scholarly journals The Effect of a Longitudinal Gravitational Field on the Supercavitating Flow Over a Wedge

1961 ◽  
Vol 28 (2) ◽  
pp. 188-192 ◽  
Author(s):  
A. J. Acosta
Keyword(s):  
Gravitational Field ◽  
Drag Coefficient ◽  
Froude Number ◽  
Cavitation Number ◽  
Streamline Flow ◽  
Flow Past ◽  
Supercavitating Flow ◽  
Linearized Theory

The free-streamline flow past a symmetrical wedge in the presence of a longitudinal gravitational field is determined with a linearized theory. The proportions of the cavity depend upon the cavitation number and Froude number. The drag coefficient is likewise affected by gravity, though to a smaller extent.

Experiments on Gravity Effects in Supercavitating Flow

1966 ◽  
Vol 10 (02) ◽  
pp. 119-121
Author(s):  
T. Kiceniuk ◽  
A. J. Acosta
Keyword(s):  
Gravitational Field ◽  
Froude Number ◽  
Flow Past ◽  
Supercavitating Flow ◽  
Gravity Effects

Experiments on the effect of a transverse gravitational field on the supercavitating flow past a wedge tend to confirm predictions based on linearized free-streamline theory. A small though systematic dependence upon Froude number not accounted for by the existing theory is revealed, however.

A Note on Gravity Effects in Supercavitating Flow

1965 ◽  
Vol 9 (01) ◽  
pp. 39-45
Author(s):  
R. L. Street
Keyword(s):  
Gravity Field ◽  
Quantitative Agreement ◽  
Cavitation Number ◽  
Number Range ◽  
First Order ◽  
Average Value ◽  
Flow Past ◽  
Supercavitating Flow ◽  
Gravity Effects ◽  
Linearized Theory

Two approximations to the linearized theory for supercavitating flow about slender bodiesare applied to the case of flow past a slender wedge in a transverse gravity field. The additional lift and moment forces arising as a result of the gravity field are calculated by theories that are expected to hold when the gravity effects are of first-order smallnessconsistent with the linearization appi'oximations. The lift and moment coefficients obtained from the two approximations are in general quantitative agreement over the most important cavitation-number range. The results obtained confirm the validity of the average-value approximation introduced by Parkin.

A linearized theory for rotational supercavitating flow

1963 ◽  
Vol 17 (4) ◽  
pp. 513-545 ◽  
Author(s):  
Robert L. Street
Keyword(s):  
Shear Flow ◽  
Flow Past ◽  
Supercavitating Flow ◽  
Harmonic Perturbation ◽  
Two Dimensional Flow ◽  
Slender Bodies ◽  
Linearized Theory ◽  
Particular Solution ◽  
Effects Of Rotation ◽  
Rotational Problem

In this paper methods are given for establishing qualitative and quantitative measures of the effects of rotation in supercavitating flows past slender bodies. A linearized theory is developed for steady, two-dimensional flow under the assumption that the flow has a constant rotation throughout. The stream function of the rotational flow satisfies Poisson's equation. By using a particular solution of this equation, the rotational problem is reduced to a problem involving Laplace's equation and harmonic perturbation velocities. The resulting boundary-value problem is solved by use of conformal mapping and singularities from thinairfoil theory. The theory is then applied to asymmetric shear flow past wedges and hydrofoils and to symmetric shear flow past wedges. The presence of rotation is shown to create significant changes in the forces acting on the slender bodies and in the shape and size of the trailing cavities.

Supercavitating Flow About a Slender Wedge in a Transverse Gravity Field

1963 ◽  
Vol 7 (03) ◽  
pp. 14-23
Author(s):  
R. L. Street
Keyword(s):  
Gravity Field ◽  
First Order ◽  
Flow Past ◽  
Supercavitating Flow ◽  
Linearized Theory

In this paper a linearized theory is developed for supercavitating flow past a slender strut or wedge in a transverse gravity field. The theory is expected to be valid when the effects of the gravity field are of first-order smallness consistent with the linearization approximations. The additional lift and moment forces acting on the strut as a result of the gravity field are calculated. The transverse gravity field is found to produce additional forces which should be considered in hydrodynamic design.

scholarly journals Numerical investigation on the gas entrainment rate on ventilated supercavity body

2016 ◽  
Vol 8 (4) ◽  
pp. 169-177
Author(s):  
WuGang Yang ◽  
ZhenCai Yang ◽  
KaiGe Wen ◽  
ZhaoHui Yang ◽  
YuWen Zhang
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
Drag Coefficient ◽  
Froude Number ◽  
Gravitational Effect ◽  
Cavitation Number ◽  
Reduction Ratio ◽  
Entrainment Rate ◽  
Towing Tank ◽  
Ventilated Supercavity

