Hydrofoil Surface Research Articles

Research on pressure reconstruction of cavitation hydrofoil surface based on compressed sensing

The development of hydrofoil cavitation has obvious unsteady characteristics that induce complex pressure variation on the hydrofoil surface. In this work, an algorithm for the pressure reconstruction of the foil based on compressed sensing (CS) technology combined with proper orthogonal decomposition (POD) and particle swarm optimization (PSO) is proposed. Based on the dataset produced by numerical simulation, the pressure field reconstruction with the algorithm is demonstrated to have good accuracy, generalization, and robustness. Firstly, the impact of the number of truncated POD modes and measuring points on the error of the algorithm reconstruction is researched that the error shows a downward trend with the rise in these two elements. Then the sensitivity of the algorithm reconstruction to the hydrofoil characteristics is investigated. It is found that the reconstruction results are more accurate than other stages when the foil is attached to the cloud cavitation and the reconstruction accuracy of the algorithm is proportional to the stability of the flow field. Finally, it is shown that the algorithm can be applied for the reconstruction of different flow parameters of the same model. The placements of the measuring points learned by the algorithm are more likely to be trained to the relatively unstable region.

Unsteady numerical simulation method of hydrofoil surface cavitation

To improve the accuracy of hydrofoil unsteady cavitation simulations, we investigate grid irrelevance and discrete error using the GCI evaluation method to determine the optimal number of grids. Numerous turbulent viscosity correction approaches are used to improve the turbulence model, and numerical simulations are conducted in conjunction with unsteady cavitation of the hydrofoil with a 3° angle of attack, as well as application evaluation. The results indicate that the DCMFBM model produces the most accurate unsteady cavity shape of the hydrofoil surface. The details of the cavity's primary and secondary shedding are captured during the cavitation process. The DCMFBM turbulence model with a density correction index of 10 and a filter parameter of 0.15c has the highest simulation accuracy. The flow structures of sheet cavitation, transition state cavitation, cloud cavitation, and cavitation shedding are analyzed. The mechanism of hydrofoil cavitation instability and shedding is revealed, providing a theorem.

Evaluation of effect of micro-vortex generator on dynamic characteristics of unsteady partial cavitating flow over hydrofoil

The unsteady characteristics of cavitation induce a series of destructive effects, such as cavitation erosion, vibration, and noise. Passive control of hydrofoil cavitation involves changing the structure or material of the hydrofoil surface, thereby inhibiting cavitation damage, and vortex generators (VGs) are the most popular means of passive control because of their effectiveness, simplicity, and lower production and installation costs. In this study, a new VG structure that can improve the cavitating flow state of a hydrofoil is proposed. A multiphase volume-of-fluid model is used to capture the interface between different phases, the Schnerr–Sauer model is used to describe the cavitation process, and turbulence is modeled by large-eddy simulation. The evolution characteristics of the cavitating flow field around a National Advisory Committee for Aeronautics (NACA) 0015 hydrofoil are investigated numerically both with and without the VG to illustrate its control effect. It is found that the VG can change the hydrodynamic characteristics of the cavitating flow field around the hydrofoil, such as the cavity morphology, the vortex structures, and the peak and power spectral density of the pressure. Upon using Lagrangian coherent structures, the motion state of the fluid particles and the distance between adjacent fluid particles are found to change dramatically with time under the effect of the VG. Upon using dynamic mode decomposition, the VG is found to decrease the energy in the first three modes, whereas that in mode 4 is larger without the VG, thereby suggesting that the VG might help to reduce flow noise. Finally, it is found that the VG converts laminar flow to turbulence, thereby increasing the turbulence intensity of the wake flow field and decreasing the maximum value of the turbulence integral scale.

Experimental and Numerical Studies into the Cavitation Impact of the Hydrofoil Surface with Different Treatments

Experimental and Numerical Studies into the Cavitation Impact of the Hydrofoil Surface with Different Treatments

Numerical study on drag reduction and wake modification for the flows over a hydrofoil in presence of surface heterogeneity

