scholarly journals Effect of submerged body shape upon its movement pattern near free surface

2021 ◽  
Vol 4 (398) ◽  
pp. 35-42
Author(s):  
Vitaly Zemlyak ◽  
◽  
Viktor Kozin ◽  
Aleksey Vasiliev ◽  
◽  
...  
Keyword(s):  
Free Surface ◽  
Test Procedure ◽  
Movement Pattern ◽  
Vertical Displacement ◽  
Shape Effect ◽  
Horizontal Movement ◽  
Submerged Body ◽  
Section Shape ◽  
Movement Stability ◽  
Vertical Lift

Object and purpose of research. This paper discusses the tests with submerged models of different shape moving near the free surface in the test tank. The purpose of the study was to determine how relative vertical displacement and crosssection shape lift of submerged body depend on the speed of its movement at different immersion depths. Materials and methods. Model test procedure, techniques and results of model. Numerical simulation was performed in ANSYS software package. Main results. Experimental and theoretical study on cross-section shape effect of submerged body upon its wave generation, vertical lift and movement pattern near free surface. Conclusion. The results of this research will be useful for further work towards greater horizontal movement stability of submerged body at various speeds depending on its hull shape and immersion depth.

scholarly journals Vertical shift of submerged body moving near the free surface

2020 ◽  
Vol 4 (394) ◽  
pp. 43-52
Author(s):  
Vitalyov L. Zemlyak ◽  
Viktor M. Kozin ◽  
Aleksey S. Vasiliev
Keyword(s):  
Numerical Modeling ◽  
Free Surface ◽  
Software Package ◽  
Numerical Experiments ◽  
Vertical Displacement ◽  
Model Tests ◽  
Ansys Software ◽  
Vertical Shift ◽  
Submerged Body ◽  
Horizontal Stabilization

Object and purpose of research. The object of the research is model tests of the submerged body motions near the free surface in test basin. The purpose of the study is to determine how the magnitude of the relative vertical shift of the submerged body depends on its speed. Materials and methods. The material for research is the modeling technique, technology and the results of model experiments in the test basin. Numerical modeling was performed using the ANSYS software package. Main results. Model tests and numerical experiments were carried out to determine the magnitude of the vertical displacement of the submerged body moving near the free surface and the forces acting on it. Conclusion. The results obtained are useful for horizontal stabilization of submerged body moving near free surface at different speeds.

The Cedar Mountain, Nevada, earthquake of December 20, 1932*

1934 ◽  
Vol 24 (4) ◽  
pp. 345-384 ◽  
Author(s):  
Vincent P. Gianella ◽  
Eugene Callaghan
Keyword(s):  
Sierra Nevada ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Relative Movement ◽  
East Side ◽  
Owens Valley ◽  
The West ◽  
Horizontal Movement ◽  
San Andreas

Summary The Cedar Mountain, Nevada, earthquake took place at about 10h 10m 04s p.m., December 20, 1932. It was preceded by a foreshock noted locally and followed by thousands of aftershocks, which were reported as still continuing in January 1934. No lives were lost and there was very little damage. The earthquake originated in southwest central Nevada, east of Mina. A belt of rifts or faults in echelon lies in the valley between Gabbs Valley Range and Pilot Mountains on the west and Cedar Mountain and Paradise Range on the east. The length of this belt is thirty-eight miles in a northwesterly direction, and the width ranges from four to nine miles. The rifts consist of zones of fissures which commonly reveal vertical displacement and in a number of places show horizontal displacement. The length of the rifts ranges from a few hundred feet to nearly four miles, and the width may be as much as 400 feet. The actual as well as indicated horizontal displacement is represented by a relative southward movement of the east side of each rift. The echelon pattern of the rifts within the rift area indicates that the relative movement of the adjoining mountain masses is the same. The direction of relative horizontal movement corresponds to that along the east front of the Sierra Nevada at Owens Valley and on the San Andreas rift.

