Cavitation Patterns Research Articles

균일 유입류에서의 모형추진기 캐비테이션 소음특성 실험연구

In this study, propeller cavitation and the resulting noise were analyzed experimentally in uniform inflow conditions. The propeller cavitation observation and noise measurements tests were conducted in the KRISO Large Cavitation Tunnel (LCT), with size 2.8 m (B) × 1.8 m (H) × 12.5 m (L). The test setup and conditions are introduced and the propeller noise test procedure is briefly described. To investigate the propeller cavitation and induced noise, propeller noise measurement tests were performed under various pressure and propeller loading conditions. Propeller noise results are presented along with the cavitation observation. The relation between the cavitation patterns and measured noise were analyzed.

An improved Mesh Adaption and Refinement approach to Cavitation Simulation (MARCS) of propellers

This paper presents the improvements of cavitation modelling for marine propellers particularly developing tip vortex cavitation. The main purpose of the study is to devise a new approach for modelling tip vortex cavitation using Computational Fluid Dynamics (CFD) methods with commercial software, STAR-CCM+. The INSEAN E779A model propeller was used for this study as a benchmark propeller. Utilizing this propeller, firstly, validation studies were conducted in non-cavitating conditions together with grid and time step uncertainty studies. Then, the cavitation was simulated on the propeller using a numerical cavitation model, which is known as the Schnerr–Sauer model, based on the Rayleigh-Plesset equation. While a Reynolds Averaged Navier Stokes (RANS) model was used for open water simulations, Detached Eddy Simulations (DES) and Large Eddy Simulations (LES) models were preferred for cavitation simulations to capture the cavitation and evaluate its effect on propeller performance accurately. Although the comparison with the benchmark experimental data showed good agreement for the thrust and torque coefficients as well as sheet cavitation pattern, tip vortex cavitation could not be adequately simulated using the existing method. After an evaluation of the interaction between cavitation modelling and generated meshes, two techniques, which involved volumetric control and adaptive mesh refinement, were used in combination on the region where the tip vortex cavitation is likely to occur. The first technique, which is called a ‘volumetric control method’, was developed using spiral geometry around the propeller tip region to generate a finer mesh for capturing tip vortex cavitation. Although this method gave better tip vortex cavitation extension than the method without any mesh refinement or with tube refinement, it still required to be improved to extend the tip vortices further into the propeller slipstream. The second method, which is called ‘adaptive mesh refinement’, was introduced using the pressure distribution data from the results of the ‘volumetric control method’. This improved approach, which is called “Mesh Adaption and Refinement for Cavitation Simulation (MARCS)”, has been successfully applied to simulate the tip vortices trailing from the blades of the INSEAN E779A propeller as demonstrated in the paper. The results of the simulations showed an excellent agreement with the experiments in the open literature by tracking the tip vortex cavitation along this propeller's slipstream.

Numerical and experimental analysis of cavitation inception behaviour for high-skewed low-noise propellers

Numerical and experimental investigations of two highly skewed low-noise propellers with a slight alteration in the tip geometry are conducted in both wetted and cavitating flows. The performance of the propellers is measured in open water and inclined setups at different operating conditions and high speed video recordings are used to determine tip vortex cavitation inception behaviour. The numerical simulations are conducted by employing the Implicit Large Eddy Simulation on appropriate grid resolutions for tip vortex propagation, at least 32 cells per vortex diameter according to our previous studies. In order to investigate cavitation inception characteristics of the propellers, different inception prediction methods are employed and evaluated at different advance ratios.It is shown that in addition to the well-captured difference in e.g. the amount of cavitation, the simulations are capable of correctly predicting the small but crucial differences in flow features and cavitation inception characteristics of the two propeller designs. Numerical predictions of the cavitation inception charts are also compared successfully with the measured data where three different types of cavitation patterns are investigated in details. Supported by the experimental videos, the interaction between the tip vortex and trailing vortices and their impact on the pressure field and the cavitation inception are analyzed. It is shown that the numerical simulation can provide further details about the vortical flow structures, and their contributions to cavitation, and is a powerful tool in advanced propeller design stages.

