Cavity Shedding Research Articles

Dynamics of unsteady compressible cavitating flows associated with the cavity shedding

The main purpose of this work is to shed light on the physics involved in the two distinct cavity cloud shedding mechanisms in cloud cavitating flows, namely re-entrant jet mechanism (RJM) and shock wave propagation mechanism (SWM). A compressible cavitating flow solver, which considers the compressibility effects of both liquid and vapor, is used to account for the wave dynamics in cavitating flows. The compressible Navier-Stokes equations, coupling the mass, momentum energy equations, and phase fraction transport equation, along with the thermodynamic equations of state for both liquid and vapor, Saito cavitation model and the SST-SAS turbulence model, are solved. Numerical results are presented for the conditions of both the re-entrant jet mechanism and shock wave mechanism around a NACA66 (mod) hydrofoil (Leroux et al., 2005), respectively, with emphasis on the process of re-entrant jet development and shock wave formation and propagation. The results show that the re-entrant jet can cause the attached cavity sheet breakup for both the two cavity cloud shedding mechanisms in both high and low angle of attack, while the shock wave formation and propagation process only occurs under shock wave mechanism at low angles of attack. Pressure evolution illustrates that in the re-entrant jet mechanism, cavity cloud collapse will induce high pressure load, while no shock wave and thus the corresponding rebound phenomenon are observed. In shock wave mechanism, during the whole process of the shock wave dynamics, namely generation, propagation and rebound process, pressure fluctuations increase sharply along with the generation of the pressure peaks with large amplitude and short time interval. Further study on the compressible characteristics involved in the two cavity shedding mechanisms illustrates that vapor fraction and mass transfer have a significant effect in sonic speed and Mach number characteristics. The average and standard derivation of maximum Mach number (Mamax) in shock wave mechanism is lower than that in re-entrant jet mechanism. Cavitating flows are characterized by low sonic speed value in the cavitation region and high sonic speed value in the pure liquid region and a sonic speed boundary layer exists between the two regions, the thickness of which is about the size of the local attached cavity sheet on foil surface. In the process of shock wave generation and rebound, cavity volume and cavity volume rate experience large fluctuations, showing strong cavitation instabilities in shock wave mechanism.

Numerical investigation of the cavity shedding mechanism in a Venturi reactor

The shedding mechanism is a hot topic in cavitation research, and the shedding mechanisms induced by the re-entrant jet and bubbly shock, respectively, have been long studied and debated. In this study, based on experimental research, a numerical investigation of a Venturi reactor is performed using a self-developed compressible cavitation phase-change solver in order to determine the shedding mechanism. Through the quasi-periodic evolution of the cavity, combined with the contour of streamwise velocity and pressure, the main characteristics and physical signs of the re-entrant jet and bubbly shock mechanisms are studied. The effect of the pressure ratio on the shedding mechanism is also studied. It was found that, in a Venturi reactor with a long throat, the evolution of cavitation is divided into an inception stage, a development stage, two shedding stages, and a collapse stage. The main characteristic of the shedding mechanism induced by the re-entrant jet is the separation between the cavity and the wall. The physical sign of this type of shedding is the axial fracture of the whole cavity. Shedding induced by the re-entrant jet dominates the first shedding in the diffusion section. The main characteristic of the bubbly shock shedding mechanism is damage to the cavity caused by pressure waves or shocks, which accelerates cavity shedding and restrains cavity development. The physical sign of this type of shedding is circumferential defects and fractures in the cavity. The second shedding is jointly caused by the re-entrant jet and bubbly shock. The second shedding cavity may collapse rapidly or merge with the newly formed cavity, which can damage or strengthen the newly formed cavity, respectively. With the decrease of the pressure ratio, the effect of the bubbly shock shedding mechanism is weakened.

Data-based analysis of multimodal partial cavity shedding dynamics

Time-resolved X-ray densitometry void fraction measurements and accompanying acoustic emissions have revealed that partial cavity shedding on a hydrofoil can be multimodal, with spontaneous changes in shedding sequence (referred to here as cavitation style) for fixed inlet flow conditions. These spontaneous, intermittent transitions between two physically different shedding styles are examined using data-based image analysis of the cavity flow fields in order to extract the associated physical mechanism leading to style transition. Three data-driven decomposition techniques are compared: proper orthogonal decomposition (POD), dynamic mode decomposition (DMD), and cluster-based reduced-order modeling (CROM), with a primary focus on the latter. The results highlight the utility of CROM over DMD and POD in the context of intermittent event analysis, both in terms of mode interpretability and transition mechanism identification. A frequency-based analysis of the CROM output revealed the existence of a shared harmonic between the different physical cavitation modes which gave further insight to the transition process. The data-based analysis ultimately illuminates the underlying flow mechanism that leads to the style transition, namely the key role of maximum cavity length buildup as it interacts with the vapor cloud collapse downstream of the hydrofoil.

