scholarly journals THEORETICAL FORMS OF SHORELINES

1964 ◽  
Vol 1 (9) ◽  
pp. 14 ◽  
Author(s):  
W. Grijm
Keyword(s):  
Wave Front ◽  
Laboratory Tests ◽  
Coastal Engineering ◽  
Mathematical Treatment ◽  
Maximum Value ◽  
The Waves

Laboratory tests say that the littoral transport by waves reaches a maximum value when the waves approach the shore obliquely. In some way this must lead to peculiarities in the forms of shorelines. Therefore we put the question what types of shorelines can mathematically exist assuming the littoral transport is ruled by the function sin 2oC where c< is the angle between the wave front and the shoreline. This yields some basic types of shorelines. After a brief description of the mathematical treatment these results will be discussed. This paper is a continuation of the paper presented on the same subject at the 7 conference on coastal engineering.

scholarly journals PHYSICAL REQUIREMENTS FOR A TAKEOFF IN SURFING

2017 ◽  
pp. 30
Author(s):  
Akihiko Kimura ◽  
Taro Kakinuma
Keyword(s):  
Wave Front ◽  
Time Variation ◽  
Wave Breaking ◽  
Horizontal Component ◽  
Breaking Point ◽  
Front Face ◽  
The Waves

The conditions required for a takeoff in surfing, are discussed, with the waves simulated numerically, considering two types of wave breaking, i.e., a plunging type, and a spilling type. First, a surfer is required to obtain a sufficient value for the horizontal component of paddling speed, not to be overtaken by a wave peak. Second, when the surfer stops paddling, he needs to be floating at a location where the force on him is downward, along the wave front face. On the basis of both conditions, the time variation of the required value for the horizontal component of paddling speed, is evaluated for both the plunging-type, and spilling-type, cases. When the paddling speed is sufficient, the surfable area is larger in the former case, than in the latter, on the offshore side of the wave-breaking point.

scholarly journals Solitary Wave Formation from a Generalized Rosenau Equation

2016 ◽  
Vol 2016 ◽  
pp. 1-17 ◽  
Author(s):  
J. I. Ramos ◽  
C. M. García-López
Keyword(s):  
Wave Front ◽  
Fourth Order ◽  
Accurate Method ◽  
Amplitude Curve ◽  
Convective Term ◽  
Compact Finite Differences ◽  
Rosenau Equation ◽  
Spatial Derivatives ◽  
Fifth Order ◽  
The Waves

A generalized viscous Rosenau equation containing linear and nonlinear advective terms and mixed third- and fifth-order derivatives is studied numerically by means of an implicit second-order accurate method in time that treats the first-, second-, and fourth-order spatial derivatives as unknown and discretizes them by means of three-point, fourth-order accurate, compact finite differences. It is shown that the effect of the viscosity is to decrease the amplitude, curve the wave trajectory, and increase the number and width of the waves that emerge from an initial Gaussian condition, whereas the linear convective term pushes the wave front towards the downstream boundary. It is also shown that the effect of the nonlinear convective term is to increase the steepness of the leading wave front and the number of sawtooth waves that are generated behind it, while that of the first dispersive term is to increase the number of waves that break up from the initial condition as the coefficient that characterizes this term is decreased. It is also shown that, for reasons of stability, the second dispersion coefficient must be much smaller than the first one and its effects on wave propagation are relatively small.

scholarly journals Railway catenary tension force monitoring via the analysis of wave propagation in cables

2020 ◽  
pp. 095440972094172
Author(s):  
Stefano Derosa ◽  
Petter Nåvik ◽  
Andrea Collina ◽  
Anders Rønnquist
Keyword(s):  
Laboratory Tests ◽  
Vertical Acceleration ◽  
Analytical Formulation ◽  
Contact Wire ◽  
The Status ◽  
Force Monitoring ◽  
Catenary System ◽  
The Wire ◽  
Propagation Of Waves ◽  
The Waves

The tensioning forces applied to the contact wire in a railway catenary system influence the performance of the line. In this paper, a method to monitor the status of such tensioning forces is proposed based on the dependency that the waves that propagate through a tensioned wire have on the forces that pull the wire itself. A novel analytical formulation for the propagation of waves in a tensioned wire was proposed, and it was used to obtain the vertical acceleration of the wire when an external force acts as a concentrated input. The analysis of the acceleration with a moving standard deviation allowed a method to be defined for the generation of an index that describes the trend of the tensioning forces. The method was then tested on the wire accelerations obtained with laboratory tests and, afterwards, on the accelerations recorded on a contact wire of an electric railway regularly in operation and excited with the same kind of input.

