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Old   January 27, 2006, 11:27
Default Jameson Dissipation.
  #1
Peter Cook
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I have a quasi-one-dimension nozzle flow problem and I need to solve the equation using Jameson's scheme coding a cell vertex version as well as suitable second and fourth order disspipation. I can't seem to find the right equations for the dissipation anywhere and could do with some help in finding them.

Any suggestions?

Any more info needed just let me know.

Pete
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Old   January 27, 2006, 13:20
Default Re: Jameson Dissipation.
  #2
Jeff Moder
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Try looking through the extensive list of pdf files (mostly near the bottom) at

http://aero-comlab.stanford.edu/jame...tion_list.html

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Old   January 28, 2006, 09:22
Default Re: Jameson Dissipation.
  #3
Peter Cook
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Ok I have had a look through those and I still can't seem to get it right. Maybe if I post up the problem and the code I have got so far, maybe someone could let me know how to code what I need. The area I need coded is currently filled with stars:

<https://www.bris.ac.uk/fluff/u/pc583...lk4ahwCr9fgi7/> - Problem (pdf)

<https://www.bris.ac.uk/fluff/u/pc583...ClluM6LIigwi7/> - Code (cpp)

<https://www.bris.ac.uk/fluff/u/pc583..._OHZJoDJZDQi7/> - Include / Library File

<https://www.bris.ac.uk/fluff/u/pc583...e4UgDc9etOwi7/> - Include / Library File

<https://www.bris.ac.uk/fluff/u/pc583...RuIV0agK4Igi7/> - Include / Library File

<https://www.bris.ac.uk/fluff/u/pc583...0h_WzCDWaXgi7/> - Include / Library File

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Old   January 28, 2006, 21:06
Default Re: Jameson Dissipation.
  #4
Mani
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The reference you are looking for is number 62 in the list for which Jeff provided the link. That paper describes the original JST scheme in all the detail that you will need for implementation. Read it carefully and all your questions should be answered.
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Old   January 29, 2006, 15:31
Default Re: Jameson Dissipation.
  #5
vm
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I enter this thread with a question. The paper 62 is ok. But I found nowhere (after extensive searching) the contruction of the di-1/2,j therm. Is there (rho i,j -rho i-1,j) or (rho i-1,j - rho i,j) ? And the second therm in eq.(11)? I tray now to implement the Jameson's diffusion in a 3D transonic compressor code, but it does not work. I reduced the cfl from 2.8 down to 0.5. There are this constants 1/4, 1/256 free for variation. I do something wrong but I do not know why. Is somebody experienced with writing such a code?
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Old   February 1, 2006, 05:52
Default Re: Jameson Dissipation.
  #6
Peter Cook
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That's exactly what I am looking for. I need someone to treat me like the idiot that I am and show me step by step how to implement Jameson's equations into code as everything I am doing at the moment doesn't seem to be working.
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Old   February 1, 2006, 08:31
Default Re: Jameson Dissipation.
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A.S.
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Try using 1/2 and 1/64 they are more stable as per my experience
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Old   February 1, 2006, 14:52
Default Re: Jameson Dissipation.
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vm
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Thanks,

I apply the diffusion term something like this [simplyfied in 1D, u1 is density, x momentum, etc., in general u1(i,j,k)]

d(i)= 1scalep*(eps2p*(u1(i+1)-u1(i))- 1 eps4p*(u1(i+2)-3.*u1(i+1)+3.*u1(i)-u1(i-1)))- 1scalem*(eps2m*(u1(i)-u1(i-1))- 1 eps4m*(u1(i-2)-3.*u1(i-1)+3.*u1(i)-u1(i+1)))

This gives in the result something similar like 2nd derivative minus 3rd derivative (?????).

The scalep and scalem are scaling factors. I tried to set the ratio of (volume(i+1)+volume(i))/2./timestep for scalep, etc. but I do not know if it is ok.

eps2p,etc. are Jamesons factors

The d(i) values I calculate in all 3 dimesions and add it to one number. For each control volume I sum the fluxes in x, y, z directions and substract d. That is all. But will not work.

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Old   February 3, 2006, 11:31
Default Re: Jameson Dissipation.
  #9
vm
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Other interpretation of Jamesons' AIAA paper is

d(i)=

1 scalep*(eps2p*(u1(i+1)-u1(i))-

1 ........eps4p*(u1(i+2)-3.*u1(i+1)+3.*u1(i)-u1(i-1)))-

1 scalem*(eps2m*(u1(i)-u1(i-1))+ plus here!!!!!!

1 ........eps4m*(u1(i-2)-3.*u1(i-1)+3.*u1(i)-u1(i+1)))

This gives in the result something similar like 2nd derivative minus 4th derivative (?????). And it seems to work with 1/2 and 1/64 excelent for Q1D.

But in 3D case there must be some trick else. It works but not satisfactory.

Who knows how are treated the cells at wall, where the points i+1, i+2 are not present.

The next trick maz be the scaling scalep,...etc.

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