Hydrodynamic Cavitation Downstream a Micropillar Entrained Inside a Microchannel—A Parametric Study

Hydrodynamic cavitation downstream a range of micropillar geometries entrenched in a microchannel were studied experimentally. Pressurized helium gas at the inlet tank and vacuum pressure at the outlet propelled distilled water through the device and trigger cavitation. The entire process from cavitation inception to the development of elongated attached cavity was recorded. Three modes of cavitation inception were observed and key parameters of cavitation processes, such as cavity length and angle of attachment, were compared among various micropillar geometries. Cavitation downstream of a triangular micropillar was found to have a distinct inception mode with relatively high cavitation inception numbers. After reaching its full elongated form, it prevailed through a larger system pressures and possessed the longest attached cavity. Cavity angle of attachments was predominantly related to the shape of the micropillar. Micropillars with sharp vertex led to lower cavity attachment angles close to the flow separation point, while circular micropillars resulted in higher angles. Twin circular micropillars have a unique cavitation pattern that was affected by vortex shedding. Fast Fourier transformation (FFT) analysis of the cavity image intensity revealed transverse cavity shedding frequencies in various geometries and provided an estimation for vortex shedding frequencies.

Cavitation on hydrofoils with leading edge protuberances

Cavitation characteristics and hydrodynamic forces of hydrofoils with bioinspired, wavy leading edges were examined experimentally in a water tunnel. Force measurements were carried out using a waterproof load cell, and cavitation patterns were recorded by directly imaging the hydrofoil surface. All semi-span hydrofoils had an underlying NACA 634-021 profile with either a rectangular or swept leading edge planform. The sinusoidal leading edge geometries were defined by three amplitudes of 2.5%, 5%, and 12% and two wavelengths of 25% and 50% of the mean chord length. Results revealed that cavitation on the modified hydrofoils with the two larger amplitudes was largely confined to the regions directly behind the protuberance troughs, whereas a baseline with flat leading edge and the smaller amplitude hydrofoils exhibited sheet cavitation over the entire span. Additionally, cavitation on the modified hydrofoils appeared at consistently lower angles of attack than on the baseline model. Lift coefficient for the baseline model was generally comparable to or greater than that of the modified hydrofoils at the angles of attack considered. Except for the largest amplitude hydrofoils, drag for the modified hydrofoils was equal to the baseline model for nearly the entire angle of attack range.

DDES of Wetted and Cavitating Marine Propeller for CHA Underwater Noise Assessment

In this paper we present results of delayed detached eddy simulation (DDES) and computational hydroacoustics (CHA) simulations of a marine propeller operating in a cavitation tunnel. DDES is carried out in both wetted and cavitating conditions, and we perform the investigation at several propeller loadings. CHA analyses are done for one propeller loading both in wetted and cavitating conditions. The simulations are validated against experiments conducted in the cavitation tunnel. Propeller global forces, local flow phenomena, as well as cavitation patterns are compared to the cavitation tunnel tests. Hydroacoustic sources due to the propeller are evaluated from the flow solution, and corresponding acoustic simulations utilizing an acoustic analogy are made. The propeller wake flow structures are investigated for the wetted and cavitating operating conditions, and the acoustic excitation and output of the same cases are discussed.

Analysis of Ventilation Regimes of the Oblique Wedge-Shaped Surface Piercing Hydrofoil During Initial Water Entry Process

Abstract The suction side of a surface piercing hydrofoil, as a section of a Surface Piercing Propeller (SPP), is usually exposed to three phases of flow consisting air, water, and vapour. Hence, ventilation and cavitation pattern of such section during the initial phase of water entry plays an essential role for the propeller’s operational curves. Accordingly, in the current paper a numerical simulation of a simple surface piercing hydrofoil in the form of an oblique wedge is conducted in three-phase environment by using the coupled URANS and VOF equations. The obtained results are validated against water entry experiments and super-cavitation tunnel test data. The resulting pressure curves and free surface profiles of the wedge water entry are presented for different velocity ratios ranging from 0.12 to 0.64. Non-dimensional forces and efficiency relations are defined in order to present the wedge water entry characteristics. Congruent patterns are observed between the performance curves of the propeller and the wedge in different fully ventilated or partially cavitated operation modes. The transition trend from fully ventilated to partially cavitated operation of the surface piercing section of a SPP is studied and analyzed through wedge’s performance during the transitional period.

