Characteristics of Breaking Bow Waves Generated by a 2D+T Wave Maker

2006 ◽  
Author(s):  
Mostafa Shakeri ◽  
Mohammadreza Tavakolinejad ◽  
Matthias Mayer ◽  
James H. Duncan
Keyword(s):  
Water Surface ◽  
Wave Pattern ◽  
Wave Crest ◽  
Maximum Speed ◽  
T Wave ◽  
Bow Waves ◽  
Maximum Water ◽  
Wave Maker ◽  
Rise Height ◽  
Plunging Breaker

Ship bow waves simulated experimentally with a 2D+T wave maker were investigated experimentally. Wave profile measurements are presented for a range of equivalent full-scale ship speeds ranging from 16.5 to 27 knots. At the beginning of the wave maker motion, the water surface rises rapidly up the surface of the wave board which represents the hull of the equivalent ship model. The maximum rise height and the rate of rise increase with increasing equivalent ship speed. Later in the wave maker motion, this point of maximum water height moves away from the wave board and forms the primary crest in the wave pattern. This crest moves at a speed that is about 1.8 times the maximum speed of the wave board. At the higher speeds, this wave crest evolves into a strong plunging breaker with a jet that hits the water surface ahead of the breaker, creating a large splash and entraining large amounts of air. The temporal histories of various geometrical characteristics of the breaker are presented.

scholarly journals The impact of a deep-water plunging breaker on a wall with its bottom edge close to the mean water surface

2018 ◽  
Vol 843 ◽  
pp. 680-721 ◽  
Author(s):  
An Wang ◽  
Christine M. Ikeda-Gilbert ◽  
James H. Duncan ◽  
Daniel P. Lathrop ◽  
Mark J. Cooker ◽  
...  
Keyword(s):  
Deep Water ◽  
Water Surface ◽  
Front Face ◽  
Wave Crest ◽  
Bottom Surface ◽  
Mean Water Level ◽  
The Mean ◽  
The Impact ◽  
Plunging Breaker ◽  
Range Of Values

The impact of a deep-water plunging breaker on a finite height two-dimensional structure with a vertical front face is studied experimentally. The structure is located at a fixed horizontal position relative to a wave maker and the structure’s bottom surface is located at a range of vertical positions close to the undisturbed water surface. Measurements of the water surface profile history and the pressure distribution on the front surface of the structure are performed. As the vertical position,$z_{b}$(the$z$axis is positive up and$z=0$is the mean water level), of the structure’s bottom surface is varied from one experimental run to another, the water surface evolution during impact can be categorized into three classes of behaviour. In class I, with$z_{b}$in a range of values near$-0.1\unicode[STIX]{x1D706}_{0}$, where$\unicode[STIX]{x1D706}_{0}$is the nominal wavelength of the breaker, the behaviour of the water surface is similar to the flip-through phenomena first described in studies with shallow water and a structure mounted on the sea bed. In the present work, it is found that the water surface between the front face of the structure and the wave crest is well fitted by arcs of circles with a decreasing radius and downward moving centre as the impact proceeds. A spatially and temporally localized high-pressure region was found on the impact surface of the structure and existing theory is used to explore the physics of this phenomenon. In class II, with$z_{b}$in a range of values near the mean water level, the bottom of the structure exits and re-enters the water phase at least once during the impact process. These air–water transitions generate large-amplitude ripple packets that propagate to the wave crest and modify its behaviour significantly. At$z_{b}=0$, all sensors submerged during the impact record a nearly in-phase high-frequency pressure oscillation indicating possible air entrainment. In class III, with$z_{b}$in a range of values near$0.03\unicode[STIX]{x1D706}_{0}$, the bottom of the structure remains in air before the main crest hits the bottom corner of the structure. The subsequent free surface behaviour is strongly influenced by the instantaneous momentum of the local flow just before impact and the highest wall pressures of all experimental conditions are found.

