Numerical study of periodically forced-pitching of a supercavitating vehicle

Pan, Zhan-cheng; Lu, Cewu; Chen, Ying; Hu, Shiliang

doi:10.1016/s1001-6058(10)60049-2

Cited by 8 publications

(3 citation statements)

References 7 publications

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“…This pressure difference is constructed in a dimensionless form as P = (P out − P in )/q = P out −P in , where q (= 1/2ρU 2 ) is the dynamic pressure of water in the test section andP in andP out are the dimensionless static pressures inside and just outside the cavity at the closure, respectively (illustrated in figure 11). Note that P in may deviate from the mean cavity pressure due to the internal flows of the supercavity (Pan et al 2010). We hypothesize that the change of Fr, C Qs , B or type of experimental facility leads to the change of P , resulting in the variation of closure modes.…”

Section: Hypothesis and Explanation Of Observationsmentioning

confidence: 94%

An experimental investigation into supercavity closure mechanisms

2016

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Substantial discrepancy in the conditions for attainment of different closure modes of a ventilated supercavity has existed widely in the published literature. In this study, supercavity closure is investigated with an objective to understand the physical mechanisms determining closure formation and transition between different closure modes and to reconcile the observations from prior studies under various flow settings. The experiments are conducted in a closed-wall recirculating water tunnel to image ventilated supercavity closure using high speed and high-resolution photography and simultaneously measure pressure inside the cavity. The flow conditions are varied systematically to cover a broad range of water velocity, ventilation flow rate and cavitator size, which correspond to different Froude numbers, air entrainment coefficients and blockage ratios, respectively. In addition to the classical closure modes reported in the literature (e.g. re-entrant jet, twin vortex, quad vortex, etc.), the study has revealed a number of new closure modes that occur during the transition between classical modes, or under very specific flow conditions. Closure maps are constructed to depict the flow regimes, i.e. the range of Froude number and air entrainment coefficient, for various closure modes at different blockage ratios. From the closure map at each blockage ratio, a critical ventilation flow rate, below which the supercavity collapses into foamy cavity upon reduction of Froude number, is identified. The air entrainment coefficients corresponding to such critical ventilation rate are found to be independent of blockage ratio. It has been observed that in the process of generating a supercavity by increasing ventilation flow rate, the cavitation number gradually reduces to a minimum value and stays fixed upon further increments in the ventilation rate. Once a supercavity is formed, the ventilation rate can be decreased to a much lower value with no change in cavitation number while still maintaining a supercavity. This process is accompanied by a change in closure modes, which generally goes from twin vortex, to quad vortex, and then to re-entrant jet. In addition, the blockage effect is shown to play an important role in promoting the occurrence of twin-vortex closure modes. Subsequently, a physical framework governing the variation of different closure modes is proposed, and is used to explain mode transition upon the change of flow conditions, including the blockage effect. This framework is further extended to shed light on the occurrence of closure modes for ventilated supercavitation experiments across different types of flow facilities, the natural supercavity closure and the pulsating supercavity reported in the literature. † Finally, in combination with a recent numerical study, our research discusses the role of the internal flow physics on the observed features during supercavity formation and closure-mode transition, paving the way for future investigations in this direction.

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Section: Hypothesis and Explanation Of Observationsmentioning

confidence: 94%

An experimental investigation into supercavity closure mechanisms

2016

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“…Li [9] measured the hydrodynamic forces and the pressure distribution of a forced-pitching supercavitating vehicle in a circular cavitation tunnel, and discussed the interaction between the supercavity and the slender vehicle. Pan et al [10] simulated supercavitating flow in a close cavitation tunnel for both steady and dynamic cases, and the computational results agreed well with the experimental data.…”

Section: Introductionmentioning

confidence: 64%

Study on the characteristic of a forced pitching supercavitating vehicle

Pan

Chen

2015

J. Shanghai Jiaotong Univ. (Sci.)

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During the cruising of a supercavitating vehicle, the relative motion between the supercavity and the vehicle has a significant effect on the stability of the supercavity and the trajectory of the vehicle. In this paper, periodically forced pitching of a supercavitating vehicle is investigated numerically by a dynamic mesh method. The simulated result of the flow field around a pitching ventilated supercavitating vehicle in a water tunnel is compared with the experimental result. The evolution of the cavity morphology, the pressure distribution and the hydrodynamics of the vehicle are in good agreement with the experimental data. The effect of different pitching amplitudes and frequencies is studied. Also, the effect of the tunnel wall and the bracing structure is analyzed.

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“…Many efforts devoted to studying the cavity behavior are widely based on two main methods: the computational fluid dynamics (CFD) and the boundary element method (BEM) (Mirzaei et al 2015). CFD method is more accurate than BEM, but it requires a higher computational cost (Yu et al 2012;Pan et al 2010).…”

Section: Introdutionmentioning

confidence: 99%

A Study on the Motion of High Speed Supercavitating Projectiles

Forouzani

Saranjam

Kamali

2018

JAFM

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In the last two decades much research works have been performed in order to model the dynamics of highspeed supercavitating projectiles. In the present study, the high speed supercavitating projectiles have been investigated analytically. In this context, the equations of motion were developed for the projectile inside the supercavity. To achieve this purpose, the projectile is described by its mass, geometry and moment of inertia relative to a body-fixed coordinates system. Two experimental based models were used for simulation of supercavity dynamics and the planing force. Furthermore, a detailed parametric study was performed to investigate effect of three main parameters including the mass, cavitator diameter and length of projectile, on the flight performance of a high speed supercavitating projectile. Results obtained in this parametric study can provide some physical insights into high-speed supercavitating projectile design.

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Numerical study of periodically forced-pitching of a supercavitating vehicle

Cited by 8 publications

References 7 publications

An experimental investigation into supercavity closure mechanisms

An experimental investigation into supercavity closure mechanisms

Study on the characteristic of a forced pitching supercavitating vehicle

A Study on the Motion of High Speed Supercavitating Projectiles

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