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sreenivas July 2, 2004 02:01

problem in getting second derivatives
hello, i wanted to solve an additional equation using USER FORTRAN code. in this equation I require second order derivatives of velocity. As in CFX there is no direct way to get second derivative (i e gradient of a gradient), i defined a temporary additional variable ( unspecified and hence algebraic type) to get the first derivative and then in one point of my main fortran program i am calling the gradient of the temporary variable (so that i can get the second derivative of velocity). the fortran program is compiling well. but when i link up the program with solver , it is returning an error. now i am getting doubt whether i will be able to solve second derivatives or not or is there is any care that should be taken while getting gradient of a gradient.

i will be extremely thankful if i get any solutions or suggestions for this

regards sreenivas

Jeff July 11, 2004 19:27

Re: problem in getting second derivatives
Note that there is an example related to this in the documentation (calculating one AV as the gradient of another). The gradients are not actually stored, unless something tries to use them as a source term though CEL for another variable (at least this was the behavior in 5.6). Use the gradient as the source to a dummy equation, and then the gradients will be available for further calculations.


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