CFD Comparison to 3D Laser Anemometer and Rotordynamic Force Measurements for Grooved Liquid Annular Seals

A pressure-based computational fluid dynamics (CFD) code is employed to calculate the flow field and rotordynamic forces in a whirling, grooved liquid annular seal. To validate the capabilities of the CFD code for this class of problems, comparisons of basic fluid dynamic parameters are made to three-dimensi onal laser Doppler anemometer (LDA) measurements for a spinning, centered grooved seal. Predictions are made using both a standard and low Reynolds number K-B turbulence model. Comparisons show good overall agreement of the axial and radial velocities in the through flow jet, shear layer, and recirculation zone. The tangential swirl velocity is slightly under-predicted as the flow passes through the seal. By generating an eccen­ tric three-dimensional, body fitted mesh of the geometry, a quasi-steady solution may be obtained in the whirling reference frame allowing the net reaction force to be calculated for different whirl frequency ratios, yielding the rotordynamic force coeffi­ cients. Comparisons are made to the rotordynamic force measurements for a grooved liquid annular seal. The CFD predictions show improved stiffness prediction over traditional multi-control volume, bulk flow methods over a wide range of operating conditions. In cases where the flow conditions at the seal inlet are unknown, a twodimensional, axisymmetric CFD analysis may be employed to efficiently calculate these boundary conditions by including the upstream region leading to the seal. This approach is also demonstrated in this study.