Cavitation-Vortex-Pressure Fluctuation Interaction in a Centrifugal Pump Using Bubble Rotation Modified Cavitation Model Under Partial Load

Abstract Cavitation is a complicated phenomenon in the centrifugal pump. In this work, the improved unsteady calculation model based on bubble-rotation-based Zwart–Gerber–Belamri (BRZGB) cavitation model is used to investigate the cavitation-vortex-pressure fluctuation interaction in a centrifugal pump under partial load with experimental validation. Spatial–temporal evolution of cavitation can be classified into three stages: developing stage, shedding stage, and collapsing stage. The cavitation evolution period is found as 1/4T (T is impeller rotation period), corresponding to the frequency 4fi (fi is impeller rotation frequency). On the analysis of the relative vorticity transport equation, it is revealed that the cavity is stretched by the relative vortex stretching term (RVS) and developed by the relative vortex dilation term (RVD), and they have great influence on the cavity shedding. The peak value of pressure fluctuation intensity occurs near the vapor–liquid interface at cavity rear, and shifts downstream with the cavitation development. The hysteresis between the vapor volume fraction, vorticity, and pressure fluctuation is observed, and the variation of vapor volume fraction is the source of cavitation-vortex-pressure interaction.

Spatial and spectral investigation of turbulent kinetic energy in cavitating flow generated by Clark-Y hydrofoil

In the present paper, the turbulent cavitating flow generated by a Clark-Y hydrofoil is investigated by large eddy simulation (LES) combined with Zwart-Gerber-Belamri (ZGB) cavitation model. In order to shed light on the influence of cavitation on turbulent energy distribution among scales, energy spectrum obtained from the three-dimensional velocity field is firstly applied to turbulent cavitating flow. Spatial and spectral distributions of turbulent kinetic energy are studied for both non-cavitating flow and cavitating flow. Cavitation is found to have a significant effect on the original turbulent flow by inducing more large-scale turbulent structures. The energy spectrum of cloud cavitating flow also experiences a periodic evolution as cavitation develops, and a large amount of turbulent kinetic energy is found to generate as the first shedding, cutoff and second shedding of cavities happen.

Numerical simulation of condensation shock in partial cavitating flow on a hydrofoil

We present a numerical simulation of the so-called condensation shock on a NACA0015 hydrofoil with a finite mass transfer model for the first time. Most recently, condensation shock was indentified in the experimental measurement as a mechanism for partial cavity shedding in the flow past a hydrofoil. Compressible solvers, which were adopted in the previous simulations to study such phenomenon numerically, are extremely time consuming due to the limitation of acoustic Courant number. In this work, we consider a finite mass transfer model for cavitation flow with slightly modification. Our numerical results show that the finite mass transfer model can be successfully applied for calculating the condensation shock in the flow past a hydrofoil. The dynamics of the condensation shock on the hydrofoil is also discussed. The model is proved to be useful for further understanding of the underlying phyiscs of such flow.

Effect of compressibility on bubbly cavitating flows

Cavitating bubbly flows can form in separated flows and shear layers leading to local regions high vapor void fraction, and these flows often exhibit periodic shedding of vaporous clouds. Historically, the presence of a liquid re-entrant flow, driven by the kinematics of liquid flow stagnation, has been identified as an important mechanism leading to cavity shedding. However, high local vapor void fractions can also result in a reduced mixture speed of sound and a possible supersonic flow. Our recent findings on different geometries indicate that propagating bubbly shocks in these flows are a primary mechanism of flow instability. In this study, we discuss the effect of compressibility on four geometries, mainly in the generation of propagating bubbly shocks that can influence the cavitation shedding dynamics. In order to elucidate the differences and similarities of the observed cavitation dynamics, and the influence of compressibility, we report observations from a backward facing step, backward facing wedge, NACA0015 hydrofoil, and a bluff body with a wedge cross section.

