Farfield BC: vortex correction for lifting bodies
 

Hi,

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!

Re: Farfield BC: vortex correction for lifting bod
 

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

Re: Farfield BC: vortex correction for lifting bod
 

ok thanks. but has anyone used this correction before? Is it effective ie reducing the farfield location by quite a bit?

Thanks