Flow and Heat Transfer in Co-Rotating Disc Cavities With Various Cob Opening Ratios

Abstract Flow and heat transfer in compressor rotating disc cavities with various cob opening ratios is investigated using validated open-source computational fluid dynamics (CFD). Wall-modelled large-eddy simulations (WMLES) are performed on three geometric configurations with different cob clearances. Full-annulus numerical simulations are carried out for rotational Reynolds numbers of 8.0 × 105 and 3.0 × 106 and Rossby numbers of 0, 0.2 and 0.4. The results show that centrifugal buoyancy dominates turbulent kinetic energy (TKE) production at high radius, while at low radius, shear becomes the primary source of TKE and the contribution of rotational shear exceeds that of axial shear. A larger cob opening ratio leads to fewer vortex pairs, a longer radial arm region and more intense velocity fluctuations within the cavity. Moreover, varying the cob opening ratios has a negligible effect on shroud Nu ∼ Ra1/3 scaling. The increase in the shroud Nusselt number resulting from a larger opening ratio is significantly smaller than that resulting from an increase in the rotational Reynolds number. Notably, the cob opening ratio has a nonlinear positive effect on the mass flow exchange rate between the cavity flow and the throughflow, which is not only due to the increased intersection area, but also from the reduced relative scale of shear vortices near the cob which enhances the effective intersection area. This study gives insight to the original compressor disc cavity heat transfer prediction model under variable geometry conditions.