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Open Access Research Article Issue
Experimental study on interaction between deflected tail jet and ventilated cavitation
Acta Aerodynamica Sinica 2025, 43(2): 40-50
Published: 17 July 2024
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The tail high-velocity jet is one of the key factors affecting the morphology and stability of the cavitation on a supercavitating vehicle, with the cavitation shape being related to various factors including the intensity, flow, and angle of the tail jet. This study, conducted using an open gravity water tunnel and employing a time-sequence control method, investigates the coupling effects of the tail jet and ventilated cavitation. The primary focus is on analyzing the impact mechanisms of tail jet angle on the cavitation scale and the wake entrainment effect under different jet intensities. The findings indicate that variations in the tail jet angle and intensity lead to changes in the angle between the core velocity of the tail jet and the cavitation axis direction, thereby altering the coupling mode of interaction between the jet and the cavitation. Increasing the angle between the tail jet and the cavitation axis enhances the jet's recirculation and air replenishment effect, while decreasing this angle increases the deflating velocity, causing a reduction in cavitation size. Within a certain range, increasing the angle between the tail jet and the cavitation axis can enhance the cavitation stability. However, an excessively large deflection angle can result in jet impact on the cavitation wall, leading to cavitation breakup and collapse. The research outcomes provide significant support for the thrust vector control of supercavitating vehicles.

Open Access Research Article Issue
Research on the multiphase flow characteristics of the near free-surface supercavitating vehicle
Acta Aerodynamica Sinica 2023, 41(7): 64-73
Published: 19 August 2022
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In the context of near-free surface supercavitating vehicle, the method of combining theoretical analysis and numerical simulation was adopted to carry out the research on the dynamic mechanism of the near-free surface cavity evolution. A multiphase flow solver based on the OpenFOAM open source software platform was built to achieve two-phase numerical simulation of free-surface flow, ventilated cavitation and air entrainment. Simulation analysis of near-free surface cavitating flow for axisymmetric and projectile-wing combination configurations was carried out respectively. The effect of ventilation rate, projectile length-to-diameter ratio, sailing depth, sailing speed, etc, was further investigated and the mechanism of interaction between free surface and cavity was revealed. Furthermore analysis of the influence mechanism of the trans-media hydrofoil on the gas-liquid interface fluctuation and the pressure distribution of the projectile was obtained. It was found that the increase in the length-to-diameter ratio of the projectile will lead to an increase in the wavelength and a decrease in the amplitude of the cavity induced wave, which will help to improve the stability of the supercavity and enhance the drag reduction rate. When the Froude number is high, too large ventilation coefficient will lead to deflecting downward of the cavity central axis and the increase of the cavity flow area. The pressure drag will be increases significantly. For the projectile-wing combination configuration, the hydrofoil cuts the tail of the main cavity, which is easy to cause intermittent wetting of the tail section, and the amplitude of the wave above the main cavity is significantly reduced, indicating that the hydrofoil has a suppressing effect on the main wave.

Research Article Issue
Unsteady dynamic analysis for the cavitating hydrofoils based on OpenFOAM
Experimental and Computational Multiphase Flow 2019, 1(2): 101-108
Published: 27 March 2019
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Recently, cavitation has attracted great attention not only due to its negative effect on the performance of fluid machinery, but also owing to its vigorous prospect in drag reduction for underwater vehicles. However, strong instability and obvious nonlinearity exist for cavitating flow, making it hard to predict it precisely. In this paper, a cavitating solver coupled with the Bubble-Droplet cavitation model has been established based on the OpenFOAM platform. Simulation has been carried out for the cavitating hydrofoil of Clark-Y. Transient evolutions of the flow parameters including the void fraction, velocity, and pressure have been obtained, giving detail insights on the unstable shedding dynamics for the cavitating hydrofoil. Evaluation of the Bubble-Droplet cavitation model has been implemented by varying the threshold value in the model. The transient cavity shape, shedding frequency, and time-dependent curves for the hydrodynamic coefficient have been carefully compared, indicating that this threshold value has obvious effect on the cavity profile during the shedding process. By comparing with the experimental data, the predicted lifts are slightly under-predicted while the drags are over-predicted, but basically the numerical results agree with the experiment well.

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