scholarly journals WAVE HEIGHT MEASURING EQUIPMENT

2011 ◽  
Vol 1 (7) ◽  
pp. 7
Author(s):  
E.H. Boiten
Keyword(s):  
Wave Height ◽  
Water Surface ◽  
Measuring Equipment ◽  
Wave Motion ◽  
Sea Waves ◽  
Recording Equipment ◽  
Wave Measurements ◽  
Frequency Modulate ◽  
The Waves ◽  
Made In

The equipment was designed to obtain data from sea waves. It was developed by the Organization for Applied Scientific Research at Delft in coordination with the Royal Dutch Navy. The intention of the measurements with the wave height measuring equipment was to establish a correlation between the sea motion and the movements of a ship, which is steaming in that sea. So wave measurements and measurements of the ship movements were always carried out simultaneously. To have the movement of the ship free from the position of the wave meter, a telemetering system was chosen to transmit the data from the wave meter. The receiving and recording instruments are placed on board the ship. The first measurement was made in December 1958. At that moment, the wave meter consisted of a buoy assembly in which was mounted a transmitter coupled with an accelerometer. The accelerometer measured the accelerations of the wave meter in a direction perpendicular to the water surface. The carrier of the transmitter was direct frequency modulated by the signal of the accelerometer. After this measurement it became desirable to gather more data from the sea waves. For that reason the instrumentation of the wave meter was extended with a gyro, which measures the slope of the waves. The slope is determined by the angles of the water surface with respect to the horizontal plane in two directions perpendicular to each other. The angle signals frequency-modulate two subcarriers, which in their turn amplitude-modulated the transmitter carrier . With this more complicated equipment a measurement was made in November 1959. In this paper a description is given of the instrumentation of the wave meter and the receiving and recording equipment as it is at the present with a slightly changed modulating system. As the data from the wave meter could be used to study only the wave motion apart from the ship, it seems reasonable to present this paper at this conference.

scholarly journals WAVES IN WETLANDS: HURRICANE GUSTAV

2011 ◽  
Vol 1 (32) ◽  
pp. 29 ◽  
Author(s):  
Jane McKee Smith ◽  
Robert E. Jensen ◽  
Andrew B. Kennedy ◽  
J. Casey Dietrich ◽  
Joannes J. Westerink
Keyword(s):  
Circulation Model ◽  
Wave Model ◽  
High Energy ◽  
Generation Model ◽  
Wave Modeling ◽  
Wave Measurements ◽  
The Waves ◽  
Variable Water ◽  
Water Depths ◽  
Made In

Few wave measurements have been made in wetlands during high-energy, surge events, such as hurricanes. During Hurricane Gustav in 2008, many nearshore wave measurements were made in Southeastern Louisiana. These data are used to verify a nearshore wave modeling system and to explore the characteristics of hurricane waves in wetlands. The modeling system consists of the wave generation model WAM, the nearhsore wave model STWAVE, and the circulation model ADCIRC. The measurements confirm reasonable success in modeling the waves. The measurements and modeling also expose some of the problems of measuring waves in highly-variable water depths under hurricane forcing and modeling waves in rapidly degrading wetlands.

scholarly journals THE INTERACTION OF WAVES AND CURRENTS OVER A LONGSHORE BAR

1986 ◽  
Vol 1 (20) ◽  
pp. 116 ◽  
Author(s):  
I.A. Svendsen ◽  
J. Buhr Hansen
Keyword(s):  
Wave Height ◽  
Wave Motion ◽  
Surf Zone ◽  
Wave Theory ◽  
Runge Kutta Method ◽  
Waves And Currents ◽  
Set Up ◽  
The Waves ◽  
Wave Properties ◽  
A Current

A two-dimensional model for waves and steady currents in the surf zone is developed. It is based on a depth integrated and time averaged version of the equations for the conservation of mass, momentum, and wave energy. A numerical solution is described based on a fourth order Runge-Kutta method. The solution yields the variation of wave height, set-up, and current in the surf zone, taking into account the mass flux in the waves. In its general form any wave theory can be used for the wave properties. Specific results are given using the description for surf zone waves suggested by Svendsen (1984a), and in this form the model is used for the wave motion with a current on a beach with a longshore bar. Results for wave height and set-up are compared with measurements by Hansen & Svendsen (1986).

Severe Wave Conditions at Sea

1971 ◽  
Vol 24 (3) ◽  
pp. 273-277 ◽  
Author(s):  
Laurence Draper
Keyword(s):  
Wave Height ◽  
North Sea ◽  
The Other ◽  
Sea Waves ◽  
Fixed Length ◽  
Southern North Sea ◽  
Wide Range ◽  
Casual Observer ◽  
The Waves ◽  
Vast Range

Perhaps the most surprising thing about sea waves is that they come in a vast range of shapes and sizes. The casual observer on a ship in waters not exposed to an ocean, for example the southern North Sea, may rightly think that the waves he can see have all been generated by the same wind blowing over some particular stretch of water for a fixed length of time. It then seems almost logical to deduce that all the waves ought to be of the same height, length and shape. Unfortunately this is not the case, the energy of sea waves is locked in wave components spread over a wide range of wave periods, each of which travels at a speed dictated by its period. Considering the very simple case of a sea with only wave components, when a crest of one component overtakes the other, a higher wave will ensue. As a result of this process, high waves come in groups; during the time in which the components gradually get into phase the wave height builds up giving a train of waves of increasing, which then decreases as the faster component travels away, until when they are out of phase the sea is temporarily fairly calm. This is the reason why it is commonly said that every seventh wave is the highest, although whether it is every fourth or every fourteenth depends on the relative speeds of the components.