Nonlinear Aspects of Subcritical Shallow-Water Flow Past Two-Dimensional Obstructions

1978 ◽  
Vol 22 (04) ◽  
pp. 203-211
Author(s):  
Nils Salvesen ◽  
C. von Kerczek
Keyword(s):  
Free Surface ◽  
Shallow Water ◽  
Flow Problem ◽  
Free Stream ◽  
The Body ◽  
Two Dimensional ◽  
Third Order ◽  
Submerged Body ◽  
The Mean ◽  
The Waves

Some nonlinear aspects of the two-dimensional problem of a submerged body moving with constant speed in otherwise undisturbed water of uniform depth are considered. It is shown that a theory of Benjamin which predicts a uniform rise of the free surface ahead of the body and the lowering of the mean level of the waves behind it agrees well with experimental data. The local steady-flow problem is solved by a numerical method which satisfies the exact free-surface conditions. Third-order perturbation formulas for the downstream free waves are also presented. It is found that in sufficiently shallow water, the wavelength increases with increasing disturbance strength for fixed values of the free-stream-Froude number. This is opposite to the deepwater case where the wavelength decreases with increasing disturbance strength.

Three-Dimensional Large Amplitude Body Motions in Waves

2007 ◽  
Author(s):  
Xinshu Zhang ◽  
Robert F. Beck
Keyword(s):  
Free Surface ◽  
Three Dimensional ◽  
Surface Boundary ◽  
Forward Speed ◽  
Time Step ◽  
Surface Boundary Conditions ◽  
Submerged Body ◽  
Calm Water ◽  
Wigley Hull ◽  
Constant Strength

Three-dimensional, time-domain, wave-body interactions are studied in this paper for cases with and without forward speed. In the present approach, an exact body boundary condition and linearized free surface boundary conditions are used. By distributing desingularized sources above the calm water surface and using constant-strength panels on the exact submerged body surface, the boundary integral equations are solved numerically at each time step. Once the fluid velocities on the free surface are computed, the free surface elevation and potential are updated by integrating the free surface boundary conditions. After each time step, the body surface and free surface are regrided due to the instantaneous changing submerged body geometry. The desingularized method applied on the free surface produces non-singular kernels in the integral equations by moving the fundamental singularities a small distance outside of the fluid domain. Constant strength panels are used for bodies with any arbitrary shape. Extensive results are presented to validate the efficiency of the present method. These results include the added mass and damping computations for a hemisphere. The calm water wave resistance for a submerged spheroid and a Wigley hull are also presented. All the computations with forward speed are started from rest and proceed until a steady state is reached. Finally, the time-domain forced motion results for a modified Wigley hull with forward speed are shown and compared with the experiments for both linear computations and body-exact computations.

Calculation of Wave Height Dependent Force RAO’s on Submerged Bodies in Close Proximity to the Free Surface

2013 ◽  
Author(s):  
Ivan van Winsen ◽  
Job S. Bokhorst ◽  
René H. M. Huijsmans
Keyword(s):  
Free Surface ◽  
Wave Height ◽  
High Water ◽  
Wave Frequency ◽  
Parameter Study ◽  
Submerged Body ◽  
Close Proximity ◽  
Submerged Cylinder ◽  
Water Elevations ◽  
Water Elevation

Diffraction calculations overpredict motion RAO’s and force RAO’s in cases where a small layer of water is present on top of a submerged body. This was observed after conducting model tests on a free floating SSCV Thialf and a captive submerged cylinder. A parameter study is done to get a better understanding of why diffraction calculations overpredict the forces in heave direction. From this study it was observed that unrealistically high water elevations existed on top of the cylinder causing the heave forces to be overestimated. A damping lid is therefore implemented to decrease this water elevation. On top of that, a new method is developed to be able to capture the dependency of the force RAO on the wave height. This method uses the instantaneous submergence height (the height of water on top of the submerged body) to determine the time averaged force RAO for a given wave height and wave frequency.

The effect of a semi-contaminated free surface on mass transport

1974 ◽  
Vol 75 (2) ◽  
pp. 283-294 ◽  
Author(s):  
D. Porter ◽  
B. D. Dore
Keyword(s):  
Free Surface ◽  
Velocity Field ◽  
Mass Transport ◽  
Mixed Boundary ◽  
Surface Film ◽  
Vertical Displacement ◽  
Mass Transport Velocity ◽  
Harmonic Equation ◽  
The Waves

AbstractThe mass transport velocity field is determined for surface waves which propagate from a region with a clean free surface into a region beneath an inextensible surface film. The waves are assumed to be incident normally on the edge of the film. Determination of this velocity field requires the investigation of a mixed boundary value problem for the bi-harmonic equation, the solution of which is obtained using the Wiener–Hopf technique. Streamlines for the mean motion of the fluid particles are thus obtained. It is found that considerable vertical displacement of fluid is possible due to the presence of the surface film.