ON DISTRTBUTION PATTERN OF AMORPHA FRUTICOSA L. IN THE REGION OF KANEVSKAYA HYDROPOWER STATION (UKRAINE) IN CONNECTION WITH HYDROCHORY

2021 ◽  
Vol 14 (1) ◽  
pp. 107-115
Author(s):  
T. V. Shevchik ◽  
T. S. Dvirna ◽  
V. L. Shevchik
Keyword(s):  
Water Surface ◽  
Water Yield ◽  
Surface Level ◽  
Amorpha Fruticosa ◽  
Active Dispersal ◽  
Active Dissemination ◽  
Maximum Water ◽  
Hydropower Stations ◽  
Determining Factor ◽  
Natural Way

Amorpha fruticosa L. is a kenophyte of North American origin, ergaziophyte. Currently, this species naturalized over large areas and became the background on the coast waters of the Dnieper reservoirs of hydropower stations. It is necessary to clarify the reasons for the distribution of A. fruticosa populations in different parts of the Middle Dnieper coast under conditions of artificial regulation of its water yield. It has been proven that the high buoyancy of A. fruticosa fruits provides the possibility of its active dispersal along river beds in a natural way under conditions of fluctuations in the level of surface water yield right in spring floods. The main and determining factor in the active dissemination of the species on the coast of the Kanev and Kremenchug reservoirs is the frequent variability of the maximum water surface level. The narrow altitudinal range of distribution of this species on the coast in the lower parts, and accordingly, wider in the upper parts of the reservoirs is determined by the corresponding indicators of water level differences. The possibility of artificial regulation of the water surface level with knowledge of the characteristics of hydrochory of this invasive species makes it possible to influence its distribution in the territory near the reservoirs.

scholarly journals Surface Heat Budget estimation for Laurance Lake, US

2021 ◽  
Vol 877 (1) ◽  
pp. 012005
Author(s):  
Dahlia S. Abed-Zaid ◽  
Hussein A. M. Al-Zubaidi
Keyword(s):  
Surface Temperature ◽  
Water Surface ◽  
Heat Budget ◽  
Meteorological Data ◽  
Longwave Radiation ◽  
Atmospheric Conditions ◽  
Large Lakes ◽  
Water Surface Temperature ◽  
Maximum Water ◽  
The Many

Abstract Estimating heat budget factors are important to understand the many physical processes of large lakes and their reaction to the atmosphere. Some of these components are affected by water temperature, while the other depends on atmospheric conditions. This paper estimates the total heat flux for Lawrence lake via a code developed in MATLAB environment. The code can deal with different time resolutions if the lake water surface temperature data were at different time resolutions from the meteorological data. Results showed that solar energy peaks at 842 Watt/m2 at 540 Julian day, which is very normal for a sunny summer day, while the longwave radiation has 204 Watt/m2 as a min value. The back radiation did not make any reaction for the variation, but it revealed a small gradient. Furthermore, evaporation recorded - 67 Watt/m2 as a minimum value at 659 Julian day and 360 Watt/m2 as a maximum value at 578.43 Julian day close to the maximum water surface temperature event.

Surface Gravity Waves

2017 ◽  
Author(s):  
John A. Adam
Keyword(s):  
Gravity Waves ◽  
Water Waves ◽  
Water Surface ◽  
Wave Pattern ◽  
The Body ◽  
Surface Gravity ◽  
Shallow Water Waves ◽  
Ship Waves ◽  
Surface Gravity Waves ◽  
Basic Fluid

This chapter deals with the underlying mathematics of surface gravity waves, defined as gravity waves observed on an air–sea interface of the ocean. Surface gravity waves, or surface waves, differ from internal waves, gravity waves that occur within the body of the water (such as between parts of different densities). Examples of gravity waves are wind-generated waves on the water surface, as well tsunamis and ocean tides. Wind-generated gravity waves on the free surface of the Earth's seas, oceans, ponds, and lakes have a period of between 0.3 and 30 seconds. The chapter first describes the basic fluid equations before discussing the dispersion relations, with a particular focus on deep water waves, shallow water waves, and wavepackets. It also considers ship waves and how dispersion affects the wave pattern produced by a moving object, along with long and short waves.

