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

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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Study of wave effect on vorticity in Langmuir turbulence using wave-phase-resolved large-eddy simulation

Journal of Fluid Mechanics ◽

10.1017/jfm.2019.481 ◽

2019 ◽

Vol 875 ◽

pp. 173-224 ◽

Cited By ~ 3

Author(s):

Anqing Xuan ◽

Bing-Qing Deng ◽

Lian Shen

Keyword(s):

Large Eddy Simulation ◽

Correlation Effect ◽

Wave Turbulence ◽

Langmuir Turbulence ◽

Streamwise Vorticity ◽

Wave Phase ◽

Eddy Simulation ◽

Large Eddy ◽

Vorticity Dynamics ◽

The Mean

The effects of a water surface wave on the vorticity in the turbulence underneath are studied for Langmuir turbulence using wave-phase-resolved large-eddy simulation. The simulations are performed on a dynamically evolving wave-surface-fitted grid such that the phase-resolved wave motions and their effects on the turbulence are explicitly captured. This study focuses on the vorticity structures and dynamics in Langmuir turbulence driven by a steady and co-aligned progressive wave and surface shear stress. For the first time, the detailed vorticity dynamics of the wave–turbulence interaction in Langmuir turbulence in a wave-phase-resolved frame is revealed. The wave-phase-resolved simulation provides detailed descriptions of many characteristic features of Langmuir turbulence, such as elongated quasi-streamwise vortices. The simulation also reveals the variation of the strength and the inclination angles of the vortices with the wave phase. The variation is found to be caused by the periodic stretching and tilting of the wave orbital straining motions. The cumulative effect of the wave on the wave-phase-averaged vorticity is analysed using the Lagrangian average. It is discovered that, in addition to the tilting effect induced by the Lagrangian mean shear gradient of the wave, the phase correlation between the vorticity fluctuations and the wave orbital straining is also important to the cumulative vorticity evolution. Both the fluctuation correlation effect and the mean tilting effect are found to amplify the streamwise vorticity. On the other hand, for the vertical vorticity, the fluctuation correlation effect cancels the mean tilting effect, and the net change of the vertical vorticity by the wave straining is negligible. As a result, the wave straining enhances only the streamwise vorticity and cumulatively tilts vertical vortices towards the streamwise direction. The above processes are further quantified analytically. The role of the fluctuation correlation effect in the wave-phase-averaged vorticity dynamics provides a deeper understanding of the physical processes underlying the wave–turbulence interaction in Langmuir turbulence.

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Cut-Cell Method Based Large-Eddy Simulation of a Tip-Leakage Vortex of an Axial Fan

53rd AIAA Aerospace Sciences Meeting ◽

10.2514/6.2015-1979 ◽

2015 ◽

Cited By ~ 3

Author(s):

Alexej Pogorelov ◽

Matthias H. Meinke ◽

Wolfgang Schroeder ◽

Roland Kessler

Keyword(s):

Large Eddy Simulation ◽

Axial Fan ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Cell Method ◽

Eddy Simulation ◽

Cut Cell ◽

Large Eddy

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

Journal of the Global Power and Propulsion Society ◽

10.33737/jgpps/133601 ◽

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.

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

International Journal of Turbomachinery Propulsion and Power ◽

10.3390/ijtpp6030027 ◽

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.

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Vortex Structures Analysis and Loss Mechanisms in Axial Compressor Cascade With and Without Bleeding Slot Using Large Eddy Simulation

Volume 2A: Turbomachinery ◽

10.1115/gt2020-15180 ◽

2020 ◽

Author(s):

Yun Gong ◽

Shaowen Chen ◽

Haipeng Zheng ◽

Songtao Wang

Keyword(s):

Large Eddy Simulation ◽

Axial Compressor ◽

Vortex Structures ◽

Leakage Flow ◽

Compressor Cascade ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Eddy Simulation ◽

Passage Vortex ◽

Large Eddy

Abstract Tip leakage flow is one of the main sources of flow losses in an axial compressor, and the understanding of the tip leakage flow helps to explore better flow control methods and design more advanced compressors. Therefore, the vortex structures and loss mechanisms were analyzed in a compressor cascade with tip clearance in the present paper. Large eddy simulation was used to better resolve the vortices with more accurate numerical results. The iso-surface of Q criterion in the compressor cascade is captured for recognizing and analyzing the vortex structures. The horse shoe vortices, tip leakage vortex, induced vortex, tip separation vortex and passage vortex were well captured and their interactions were interpreted. Fast Fourier Transformation was also applied to analyze the frequency signal in the flow field. Afterwards, the case with an upstream bleeding slot was also calculated and compared with the original case without a bleeding slot. The bleeding rate is 2.8% of the mass flow rate at inlet. The removal of the inlet boundary layer resulting from the bleeding leads a 42.4% reduction of the total pressure loss coefficient compared with that of the case without the bleeding slot. In the case with the bleeding slot, the size of the passage vortex is greatly reduced, and the mixing between the tip leakage vortex and passage vortex is postponed. Better performance is achieved with the bleeding slot accordingly.

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

Journal of Fluid Mechanics ◽

10.1017/s0022112007006842 ◽

2007 ◽

Vol 586 ◽

pp. 177-204 ◽

Cited By ~ 90

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.

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Large Eddy Simulation of Vortex Structures and Frequency Characteristics in Turbulent Flow through an Axisymmetric Sudden Expansion

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.73.751 ◽

2007 ◽

Vol 73 (727) ◽

pp. 751-758 ◽

Cited By ~ 1

Author(s):

Hideki YANAOKA ◽

Takao INAMURA ◽

Takanori SHIMOMACHI

Keyword(s):

Large Eddy Simulation ◽

Turbulent Flow ◽

Vortex Structures ◽

Frequency Characteristics ◽

Sudden Expansion ◽

Eddy Simulation ◽

Large Eddy ◽

Flow Through

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

Physics of Fluids ◽

10.1063/1.4926515 ◽

2015 ◽

Vol 27 (7) ◽

pp. 075106 ◽

Cited By ~ 29

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

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Large Eddy Simulation of Round Impinging Jets With Large Stand-Off Distance

Volume 7: Fluids Engineering Systems and Technologies ◽

10.1115/imece2014-37194 ◽

2014 ◽

Author(s):

Mehrdad Shademan ◽

Vesselina Roussinova ◽

Ron Barron ◽

Ram Balachandar

Keyword(s):

Large Eddy Simulation ◽

Flow Characteristics ◽

Impinging Jet ◽

Impinging Jets ◽

Vortical Structures ◽

Nozzle Height ◽

Eddy Simulation ◽

Large Eddy ◽

The Mean ◽

Good Agreement

Large Eddy Simulation (LES) has been carried out to study the flow of a turbulent impinging jet with large nozzle height-to-diameter ratio. The dynamic Smagorinsky model was used to simulate the subgrid-scale stresses. The jet exit Reynolds number is 28,000. The study presents a detailed evaluation of the flow characteristics of an impinging jet with nozzle height of 20 diameters above the plate. Results of the mean normalized centerline velocity and wall shear stress show good agreement with previous experiments. Analysis of the flow field shows that vortical structures generated due to the Kelvin-Helmholtz instabilities in the shear flow close to the nozzle undergo break down or merging when moving towards the plate. Unlike impinging jets with small stand-off distance where the ring-like vortices keep their interconnected shape upon reaching the plate, no sign of interconnection was observed on the plate for this large stand-off distance. A large deflection of the jet axis was observed for this type of impinging jet when compared to the cases with small nozzle height-to-diameter ratios.

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