In this article, direct numerical simulations of flow around NACA0012 hydrofoil with superhydrophobic surface (SHS) is presented. Surface heterogeneity takes into account by periodic no-slip and shear-free grates on the surface. The study is conducted for a range of [Formula: see text] degree angles of attack and at fixed Reynolds number ( Re) 1000. SHS leads to effective Navier slip on the hydrofoil surface and corresponding changes in velocity profile. Bubble separation delays for higher gas-fraction ( G.F), and minimizes the vortex shedding effects. As a result, flow remains two-dimensional (2D) for higher angles of attack as compared to flow over three-dimensional (3D) hydrofoil with no-slip boundary. Both the drag reduction and enhancement of lift force are observed. Maximum lift are observed at [Formula: see text], while the drag force continues to decrease with the gradual increase in angle of attack and patterned micro-grates fraction. Mode C with smaller wavelength is observed at [Formula: see text]. Furthermore, increase in gas-fraction leads to increase in slip length which thickens the boundary layer and mimics the vorticity implies drag reduction. Thus, replacement of the no-slip surfaces by superhydrophobic surfaces can be treated as a promising drag reduction technology.

Investigating The Effects Of Cylindrical Appandages On Hydrofoil Surface To Formation Of Cavitation

Bilgisayar teknolojilerindeki gelişmelere paralel olarak hesaplamalı akışkanlar dinamiği (HAD) yaklaşımlarındaki büyük ilerlemeler, kavitasyon alanında da gerçekçi analizlerin yapılabilmesine imkan vermiştir. Bu çalışmada NACA661-012 kanat profiline sahip bir hidrofoilin önder kenar bölgesinde, emme yüzeyine farklı konumlarda ve yarıçaplarda silindirik eklentiler yerleştirilmiş ve bunların kavitasyon oluşumuna etkileri araştırılmıştır. Öncelikle orijinal hidrofoil için kavitasyonlu ve kavitasyonsuz durumda analizler gerçekleştirilmiş ve uygulanan HAD yaklaşımının literatürde bulunan deneysel ve sayısal sonuçlar kullanılarak doğrulaması yapılmıştır. Daha sonra silindirik eklentilerin yerleştirildiği, 6o hücum açısına sahip modifikasyonlu hidrofoillerin kavitasyonlu durumdaki analizleri gerçekleştirilmiş ve hidrodinamik parametreleri belirlenmiştir. Analiz sonrası süreçlerde, söz konusu eklentilerin kavitasyon oluşumuna ve diğer hidrodinamik parametrelere olan etkileri incelenmiştir. Eklentilerin bir kısmının kavitasyon oluşumunu azalttığı, bir kısmının önemli bir etki yaratmadığı ve bir kısmının da olumsuz etki yaratarak kavitasyon miktarını artırdığı görülmüştür. Bununla birlikte bir hidrofoilin performansını belirleyen kaldırma ve sürükleme kuvvetlerinin de farklı eklentilerle olumlu veya olumsuz yönde değişebildiği görülmüştür. Sonuç olarak mevcut bir kanat profiline yapılacak küçük modifikasyonlarla kanat profilini değiştirmeden kavitasyonun olumsuz etkilerinin iyileştirilebildiği anlaşılmıştır.

Numerical investigations of the free surface flow around a surface piercing hydrofoil

Starting with January 2013, naval architects faces new challenges, as all ships greater than 400 tons must comply with energy efficiency index (MPEC 62, 2011). From ship hydrodynamics point of view one handy solution is using Energy Saving Devices (ESD), with the main purpose to improve the flow parameters entering the propeller. For ballast loading condition the ESD may intersect the free surface disturbing and complicating the flow due to free surface /boundary layer interaction, turbulence and breaking wave effects that coexist and which are not completely clarified so far. Therefore, a free surface flow around a NACA 0012 surface piercing hydrofoil is numerically investigated and the results are compared to experimental results obtained in the Towing Tank of the Naval Architecture Faculty, “Dunarea de Jos” University of Galati. The comparison includes drag and free surface elevation on hydrofoil surface together with numerical uncertainty.

Statistical analysis of vapor distribution in a cavitation flow based on an ensemble of instantaneous liquid velocity fields

A new method was developed for statistical analysis of ensembles of instantaneous velocity fields measured by PIV in liquid (continuous phase) to determine the distribution of the vapor phase in cavitating flow. The method is based on two main principles: the absence of tracers used for PIV measurements in vapor, and the statistical independence of individual measurements. This allowed establishing an exponential dependence of repeatability of the vapor phase at a certain point of a cavitating flow. Compliance with this theoretical law was verified using the Pearson chi-square test. All theoretical distributions were divided into several groups depending on the time-averaged local vapor content calculated over the entire ensemble of realizations and the probability of a single event. As a result, dimensions of the stationary part of an attached cavity and the place of detachments of cloud cavities from the hydrofoil surface were determined using the new method of statistical analysis for an unsteady cloud cavitation regime.

