Experimental Study of Scour Due to Breaking Waves in Front of Vertical-Wall Breakwaters

2004 ◽  
Author(s):  
Ali Hasanzadeh Daloui ◽  
Mirmosadegh Jamali
Keyword(s):  
Experimental Study ◽  
Empirical Equation ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Scour Depth ◽  
Regular Waves ◽  
Factors Affecting ◽  
Wave Flume ◽  
Wave Heights

Scour is an important cause of instability of breakwaters. In case of vertical-wall breakwaters, toe scour can cause collapse of the whole structure. This paper is concerned with an experimental study of the effects of regular breaking waves on scour at toe of vertical-wall breakwaters. Experiments were carried out in a wave flume with regular waves for two cases of a beach with and without a breakwater. Bed profiles and scour depths for various wave heights, periods and depths were recorded. For the case of a beach without a breakwater, the observed bed profile types are compared to predictions. For the case of a beach with a breakwater, factors affecting the scour are investigated, and an empirical equation for scour depth at toe of a vertical wall is proposed.

Numerical Simulation of Breaking Waves in a Wave Group by SPH

2015 ◽  
Vol 776 ◽  
pp. 151-156
Author(s):  
Ni Nyoman Pujianiki
Keyword(s):  
Surf Zone ◽  
Breaking Waves ◽  
Return Flow ◽  
Wave Group ◽  
Regular Waves ◽  
Wave Groups ◽  
Smoothed Particle ◽  
Wave Heights ◽  
Smoothed Particle Hydrodynamic ◽  
Wave Break

Smoothed Particle Hydrodynamic (SPH) numerical model is used to investigate wave group effects at breaking and after breaking by comparing individual waves in a group with equivalent regular waves. Regular wave break almost at the same position and with the same wave height. Meanwhile in a wave group, the wave breaks in the variant positions and with variant wave heights. These phenomena cause the breaking point to be more scattered in a wave group rather than in regular waves. Return flow due to the breaking of wave groups appears more significant and is extended to the full depth in the surf zone rather than in regular waves. Swash oscillations of the wave group in the surf zone appear irregular. Meanwhile in regular waves, swash oscillations are almost constant.

Experimental Study of Turbulent Flow Induced by Regular and Irregular Waves Above a Rock-Armored Slope

2014 ◽  
Author(s):  
Konstantina A. Galani ◽  
Giannis D. Dimou ◽  
Athanassios A. Dimas
Keyword(s):  
Experimental Study ◽  
Turbulent Flow ◽  
Velocity Profiles ◽  
Irregular Waves ◽  
Wave Crest ◽  
Regular Waves ◽  
Mean Velocity ◽  
Peak Period ◽  
Wave Trough ◽  
Wave Heights

The aim of the present work is the experimental study of the turbulent flow induced by waves above a physical model of a rock-armored slope of 1/3. The armor consisted of two layers of rocks with characteristic diameter D50 = 4.4cm. Measurements of the instantaneous velocity fields were conducted using an underwater planar PIV system. Four cases of incoming waves were tested, two cases of regular waves of 1st order Stokes theory with wave period of 1.134s and wave heights of 0.04m and 0.08m, respectively, and two cases of irregular waves, generated from a JONSWAP spectrum, with a peak period of 1.134s and significant wave heights of 0.04m and 0.08m, respectively. For the regular waves, the period-averaged velocity profiles show the existence of a strong undertow current heading towards deep water, while turbulence is not homogeneous with larger horizontal fluctuations. The phase-averaged horizontal velocity profiles present systematically larger values during wave trough passage than during wave crest passage. Furthermore, as the depth becomes smaller, the waveform loses its symmetry, with the wave trough becoming wider and the wave crest steeper. For the irregular waves, the mean velocity profiles show the existence of an undertow current weaker in magnitude than the one in the regular waves, while turbulence is still not homogeneous with larger horizontal fluctuations. For both wave cases, spanwise vorticity, which is generated at the rough surface of the rock-armored slope, is transported landward by the turbulent velocities.

Effectiveness of Small Onshore Seawall in Reducing Forces Induced by Tsunami Bore: Large Scale Experimental Study

2009 ◽  
Vol 4 (6) ◽  
pp. 382-390 ◽  
Author(s):  
Mary Elizabeth Oshnack ◽  
◽  
Francisco Aguíñiga ◽  
Daniel Cox ◽  
Rakesh Gupta ◽  
...  
Keyword(s):  
Experimental Study ◽  
Large Scale ◽  
Rigid Wall ◽  
Wave Profile ◽  
Small Individual ◽  
Wave Flume ◽  
Pressure Distributions ◽  
Field Reconnaissance ◽  
Wave Heights ◽  
Wire Resistance

