EXPERIMENTAL AND COMPUTATIONAL INVESTIGATION OF FLOW STRUCTURE IN BUOYANCY DOMINATED ROTATING CAVITIES

The flow and heat transfer inside HP compressor rotating cavities are buoyancy driven and are known to be extremely difficult to predict. The experimental data of Laser-Doppler Anemometry (LDA) measurements inside an engine representative cavity rig is presented in this paper. Traverses using a two component LDA system have been carried out in the shaft bore and the cavity regions in order to map the axial and tangential velocity components. The velocity data is collected for a range of Rossby, Rotational and Axial Reynolds numbers, Ro, Re-theta and Re-z : 0:08 < Ro < 0:64, 7 x 10(5) < Re-theta < 2:83 x 10(6), 1:2 x 10(4) < Rez < 4:8 x 10(4) and for values of the buoyancy parameter beta Delta T, 0:284 < beta Delta T < 0:55. Numerical study using unsteady Reynolds Averaged Navier-Stokes (URANS) simulations have been carried out to elucidate flow details for a few selected cases. The experimental results revealed that the Swirl number (Xk) varies from a value < 1 near the bore to near solid body rotation at increased radii within the cavity. The analysis of frequency spectrum of the tangential velocity inside the cavities has also shown the existence of pairs of rotating and contra-rotating vortices. There is generally satisfactory agreement between measurements and CFD simulations. There is also convincing evidence of two or more separate regions in the flow dominated by the bore flow and rotation.