Numerical simulation and analysis of condensation shocks in cavitating flow

We analyse unsteady cavity dynamics, cavitation patterns and instability mechanisms governing partial cavitation in the flow past a sharp convergent–divergent wedge. Reproducing a recent reference experiment by numerical simulation, the investigated flow regime is characterised by large-scale cloud cavitation. In agreement with the experiments, we find that cloud shedding is dominated by the periodic occurrence of condensation shocks, propagating through the two-phase medium. The physical model is based on the homogeneous mixture approach, the assumption of thermodynamic equilibrium, and a closed-form barotropic equation of state. Compressibility of water and water vapour is taken into account. We deliberately suppress effects of molecular viscosity, in order to demonstrate that inertial effects dominate the flow evolution. We qualify the flow predictions, and validate the numerical approach by comparison with experiments. In agreement with the experiments, the vapour volume fraction within the partial cavity reaches values${>}80\,\%$for its spanwise average. Very good agreement is further obtained for the shedding Strouhal number, the cavity growth and collapse velocities, and for typical coherent flow structures. In accordance with the experiments, the simulations reproduce a condensation shock forming at the trailing part of the partial cavity. It is demonstrated that it satisfies locally Rankine–Hugoniot jump relations. Estimation of the shock propagation Mach number shows that the flow is supersonic. With a magnitude of only a few kPa, the pressure rise across the shock is much lower than for typical cavity collapse events. It is thus far too weak to cause cavitation erosion directly. However, by affecting the dynamics of the cavity, the flow aggressiveness can be significantly altered. Our results indicate that, in addition to classically observed re-entrant jets, condensation shocks feed an intrinsic instability mechanism of partial cavitation.

Study on tip leakage vortex cavitating flows using a visualization method

Experimental investigations of unsteady cavitating flows in a hydrofoil tip leakage region with different gap sizes are conducted to highlight the development of gap cavitation. The experiments were taken in a closed cavitation tunnel, during which high-speed camera had been used to capture the cavitation patterns. A new visualization method based on image processing was developed to capture time-dependent cavitation patterns. The results show that the visualization method can effectively capture the cavitation patterns in the tip region, including both the attached cavity in the gap and the tip leakage vortex (TLV) cavity near the trailing edge. Moreover, with the decrease of cavitation number, the TLV cavity develops from a rapid onset-growth-collapse process to a continuous process, and extends both upstream and downstream. The attached cavity in the gap develops gradually stretching beyond the gap and combines with the vortex cavity to form the triangle cavitating region. Furthermore, the influences of gap size on the cavitation are also discussed. The gap size has a great influence on the loss across the gap, and hence the locations of the inception attached cavity. Besides, inception locations and extending direction of the TLV cavity with different gap sizes also differ. The TLV in the case with [Formula: see text] = 0.061 is more likely to be jet-like compared with that in the case with [Formula: see text] = 0.024, and the gap size has a great influence on the TLV strength.

Numerical analysis of the unsteady cavitation shedding flow around twisted hydrofoil based on hybrid filter model

Cavitation is a common phenomenon in components of fluid machinery and it may induce material damage and vibration. A more accurate and commercial turbulence model is required to predict cavitation. In this paper, we make a combination of filter-based model (FBM) and density correction method (DCM) to propose a new DCM FBM. Firstly, the new DCM FBM and the homogeneous cavitation model are validated by comparing the simulation result with the experiment of cavitation shedding flow around the Clark-y hydrofoil and the filter size is determined as well. Then, the cavitation pattern cycle and shedding vortex structure of the twist hydrofoil experimented by Delft University of Technology were predicted using the DCM FBM. The predicted 3-D cavitation structures and development cycle of twist hydrofoil as well as the collapsing features show a good qualitative agreement with the high speed photography results. Numerical results show that the improved turbulence model could predict the cloud cavity evolution well, including the cloud cavity generation, shedding and dissipation. It is found that the re-entrant jet induced by the by adverse pressure gradient is the main reason to generate the cloud cavity shedding. The secondary shedding is al-so observed which is result from the combination of the radially advancing re-entrant jet and side-entrant jet simulated by the DCM FBM turbulence method.

