[usergk]

Hello Foamers,

I am trying to implement swirl input in a cylindrical tube (axis along z dir). I came across the groovyBC code to implement swirl input:

inlet
{
type groovyBC;
variables "rpm=8000.0;Un=55.8;c=sum(pos()*mag(Sf()))/sum(mag(Sf()));n=sum(normal())/mag(sum(normal()));p=pos()-c;r=mag(p)+1.0e-10;R=max(r);
xt=vector(0,n.z,-n.y);xT=xt/mag(xt);yt=vector(n.y*n.y+n.z*n.z,-n.x*n.y,-n.x*n.z);yT=yt/mag(yt);";
valueExpression "-Un*normal() + (rpm*pi/30)*((p & yT)*xT - (p & xT)*yT)";
}

Can someone explain what xt, yt, and (p & yT)*xT - (p & xT)*yT refer to?

Thanks so much,

Regards,
gk