Study on energy extraction of Kármán gait hydrofoils from passing vortices

How swimming fish extract energy from environmental vortices is still an open question. In this work, fish swimming in unsteady flow is numerically investigated by using the immersed boundary lattice Boltzmann method. The swimming fish is modeled as a forced Kármán gait hydrofoil, and the vortical flow is generated by a stationary circular cylinder. We calculate the Fourier spectra of hydrodynamic forces on the hydrofoil surface and found that there is a coupling between lateral force and drag, which results from a nonlinear wave interaction. The Kármán gait hydrofoil adjusts the lateral force by applying lateral excitation to the vortical flow and improves the drag/thrust through nonlinear wave interaction. We find that suppressing the harmonic energy of the viscous mode is the key ingredient to extract energy from the passing vortex. In turn, the downstream distance LN and foil-vortex phase φ determine whether the viscous harmonic energy can be suppressed. If the viscous mode harmonic is strong, the interaction between the vortex shedding mode and the viscous mode leads to a series of combined modes, which extract energy from the fundamental mode. These combined modes that appear in the fluid force spectra reduce the efficiency of energy extraction.

Cavitation generation and inhibition. II. Invisible tail wing of cloud cavitation and non-cavitation control mechanism

The cloud-cavitation shedding mechanism was numerically investigated around the NACA 0015 hydrofoil of α = 7° and σ = 0.7, 0.67 under the identical computational conditions as in Paper I [W. Jin, AIP Adv. 11, 065028 (2021)]. We discovered the invisible tail wing and self-inhibition effects of cloud cavitation. As the invisible tail wing of cloud cavitation swings up, the generated re-entrant jet causes cavitation shedding or collapse by the “sweeping and ejection” processes and simultaneously moves away turbulence kinetic energy (TKE) from the near-wall flow fields of the leeward hydrofoil surface, stopping the cavitation generation. In low pressure regions, non-uniform TKE intensity distributions cause different water-vapor volume fractions, resulting in discontinuity of cavitation generation. The attached vortex accompanying an individual cavity is defined, which causes fluctuations and cavitation instability on the bottom of the cavity. The cavity-bubble truncation and stretching are two primary transition mechanisms from the sheet to cloud cavitation. Compared with the invisible tail wing of cloud cavitation, the fixed unilateral wing can more effectively inhibit the cloud shedding because it can redistribute energies to two hydrofoil surfaces and transfer the strong TKE intensity from the minimum to the high-pressure region, which inhibits flow boundary layer separation and achieves non-cavitation control of the hydrofoil. Energy transfer and balance are the most effective mechanisms for inhibiting cloud cavitation. Larger unilateral wing sizes result in weaker TKE intensity along the leeward hydrofoil surface as well as more significant cloud-cavitation inhibition. The TKE intensity in the leading edge of the leeward hydrofoil surface determines the fluid boundary layer separation and cloud-cavitation stability.

Euler–Lagrange study of cavitating turbulent flow around a hydrofoil

This study presented a multi-scale Eulerian–Lagrangian approach to simulate cavitating turbulent flow around a Clark-Y hydrofoil to study the bubble dynamics. A large eddy simulation was coupled with the volume of fluid method to capture the large vapor volumes in an Eulerian analysis. Micro-scale Lagrangian bubbles were then tracked by solving compressible the Rayleigh–Plesset equation and a bubble motion equation. A Gaussian kernel function was used to model the interactions between the flow field and the vapor bubbles in a coupled two-way algorithm. The predictions give satisfactory agreement with experimental data for the bubble size oscillations, bubble motion, and cavity shedding characteristics. Further investigations analyzed the influence of various parameters on the transformation between the Euler and Lagrange models. The numerical results provide detailed information about the influence of the cavitating turbulent flow on the bubble behavior, especially how the reentrant jet significantly affects the bubble generation and motion. The calculations also capture the bubble size oscillations caused by the surrounding liquid pressure variations and how these generate very high local pressures near the surface. The results show that the pressure wave released as a bubble is compressed reaches 107 Pa, which may cause cavitation erosion of the hydrofoil surface. This research provides a promising method to better investigate the bubble motion characteristics in macroscopic flows and demonstrates that the cavitation erosion caused by bubble size oscillations is significant and deserves attention.

