scholarly journals EROSION AROUND A PILE DUE TO CURRENT AND BREAKING WAVES

1988 ◽  
Vol 1 (21) ◽  
pp. 102 ◽  
Author(s):  
E.W. Bijker ◽  
C.A. De Bruyn
Keyword(s):  
Shear Stress ◽  
Breaking Waves ◽  
Velocity Profiles ◽  
Long Waves ◽  
Orbital Velocity ◽  
Bottom Shear Stress ◽  
Normal Waves ◽  
Short Waves ◽  
A Current

Tests have been performed on a vertical pile subject to current only and to a combination of current with normal waves and current with breaking waves. The scour around the pile produced by current only is decreased by normal short waves superimposed upon that current and increased when breaking waves are superimposed upon the current. After analysis of the velocity profiles in the undisturbed area upstream of the pile and next to the pile, the following explanation is found for this phenomenon. When normal short waves are superimposed upon a current, the bottom shear stress of the combination of current with waves is increased more in the undisturbed area than next to the pile in the scour area. This results in a decrease of the scour around the pile. Due to the large values of the orbital velocity under breaking waves this effect is reversed for the combination of a current with breaking and relatively long waves. This results in an increase of the scour around the pile.

scholarly journals The modulation of short gravity waves by long waves or currents

1988 ◽  
Vol 29 (4) ◽  
pp. 410-429 ◽  
Author(s):  
R. Grimshaw
Keyword(s):  
Gravity Waves ◽  
Finite Amplitude ◽  
Basic Flow ◽  
Long Waves ◽  
Water Current ◽  
Kinematic Equation ◽  
Local Dispersion ◽  
Short Waves ◽  
First Case ◽  
A Current

AbstractThe modulation of short gravity waves by long waves or currents is described for the situation when the flow is irrotational and when the short waves are described by linearised equations. Two cases are distinguished depending on whether the basic flow can be characterised as a deep-water current, or a shallow-water current. In both cases the basic flow has a current which has finite amplitude, while in the first case the free surface slope of the basic flow can be finite, but in the second case is small. The modulation equations are the local dispersion relation of the short waves, the kinematic equation for conservation of wave crests and the wave action equation. The results incorporate and extend the earlier work of Longuet-Higgins and Stewart [10, 11].

Measurement and numerical modeling studies of the highest bottom shear stress in the Randle Reef area

2014 ◽  
Vol 41 (9) ◽  
pp. 828-838 ◽  
Author(s):  
Cheng He ◽  
Eric Scott ◽  
Matthew Graham ◽  
Andrew Binns
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Open Water ◽  
Bottom Layer ◽  
Velocity Profiles ◽  
Flow Speed ◽  
Model Verification ◽  
Bottom Shear Stress ◽  
Study Region ◽  
Quadratic Formula

The purpose of this study was to investigate the highest bottom shear stress, induced by wind in an area of Hamilton Harbour, Ontario, Canada known as Randle Reef. The study was conducted in support of a component of a contaminated sediment remediation plan utilizing a thin layer of sand to manage contaminated sediments. Toward this end, four acoustic Doppler current profilers (ADCPs) were deployed at two locations in the study region to measure velocity profiles for the purpose of indirectly measuring bottom shear stress (BSS) and model verification. There is no easy way to directly measure BSS in the field. As a result, the use of the logarithmic-profile method from the ADCP measured high resolution velocity profiles in the bottom layer was explored. This approach, according to our best knowledge, has not been published for a wind driven flow in a small open water body. To use the indirectly measured BSS to estimate the highest BSS in the study area, a three-dimensional hydrodynamic model was adopted to provide the spatial and temporal information of the bottom flow. The results showed that the modeled and measured flow velocity components agreed reasonably well at most of the water depths with the correlation coefficients being greater than 0.6. However, agreements between the modeled and measured bottom flow speeds were worse than expected due to the error contributions from both the modeled velocity components. Therefore, the modeled flow speed required rescaling based on ADCP velocity measurements before it could be deemed reliable. This is especially important in estimation of the BSS with a quadratic formula because the calculated BSS is proportional to the square of the speed.