Numerical investigation of the cavitating flow structure with special emphasis on the vortex identification method

The three kinds of vortex identification methods, namely, [Formula: see text] criterion, [Formula: see text] criterion and [Formula: see text] method, are then employed to investigate the physical interactions between the cavitation and vortex dynamics around two-dimensional Clark-Y hydrofoil. The results show that compared to the [Formula: see text] and [Formula: see text] criterion, the [Formula: see text] method can capture the vortex structures with both strong and weak vortices, especially for the weak vortices located in the boundary of the cavity and the back region of the re-entrant flow. A proper value of [Formula: see text] in [Formula: see text] method based on the previous studies is then suggested to avoid the pseudo-vortex structure in cavitating flow field due to division by zero. The modified [Formula: see text] method with a proper [Formula: see text] is then applied to analyze the details of vortical structures in the growth of attached cavity, the re-entrant flow development stage and the cloud cavity shedding stage. The results show that the vortical structures are captured in the boundary and rear region of the attached cavity, the intensity and complexity of strong vortices in the rear boundary region of re-entrant flow increased with its development, and the strength and area of vortical structures at the trailing edge of hydrofoil increased with propulsion of cloud cavity before it sheds completely.

Compressibility Effects on Cavity Dynamics behind a Two-Dimensional Wedge

To understand cavity dynamics, many experimental and computational studies have been conducted for many decades. As computational methods, incompressible, isothermal compressible, and fully compressible flow solvers were used for the purpose. In the present study, to understand the compressibility effect on cavity dynamics, both incompressible and fully compressible flow solvers were developed, respectively. Experiments were also carried out in a cavitation tunnel to compare with the computational results. The cavity shedding dynamics, re-entrant jet, transition from bounded shear layer vortices to Karman vortices, and pressure and velocity contours behind the two-dimensional wedge by the two developed solvers were compared at various cavitation numbers.

Numerical investigation of passive cavitation control using a slot on a three-dimensional hydrofoil

Purpose The purpose of this paper is to study the mechanism and suppression of instabilities induced by cavitating flow around a three-dimensional hydrofoil with a particular focus on cavitation control with a slot. Design/methodology/approach The transient cavitating flow around a Clark-Y hydrofoil was investigated using a transport-equation-based cavitation model and the stress-blended eddy simulation model was used to capture the flow turbulence. A homogeneous Rayleigh–Plesset cavitation model was used to model the transient cavitation process and the results were validated with test data. A slot was applied to the hydrofoil to suppress cavitation instabilities, and various slot widths and exit locations were applied to the blade and the cavitation behavior, as well as drag/lift forces, were simulated and compared to investigate the effects of slot geometries on cavitation suppression. Findings The large eddy simulation based turbulence model was able to capture the interactions between the cavitation and turbulence. Moreover, the simulation revealed that the re-entrant jet was responsible for the periodic shedding of cavities. The results indicated that a slot was able to mitigate or even suppress cavitation-induced instabilities. A jet flow was generated at the slot exit and disturbed the re-entrant jet. If the slot geometry was properly designed, the jet could block the re-entrant jet and suppress the unsteady cavitation behavior. Originality/value This study provides unique insights into the complicated transient cavitation flows around a three-dimensional hydrofoil and introduces an effective passive cavitation control technique useful to researchers and engineers in the areas of fluid dynamics and turbomachinery.

LES investigation of sheet-cloud cavitation around a 3-D twisted wing with a NACA 16012 hydrofoil

In this paper, we sought to investigate unsteady cavitating turbulent flows around a twisted three-dimensional NACA 16012 hydrofoil using the large eddy simulation (LES) and volume of fluid (VOF) methods. The one-equation eddy viscosity model (OEEVM) was used to calculate the sub-grid scale (SGS) stress tensor. The compressive velocity VOF technique and the Kunz cavitation model were also employed. Numerical simulation was performed using the interPhaseChangeFoam solver within the OpenFOAM framework. Cavitation simulation was performed at three cavitation numbers within the cloud cavitation regime; that is to say, cavitation numbers: 0.95, 1.15, and 1.35. Afterwards, the details of flow predictions including the pressure, velocity, streamlines, volume fraction of water phase, and turbulent kinetic energy were reported. Cavity behaviours, including growth, shedding, and collapse of the cavity, were considered in detail. Three-dimensional cavity structures such as primary and secondary shedding and the shedding of the U-shaped horseshoe vortex were reported as well. The present work illustrated the side-entrant jets and the radially diverging re-entrant jet corresponding to the three-dimensional effect of the twisted wing. The cavity pattern and the shedding cycle frequency agreed well with the available experimental observations.