Focusing of weak shock waves at an arête

1978 ◽  
Vol 88 (2) ◽  
pp. 209-222 ◽  
Author(s):  
M. S. Cramer ◽  
A. R. Seebass
Keyword(s):  
Shock Waves ◽  
Rate Of Convergence ◽  
Wave Front ◽  
Initial Conditions ◽  
Pressure Coefficient ◽  
Weak Shock ◽  
Linear Solution ◽  
Initial Strength ◽  
Maximum Value

The focusing of very weak and slightly concave symmetrical shock waves is examined. The equation that describes this focusing is derived and the resulting similitude discussed. The initial conditions come from a formal matching of this nonlinear description with the linear solution. The maximum value of the pressure coefficient is shown to be proportional to the two-thirds power of both the initial strength of the wave front and a parameter characterizing its rate of convergence.

scholarly journals Acute Kidney Injury and Creatine Kinase Elevation After Beginning Treatment with Levetiracetam

2018 ◽  
Vol 13 (2) ◽  
pp. 113
Author(s):  
Francisco-Javier Mena-Martin ◽  
Alfonso Gutierrez-Garcia ◽  
Juan-Carlos Martin-Escudero ◽  
Olga Fernandez-Arconada ◽  
◽  
...  
Keyword(s):  
Intensive Care Unit ◽  
Acute Kidney Injury ◽  
Creatine Kinase ◽  
Adverse Effects ◽  
Laboratory Tests ◽  
Excretion Rate ◽  
Kidney Injury ◽  
Albumin Excretion Rate ◽  
Blood Tests ◽  
Maximum Value

Levetiracetam (LEV) is one of the most common anti-epileptic drugs available. In general, it is tolerated relatively well; the majority of adverse effects are moderate and normally occur during the initial titration. We present a patient who developed two moderately serious adverse effects after an initial LEV dose: a 28-year-old male was admitted to intensive care unit after suffering two generalised seizures, and was given 1000 mg of LEV. Twenty-four hours after admittance, the laboratory tests showed a serum creatinine of 2.84 mg/dL and creatine kinase (CK) of 421 U/L (normal, 0–171 U/L). At all times the diuresis was normal, with a maximum value of creatinine of 4.67 mg/dL 48 hours following admittance, and the CK values ranged between 421–681 U/L with proteinuria of 840 mg/day. On the seventh day, blood tests showed a CK of 1,559 U/L and a creatinine of 1.55 mg/dL. LEV was progressively substituted for lacosamide, after which creatinine, CK and albumin excretion rate were normalised. Thus, CK and renal function during treatment with LEV should be monitored, and acute kidney injury due to LEV should be considered in the differential diagnosis for any unexplained acute renal failure.

scholarly journals EXPERIMENTAL DATA ON THE OVERTOPPING OF SEAWALLS BY WAVES

2011 ◽  
Vol 1 (7) ◽  
pp. 36
Author(s):  
A. Paape
Keyword(s):  
Wave Height ◽  
Know How ◽  
The Past ◽  
Maximum Value ◽  
Wave Heights ◽  
Run Up ◽  
Materials Used ◽  
The Stability ◽  
The Waves ◽  
Made In

In the past it has been found that serious damage and breaching of seawalls is most frequently caused by overtopping. Hence for the design of seawalls data must be available about the overtopping by waves of the different profiles that might be possible. Naturally the conditions under which damage is caused to the seawall also depend on the type of construction and the materials used, for example: the stability of grass covered dikes can be endangered seriously by water flowing over the inner slope. In many designs the necessary height of a seawall has been defined such that not more than 2% of the waves overtop the crest, under chosen design conditions. This criterion has been determined on the assumption that the overtopping must remain very small. Some overtopping has to be accepted because no maximum value for wave height and wave run-up can be given, unless of course the wave height is limited by fore-shore conditions. Unfortunately this criterion gives no information about the volume and concentration of water overtopping the crest in each instance. Moreover it is of interest to know how this overtopping varies with other conditions, such as changes in the significant wave height. Information about the overtopping by waves was obtained from model investigations on simple plane slopes w^th inclinations varying from 1 : 8 to 1 : 2. The experiments were made in a windflume where wind generated waves as well as regular waves were employed. Using wind generated waves, conditions from nature regarding the distribution of wave heights could be reproduced. It appeared that the overtopping depends on the irregularity of the waves and that the same effects cannot be reproduced using regular paddle generated waves. In this paper a description of the model and the results of these tests are given. Investigations are m progress on composite slopes, including the reproduction of conditions for a seawall which suffered much overtopping but remained practically undamaged during the flood of 1953.

scholarly journals WAVE DIRECTION COMPUTATIONS WITH THREE GAGE ARRAYS

1976 ◽  
Vol 1 (15) ◽  
pp. 19 ◽  
Author(s):  
D. Esteva
Keyword(s):  
Pressure Sensors ◽  
Coastal Engineering ◽  
Aerial Photographs ◽  
Wave Direction ◽  
Coastal Structures ◽  
Linear Arrays ◽  
Directional Spectrum ◽  
Engineering Research ◽  
Mathematical Expressions ◽  
The Waves

