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Old   May 25, 2010, 09:53
Default 3-D Stream Function
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Mohsen
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Dear Friends,

I am solving 2-D Navier Stocks equation in Biharmonic formulation.
But now I want to know that is it possible to solve this equation in 3-D ?
Indeed the Biharmonic equations in 2-D come from Stream Function-Vorticity method. We know that we don't have Stream Function -Vorticity in 3-D space But we have 3-D operator for Biharmonic equation.

E-mail: mlashckar@yahoo.com

Many Thanks
M.Lashckar
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Old   May 25, 2010, 11:21
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In 3-D, a stream function exists for axisymmetric flows only. That makes it essentially 2-D of course.
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Old   May 26, 2010, 10:09
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Actually the stream function and vorticity are vectors.

In a two-d problem, each vector has only one component.

In a three-d problem, each vector has 3 components, and the bi-harmonic equation becomes three biharmonic equations. Instead of a two-scalar (stream function and vorticity) one solves for six scalars (three for the stream function vector and three for the vorticity vector).

Probably someone has tried to solve such a system.
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Old   May 28, 2010, 02:42
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the problem of a vectorial poisson equation for the "stream function" with vectorial vorticity as its source is at the heart of Lagrangian vortex particle methods and is routinely solved in its integral form (Biot Savart formula). I have also seen at least one paper where the "stream-function"-vorticity method is solved in 3-D using finite difference methods (I forget the author now).

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Old   October 29, 2010, 08:26
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hi i am hari.

iam not fimililar with these stream function & velocity potential.
why we have 2 use these.
what is the use of these things...
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Old   October 29, 2010, 16:44
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Hi,

There exist 3D stream functions (two functions). See, for example,
R. G. Campbell, Foundaitons of Fluid Flow Theory, Addison-Wesley, 1973.

Here is a paper on the application of 3D stream functions to CFD:

A. Sherif and M. Hafez, Computation of three-dimensional transonic flows by
using two stream functions. International Journal for Numerical Methodsin Fluids, 8, 17-29, 1988.
http://onlinelibrary.wiley.com/doi/1...80103/abstract

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