Turbulence Models Assessment for Large-Scale Tip Vortices in an Axial Compressor Rotor

Abstract

Six turbulence models frequently used in compressor aerodynamics were employed in the detailed numerical investigations of a low-speed large-scale axial compressor rotor, for which the tip flows were measured in detail with stereoscopic particle image velocimetry, to assess the predictive capabilities of the turbulence models for large-scale vortices in the tip region of the rotor. The six turbulence models include: the mixing-length model, the SpalartAllmaras model, the standard k " model, the shear-stress transport k ! model, the v 2 f model, and the Reynolds stress model. Their results were carefully discussed and compared with the measurements both on velocity fields and turbulence stresses. It was found that the Reynolds stress model is superior to the others in the prediction of the tip-leakage vortex at the design condition, whereas the standard k " model shows the best results in the prediction of the corner vortex at the near-stall condition. Although the simulation could predict the large-scale tip vortices well in the mean flowfield, the computed flow mechanism has large discrepancy with the reality. Nomenclature A = compressor axial direction H = distance from the hub to the tip in the radial direction p = static pressure R = compressor radial direction T = compressor tangential direction u, v, w = mean velocity components in the x, y, and z directions X = distance from the rotor suction surface in the x direction x, y, z = Cartesian coordinates Y = distance from the rotor hub in the y direction y = nondimensional turbulence wall function = kinematic viscosity = fluid density ! = vorticity Subscript c = the center of the tip-leakage vortex Superscripts = time average 0 = fluctuating quantity

Modification of Spalart–Allmaras model with consideration of turbulence energy backscatter using velocity helicity

“…Hence, we try to take account of the energy backscatter in turbulence models with helicity based on the above results. It is generally accepted that no single turbulence model is universally superior for all classes of problems in compressors [11,12]. Three-dimensional separations have been identified as an inherent flow feature of the corner formed by the blade suction surface and endwall of axial compressors (as shown in Fig.…”

Effects of endwall motion on thermal performance of cavity tips with different squealer width and height

“…This was observed by Yaras and Sjolander [9] using three-hole probe measurements inside the tip gap, by Palafox et al [10] using PIV measurement and by Krishnababu et al [11] using numerical methods. Liu et al [13] assessd different turbulence models for the predction of tip leakage vortex. Most studies observed a reduction of tip leakage mass flow rate due to endwall motion.…”

Investigation on Influence of Design Parameters for Tandem Cascades Diffuser Using DOE Method

“…The equations solved are the fully three-dimensional, compressible, Reynolds averaged, Navier-Stokes equations. Six different turbulence models frequently used in compressor aerodynamics, namely the mixinglength model, the Spalart-Allmaras model, the standard k-ω model, the SST k-ω model, the 2 v -f model, and the Reynolds stress model were employed as detailed in the numerical investigation of Liu and Liu (2008). The results showed that none of them exhibited absolute superiority for the prediction of the complex turbomachinery flow.…”