Tsunami force and pressure distributions on a rigid wall fronted by a small seawall were determined experimentally in a large-scale wave flume. Six different seawall heights were examined, two of which were exposed to a range of solitary wave heights. The same experiment was done without a seawall for comparison. The measured wave profile contained incident offshore, incident broken, reflected broken, and transmitted wave heights measured using wire resistance and ultrasonic wave gauges. Small individual seawalls increased reflection of the incoming broken bore front and reduced force on the rigid landward wall. These findings agree well with published field reconnaissance on small seawalls in Thailand that showed a correlation between seawalls and reduced damage on landward structures.

scholarly journals TRANSMISSION OF REGULAR WAVES PAST FLOATING PLATES

1974 ◽  
Vol 1 (14) ◽  
pp. 112
Author(s):  
Uygur Sendil ◽  
W.H. Graf
Keyword(s):  
Water Depth ◽  
Wave Length ◽  
Wave Theory ◽  
Finite Amplitude ◽  
Linear Wave ◽  
Regular Waves ◽  
Transmission Coefficients ◽  
Wave Flume ◽  
Wave Heights ◽  
Incident Waves

Theoretical solutions for the transmission beyond and reflection of waves from fixed and floating plates are based upon linear wave theory, as put forth by John (1949), and Stoker (1957), according to which the flow is irrotational, the fluid is incompressible and frictionless, and the waves are of small amplitude. The resulting theoretical relations are rather complicated, and furthermore, it is assumed that the water depth is very small in comparison to the wave length. Wave transmissions beyond floating horizontal plates are studied in a laboratory wave flume. Regular (harmonic) waves of different heights and periods are generated. The experiments are carried out over a range of wave heights from 0.21 to 8.17 cm (0.007 to 0.268 ft), and wave periods from 0.60 to 4.00 seconds in water depth of 15.2, 30.5, and 45.7 cm (0.5, 1.0 and 1.5 ft). Floating plates of 61, 91 and 122 cm (2, 3 and 4 ft) long were used. From the analyses of regular waves it was found that: (1) the transmission coefficients, H /H , obtained from the experiments are usually less than those obtained from the theory. This is due to the energy dissipation by the plate, which is not considered in the theory. (2) John's (1949) theory predicts the transmission coefficients, H /H , reasonably well for a floating plywood plate, moored to the bottom and under the action of non-breaking incident waves of finite amplitude. (3) a floating plate is less effective in damping the incident waves than a fixed plate of the same length.

scholarly journals Experimental Evidence of the Influence of Recurves on Wave Loads at Vertical Seawalls

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 889 ◽  
Author(s):  
Dimitris Stagonas ◽  
Rajendran Ravindar ◽  
Venkatachalam Sriram ◽  
Stefan Schimmels
Keyword(s):  
Large Scale ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Wave Loads ◽  
Incoming Wave ◽  
Wave Heights ◽  
The Mean ◽  
Peak Pressures ◽  
Wave Induced ◽  
Incident Waves

The role of recurves on top of seawalls in reducing overtopping has been previously shown but their influence in the distribution and magnitude of wave-induced pressures and forces on the seawall remains largely unexplored. This paper deals with the effects of different recurve geometries on the loads acting on the vertical wall. Three geometries with different arc lengths, or extremity angles (αe), were investigated in large-scale physical model tests with regular waves, resulting in a range of pulsating (non-breaking waves) to impulsive (breaking waves) conditions at the structure. As the waves hit the seawall, the up-rushing flow is deflected seawards by the recurve and eventually, re-enters the underlying water column and interacts with the next incoming wave. The re-entering water mass is, intuitively, expected to alter the incident waves but it was found that the recurve shape does not affect wave heights significantly. For purely pulsating conditions, the influence of αe on peak pressures and forces was also negligible. In marked contrast, the mean of the maximum impulsive pressure and force peaks increased, even by a factor of more than two, with the extremity angle. While there is no clear relation between the shape of the recurve and the mean peak pressures and forces, interestingly the mean of the 10% highest forces increases gradually with αe and this effect becomes more pronounced with increasing impact intensity.

Experimental Study on Changes of Sloping Sandy Bed Profile under Breaking Waves

2012 ◽  
Vol 212-213 ◽  
pp. 163-168
Author(s):  
Yun Pan ◽  
Yong Zhou Cheng ◽  
Qing Feng Li ◽  
Wen Cheng Wang
Keyword(s):  
Wave Breaking ◽  
Orbital Motion ◽  
Breaking Waves ◽  
Coastal Structures ◽  
Wave Flume ◽  
Sand Ripple ◽  
Wide Range ◽  
Wave Heights ◽  
Formation And Evolution ◽  
Sand Bar