On the solution near the critical frequency for an oscillating and translating body in or near a free surface

1993 ◽  
Vol 254 ◽  
pp. 251-266 ◽  
Author(s):  
Yuming Liu ◽  
Dick K. P. Yue
Keyword(s):  
Free Surface ◽  
Closed Form Solution ◽  
Geometric Interpretation ◽  
Form Solution ◽  
The Body ◽  
Geometric Condition ◽  
Sufficient Condition ◽  
Gravitational Acceleration ◽  
Submerged Body ◽  
Necessary And Sufficient

We consider a floating or submerged body in deep water translating parallel to the undisturbed free surface with a steady velocity U while undergoing small oscillations at frequency ω. It is known that for a single source, the solution becomes singular at the resonant frequency given by τ ≡ Uω/g=¼, where g is the gravitational acceleration. In this paper, we show that for a general body, a finite solution exists as τ → ¼ if and only if a certain geometric condition (which depends only on the frequency ω but not on U) is satisfied. For a submerged body, a necessary and sufficient condition is that the body must have non-zero volume. For a surface-piercing body, a sufficient condition is derived which has a geometric interpretation similar to that of John (1950). As an illustration, we provide an analytic (closed-form) solution for the case of a submerged circular cylinder oscillating near τ = ¼. Finally, we identify the underlying difficulties of existing approximate theories and numerical computations near τ = ¼, and offer a simple remedy for the latter.

The Flat Solitary Waves Due to a Submerged Moving Body in a Two-Layer Fluid With a Free Surface

2005 ◽  
Author(s):  
Gang Wei ◽  
Xiao-Bing Su ◽  
Yun-Xiang You
Keyword(s):  
Free Surface ◽  
Theoretical Analysis ◽  
Solitary Wave ◽  
Solitary Waves ◽  
Experimental Results ◽  
Stable System ◽  
Weakly Nonlinear ◽  
Submerged Body ◽  
Moving Body

The flat solitary wave with the behavior of conjugate flow, generated by a submerged body moving in a two-layer fluid, is investigated. A criteria about the existence of weakly nonlinear weakly dispersive flat solitary wave is given. The condition of the stable system of conjugate flow is obtained. The solution of the flat solitary wave satisfying the criteria is numerically verified to be unique. Theoretical analysis is qualitatively consistent with the experimental results obtained by the authors.

THE MECHANISM OF GENERATION OF LONG WAVES FROM EXPLOSIONS

Geophysics ◽  
1955 ◽  
Vol 20 (1) ◽  
pp. 87-103 ◽  
Author(s):  
C. Hewitt Dix
Keyword(s):  
Free Surface ◽  
Surface Waves ◽  
Elastic Solid ◽  
Vertical Axis ◽  
Vertical Displacement ◽  
Transverse Waves ◽  
Displacement Potential ◽  
Long Period ◽  
Duhamel Integral ◽  
Ground Roll

Cagniard’s method is applied to the numerical calculation of the vertical displacement due to a point source in a semi‐infinite elastic solid medium at three points on a vertical line through the source. The source is a step in the scalar displacement potential. From these calculated responses the response for any physically possible spherically symmetric source can be computed by application of the Duhamel integral. Clear evidence of backward transmission of transverse wave energy is found along the vertical axis through the source. This, together with the energy of the longitudinal waves, also transmitted backwards, accounts for the mechanism by which energy is held near the source and near the free surface long enough to account for the generation of long period surface waves. This mechanism of generation of long period surface waves is not restricted to the free surface case. Any good reflector, which also generates secondary transverse waves from longitudinal primary waves, will serve the purpose. It is suggested that this gives a clue to the mechanism of the formation of “ground roll” in many practical cases.

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