scholarly journals Zonal Large-Eddy Simulation of a Fan Tip-Clearance Flow, With Evidence of Vortex Wandering

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Jérôme Boudet ◽  
Adrien Cahuzac ◽  
Philip Kausche ◽  
Marc C. Jacob
Keyword(s):  
Large Eddy Simulation ◽  
Good Description ◽  
Region Of Interest ◽  
Tip Clearance ◽  
Velocity Spectrum ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Large Eddy

The flow in a fan test-rig is studied with combined experimental and numerical methods, with a focus on the tip-leakage flow. A zonal RANS/LES approach is introduced for the simulation: the region of interest at tip is computed with full large-eddy simulation (LES), while Reynolds-averaged Navier–Stokes (RANS) is used at inner radii. Detailed comparisons with the experiment show that the simulation gives a good description of the flow. In the region of interest at tip, a remarkable prediction of the velocity spectrum is achieved, over about six decades of energy. The simulation precisely captures both the tonal and broadband contents. Furthermore, a detailed analysis of the simulation allows identifying a tip-leakage vortex (TLV) wandering, whose influence onto the spectrum is also observed in the experiment. This phenomenon might be due to excitation by upstream turbulence from the casing boundary layer and/or the adjacent TLV. It may be a precursor of rotating instability. Finally, considering the outlet duct acoustic spectrum, the vortex wandering appears to be a major contribution to noise radiation.

Cut-cell method based large-eddy simulation of tip-leakage flow

2015 ◽  
Vol 27 (7) ◽  
pp. 075106 ◽  
Author(s):  
Alexej Pogorelov ◽  
Matthias Meinke ◽  
Wolfgang Schröder
Keyword(s):  
Large Eddy Simulation ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Cell Method ◽  
Eddy Simulation ◽  
Cut Cell ◽  
Large Eddy

Investigation of Turbulence Characteristics in a Tip Leakage Flow Model Using Large-Eddy Simulation

2019 ◽  
Author(s):  
Yanfei Gao ◽  
Yangwei Liu ◽  
Lipeng Lu
Keyword(s):  
Large Eddy Simulation ◽  
Flow Model ◽  
Side Wall ◽  
Leakage Flow ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Turbulence Characteristics ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Large Eddy

Abstract A simple tip leakage flow (TLF) model which consists of a square duct with a longitudinal slit on the top of a side wall is proposed to reproduce the jet flow/main flow shear mechanism of the tip leakage vortex (TLV) rolling-up in turbomachinery. Large-eddy simulation (LES) is employed to investigate the turbulence characteristics of the flow model under low Reynolds number condition. The geometry and boundary conditions of the flow model are simplified from a compressor rotor and modified to apply to low-Re condition for LES. The vortex structures and turbulence characteristics of the LES results are compared with the measurements of the rotor. It is found that the flow model could reproduce similar flow field and turbulence structures compared with the TLF in the real rotor, thus it can be used to investigate the turbulence in practical flows. Reynolds-Averaged Navier-Stokes (RANS) calculations are also carried out. The mean flow and turbulence behaviors of different cases are analyzed. The budgets of turbulent kinetic energy (k) are analyzed to investigate the turbulence transport nature in the TLF model, indicating that the non-equilibrium transport process of k is significant, especially the pressure and turbulent transport, which is not predicted by RANS.

