Forced-plume virtual-origin geometry
= Forced-plume virtual-origin geometry
For a horizontal <forced plume>, the <plume virtual origin> lies downstream and below the physical source on the far-field vertical asymptote. The origin shift in centreline <arc length> is distinct from its vertical height: if $z=s-D+o(1)$ and $\hat s=s+s_0$, the virtual height is $z_v=-D-s_0$. Both geometric shifts scale with the <jet length> at fixed <entrainment coefficient>.