The supercavitation technique provides a means of significantly increasing the velocity of an underwater vehicle. This technique involves essentially the creation of stable supercavity shape. The method of artificial ventilation is most effective for generating and dominating the supercavity. This paper focuses on the numerical simulation of flow field around three-dimensional body. The method is based on the multiphase computational fluid dynamics model combined with the turbulence model and the full cavity model. The fundamental similarity parameters of ventilated supercavity flows that include cavitation number, Froude number Fr, entrainment rate CQ, and drag coefficient Cx are all investigated numerically in the case of steady flow and gravity field. We discuss the following simulations results in three parts: (1) the variations of the cavitation number and the supercavity’s relative diameter with entrainment rate; (2) the drag coefficient versus the cavitation number; and (3) deformation of supercavity axis caused by gravitational effect for three different fixed three Froude numbers. In the full paper, we give the comparison results of the drag reduction ratio among numerical simulation and experiment conducted in hydrodynamic tunnel and towing tank, respectively. We summarize our discussion of gravitational effect on the axis deformation of supercavity as follows: in the case of smaller Froude number, the inclination of the cavity axis increases monotonously with increasing horizontal length and reaches its maximal value at the end of supercavity; this deformation can be almost completely negligible when the Froude number Fr is larger than 7.0. The comparisons with the experimental data in the hydrodynamic tunnel and the towing tank indicate that the present method is effective for predicting the flows around ventilated supercavity; that the numerical results is in good agreement with the experimental ones and that the maximal value of the drag reduction ratio can be expected to reach the value of 90% compared with that of the condition of non-cavitation.

INVESTIGATIONS ON THE DRAG REDUCTION OF HIGH-SPEED NATURAL SUPERCAVITATION BODIES

2009 ◽  
Vol 23 (03) ◽  
pp. 405-408 ◽  
Author(s):  
WENJUN YI ◽  
JUNJIE TAN ◽  
TIANHONG XIONG
Keyword(s):  
Aspect Ratio ◽  
Drag Reduction ◽  
Drag Coefficient ◽  
High Speed ◽  
Cavitation Number ◽  
Drag Coefficients ◽  
Supercavitating Flow ◽  
Disk Cavitator ◽  
Reduction Characteristics ◽  
Flow Experiments

In order to investigate the drag reduction characteristics of a high-speed body with supercavitation shape, four types of typical disk cavitator models with different parameters were designed and tested. By measuring the velocity decrease histories during supercavitating flow experiments, the average drag coefficients were determined, which allows analysis and comparison of the influence of cavitator diameter, projectile aspect ratio, and cavitation number on the drag reduction. Based on the experimental results, numerical simulation of the drag reduction of supercavitation body was also carried out using a commercial software FLUENT6.2, and the results obtained agree well with the experimental data. Moreover, it is shown that the drag coefficients of the four bodies are in inverse ratio to the head area of cavitator when operating under natural supercavitating flow condition, and the smaller drag coefficient can be obtained by increasing the slender ratio of the bodies. Therefore, higher aspect ratio reduces drag coefficient, with the reduction of more than 95% under certain condition of cavitation number and supercaviation shape.

Symmetric, Rotational, Supercavitating Flow About a Slender Wedge

1964 ◽  
Vol 86 (3) ◽  
pp. 569-575 ◽  
Author(s):  
R. L. Street
Keyword(s):  
Drag Coefficient ◽  
Cavity Length ◽  
Rotational Flow ◽  
Drag Coefficients ◽  
Irrotational Flow ◽  
Supercavitating Flow ◽  
Slender Bodies ◽  
Linearized Theory

Two approximations to the linearized theory for supercavitating flow about slender bodies are applied to the case of a symmetric, rotational flow about a slender wedge. Both approximations produce relationships for the cavity length and drag coefficients; one approximation also gives certain nonunique solutions not encountered in the corresponding irrotational flow. The presence of rotation is shown to create significant changes in the length of the trailing cavity, but small changes in the drag coefficient.

scholarly journals Some New Measurements on the Drag of Cavitating Disks

1965 ◽  
Vol 9 (03) ◽  
pp. 102-104
Author(s):  
G. J. Klose
Keyword(s):  
Unsteady Flow ◽  
Drag Coefficient ◽  
Steady Flow ◽  
Circular Disk ◽  
Cavitation Number ◽  
Flow Past

As part of an experiment on unsteady flow past a cavitating circular disk, it was necessary to make calibrating measurements of the drag on disks in steady flow. The measurements were made for greater cavitation numbers than have been previously recorded, and show that the drag coefficient is essentially linearly dependent upon cavitation number up to values of this parameter as high as 1.3.

Supercavitating Flow Past Slender Delta Wings

1959 ◽  
Vol 3 (04) ◽  
pp. 17-22
Author(s):  
Marshall P. Tulin
Keyword(s):  
Jet Flow ◽  
Cavitation Number ◽  
Conical Flow ◽  
Delta Wings ◽  
Flow Past ◽  
Supercavitating Flow ◽  
Leading Edges ◽  
Surface Increase

The supercavitating flow past slender delta wings is studied. Theory is developed for a conical flow involving cavities which spring from the leading edges of the delta and cover a part of the top of the wing; the center part of the wing top is assumed to be wetted by a kind of re-entrant jet flow. Results are obtained for the two separate asymptotic cases in which the cavitation number is either very small or very large. The widths of the cavities on the wing upper surface increase with decreasing σ and the lift decreases. It is shown that the upper surface never becomes completely enveloped in a cavity even for σ = 0. Finally, the lift of a fully cavitated wing (σ = 0) is estimated to be approximately 4/10 of its fully wetted lift.

On Flow Past a Supercavitating Cascade of Cambered Blades

1972 ◽  
Vol 94 (1) ◽  
pp. 163-168 ◽  
Author(s):  
C. C. Hsu
Keyword(s):  
Numerical Results ◽  
Points Of Interest ◽  
Flow Past ◽  
Supercavitating Flow ◽  
Linearized Theory ◽  
Flow Through

A linearized theory for supercavitating flow through a cascade of cambered blades is developed. Numerical results illustrating various points of interest are presented.

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