Numerical study of the pressure wave-induced shedding mechanism in the cavitating flow around an axisymmetric projectile via a compressible multiphase solver

The periodic shedding of cloud cavitation has been previously assumed to be induced primarily by re-entrant jet based on considerable experimental and numerical studies. However, different shedding mechanisms, including that induced by pressure waves, have recently regained research interest. To conduct a corresponding numerical investigation, the cavitating flow around an axisymmetric projectile is studied using a user-designed solver that considers the compressibility of the three phases and phase change within the OpenFOAM ® framework. Results are compared with those of an experimental study based on Split Hopkinson Pressure Bar (SHPB) technology with high-speed photography. Good agreement on cavity morphology is confirmed between the results. During the first period, a typical re-entrant jet-induced shedding mechanism is observed as the re-entrant jet front coincides with cavity closure. By contrast, their evident separation is noted in the second period, and cavity closure is located in a counterflow area caused by the impact of pressure waves that are radiated by the collapse of a shedding cavity and propagate in liquid water. This observation is never predicted by an incompressible solver used for comparison, thereby indicating that the existence of a different shedding mechanism is highly relevant to compressibility.

Control effect of micro vortex generators on attached cavitation instability

The control effect of micro-vortex generators (VGs) on the instability of attached cavitation was investigated in a series of experiments. The micro-VGs, located at the leading edge of a NACA0015 hydrofoil, were used to alter the near-wall flow and control the attached cavitation dynamics. The effect of the nondimensional height of micro-VGs on the nondimensional cavity length was quantitatively evaluated by regression equations through response surface methodology. The micro-VGs increased the nondimensional cavity length. The counter-rotating streamwise vortices induced by micro-VGs had a rectifying effect on the near-wall flow and withstood the flow disturbance in the spanwise direction. Additionally, the micro-VGs partially suppressed Rayleigh–Taylor instability and Kelvin–Helmholtz instability arising from reverse flow underneath the cavity. Under a partial cavity oscillation (PCO) condition, the growth of sheet cavitation was highly two-dimensional in the spanwise direction, and the cloud cavity shedding had a strict periodicity with a smaller Strouhal number (St) than for the smooth hydrofoil. The shedding cloud cavity was captured in a single spanwise vortex core, which was advected toward the trailing edge of the hydrofoil. The transition from PCO to transitional cavity oscillation (TCO) occurred when the cavity length was larger than 0.8 of chord length. Under the TCO condition, the concave cavity closure line of sheet cavitation on the hydrofoil showed perfect symmetry and the St was nearly constant. As a result of our investigation, the micro-VGs have high potential to manipulate and control the attached cavitation dynamics.

Cavitation vortex dynamics of unsteady sheet/cloud cavitating flows with shock wave using different vortex identification methods

Cavitation is a complex multiphase flow phenomenon with an abrupt transient phase change between the liquid and the vapor, including multiscale vortical motions. The transient cavitation dynamics is closely associated with the evolution of the cavitation vortex structures. The present paper investigates the cavitation vortex dynamics using different vortex identification methods, including the vorticity method, the Q criterion method, the Omega method (Ω), the λ2 method and the Rortex method. The Q criterion is an eigenvalue-based criterion, and in the Omega method, the parameter is normalized, is independent of the threshold value and in most conditions Ω=0.52. The Rortex method is based on an eigenvector-based criterion. Numerical simulations are conducted using the implemented compressible cavitation solver in the open source software OpenFOAM for the sheet/cloud cavitating flows around a NACA66 (mod) hydrofoil fixed at α=6°, σ=1.25 and Re=7.96×105. The flow is characterized by the alternate interactions of the re-entrant flow and the collapse induced shock wave. Results include the vapor structures and the vortex dynamics in the unsteady sheet/cloud cavitating flows, with emphasis on the vortex structures in the cavitation region, the cavity interface, the cavity closure, the cavity wakes, and the foil wakes with the shedding cavity. The comparisons of the various methods, including that the vorticity method, the Q criterion method, the Omega method, the λ2 method and the Rortex method, show the performances of different methods in identifying the cavitation vortex structures. Generally, during the attached cavity growth stage, the Q criteria can well predict the vortex structures in the cavitation region and at the foil trailing edge in the pure liquid region, while with the Omega method and the Rortex method, the vortex structures outside the attached cavity and on the foil pressure side can also be predicted. The λ2 method can well predict the vortex structures in the cavity closure region. During the re-entrant jet development stage, the vortex structures in the re-entrant jet region is weak. During the cavity cloud shedding stage, the vortex dynamics at the foil leading edge covered by newly grown cavity sheet is different from that during the attached cavity sheet growth stage. During the shock wave formation and propagation stage, strong vortex structures with both the size and the strength are observed owing to the cavity cloud shedding and collapse behavior. The influence of the small parameter e in the Omega method on the cavitation vortex identification is discussed.