scholarly journals ON WAVE DEFORMATION AFTER BREAKING

1974 ◽  
Vol 1 (14) ◽  
pp. 27
Author(s):  
Toru Sawaragi ◽  
Koichiro Iwata
Keyword(s):  
Shear Stress ◽  
Energy Dissipation ◽  
Basic Equation ◽  
Air Entrainment ◽  
Breaking Waves ◽  
Bottom Friction ◽  
Bottom Shear Stress ◽  
Frequency Wave ◽  
Horizontal Roller ◽  
Plunging Breaker

Waves will dissipate their energy rapidly after breaking. In this paper, the three factors , (i) formation of a horizontal roller,(11) bottom friction, and (in) turbulence with air entrainment, which will contribute to the energy dissipation, are dealt with experimentally and theoretically The horizontal roller formed by a plunging breaker is approximated as a Rankme-type vortex by experiments, and it is calculated that 15$-30%of wave energy is dissipated due to the formation of horizontal roller alone from a breaking point to a point of the roller disappearance. A bottom shear stress due to a breaker is measured by the shear meter deviced by the authors and it is clarified that the energy dissipation due to bottom friction is a little Mam part of the energy dissipation is taken to be caused by the turbulence with air entrainment. It is indicated that an incident monocromatic wave is transformed into a higher frequency wave due to the turbulence. Furthermore, a new basic equation for breaking waves with a turbulence term expressed by a Reynolds stress is presented The theoretical curves computed numerically have a consistent agreement with the experimental results.

scholarly journals RELATIONSHIP BETWEEN BOTTOM SHEAR STRESS AND TURBIDITY IN ESTUARIES

2011 ◽  
Vol 67 (4) ◽  
pp. I_1591-I_1596
Author(s):  
Jun-ichi SAKAMOTO ◽  
Haruhiko MATSUMOTO ◽  
Kesayoshi HADANO ◽  
Takuzo AMANO ◽  
Kiyonobu MITSUNOBU
Keyword(s):  
Shear Stress ◽  
Bottom Shear Stress

The Propagation of Compressional Waves in a Dispersive Elastic Rod: Part II—Experimental Results and Comparison With Theory

1957 ◽  
Vol 24 (2) ◽  
pp. 240-244
Author(s):  
Julius Miklowitz ◽  
C. R. Nisewanger
Keyword(s):  
Shock Tube ◽  
Longitudinal Mode ◽  
Long Waves ◽  
Experimental Results ◽  
Radial Mode ◽  
Approximate Representation ◽  
Elastic Rod ◽  
Compressional Waves ◽  
Short Waves

Abstract Experimental results, obtained by employing an aerodynamic shock tube for rod excitation, are presented. Comparison of these results with the theoretical information presented in Part I is made. It is shown that the Mindlin-Herrmann theory, through its upper mode (radial), offers a good approximate representation of the moderately short waves that predominate at the later times at a random station of the rod. The very short waves of this same radial mode, however, govern the early disturbance, thus precluding the possibility of representing this portion of the disturbance, which the experiment shows to be composed of relatively long waves, by the longitudinal mode of the theory.

Extreme long waves over a varying bathymetry

2019 ◽  
Vol 878 ◽  
pp. 481-501 ◽  
Author(s):  
James G. Herterich ◽  
Frédéric Dias
Keyword(s):  
Conformal Mapping ◽  
Wave Breaking ◽  
Breaking Strength ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Long Waves ◽  
Amplitude Wave ◽  
One Dimensional ◽  
Wave Interference ◽  
Initial Wave

Recent modelling work has shown that abrupt bathymetric transitions can produce dramatic amplifications of long waves, under the influence of both nonlinearity and dispersion. Here, the evolution of wave packets towards a vertical wall over a varying bathymetry is investigated with a one-dimensional conformal-mapping spectral code. In this system, wave breaking, runup and reflection, wave interference and bathymetric effects are highlighted. Wave breaking is examined with respect to geometric, kinematic and energetic conditions, with consistent results. The breaking strength is characterized for spilling and plunging based on initial wave period and amplitude. Non-breaking waves are amplified by reflection, interference and the bathymetry leading to large runups. In a typical example inspired by a real-world bathymetry, the maximum runup amplification approaches a factor of 12 – large enough for a 3 m amplitude wave to overtop a 30 m cliff.

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