Influence of water injection on broadband noise and hydrodynamic performance for a NACA66 (MOD) hydrofoil under cloud cavitation condition

Cavitation and its induced noise have negative effects on the hydrodynamic performance of underwater devices such as marine propellers. In this paper, a new flow control method of water injection is proposed to investigate its influence on the flow field around NACA66 (MOD) hydrofoil under the condition of cloud cavitation (Cavitation number σ = 0.83, Reynolds number Re = 5.1 × 105). The density corrected turbulence model (DCM) combined with Zwart-Gerber-Belamri cavitation model (ZGB) is used to simulate the hydrodynamic performance and the pressure fluctuation, while the dipole noise and quadrupole noise are calculated by Broadband noise source models. The numerical results are in good agreement with our previous experimental observations. The results are all compared with those for the original hydrofoil without water injection and show that the injected water noticeably weakens the severe pressure fluctuation on the hydrofoil suction surface and reduce the volume of cavitation by 72.89%. The water injection also performs well on drag reduction, which reduces the drag coefficient by 17.9%. The dipole noise on the hydrofoil surface is effectively suppressed, and the Curle Acoustic Power (AP) for over 50 dB is decreased by 28.99%. It is also found that the water injection significantly reduces the region of over 45 dB for Proudman AP by 46.21%. The water injection improves the stability of the flow field by means of providing extra energy, blocking the re-entrant jet, hindering the evolution process of turbulence and weakening the impact of the fluid on the hydrofoil wall.

Numerical study on hydrodynamic performance and flow noise of a hydrofoil with wavy leading-edge

Flow control based on bionics provides new research ideas for noise reduction. As one of the flow control methods, the wavy leading edge (WLE) inspired by the leading edge tubercles of the humpback whale is proposed in this paper. The hydrodynamic performance and flow noise of a National Advisory Committee for Aeronautics 0020 hydrofoil subjected to three WLEs are numerically investigated. A hybrid numerical method of large eddy simulation combined with the Ffowcs Williams–Hawkings equation is adopted to obtain the unsteady flow properties and predict the far-field noise. At a Reynolds number of 3.05 × 105, the simulation results show that the addition of WLEs can reduce the lift coefficient fluctuation but will increase the drag coefficient slightly. In addition, the WLE can reduce the OverAll Sound Pressure Level of the hydrofoil by up to 7.28 dB. The analysis of the flow features shows that the WLE can reduce the pressure fluctuation on the hydrofoil surface, which is directly beneficial to the noise reduction. Moreover, the WLE enhances the spanwise flow of the hydrofoil, produces streamwise vortices, and reduces the spanwise coherence coefficient at both the leading edge and trailing edge.

Temperature and skin-friction maps on a lifting hydrofoil in a propeller wake

There are at least two direct links between the friction acting on the surface of a (slightly warmer or colder) body under the influence of an incompressible flow and the temperature distribution on the surface of the body itself. The first relies on the energy equation, which connects the evolution of the temperature distribution at the wall to the action of the skin-friction field. On the other hand, the equation of passive transport of temperature perturbations at the wall unveils a direct relationship between the celerity of propagation of thermal blobs and the friction velocity. Grounding on these relationships, this paper reports about the application of different methodologies, developed to determine skin-friction fields from surface temperature maps, to the analysis of the complex flow evolution on a lifting NACA 0015 hydrofoil immersed in a non-uniform, unsteady wake induced by a marine propeller. The adopted temperature-sensitive paint technique allows obtaining the global temperature data with the appropriate, high resolution in space and time. The approach based on the energy equation leads to an unconventional, single-snapshots optical-flow-like methodology, which allows obtaining time-resolved, relative skin-friction fields. The two approaches based on the displacement of the wall temperature perturbations enable the determination of time- and phase-averaged, quantitative skin-friction fields. One approach grounds on a classical tracking of the thermal disturbances via optical flow, the other one relies on minimizing the discrepancy between the celerity of propagation of thermal fluctuations and the behavior expected according to the Taylor hypothesis. The analysis of the skin-friction fields obtained via the three uncorrelated, complementary approaches discloses the evolution and the mutual interaction of different flow structures (manifolds) over the hydrofoil surface at lifting and zero-lift conditions: the hub and tip vortices, the blade wake, the laminar separation bubble, and the separation at trailing edge.

