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Farfield BC: vortex correction for lifting bodies

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Old   August 30, 2005, 11:17
Default Farfield BC: vortex correction for lifting bodies
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i'm reading Blazek's CFD book and he said that for the farfield BC of lifting bodies, some corrections have to be made, namely in 2D,

u(inf)(new) = u(inf) + (tau*sqrt(1-M(inf)^2)/2*pi*d)*sin(theta)/(1-M(inf)^2* (sin(theta-alpha))^2)

v(inf)(new) = v(inf) + (tau*sqrt(1-M(inf)^2)/2*pi*d)*cos(theta)/(1-M(inf)^2* (sin(theta-alpha))^2)

tau is circulation, (d,theta) are polar coordinates of farfield, M(inf) is freestream mach no.

I would like to check if I can apply this to incompressible NS eqns. I'm using the fractional-step btw. Moreover, is this helpful in incompressible flow? It's stated that the farfield radius can be reduced by an order of magnitude when used.

please comment. thanks!

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Old   August 30, 2005, 22:52
Default Re: Farfield BC: vortex correction for lifting bod
Praveen. C
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This correction can be applied for lifting flows. Hence it is most appropriate for subsonic flows but might also help for transonic flows. For imcompressible flow, I think it is enough to put M(inf)=0 in those formulae. Also see the following reference

MD Salas JL Thomas, Far-Field Boundary Conditions for Transonic Lifting Solutions to the Euler Equations, AIAA Journal, vol. 24, no. 7, 1986
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Old   September 6, 2005, 02:10
Default Re: Farfield BC: vortex correction for lifting bod
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ok thanks. but has anyone used this correction before? Is it effective ie reducing the farfield location by quite a bit?

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