A Generalized Potential/RANS Interactive Method for the Prediction of Propulsor Performance

This article introduces a generalized potential/Reynolds-averaged Navier-Stokes (RANS) interactive method for the prediction of propulsor performance with an emphasis on the calculation of the steady (axisymmetric) or the time-averaged (non-axisymmetric) effective wake fields. In the RANS solver, the propeller boundary is represented by local source terms. Therefore, this method can be used to efficiently handle different types of propulsor-related multicomponent interaction problems. The scheme is first validated by an open propeller application with a uniform inflow and then applied to a vortical-inflow-propeller interaction case, a contra-rotating propeller case, as well as a hull-rudder-propeller interaction case. Results are compared with RANS (with the propeller modeled as wall boundaries) and experiments. 1. Introduction Predictions of propeller efficiency, propeller forces, and propeller cavitation patterns are of great importance in maritime and offshore industry. These predictions are directly related to fuel efficiency, structural vibration analysis, and noise control. To accurately evaluate the propeller performance, it is essential to consider the mutual influence between the ship hull and the propeller, between different propellers if multiple propellers are used, and between different rows of a propeller if multirow propulsion is employed. To predict the flow field around multiple bodies, finite volume methods are commonly used. In these methods, the fluid domain is usually split into one static domain and one (or several) revolving domain(s) and a mixing plane condition is applied to the sliding interfaces between different domains (Zhuang et al. 2004; Sanchez-Caja et al. 2009). The mixing plane condition circumferentially averages certain fluid quantities on each side of the interface and uses these averaged quantities as the boundary condition to the other side. This treatment neglects the unsteady component of the interaction effect between different bodies (between ship hull/propeller or between different rows of the propeller) so that the problem can be solved as steady. The computational cost of this method can range from several hours to several days depending on the size of the mesh, the type of the propeller, and the computing power (Kinnas et al. 2015). In fact, when the mixing plane condition is applied to the sliding interfaces, the Reynolds-averaged Navier-Stokes method (RANS) actually solves for the mean performance of the propeller. On the other hand, if the mixing plane condition is not applied, RANS can be solved as unsteady, but the computational cost will be much higher.

Tip-leakage cavitation in the clearance of a 2D hydrofoil with fillets: high-speed visualization and PIV/PTV measurements

Tip-clearance cavitation is one of the most aggressive forms of cavitation as it can cause surface erosion of hydraulic machinery elements and, as a result, their fatigue damage and disturb designed operating conditions. At present, the literature lacks for detailed experimental data on the inception and development of this type of cavitation at various flow conditions. In the paper, a tip-leakage cavitation occurring in the clearance between an end face of a 2D hydrofoil (a scaled-down model of guide vanes (GV) of a Francis turbine) and a transparent wall of the test section was studied. The experiments were carried out for different cavitating regimes on the cavitation number and two attack angles of 3° and 9°, with the gap size (tip clearance width) varied in the range from 0.4 to 0.8 mm. In order to determine the cavitation inception conditions and investigate the dynamics of the tip-leakage cavitation, a high-speed visualization was applied. A modified PIV/PTV technique with a diverging laser beam instead of a laser light sheet was used to measure the mean velocity distributions within the gap. It was shown that the cavitation pattern on the suction side of the GV model impacts the dynamics of the leakage flow in the gap but does not affect the sheet cavity formed close to the foil leading edge in the clearance as well as its size and dynamics. When the gap size is increased, the tip-leakage cavitation initiates at higher cavitation numbers or, in other words, conditions for the cavitation occurrence become more favorable.

Experimental investigation of cavitating flow-induced vibration of hydrofoils

The objective of this paper is to investigate the unsteady cavitation behaviors and corresponding cavity-induced vibrations. Experimental results are presented for NACA66 hydrofoils made of stainless steel and POM Polyacetate for various cavitation regimes. A simultaneous sampling technique is applied to analyse the transient cavitating flow structure and corresponding structural vibration characteristics. The results showed that the maximum vibration amplitude keeps relative small for the inception and sheet cavitation, increases dramatically for the cloud cavitation and declines for the supercavitation. As for the cloud cavitation regime, the trend of the vibration velocity goes up with the growth of the attached cavity, accompanied with small amplitude fluctuations, and decreases with large amplitude fluctuations. At the moment the cloud cavity breaks from the primary attached cavity, the vibration velocity hits the peak. As for the effect of hydroelastic response, the main vibration frequency for POM Polyacetate hydrofoil is larger than that for stainless steel hydrofoil due to the larger angle of attack caused by the twist deformation. The cavitation pattern for POM Polyacetate hydrofoil appears to be fragmentized, corresponding to the chaotic hydroelastic response of the hydrofoil, which is mainly attributed to the disturbance caused by the deformation and cavity-induced vibration.