Cavitation generation and inhibition. I. Dominant mechanism of turbulent kinetic energy for cavitation evolution

Through energy conservation and transformation perspectives, we numerically investigated the physical mechanism of cavitation generation surrounding the two-dimensional NACA 0015 hydrofoil using the mass-transfer cavitation model and modified-RNG k-epsilon model. Cavitation generation is triggered by strong turbulent kinetic energy (TKE) with pressure below the saturation pressure. However, cavitation development absorbs TKE as phase-change energy and decreases kinetic energy in near-wall flow fields, thereby increasing pressure according to the energy conservation law. The increased pressure closes the cavity and generates an attached vortex or re-entrant jet, which causes cavitation collapse, conversely decreasing the pressure to the saturation pressure in the leading edge. Simultaneously, the cavitation collapse releases phase-change energy that increases TKE to a maximum so that a new period begins. Cavitation evolution is an interaction between the vapor and liquid flow fields associated with energy conservation and transformation among TKE, pressure, and phase-change energy. Beyond 50% of the chord length, the TKE and pressure-energy in the near-wall flow fields decrease, resulting in the cavitation instability. Within the cavity, the relationship between the local TKE intensity and the volume fraction of water vapor is quantitatively defined as a linear function. Two designs are proposed for the verification of the mechanism and cavitation inhibition, namely, grooves on the hydrofoil surface and bilateral wings in the tail. Grooves do not affect TKE intensity significantly and hence cannot change the cavitating flows. Bilateral tail-wings transfer TKEs from the leading edge to the wake flows and inhibit the cavitation remarkably. The TKE distribution is the dominant mechanism for cavitation generation and stability.

Dynamics of the supercavitating hydrofoil with cavitator in steady flow field

Maintaining stability remains a crucial issue for the safety of underwater vehicles, especially during high-speed navigation where flow cavitation may occur. Cavitators are small protrusions on the hydrofoil surface, which can be used to control the patterns of flow cavitation. In this study, we investigate the effect of cavitators on supercavitating flow and hydrodynamic forces for high-speed hydrofoil. The volume of fluid method and the large eddy simulation turbulence model with the Kunz cavitation model are used in the simulations in order to accurately capture the interface between two phases (water and vapor) and the region of flow supercavitation. To validate the numerical method, the time-averaged simulated results of the supercavitating flow over a wedge-shaped hydrofoil are compared and validated against the experimental data by Kermeen (“Experimental investigations of three-dimensional effects on cavitating hydrofoils,” Technical Report No. 47-14, Engineering Division of the California Institute of Technology, Pasadena, CA, 1960). Then, the numerical method is used to simulate the supercavitating flow of two-dimensional and three-dimensional cases with and without the cavitator placed on the lower side of the hydrofoil. The simulations were conducted for the cavitator located at the 1/32, 1/16, 1/8, and 1/4 chord of the hydrofoil at various angles of attack 1°–12° and cavitation numbers at 0.1, 0.2, and 0.4. A detailed analysis is made to examine the relations between cavitation pattern, hydrodynamic forces, and cavitator placement location. Compared to the cases without the cavitator, the supercavitating flow over the hydrofoils controlled by the cavitator demonstrates a significant difference in lift, whereas the drag does not change much. The changes in lift are closely related to the cavitator location. These findings can serve as a good guidance on how to improve the hydrodynamic performance and stability condition of a high-speed hydrofoil/wing using the cavitator.

Evaluation of vorticity forces in thermo-sensitive cavitating flow considering the local compressibility

The correlation between hydrodynamic forces and cavity evolution has been widely investigated but has not been deeply revealed. This study uses force element method to analyse the characteristics of force evolution along with cavitation around a NACA0015 hydrofoil. A modeling framework using the mixture two-phase flow model considering the energy convection and compressibility is proposed, to investigate the compressibility and thermal effects in the thermo-sensitive cavitating flow. Moreover, a force element method is applied for evaluating vorticity forces. The evolution of lift and drag coefficients under different cavitation numbers is mainly studied. Results indicate that, with increasing cavitation number, the time-averaged lift and drag coefficients firstly rise and then decline. However, the drag coefficient decline trend is greater than the lift coefficient. Combined with cavity evolution, the transient lift and drag evolution is analysed. Positive lift elements are mainly concentrates on the cavity surface and transport with cavity development, but the rupture of detached cavity and the pressure wave will inhibit the growth. The lift force reaches its peak when the cavity forms with the attached cavity that is completely detached from the hydrofoil surface, because of the volume of positive lift element reaches its maximum. Except for the shearing fracture of leading edge with the effect of fluid impact, the evolution of drag elements is similar to the lift. This studies shows that the force element method can well reveal the mechanism of force evolution due to the cavitation.

