Replies: 75
Views: 18,833
Posted By ghorrocks
Please show what faces are moving and what...

Please show what faces are moving and what direction they are moving in. I do not understand what is happening from that image.
Forum: CFX August 13, 2018, 07:55
Replies: 75
Views: 18,833
Posted By ghorrocks
Please post an image showing what faces you have...

Please post an image showing what faces you have defined motion on, and what direct they move in.

Things will work a lot better if you keep the inlet stationary and move the rest of the actuator...
Forum: CFX August 13, 2018, 07:21
Replies: 75
Views: 18,833
Posted By ghorrocks
Applying moving mesh to inlets and outlets is...

Applying moving mesh to inlets and outlets is going to cause problems. I have had a quick look at the other thread and do not understand why you think a moving inlet is required.
Forum: CFX August 13, 2018, 06:30
Replies: 75
Views: 18,833
Posted By ghorrocks
Are you sure your motion is correct? Use the...

Are you sure your motion is correct? Use the debugging technique here...
Forum: CFX August 7, 2018, 08:04
Replies: 75
Views: 18,833
Posted By ghorrocks
Rather than asking me whether it is well posed it...

Rather than asking me whether it is well posed it is better for you to understand the concept and confirm it for yourself. But in short there needs to be somewhere for the fluid to go. An inlet and...
Forum: CFX August 6, 2018, 06:59
Replies: 75
Views: 18,833
Posted By ghorrocks
Both approaches can work and are numerically well...

Both approaches can work and are numerically well posed. But whether the approaches are suitable for what you are modelling and and what you are trying to do depends on many factors you have not...
Forum: CFX August 5, 2018, 19:01
Replies: 75
Views: 18,833
Posted By ghorrocks
Yes, you can do this analysis but you need to...

Yes, you can do this analysis but you need to define it properly before you will get anything sensible. You have to model the actuator somehow, as the oil needs somewhere to go otherwise nothing...
Forum: CFX August 5, 2018, 07:30
Replies: 75
Views: 18,833
Posted By ghorrocks
Your description of the system appears to suggest...

Your description of the system appears to suggest that there should be an outlet in your system to a hydraulic actuator, or one of the walls in your modelled system should move as it is the actuator....
Forum: CFX August 3, 2018, 19:09
Replies: 75
Views: 18,833
Posted By ghorrocks
Think about it - the fluid is incompressible and...

Think about it - the fluid is incompressible and you have only one entry/exit. Nothing can happen.

You say you want to study pressure drop - but pressure drop from where to where? You only have...
Forum: CFX August 3, 2018, 07:57
Replies: 75
Views: 18,833
Posted By ghorrocks
OK, then And I should add that it will...

OK, then



And I should add that it will not converge either.
Forum: CFX August 3, 2018, 06:32
Replies: 75
Views: 18,833
Posted By ghorrocks
I have just gone back over this thread to remind...

I have just gone back over this thread to remind myself of the history (I am doing many threads at once, I cannot recall the history of all of them).

Are you modelling an object with a single...
Forum: CFX August 2, 2018, 21:24
Replies: 75
Views: 18,833
Posted By ghorrocks
Before you think about numerical issues you need...

Before you think about numerical issues you need to think about whether it is significant or not. If the system has significant compressibility then you need to model it regardless of whether it is...
Forum: CFX August 2, 2018, 07:53
Replies: 75
Views: 18,833
Posted By ghorrocks
This question is very similar to this FAQ:...

This question is very similar to this FAQ: https://cfd-online.com/Wiki/Ansys_FAQ#I_get_the_error_.22Floating_point_exception:_Overflow.22._What_does_this_mean_and_what_do_I_do_about_it.3F

In...
Forum: CFX August 1, 2018, 18:50
Replies: 75
Views: 18,833
Posted By ghorrocks
If you have a vessel with only one inlet, and you...

If you have a vessel with only one inlet, and you define the pressure at that boundary then the steady state result of that vessel will be the vessel just gets to the inlet pressure and stays there....
Forum: CFX August 1, 2018, 08:34
Replies: 75
Views: 18,833
Posted By ghorrocks
In a steady state simulation things can have a...

In a steady state simulation things can have a gradient with respect to position, but all gradients with respect to time are zero.
Forum: CFX August 1, 2018, 08:00
Replies: 75
Views: 18,833
Posted By ghorrocks
You have it set up as a steady state simulation....

You have it set up as a steady state simulation. This means nothing changes with time. If you want to study the effect of pressure changes then you should be doing a transient simulation. Then the...
Forum: CFX August 1, 2018, 06:34
Replies: 75
Views: 18,833
Posted By ghorrocks
You have a domain with a single boundary (other...

You have a domain with a single boundary (other than walls and symmetry planes). This boundary is a total pressure boundary. As the simulation is steady state, then the steady state answer to this is...
Forum: CFX July 31, 2018, 18:39
Replies: 75
Views: 18,833
Posted By ghorrocks
To answer that question I would have to see what...

To answer that question I would have to see what you are modelling and how you are modelling it. Please attach some images which show what boundary conditions you apply and your CCL.
Forum: CFX March 6, 2017, 17:10
Replies: 75
Views: 18,833
Posted By ghorrocks
You are correct. It does mean the absolute value...

You are correct. It does mean the absolute value of the pressure is arbitrary. So I move onto the second problem....

If you define the mass flow rate in and out of a domain in a steady state...
Forum: CFX March 1, 2017, 16:53
Replies: 75
Views: 18,833
Posted By ghorrocks
It cannot work because there is nothing to define...

It cannot work because there is nothing to define the pressure.
Forum: CFX January 23, 2010, 01:07
Replies: 75
Views: 18,833
Posted By ghorrocks
As I said, it looks like you need to do some...

As I said, it looks like you need to do some reading into well posed boundary conditions. Some combinations of boundary conditions are not possible and will never converge. Mass flow rate inlet and...
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