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-   -   Tecplot shock detection (http://www.cfd-online.com/Forums/tecplot/96574-tecplot-shock-detection.html)

aferrero January 26, 2012 07:05

Tecplot shock detection
 
Hi everyone,
I'm looking for an algorithm to detect a shock during post processing. I found a tool in Tecplot 360 which does this work quite well: does anyone know which algorithm is employed in Tecplot?
Thank you very much

Andrea Ferrero

scott_rumage January 26, 2012 20:31

Andrea,

On page 384 the Tecplot 360 user manual states ( http://download.tecplot.com/360/current/tpum.pdf ) :

Tecplot 360 can display important features in 3D fluid flow solutions that make analyzing the solutions
much easier. For trans-sonic flow, it can display shock surfaces. For all flows, including incompressible
flows, it can display lines indicating the location of vortex cores, as well as separation and attachment
lines. These calculations make use of MITís FX library. For more information on this library, please see

http://raphael.mit.edu/fx/. These features are accessed through the Extract Flow Features dialog.

This paragraph and reference may be an answer to your question.

Scott

aferrero January 27, 2012 04:43

Thank you very much, Scott.
I find the article "Shock Detection From Computational Fluid Dynamics Results" cited in your link very useful, in particular the algorithm for moving shocks.

Andrea

anqingxu November 7, 2012 09:54

Has anyone any idea that why the value of "shock" variable in Tecplot can be greater than 1 or less than -1? I tried to capture a shock interface in a 2D convergent-divergent nozzle. Although the position is deriable, but the lengend given in Tecplot has a value which can be as high as 30 and as low as -30. According to the definition,
it should be (U/a) dot (grad(P))/|grad(P)|, how could it be larger than 1?
I have read the reference listed above, it says for stationary shock the the location is the place where the value of Ma vector dot pressure gradient should be one. Can anybody tell me what's going on there? Thank you in advance.

Ophias September 1, 2013 09:21

Quote:

Originally Posted by anqingxu (Post 390800)
Has anyone any idea that why the value of "shock" variable in Tecplot can be greater than 1 or less than -1? I tried to capture a shock interface in a 2D convergent-divergent nozzle. Although the position is deriable, but the lengend given in Tecplot has a value which can be as high as 30 and as low as -30. According to the definition,
it should be (U/a) dot (grad(P))/|grad(P)|, how could it be larger than 1?
I have read the reference listed above, it says for stationary shock the the location is the place where the value of Ma vector dot pressure gradient should be one. Can anybody tell me what's going on there? Thank you in advance.

Due to numerical error of the interpolation scheme, small and undirected pressure gradient may be calculated in uniform flow region. Then (U/a) dot (grad(P))/|grad(P)| will vary from -Ma to Ma, where Ma is the local Mach number.

Ophias September 1, 2013 09:25

The following link http://authors.elsevier.com/sd/artic...00936113001143 is our paper related to shock detection and post-processing, which would be in your interest.


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