The wave breaking forces can exacerbate sediment transport, and lead to erosion of the seabed, coastal deformation and destruction of coastal structures. The experiment is carried out in a wave flume with a 1:30 sloping sandy seabed. A wide range of measurements from the regular wave runs are reported, including time series of wave heights, changes of bed profile. The video records are analysed to measure the time development of the seabed form and the characteristics of the orbital motion of the sand in the wave breaking region. The location and wave height at wave breaking point is measured by experiment. Formation and evolution of sand ripple and sand bar are studied under the breaking waves. It is found that effect of bed surface on wave breaking zone is more significant than wave non-breaking.

scholarly journals Scour downstream of a corrugated apron under wall jets

2021 ◽  
Author(s):  
Rakesh Kumar Chaudhary ◽  
Zulfequar Ahmad ◽  
Surendra Kumar Mishra
Keyword(s):  
Flow Parameter ◽  
Empirical Equation ◽  
Wave Length ◽  
Flow Characteristics ◽  
Scour Depth ◽  
Wall Jets ◽  
Factors Affecting ◽  
Scour Holes ◽  
Velocity Turbulence ◽  
Single Size

Abstract Experiments were performed over smooth and corrugated aprons with different corrugation dimensions to study the scour and flow characteristics under submerged wall jets condition. The scour depth and length are significantly lower for corrugated than smooth rigid aprons. The maximum reductions in scour depth and length are 79 and 83%, respectively. Optimum scour depth and length are found for aspect ratio (ratio of corrugation wave length to amplitude) three for corrugated apron. The factors affecting scour depth and length were analyzed graphically, and empirical equations are proposed for predicting maximum scour depth and length, and the point of maximum scour depth for corrugated aprons. Velocity, turbulence characteristics, and Reynolds stress in scour holes for smooth and corrugated aprons were also studied. HIGHLIGHT This paper presents the scour downstream of corrugated apron and flow characteristics under submerged wall jets. Here scour depth and length reduces significantly than other apron. In this we have tried to develop empirical equation on single size sediment considering all the flow parameter and apron parameter. Besides this we have also conducted study related to turbulence and shear stress and velocity vector profile.

LABORATORY EXPERIMENTS ABOUT BED PATTERNS IN THE SHOALING REGION UNDER REGULAR WAVES AND REFLECTING CONDITIONS

2017 ◽  
pp. 25
Author(s):  
Manuel Cobos ◽  
María Clavero ◽  
Sandro Longo ◽  
Asunción Baquerizo ◽  
Miguel Angel Losada
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Sediment Transport ◽  
Laboratory Experiments ◽  
Breaking Waves ◽  
Spatial Modulation ◽  
Small Scale ◽  
Growth Mechanisms ◽  
Free Surface Elevation ◽  
Regular Waves

This research is an experimental study of ripple dynamic for regular waves propagating on horizontal and sloping beds in mid- and high-reflective conditions. Small-scale laboratory experiments were carried out on shoaling region (with non breaking waves) and sediment transport in bedload regime. Our experiments showed the key role that plays the reflection in ripple development. The spatial modulation of the free surface elevation due to reflection created sandbars. Ripples grew up in the region where sandbars were appearing. These patterns were gradually reproduced from breakwater to offshore. The incidence of sandbar created a bi-modal structure of ripple geometry. The larger ripples appeared in the crest of sandbars whereas smaller ripples were found in the troughs. Furthermore, it was found that the evolution of ripples at these two locations can be explained by means of different growth mechanisms. Finally, at equilibrium stages, ripple height converges reaching the same height along the sandbar while ripple length and steepness remains almost constant.

scholarly journals HONOLULU REEF RUNWAY DIKE

1970 ◽  
Vol 1 (12) ◽  
pp. 99
Author(s):  
Robert Q. Palmer ◽  
James R. Walker
Keyword(s):  
Water Depth ◽  
Water Surface ◽  
Breaking Waves ◽  
Model Tests ◽  
Transmitted Wave ◽  
Bottom Slope ◽  
Wave Runup ◽  
Wave Flume ◽  
Economical Design ◽  
Wave Heights

Criteria for design of a wave barrier to protect the proposed Honolulu International Airport Reef Runway from breaking waves were developed in wave flume model tests Structures with tribar and quarrystone armor units placed in single and multiple layers, on homogeneous and composite slopes, were subjected to both overtopping and non-overtopping breaking waves Data on wave runup, armor unit stability, quantities of overtopping water, and transmitted wave heights were obtained using a 1 50 bottom slope, which modeled the irregular coral bathymetry seaward of the proposed structure The model to prototype scale ratios ranged from 1 5 to 1 35 Model Tests indicated that the weight of armor units placed below one-third the water depth may be three-fourths that of the units located near the water surface It was noted that the maximum wave runup was 1 8 times the water depth fronting the structure Data were obtained concerning quantities of overtopping water and transmitted wave heights over the low barriers The study augments available criteria for economical design of structures subjected to breaking waves.

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