Wave direction is an important parameter in the solution of many coastal engineering problems such as the estimation of sediment transport and the response of coastal structures. Wave-gage arrays are among the most widely proposed systems for measuring wave direction. In late March 1970, the U.S. Army Coastal Engineering Research Center (CERC) installed an array of five pressure sensors off the California coast. Figure 1 gives the location of the array, its geometry and dimensions. The water depth at the site was approximately 9.14 meters (30 feet) and the gages were positioned .76 meters (2.5 feet) from the bottom. One use for the array data would be to compare redundant values of wave direction and estimate the level of accuracy of the computations. Redundant values of direction were obtained from the ten three-gage arrays possible with five gages. Three-gage arrays offer some advantages over arrays involving a larger number of gages and have been proposed by many investigators. An obvious advantage involves economics. Non-linear arrays offer the advantage over linear arrays that straight forward mathematical expressions can be derived for the unambigous computation of direction. These expressions involve the phase differences between gage pairs for the waves present, no recourse to two-dimensional spectral analysis is necessary. However, it is necessary to assume long and relatively straight crested waves, traveling in well determined directions, and geometrically stationary over the array. The first two assumptions are supported by high altitude aerial photographs, Figure 2 and, by radar scans of the wave field, Figure 3. Fujinawa (1975) conjectures that narrow directional spread is responsible for the incomplete recovery of the true directional spectrum from field records in his computations using high directional resolution.

Laboratory observations of bedforms under directional irregular waves

1993 ◽  
Vol 20 (4) ◽  
pp. 550-563 ◽  
Author(s):  
D. H. Willis ◽  
M. H. Davies ◽  
G. R. Mogridge
Keyword(s):  
Key Words ◽  
Incident Wave ◽  
Water Waves ◽  
Laboratory Tests ◽  
Large Scale ◽  
Research Council ◽  
National Research Council ◽  
Irregular Waves ◽  
Two Dimensional ◽  
The Waves

Large-scale laboratory tests of the evolution of bedforms in sand beds, under directional irregular waves, carried out at the National Research Council Canada, are described. Preliminary observations indicate that the directionality of the waves is not an important factor; bedforms remained largely two-dimensional under all but transitional conditions. Incident wave height and period, probably combined as a wave orbital amplitude near the bed, seems to be the most important factor in determining bedform dimensions, followed by the D50 sand size on the bed. Sand gradation may be unimportant. Key words: seabed, sand, water waves, bedforms, morphology, roughness.

scholarly journals Modelling of Potential Tsunami in Makassar Strait, Indonesia: Submarine Landslide-Induced Tsunami Simulations

2021 ◽  
Author(s):  
Gugum Gumbira ◽  
Mardi Wibowo ◽  
Hanah Khoirunnisa ◽  
Shofia Karima ◽  
Widjo Kongko
Keyword(s):  
Numerical Models ◽  
Submarine Landslide ◽  
Tsunami Modelling ◽  
Maximum Value ◽  
Landslide Volume ◽  
Wave Heights ◽  
Initiation Stage ◽  
Run Up ◽  
Hazard Level ◽  
The Waves

Abstract Tsunami modelling of potential landslide-induced tsunami in Makassar Strait is carried out to quantify possible damage to the nearby cities. Two numerical models are used to represent the wave generation and propagation by using NHWAVE and FUNWAVE models, respectively. The simulations consist of a series of scenarios based on distinct size of the landslide volume. Four landslides with volume 5, 8, 70, and 200 km 3 are used as tsunami sources in the initiation stage. The sources are evenly distributed in the Strait addressing different landslide location. Maximum wave heights of 1.5 m are found in the area between Palu and Bangkir from case 1 and around Talok from case 2 simulations. The empirical run-up calculation of 7.5 m is estimated at the land for the presented wave height. The value significantly elevates the case 3 and 4 proportional to the volume values. The waves impact more than half of coastline with maximum value found in the Sulawesi side. Interestingly, wide and narrow shelf next to Kalimantan Island plays an important role in reducing the tsunami hazard level.

Solitons in a magnetized ion-beam plasma system

1993 ◽  
Vol 50 (3) ◽  
pp. 349-357 ◽  
Author(s):  
B. C. Kalita ◽  
M. K. Kalita ◽  
R. P. Bhatta
Keyword(s):  
Magnetic Field ◽  
Ion Beam ◽  
Magnetized Plasma ◽  
Plasma System ◽  
Ion Density ◽  
One Dimensional ◽  
Maximum Value ◽  
The Waves ◽  
The Magnetic Field ◽  
Constant Maximum

The formation of ion-acoustic solitary waves in a magnetized plasma with stationary ions and beam ions together with inertia-less electrons is investigated. The generation of waves in a plane is assumed to be one-dimensional, in a direction inclined at an angle θ to the direction of the magnetic field, with constant drift velocity of the ion beam. Remarkably, the amplitudes of the solitons are found to attain a maximum value at a particular beam-ion velocity γ, and then decrease slightly and remain almost constant for higher γ. The width of the waves is large at small y for small beam-ion density Nb, but it attains a constant minimum value at a particular value of γ. The amplitude decreases sharply to zero with decreasing y, whereas it remains almost constantly high for larger y. It is observed that as a wave approaches the direction of the magnetic field, its amplitude increases to a constant maximum value, which is larger for higher beam-ion velocities.

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