Analytical bow waves for fine ship bows with rake and flare

2011 ◽  
Vol 55 (01) ◽  
pp. 1-18
Author(s):  
Francis Noblesse ◽  
Gérard Delhommeau ◽  
Patrick Queutey ◽  
Chi Yang ◽  
Hyun Yul Kim
Keyword(s):  
Parametric Study ◽  
Rake Angle ◽  
Wave Profile ◽  
Wave Crest ◽  
Bow Waves ◽  
Bow Wave ◽  
Hydrodynamic Calculations ◽  
Parametric Studies ◽  
Computational Fluid Dynamics Cfd ◽  
Analytical Relations

The bow wave generated by a steadily advancing ship is considered for a family of fine ruled ship bows with rake and flare. This family of ship bows is defined in terms of four parameters: the ship draft D, the entrance angles a and a' at the top and bottom waterlines, and the rake angle 8. The corresponding bow wave similarly depends on four parameters: the draft-based Froude number F and the three angles a, a', and 8. An extensive parametric study, based on thin-ship theory, is performed to explore the variations of the water height Z0 at the ship stem X = 0, the location X0 (measured from the ship stem) of the intersection of the bow-wave profile with the mean free-surface plane Z = 0, and the bow-wave profile, with respect to the four parameters F, a, a', and 8. This parametric study extends the previously reported similar study of the height Zb of the bow wave and the location Xb of the bow-wave crest. These two complementary parametric studies yield simple analytical relations, which extend relations given previously for wedge-shaped ship bows without rake or flare. In spite of their remarkable simplicity, the analytical relations given here yield bow waves that are comparable to computational fluid dynamics (CFD) waves given by Euler-flow calculations. The analytical relations, which explicitly account for the influence of the four primary parameters F, a, a', and 8, can be used immediately—without hydrodynamic calculations—for ship design, notably at early design stages when the precise hull geometry is not yet known. The study also provides insight for ship bow design. Specifically, it suggests that a bow with positive rake and negative flare may be beneficial, and that a bulb located aft of the stem and integrated with the hull may be an advantageous alternative to a traditional bulb protruding ahead of the bow, in agreement with the results of a hull-form optimization analysis.

Wave-Induced Effect on the Airside Velocity Field Above the Wind-Generated Water Waves

2008 ◽  
Author(s):  
Nasiruddin Shaikh ◽  
Kamran Siddiqui
Keyword(s):  
Velocity Field ◽  
Water Waves ◽  
Water Surface ◽  
Flow Behavior ◽  
Wave Crest ◽  
Reynolds Stresses ◽  
Momentum Exchange ◽  
Significant Wave ◽  
Wind Speeds ◽  
Wave Induced

An experimental study was conducted to investigate the influence of surface waves on the airside flow behavior over the water surface. Two-dimensional velocity field in a plane perpendicular to the surface was measured using particle image velocimetry (PIV) at wind speeds of 3.7 and 4.4 m s−1. The results show that the wave induced velocities are significant immediately adjacent to the water surface and their magnitudes decreases with height and become negligible at a height three times the significant wave height. The structure of the wave induced vorticity indicates two different type of flow pattern on the windward and leeward sides of the wave crest. Positive and negative magnitudes of the turbulent and wave induced Reynolds stress respectively, indicates upward and down transfer of momentum flux across air water interface. The results also indicate that the flow dynamics in the region two to three times significant wave heights are significantly different than that at greater heights. Higher magnitudes of the turbulent and wave induced Reynolds stresses were observed in this region which could not be predicted from the measurements at greater heights. Thus, it is concluded the understanding of the wave effects to the airflow field especially within the crest-trough region is vital to improve our knowledge about the air-water heat, mass and momentum exchange.

scholarly journals VORTEX FORMATION IN PLUNGING BREAKER

1986 ◽  
Vol 1 (20) ◽  
pp. 54 ◽  
Author(s):  
T. Sakai ◽  
T. Mizutani ◽  
H. Tanaka ◽  
Y. Tada
Keyword(s):  
Flow Visualization ◽  
Particle Velocity ◽  
Vortex Formation ◽  
Water Particle ◽  
Mac Method ◽  
Long Wave ◽  
Wave Celerity ◽  
Maximum Water ◽  
Slope Beach ◽  
Plunging Breaker

