- The flow field and the rotordynamic coefficients for a smooth, whirling annular seal were investigated by means of a CFD study involving a full 3D model. The preliminary model (of clearance 1.27mm) was validated by comparison to existing experimental flow field data after which CFD simulations were made for a smaller clearance (0.127mm). The flow field changed significantly with the change in clearance and it was seen that the larger clearance showed an inertia dominated flow regime as opposed to the viscous flow regime for the small clearance. Upon the implementation of Childs' theory for the computation of rotordynamic coefficients, it was observed that forces for the larger clearance did not exhibit the whirl ratio dependence assumed in this theory. The smaller clearance however showed the expected trend with values of the coefficients in the range predicted. Copyright © 2010 by ASME.