The influence of surface roughness on cloud cavitation flow around hydrofoils

The aim of this study is to investigate experimentally the effect of surface roughness on cloud cavitation around Clark-Y hydrofoils. High-speed video and particle image velocimetry (PIV) were used to obtain cavitation patterns images (Prog. Aerosp. Sci. 37: 551–581, 2001), as well as velocity and vorticity fields. Results are presented for cloud cavitating conditions around a Clark-Y hydrofoil fixed at angle of attack of $$\alpha =8{^{\circ }}$$ for moderate Reynolds number of $$Re=5.6 \times 10^{5}$$ . The results show that roughness had a great influence on the pattern, velocity and vorticity distribution of cloud cavitation. For cavitating flow around a smooth hydrofoil (A) and a rough hydrofoil (B), cloud cavitation occurred in the form of finger-like cavities and attached subulate cavities, respectively. The period of cloud cavitation around hydrofoil A was shorter than for hydrofoil B. Surface roughness had a great influence on the process of cloud cavitation. The development of cloud cavitation around hydrofoil A consisted of two stages: (1) Attached cavities developed along the surface to the trailing edge; (2) A reentrant jet developed, resulting in shedding and collapse of cluster bubbles or vortex structure. Meanwhile, its development for hydrofoil B included three stages: (1) Attached cavities developed along the surface to the trailing edge, with accumulation and rotation of bubbles at the trailing edge of the hydrofoil affecting the flow field; (2) Development of a reentrant jet resulted in the first shedding of cavities. Interaction and movement of flows from the pressure side and suction side brought liquid water from the pressure side to the suction side of the hydrofoil, finally forming a reentrant jet. The jet kept moving along the surface to the leading edge of the hydrofoil, resulting in large-scale shedding of cloud bubbles. Several vortices appeared and dissipated during the process; (3) Cavities grew and shed again.

Effect of blade tip geometry on tip leakage vortex dynamics and cavitation pattern in axial-flow pump

A series of blade tip geometries, including original plain tip, rounded tip on the pressure side and diverging tip towards the suction side, were adopted to investigate the effect of blade geometry on tip leakage vortex dynamics and cavitation pattern in an axial-flow pump. On the basis of the computation, it clearly shows the flow structure in the clearance for different tip configurations by the detailed data of axial velocity and turbulent kinetic energy. The in-plain trajectory, in aspects of the angle between the blade suction side and vortex core and the initial point of tip leakage vortex, was presented using the maximum swirling strength method. The most striking feature is that the inception location of tip leakage vortex is delayed for chamfered tip due to the change of blade loading on suction side. Some significant non-dimensional parameters, such as pressure, swirling strength and turbulent kinetic energy, were used to depict the characteristics of tip vortex core. By the distribution of circumferential vorticity which dominates the vortical flows near the tip region, it is observed that the endwall detachment as the leakage flow meets the mainstream varies considerably for tested cases. The present study also indicates that the shear layer feeds the turbulence into tip leakage vortex core, but the way is different. For the chamfered tip, high turbulence level in vortex core is mainly from the tip clearance where large turbulent kinetic energy emerges, while it is almost from a layer extending from the suction side corner for rounded tip. At last, the visualized observations show that tip clearance cavitation is eliminated dramatically for rounded tip but more intensive for chamfered tip, which can be associated with the vortex structure in the clearance.

Verification and validation of URANS simulations of the turbulent cavitating flow around the hydrofoil

In this paper, we investigate the verification and validation (V&V) procedures for the URANS simulations of the turbulent cavitating flow around a Clark-Y hydrofoil. The main focus is on the feasibility of various Richardson extrapolation-based uncertainty estimators in the cavitating flow simulation. The unsteady cavitating flow is simulated by a density corrected model (DCM) coupled with the Zwart cavitation model. The estimated uncertainty is used to evaluate the applicability of various uncertainty estimation methods for the cavitating flow simulation. It is shown that the preferred uncertainty estimators include the modified Factor of Safety (FS1), the Factor of Safety (FS) and the Grid Convergence Index (GCI). The distribution of the area without achieving the validation at the Vv level shows a strong relationship with the cavitation. Further analysis indicates that the predicted velocity distributions, the transient cavitation patterns and the effects of the vortex stretching are highly influenced by the mesh resolution.

