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str6073 April 22, 2014 06:01

post processing dilemma
 
hi i've done a simulation for 3600 seconds in cfx and now want to plot a time vs temperature graph. I defined a point in geometry and when i plot,i'm only getting the final temperature at that point. I need the complete temperature variation from the zero second . Somebody please help .

ghorrocks April 22, 2014 06:12

The best way to get data at a point over a transient simulation is to set it as a monitor point and it will generate the data as the simulation progresses.

But it sounds like you have already run the simulation and are trying to extract this data from a completed simulation. By default CFD-Post loads up the last time step. If you saved transient results files you can also extract the data for any time step you saved. If you did not save any transient results files then the data does not exist and the only way of getting it is to rerun the simulation. So if you have to rerun it then make sure you put the monitor points in I mentioned in the first paragraph.

str6073 April 22, 2014 23:28

Thank you for your fast response. I checked cfx pre but no option for putting a monitor point. Do you have any video or tutorial showing how to do it ??

ghorrocks April 23, 2014 06:19

It is in CFX-Pre, under output/Monitor points (I think, I am doing this from memory)

str6073 April 24, 2014 00:26

Thanxx again.. finally i got it . But is it possible to get the monitor point results in CFD post ?? I checked it but no options available.

ghorrocks April 24, 2014 03:39

CFD-Post cannot access monitor point data to my knowledge.

str6073 April 26, 2014 01:09

If you have time please help me with this also. How can i make sure which scheme is suitable for my simulation? up wind or high resolution ?? Forgive my ignorance.its a 3d simulation

ghorrocks April 26, 2014 07:30

The forum is here to help, post your question and we will try to help. But make sure you understand the basics of CFD - have a look at a CFD textbook to explain upwinding, high resolution and what all that means. You really have to understnad these basics before attempting to use software like CFX.

str6073 April 26, 2014 09:36

i've books by Tannehill and patankar but none of them are mentioning about high resolution schemes. Do you have any suggestions ??

ghorrocks April 27, 2014 06:33

Start by understanding the difference between first and second order schemes. Then look at the more complex schemes like high resolution. The CFX documentation includes references to more detailed articles about the schemes.

str6073 May 9, 2014 02:50

Glenn i need some more guidance . i know energy equation continuity equation and navier stokes equation is used for solving fluid flow problems. i've to simulate natural circulation of water by solar radiation. For this case boussinesq approach is also considered. my confusion is , at every point of my domain the above mentioned equations are only used ?? because somebody told me it is not used everywhere . domains is fluid only

ghorrocks May 9, 2014 02:56

The fluid will conserve mass, momentum and energy. So everywhere you have fluid doing stuff you will have these three equations. If you have a solid domain then you probably only have the energy equation. If you have radiation then you have a radiation model.

str6073 May 9, 2014 03:31

thanxx for replying . and which are energies being considered in energy equation for my case ?? it will be both kinetic energies and internal energy ,right ??

ghorrocks May 9, 2014 06:37

The energy equation is thermal energy. It sounds like you need to do some reading up on basic CFD.

str6073 May 17, 2014 00:07

hi following link shows solution of finite volume equations . but in momentum equation last term on right side is confusing. can you please explain that ??

http://www.personal.psu.edu/jhm/470/lectures/8.html

ghorrocks May 17, 2014 04:11

I do not have time to read and understand that link. There are many different ways of numerically solving the Navier Stokes equations and that page is taking a very different approach to CFX.


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