The characteristics of unsteady cavitation around a sphere

The unsteady cavitation typically includes three processes: the growth of cavitation, the instability and shedding of cavitation, and the collapse of cloud cavitation and the regeneration of attached cavitation. In this paper, the unsteady features of the cavitating flow past a sphere are investigated. A detached eddy simulation turbulence model and a transport equation cavitation model are used to model the cavitating flow. The numerical results give the unsteady process of cavitation at different cavitation numbers (0.36 < σ < 1.0), which cover the cavitation state from inception to supercavitation. When the cavitation number 0.8 < σ < 1.0, the flow instability belongs to the single frequency mode; when the cavitation number σ < 0.8, the flow instability becomes the dual-frequency mode. We analyzed the Strouhal (St) number based on the length of the cavitation and found that the St numbers are stable around 0.5 and 0.2 in the dual-frequency mode. In this mode, the high frequency corresponds to the frequency of the large-scale cavity shedding caused by repeated re-entrant jets. The low frequency, caused by the combination of wake flow and cavitation, is close to the natural frequency of the sphere. In addition, the cavity leading edge position and cavity morphology are analyzed in details. Some of the numerical results are compared with existing experimental data.

Verification and validation of Large Eddy Simulation of attached cavitating flow around a Clark-Y hydrofoil

This study uses implicitly filtered Large Eddy Simulation with a homogenous cavitation model to investigate the transient turbulent cavitating flow around a Clark-Y hydrofoil with emphasis on Verification and Validation (V&V). The numerical results indicate that the present simulation can predict the time evolution process of the periodic cavity shedding and agree reasonably with the available experimental data. This study presents the first practical application of LES V&V in a transient cavitating flow. The three-equation method is used to assess the LES error magnitudes in unsteady cavitating flow. The results show that a noticeable difference can be observed between the modeling error and numerical error, and the former has a larger magnitude than the latter in cavitating flow. It is demonstrated that the unsteady cavitation has a big impact on the LES errors. Additionally, compared with non-cavitating flow, the unsteady cavitation increases the values and fluctuation amplitudes of numerical, modeling, and total errors. Grid requirement for modeling the cavitating flow has been discussed from the viewpoint of LES V&V. The numerical results also reveal that the periodic cavity shedding causes the complex and turbulent flow feature by vortex and spectrum analyses, and this has a great influence on the simulation accuracy.

Stabilization of cloud cavitation instabilities using Cylindrical Cavitating-bubble Generators (CCGs)

Unsteady cloud cavitation phenomenon is an important subject due to its undesirable effects in various applications such as ship propeller, rudder and hydraulic machinery systems. We present an efficient passive control method to control the cavitation instabilities which may be caused by the shedding of cavity structures in the vicinity of the solid surface of an immersible body. We proposed a passive control method so called Cylindrical Cavitating-bubble Generators (CCGs) on the surface of a benchmark hydrofoil and analyzed the effects of this passive controller on the dynamics of the unsteady cloud cavitation. First we modeled the unsteady cavitating flow around the hydrofoil without CCGs using a hybrid URANS model which was implemented in an open source code. Next, we studied the effect of CCGs on the mechanism of the unsteady cloud cavitation. The results show that using this method, the unsteady cavity structure was changed to a quasi-stable cavity structure compared with the cloud cavity shedding in the case without CCGs. We observed that the instability behavior of the unsteady cloud cavitation was mitigated and only small-scale cavity may be shedded from the hydrofoil in the free stream flow away from the hydrofoil surface. A notable reduction in cavitation-induced vibration and high wall-pressure peaks on the solid surface was observed.