Prediction of Unsteady Tip Leakage Flow of a Transonic Compressor Rotor by Reynolds-Stress-Constrained Large Eddy Simulation

2018 ◽  
Author(s):  
Yueqing Zhuang ◽  
Hui Liu
Keyword(s):  
Large Eddy Simulation ◽  
Reynolds Stress ◽  
Rotor Blade ◽  
Leading Edge ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
Eddy Simulation ◽  
Large Eddy

Since the unsteadiness of tip leakage flow has profound effects on both aerodynamic performance and stall margin of axial compressors, it is important to accurately predict the transient tip flow at affordable computational cost. Limited by the high requirement of grid resolution of wall turbulence flow, large eddy simulation (LES) method is greatly restricted in engineering application. In the present work, a Reynolds-stress-constrained large eddy simulation (CLES) method has been introduced, in which the whole domain is simulated using LES while Reynolds stress constraint is enforced on the subgrid-scale (SGS) stress model for near-wall regions aiming at reducing the near-wall grid resolution. The CLES simulations have been performed to investigate the flow behaviors of the unsteady tip leakage flow in a transonic compressor NASA Rotor 67 at near-stall conditions. Reliability assessments have been conducted through comparisons of experimental measurements and numerical results obtained by RANS, DES, CLES as well as LES, respectively. Both the total pressure ratio and isentropic efficiency calculated by CLES agree well with experiment. The turbulence statistical results show three distinct high flow fluctuation regions near the blade tip. The first one is a long and narrow strip ahead of the leading edge of the rotor caused by the movement of the passage shock wave. The second one is formed on the suction side from the leading-edge of the rotor blade due to the oscillation of the tip leakage vortex. And the third one, which occupies most of the blade passage from the middle part of the rotor blade, is generated under multiple factors. The frequency characteristic of the unsteady tip leakage flow has been analyzed. The energy spectrums of the local transient pressure signals are highly related with the local unsteady flow features. The originating mechanisms of the flow unsteadiness in the rotor tip leakage flow have also been discussed, and the results show that the flow unsteadiness is mainly caused by a combined interaction effect of the double leakage flow, the tip leakage vortex flow spilled from the adjacent blade passage, as well as the involved main flow.

Zonal large-eddy simulation of a tip leakage flow

2016 ◽  
Vol 15 (6-7) ◽  
pp. 646-661 ◽  
Author(s):  
Jérôme Boudet ◽  
Joëlle Caro ◽  
Bo Li ◽  
Emmanuel Jondeau ◽  
Marc C Jacob
Keyword(s):  
Large Eddy Simulation ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Verification and Validation of Large Eddy Simulation for Tip Clearance Vortex Cavitating Flow in a Waterjet Pump

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7635
Author(s):  
Chengzao Han ◽  
Yun Long ◽  
Mohan Xu ◽  
Bin Ji
Keyword(s):  
Large Eddy Simulation ◽  
Tip Clearance ◽  
Verification And Validation ◽  
Flow Structures ◽  
Tip Clearance Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Clearance Flow ◽  
Vorticity Transport ◽  
Waterjet Pump

In this paper, large eddy simulation (LES) was adopted to simulate the cavitating flow in a waterjet pump with emphasis on the tip clearance flow. The numerical results agree well with the experimental observations, which indicates that the LES method can make good predictions of the unsteady cavitating flows around a rotor blade. The LES verification and validation (LES V&V) analysis was used to reveal the influence of cavitation on the flow structures. It can be found that the LES errors in cavitating region are larger than those in the non-cavitating area, which is mainly caused by more complicated cavitating and tip clearance flow structures. Further analysis of the interaction between the cavitating and vortex flow by the relative vorticity transport equation shows that the stretching, dilatation and baroclinic torque terms have major effects on the generation and transport of vortex structure. Meanwhile the Coriolis force term and viscosity term also exacerbate the vorticity transport in the cavitating region. In addition, the flow loss characteristics of this pump are also revealed by the entropy production theory. It is indicated that the tip clearance flow and trailing edge wake flow cause the viscous dissipation and turbulent dissipation, and the cavitation can further enhance the instability of the flow field in the tip clearance.

Large-Eddy Simulation of a Single Airfoil Tip-Leakage Flow

AIAA Journal ◽  
2021 ◽  
pp. 1-12
Author(s):  
Régis Koch ◽  
Marlène Sanjosé ◽  
Stéphane Moreau
Keyword(s):  
Large Eddy Simulation ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Large Eddy
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