By a flow visualization of a plunging breaker on 1/20 slope beach in a wave tank, an existence of 2nd and 3rd horizontal vortices(Miller, 1976) and slanting vortex (Nadaoka et al., 1986) is confirmed. A MAC method is applied to simulate a violent motion after an impinging of a jet from a crest of a plunging breaker on the trough surface. The calculated maximum water particle velocity in the jet is found to reach three times the linear long wave celerity. Values of circulation of the first four horizontal vortices are calculated and their changes in time are discussed.

Steady wave patterns on a non-uniform steady fluid flow

1960 ◽  
Vol 9 (3) ◽  
pp. 333-346 ◽  
Author(s):  
F. Ursell
Keyword(s):  
Wave Length ◽  
Present Theory ◽  
Wave Pattern ◽  
Wave Crest ◽  
Stream Velocity ◽  
List Type ◽  
Mathematical Form ◽  
Local Wave ◽  
Pass Through ◽  
The Waves

A steady slightly non-uniform flow with a free surface is subject to a concentrated surface pressure which gives rise to a pattern of surface waves. (For gravity waves on deep water this is the well-known Kelvin ship-wave pattern.) The motion is assumed inviscid, and the waves are assumed small. A theory is developed for the wave pattern, based on the following assumptions: The stream velocity component normal to a wave crest is equal to the phase velocity based on the local wavelength;the separation between consecutive crests is equal to the local wave-length. These assumptions are expressed in mathematical form, and the existence of a set of characteristic curves (associated with the group velocity) is deduced from them. These characteristics are not identical with the crests. Let the additional assumption be made thatthe characteristics all pass through the point disturbance; the characteristics are then completely defined and may be constructed by a step-by-step process starting at the point disturbance. The same construction gives the direction of the wave crests at all points. The wave crests can then be deduced.Assumptions of the same type as (1) and (2) have long been familiar in various applications of ray tracing. For uniform flows the present theory gives the same pattern as the method of stationary phase.

scholarly journals GRAPHICAL ANALYSIS OF FREE-SURFACE WAVE FIELDS FROM MOVING SHIPS AND A PAIR OF CONSECUTIVE POSTS

2019 ◽  
Vol 2019 (4) ◽  
pp. 7-22
Author(s):  
Павел Бимбереков ◽  
Pavel Bimberekov
Keyword(s):  
Water Transport ◽  
Water Surface ◽  
Free Water ◽  
Wave Pattern ◽  
Graphical Analysis ◽  
Wave System ◽  
Kelvin Wave ◽  
Experimental Tank ◽  
Wave Patterns ◽  
Pattern Forming

The paper presents a comparison of the photographic material of the wave patterns resulted from the movement of a ship in situ and a model ship, as well as from two consecutive posts, their regularities being found through graphical processing. The possibility to find the fore imaginary source of Kelvin wave pattern forming the ship's wave system is given at a distance of one wavelength before the top of the bow retaining wave. The equality of the length of trans-verse waves and divergent waves along the outer boundaries of the latter zone is fixed. It has been assumed that the intermediate waves generated between the main waves in the model ship and the posts are regular, imposition of wave patterns in a pair of consistently moving racks depending on the hit of the rear rack in the wave field of the first rack has been stated. Regularly occurring flows around moving posts are discussed. The bow and stern system of Kelvin waves in a ship wave sys-tem has been illustrated (the angle of the midpoint of diverging wave crests with the ship’s diamet-rical plane and the angle of diverging wave crests with the ship’s diametrical plane). The photo-graphs presented were taken in the experimental tank of Siberian State University of Water Transport (Novosibirsk State Academy of Water Transport) in 2006. A thin film naturally generat-ed on the water surface of the experimental tank and given a structure directed along the tank due to previous runs helped to visualize the distortion of the free water surface in better quality and to obtain clearly outlined contours in lighting.

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