Large-eddy simulation analysis of mechanisms for viscous losses in a turbomachinery tip-clearance flow

2007 ◽  
Vol 586 ◽  
pp. 177-204 ◽  
Author(s):  
DONGHYUN YOU ◽  
MENG WANG ◽  
PARVIZ MOIN ◽  
RAJAT MITTAL
Keyword(s):  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Mean Velocity ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Velocity Gradients ◽  
Viscous Losses ◽  
Large Eddy ◽  
The Mean

The tip-leakage flow in a turbomachinery cascade is studied using large-eddy simulation with particular emphasis on understanding the underlying mechanisms for viscous losses in the vicinity of the tip gap. Systematic and detailed analysis of the mean flow field and turbulence statistics has been made in a linear cascade with a moving endwall. Gross features of the tip-leakage vortex, tip-separation vortices, and blade wake have been revealed by investigating their revolutionary trajectories and mean velocity fields. The tip-leakage vortex is identified by regions of significant streamwise velocity deficit and high streamwise and pitchwise vorticity magnitudes. The tip-leakage vortex and the tip-leakage jet which is generated by the pressure difference between the pressure and suction sides of the blade tip are found to produce significant mean velocity gradients along the spanwise direction, leading to the production of vorticity and turbulent kinetic energy. The velocity gradients are the major causes for viscous losses in the cascade endwall region. The present analysis suggests that the endwall viscous losses can be alleviated by changing the direction of the tip-leakage flow such that the associated spanwise derivatives of the mean streamwise and pitchwise velocity components are reduced.

scholarly journals Aerodynamic investigation of a linear cascade with tip gap using large-eddy simulation

2021 ◽  
Vol 5 ◽  
pp. 39-49
Author(s):  
Koch Régis ◽  
Sanjosé Marlène ◽  
Moreau Stéphane
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Suction Side ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Large Eddy

The flow in a linear compressor cascade with tip gap is simulated using a wall-resolved compressible Large-Eddy Simulation. The cascade is based on the Virginia Tech Low Speed Cascade Wind Tunnel. The Reynolds number based on the chord is 3.88 x 10⁵ and the Mach number is 0.07. The gap considered in this study is 4.0 mm (2.9% of axial chord). An aerodynamic analysis of the tip-leakage flow allow us identifying the main mechanisms responsible for the development and the convection of the tip-leakage vortex downstream of the cascade. A region of high turbulence and vorticity levels is located along an ellipse that borders the top of the tip-leakage vortex. The influence of the airfoil suction side boundary layer development on the tip-leakage vortex is highlighted by tripping the flow. A tripped boundary layer induces a stronger and larger tip-leakage vortex that tends to move further away from the airfoil suction side and from the endwall compared with an untripped flow. The boundary layer turbulent state influences the tip-leakage flow development.

scholarly journals Numerical Prediction of the Aerodynamics and Acoustics of a Tip Leakage Flow Using Large-Eddy Simulation

2021 ◽  
Vol 6 (3) ◽  
pp. 27
Author(s):  
David Lamidel ◽  
Guillaume Daviller ◽  
Michel Roger ◽  
Hélène Posson
Keyword(s):  
Large Eddy Simulation ◽  
Complex Structure ◽  
Flow Region ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Wall Pressure Fluctuations ◽  
Large Eddy

A Large-Eddy Simulation of the tip leakage flow of a single airfoil is carried out. The configuration consists of a non-rotating, isolated airfoil between two horizontal plates with a gap of 10 mm between the tip of the airfoil and the lower plate. The Mach number of the incoming flow is 0.2, and the Reynolds number based on the chord is 9.3 × 105. The objective of the present study is to investigate the best way to compute both the aerodynamics and acoustics of the tip leakage flow. In particular, the importance of the inflow conditions on the prediction of the tip leakage vortex and the airfoil loading is underlined. On the other hand, the complex structure of the tip leakage vortex and its convection along the airfoil was recovered due to the use of a mesh adaptation based on the dissipation of the kinetic energy. Finally, the ability of the wall law to model the flow in the tip leakage flow region was proven in terms of wall pressure fluctuations and acoustics in the far-field.

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

Numerical analysis of the groove effect on the tip leakage vortex cavitating flow

2019 ◽  
Vol 234 (6) ◽  
pp. 836-847
Author(s):  
Zhaodan Fei ◽  
Rui Zhang ◽  
Hui Xu ◽  
Tong Mu
Keyword(s):  
Flow Pattern ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Main Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Curvature Effects ◽  
The Mean

In this paper, the groove effect on the tip leakage vortex cavitating flow characteristics of a simplified NACA0009 hydrofoil with tip gap is studied. Considering local rotation characteristics and curvature effects of the tip leakage vortex flow, the rotation-curvature corrected shear-stress-transport turbulence model is applied to simulate the time-averaged turbulent flow. The Zwart–Gerber–Belamri cavitation model is used to simulate the cavitating flow. The results show that the groove could affect the tip leakage vortex cavitating flow. The groove enhances the interaction between the tip leakage flow and main flow, and then it affects the cavitation of the tip leakage vortex. Compared with the non-groove case, for groove cases of αgre ≤75°, the tip leakage vortex cavitating flow is suppressed, the flow pattern in the gap is improved, and the mean leakage velocity Vlk < 0.8. The region of high leakage velocity is eliminated and the distribution of the pressure is more uniform. The tip leakage vortex cavitation area is reduced, and the maximum decrease is 72.90%. While for groove cases of αgre≥90°, neither the tip leakage vortex cavitating flow nor flow pattern in the tip gap is ameliorated, the mean leakage velocity Vlk lies the range from 0.90 to 0.96. The region of high leakage velocity still exists and even the tip leakage vortex cavitation area is increased. Based on three-dimensional streamlines and vorticity transport equation, the interaction between the tip leakage flow and main flow leads to the variation of the tip leakage vortex cavitating flow. This paper aims for a useful reference to mitigate the tip leakage vortex cavitation and control the influence of the tip leakage vortex cavitating flow for the hydraulic machinery.

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

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

scholarly journals Large-Eddy Simulation of Cavitating Tip Leakage Vortex Structures and Dynamics around a NACA0009 Hydrofoil

2021 ◽  
Vol 9 (11) ◽  
pp. 1198
Author(s):  
Linlin Geng ◽  
Desheng Zhang ◽  
Jian Chen ◽  
Xavier Escaler
Keyword(s):  
Large Eddy Simulation ◽  
Vortex Structures ◽  
Vortex Center ◽  
Streamwise Vorticity ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean ◽  
End Wall

The tip leakage vortex (TLV) has aroused great concern for turbomachine performance, stability and noise generation as well as cavitation erosion. To better understand structures and dynamics of the TLV, large-eddy simulation (LES) is coupled with a homogeneous cavitation model to simulate the cavitation flow around a NACA0009 hydrofoil with a given clearance. The numerical results are validated by comparisons with experimental measurements. The results demonstrate that the present LES can well predict the mean behavior of the TLV. By visualizing the mean streamlines and mean streamwise vorticity, it shows that the TLV dominates the end-wall vortex structures, and that the generation and evolution of the other vortices are found to be closely related to the development of the TLV. In addition, as the TLV moves downstream, it undergoes an interesting progression, i.e., the vortex core radius keeps increasing and the axial velocity of vortex center experiences a conversion from jet-like profile to wake-like profile.

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