Numerical and experimental studies about the effect of acoustic streaming on ultrasonic processing of metal matrix nanocomposites (MMNCs)

Acoustic streaming is a non-linear physical effect which can assist in effective distribution of nanomaterials in a liquid medium subjected to ultrasonic processing. In this study, a time-dependent non-linear computational model was developed to study the effect of various geometrical configurations of the ultrasonic processing cell on the evolution of acoustic streaming flow. Three different geometrical configurations of a flat-bottomed cylindrical processing cell were analyzed for this study. The most well-developed flow pattern is obtained for the geometrical configuration providing the largest acoustic cavitation zone size. Validation of the computational model was performed by two separate experiments − a sedimentation study and processing of a metal matrix nanocomposite (MMNC) composed of an aluminum alloy mixed with carbon nanofibers (CNFs) and silicon carbide (SiC) microparticles. CNFs sonicated in water using the optimum parameters showed the most stable dispersion after 43h of observation. Microstructural analysis of a cast MMNC subjected to ultrasonic processing with the optimum parameters showed the effect of acoustic streaming in achieving more uniform distribution of solidified phases along with nanomaterials within the matrix compared to a mechanically stirred sample. Computational analysis showed that irregular bottom shapes of the processing cell significantly influence the acoustic cavitation and streaming flow patterns. These studies lay the groundwork for future research into optimizing the shape of the processing cell for scaling up ultrasonication to process larger volumes of liquid media.

A study on tip leakage vortex dynamics and cavitation in axial-flow pump

The tip leakage flows and related cavitation in the tip region of an axial-flow pump were investigated in detail using the numerical and experimental methods. The numerical results of the pump model performance were in good agreement with experimental data. The flow structures in the tip clearance were clarified clearly with detailed data involving the axial velocity and turbulent kinetic energy. When depicting the feature of vortex core, the advanced vortex identification method λ2-criterion was used. Simultaneously, the minimum tension criterion was also applied to predict the cavitation inception for different flow rates and it is consistent with the distributions of vorticity and pressure in the vortex core. The roll-up process of TLV is highly three-dimensional and the entrainment would follow different paths. Then, both the numerical and experimental approaches show the cavitation patterns for different cavitation conditions, and it also finds that slight cavitation would promote the development of tip leakage vortex (TLV) while the TLV seems to be eliminated for a low cavitation number, especially before a specific location of blade tip due to the blade loading change induced by cavitation possibly.

Numerical analysis of cavitation shedding flow around a three-dimensional hydrofoil using an improved filter-based model

The cavitation shedding flow around a 3-D Clark-Y hydrofoil is simulated by using an improved filter-based model (FBM) and a mass transfer cavitation model with the consideration of the maximum density ratio effect between the liquid and the vapor. The unsteady cloud cavity shedding features around the Clark-Y hydrofoil are accurately captured based on an improved FBM model and a suitable maximum density ratio. Numerical results show that the predicted cavitation patterns and evolutions compare well with the experimental visualizations, and the prediction errors of the time-averaged lift coefficient, drag coefficient and Strouhal number for the cavitation number, the angle of attack at a Reynolds number are only 3.29%, 2.36% and 9.58%, respectively. It is observed that the cavitation shedding flow patterns are closely associated with the vortex structures identified by the criterion method. The predicted cloud cavitation shedding flow shows clearly three typical stages: (1) Initiation of the attached sheet cavity, the growth toward the trailing edge. (2) The formation and development of the re-entrant jet flow. (3) Large scale cloud cavity sheds downstream. Numerical results also indicate that the non-uniform adverse pressure gradient is the main driving force of the re-entrant jet, which results in the U-shaped cavity and the 3-D bubbly structure during the cloud cavity shedding.

Study on unsteady tip leakage vortex cavitation in an axial-flow pump using an improved filter-based model

The aim of the present investigation is to simulate and analyze the tip leakage flow structure and instantaneous evolution of tip vortex cavitation in a scaled axial-flow pump model. The improved filter-based turbulence model based on the density correction and a homogeneous cavitation model were used for implementing this work. The results show that when entering into the tip clearance, the backward flow separates from the blade tip near the pressure side, resulting in the generation of a corner vortex with high magnitude of turbulence kinetic energy. Then, at the exit of the tip clearance, the leakage jets would re-attach on the blade tip wall. Moreover, the maximum swirling strength method was employed in identifying the TLV core and a counter-rotating induced vortex near the end-wall successfully. The three-dimensional cavitation patterns and in-plain cavitation structures obtained by the improved numerical method agree well with the experimental results. At the sheet cavitation trailing edge in the tip region, the perpendicular cavitation cloud induced by TLV sheds and migrates toward the pressure side of the neighboring blade. During its migration, it breaks down abruptly and generates a large number of small-scale cavities, leading to severe degradation of the pump performance, which is similar with the phenomenon observed by Tan et al. [35].