Numerical Simulation of Ventilated Cavitation Evolution with an Insight on How Ventilation Influences Pressure Fluctuation and Cavitation Noise

Cavitation occurred in hydraulic machines can generate severe pressure fluctuations and induce high-pitched noise. Ventilated cavitation (inject air into the cavitating flow) is one of the most effective ways to control cavitation and then alleviate the noise and fluctuations. Thus, the evolution of ventilation cavitation around a NACA0015 hydrofoil was numerically investigated with a modified model. The results indicated that the ventilated cavitation consists of two parts: the attached cavity which attached to the leading edge of the hydrofoil and the detached cavity which detached from the hydrofoil surface. With the air injection increased, the detached cavity becomes larger. Besides, the ventilated cavity evolves periodically along with two opposite vortexes which fall off in turn near the tailing edge of the hydrofoil. Among three ventilation volumes, an air injection of 250 L/min presents the best alleviation on pressure fluctuation induced by cloud cavitation. The acoustic analysis indicated that air injection is an effective way to alleviate the cavitation induced noise. With air injected into the flow, two new types noises induced by the ventilated cavitation has been detected by monitoring points along the upper side and behind of the hydrofoil: the lower frequency noise induced by the waving of attached cavity and the higher frequency noise induced by the shedding of the detached cavity. While with the air injection increased, both of the two types noises increased. The acoustic and dynamic patterns under different air injection conditions are able to provide guidance in engineering application.

Water Energy Resource Innovation on the Cavitation Characteristics

Abstract The main purpose of this study is to numerically correlate the amount of generated vapor over a hydrofoil to the lift and drag coefficients acting on it. Cavitation characteristics were investigated of a hydrofoil in the cavitating, sub-cavitating, and non-cavitating flows for different angles of attacks (AoA) with the high upstream flow velocity. The hydrofoil was tested in a square water tunnel with water entering the tunnel at various velocities for each AoA ranges from 9.1 m/s to 12.2 m/s. It was found that lift and drag forces acting on the hydrofoil follow the trend of the experimental data quite closely. While the cavitation can be identified by a unique number (averaged vapor volume fraction), the work done created an inverse correlation between this number and the cavitation number at the same angle of attack. The lift force declines with the increase in the vapor content on the hydrofoil surface, meanwhile the drag force peaks at certain vapor volume fraction, and then, a huge reduction occurs with the considerable decrease in the corresponding cavitation number. A fourth-order correlation generated between the lift to drag (L/D) and the cavitation number (σ). It was found the lift-to-drag ratio decreases by the formation of the cavitation over the hydrofoil, thus causing a drop in the efficiency of the turbomachines.

Active Control of Unsteady Cavitating Flows Over Hydrofoil

Abstract A preliminary two-dimensional (2D) numerical investigation of the active control of unsteady cavitation by means of one single synthetic jet actuator (SJA) is presented. The investigation involves the cloud-cavitating flow of water around a NACA 0015 hydrofoil with an angle of attack of 8-deg and ambient conditions. The SJA locates on the suction side at a distance of 16% of the chord from the leading edge; it has been modeled by means of a user-defined velocity boundary conditions based on a sinusoidal waveform. A Eulerian homogeneous mixture model has been used, coupled with an extended Schnerr–Sauer cavitation model and a volume of fluid interface tracking method. As first, a sensitivity analysis allowed to evaluate the influence of the main control parameters, namely, the momentum coefficient Cμ, the dimensionless frequency F+, and the jet angle αjet. As a result, the best performing SJA configuration was retrieved at Cμ=0.0002, F+=0.309, and αjet=90 deg, which led to a reduction of both the average vapor content and the average torsional load in the measure of 34.6% and 17.8%. The analysis of the coupled dynamics between vapor cavity–vorticity and their proper orthogonal decomposition (POD)-based modal structures highlighted the benefit of the SJA lies in preventing the growth of a thick sheet cavity, which causes the development of the highly cavitating cloud dynamics after the cavity breakup. This is mainly due to an additional vorticity close to the hydrofoil surface just downstream the SJA, as well as a local pressure modification close the SJA during the blowing stroke.