Development of a multiphase cavitation solver and its application for ventilated cavitating flows with natural cavitation

The aim of this article is to develop a cavitation solver capable of dealing with the cavitating flow where more than three phases coexist based on the OpenFOAM platform. A new phase change class coupled with newly reported cavitation models and turbulence models has been implemented in the solver. Firstly, validations have been carried out using cases of a two-dimensional cavitating hydrofoil and a three-dimensional projectile near the free surface. The pressure distribution and the gas-liquid interface profile agree well with the experimental data. The solver is then applied for a base-ventilated cavitating hydrofoil with different angle of attack where natural cavitation could occur simultaneously on the hydrofoil surface. The cavity shape as well as the transient cavity shedding process are correctly predicted using the PANS turbulence model. The resulting velocity and pressure distributions are clearly analyzed, giving great insights into the formation and deformation mechanisms of the ventilated cavity. The developed solver is proved to be accurate and efficient in solving the details of turbulent multiphase flows with phase change occurring and has great potential for future applications.

Multimodal partial cavity shedding on a two-dimensional hydrofoil and its relation to the presence of bubbly shocks

The shedding dynamics of partial cavitation forming on a NACA0015 hydrofoil is known from the previous studies to be multimodal, exhibiting abrupt changes in Strouhal number as the cavitation number is reduced (Arndt et al. in Instability of partial cavitation: a numerical/experimental approach. National Academies Press, Washington, D.C., Retrieved from the University of Minnesota Digital Conservancy. http://hdl.handle.net/11299/49781 , 2000). The present study aims to understand the underlying shedding mechanisms responsible for this abrupt change in dynamics. As was observed in Ganesh et al. (J Fluid Mech 802:37–78, 2016), the shedding process can result from both re-entrant liquid flow and the formation of propagating bubbly shock waves within the cavity. Time-resolved X-ray densitometry and high-speed videography are combined with time synchronous measurements of acoustic noise produced by the cavity to examine the formation and shedding of the partial cavitation on a NACA0015 hydrofoil. From the experiments on the hydrofoil, it was observed that the mean cavity length increased with decreasing cavitation number, as expected. At higher pressures, stable partial cavities formed that shed smaller vapor clouds mainly due to the re-entrant liquid flow in the cavity closure. With a reduction in cavitation number, the partial cavity grew in length, and shedding often occurred when the cavity was pinched-off from its leading edge. Once a large region of vapor was shed, the pressure pulse caused by its subsequent collapse could suppress the growth of the newly forming partial cavity. This feedback led to complex, multistep cavity shedding dynamics. At still lower cavitation numbers, bubbly shocks were found to be responsible for the strongest periodic shedding of vapor clouds. Spectral analysis of the acoustic signal revealed a multimodal nature, which was more pronounced at lower cavitation numbers, and similar dynamic behavior was also found for the time varying local void fraction measurements in the vicinity of cavity closure. The occurrence of strongest multimodal behavior was also characterized by the presence of bubbly shock waves as the dominant mechanism of shedding. From the measurements and analysis, it is concluded that at least four different types of shedding modes occurred over a range of cavitation numbers at a fixed attack angle (10°).

Numerical modeling and simulation of the shedding mechanism and vortex structures at the development stage of ventilated partial cavitating flows

Abstract Ventilated partial cavitation is a complex multi-phase turbulent flow due to the strong interactions between gas and liquid. In the present work, we specially focus on the numerical modeling and simulation of the shedding mechanism and vortex structures. The Reynolds Averaged Navier–Stokes (RANS) method combined with a filter-based turbulence model (FBM) is proposed to explore the physical mechanism of the ventilated partial cavitating flows. Experimental results of cavity evolution and pressure are utilized to assess the prediction ability of the proposed method. Good agreements are observed between experimental measurements and numerical predictions, including the ventilated cavity growth, break off, shedding and the transient dynamic pressure inside the cavity. Based on the model strategy, the cavity dynamic evolution and shedding mechanism are analyzed. The results indicate that the re-entrant flow gives birth to the gas leakage at the cavity interface and is responsible for the ventilated cavity shedding. In addition, streamline vortex is presented to reveal the ventilated cavity shedding characteristics. Moreover, based on the vorticity transport equation, the influence of velocity gradient, fluid volumetric expansion/contraction, pressure gradient and the viscous dissipation factors on the vortex production in ventilated cavitating flows is examined. The present study can provide important basis to better understand the shedding mechanism and vortex structures on the development stage of ventilated partial cavitating flows.