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.

Wind speed data analysis for predictions of sea waves in Bitung Coastal Waters

2013 ◽  
pp. 35 ◽  
Author(s):  
Joanes E Koagouw ◽  
Gybert E Mamuaya ◽  
Adrie A Tarumingkeng ◽  
P A Angmalisang
Keyword(s):  
Data Analysis ◽  
Wind Speed ◽  
Coastal Waters ◽  
Transition Period ◽  
Marine Resources ◽  
Land Uses ◽  
Sea Waves ◽  
North West ◽  
North Sulawesi ◽  
The Waves

Coastal area of Bitung Municipality is one of the economical activities centers in North Sulawesi Province such as for land-uses and the exploitation of natural resources. Those activities are exaggerating day bay day and tended to be uncontrollable. The excess of those conditions, it has been recorded the change of waves in Bitung waters that has impacts to coastal areas and can affect the utilization of coastal and marine resources. This research was aimed to observe waves altitude variations in Bitung waters with Svedrup Munk and Bretchsneider (SMB) method that had been used to predict waves altitudes. The results showed that the wind speed during West Season was 0.33 m and were dominant to the East, while during East season was 0.91m from South-East to North-West, and then on transition period (March to May) was 1.08m from South-East to East. The results of those wind speed to the waves altitudes in Bitung waters is discussed in this paper© Pesisir pantai Kota Bitung merupakan salah satu pusat aktivitas ekonomi (misalnya pemanfaatan lahan dan eksploitasi sumberdaya) di Provinsi Sulawesi Utara. Aktivitas tersebut semakin hari semakin meningkat dan memiliki kecenderungan tidak terkontrol. Akibat dari keadaan tersebut, telah terjadi perubahan fenomena gelombang di perairan Bitung yang berdampak pada keberadaan daerah pesisir pantai di mana hal ini dapat mengganggu aktivitas pemanfaatan sumberdaya pesisir dan laut tersebut. Penelitian ini bertujuan untuk mengetahui variasi tinggi gelombang di perairan Bitung dengan menggunakan metode Svedrup Munk and Bretchsneider (SMB) yang biasa digunakan untuk peramalan tinggi gelombang signifikan. Hasil penelitian menunjukkan bahwa kecepatan angin pada Musim Barat sebesar 0,33 meter dan dominan ke arah Timur, sementara pada Musim Timur sebesar 0,91 meter dari arah Tenggara ke Barat Laut, serta pada Musim Peralihan (antara bulan Maret-Mei) adalah sebesar 1,08 meter dari arah Tenggara dan Timur. Pengaruh kecepatan angin tersebut terhadap gelombang laut di perairan Bitung dibahas dalam tulisan ini©

Density Wave Measurements in a Rectangular Clarifier

1983 ◽  
Vol 18 (1) ◽  
pp. 129-150 ◽  
Author(s):  
Mark K. Watson ◽  
R.R. Hudgins ◽  
P.L. Silveston
Keyword(s):  
Power Spectrum ◽  
Internal Wave ◽  
Internal Waves ◽  
Wave Motion ◽  
Wave Amplitude ◽  
Suspended Solids ◽  
Small Volume ◽  
Density Wave ◽  
Measure Concentration ◽  
Wave Measurements

Abstract Internal wave motion was studied in a laboratory rectangular, primary clarifier. A photo-extinction device was used as a turbidimeter to measure concentration fluctuations in a small volume within the clarifier as a function of time. The signal from this device was fed to a HP21MX minicomputer and the power spectrum plotted from data records lasting approximately 30 min. Results show large changes of wave amplitude as frequency increases. Two distinct regions occur: one with high amplitudes at frequencies below 0.03 Hz, the second with very small amplitudes appears for frequencies greater than 0.1 Hz. The former is associated with internal waves, the latter with flow-generated turbulence. Depth, velocity in the clarifier and inlet suspended solids influence wave amplitudes and the spectra. A variation with position or orientation of the probe was not detected. Contradictory results were found for the influence of flow contraction baffles on internal wave amplitude.

scholarly journals WAVES AT SEKONDI, GHANA

1966 ◽  
Vol 1 (10) ◽  
pp. 1 ◽  
Author(s):  
L. Draper
Keyword(s):  
Southern Hemisphere ◽  
Sea Waves ◽  
Severe Damage ◽  
Pressure Recording ◽  
Electric Wave ◽  
International Geophysical Year ◽  
Time Of Year ◽  
The Waves ◽  
Wave Recorder ◽  
International Geophysical

During the International Geophysical Year the National Institute of Oceanography in collaboration with Ghana IGY Committee and the Ghana Railway and Harbours Administration made recordings of sea waves at a point 2,300 feet off Sekondi point in a direction 156°. The instrument used was an N.I.O. piezo-electric wave recorder of the pressure recording type. Recordings started in June, 1958, and continued until the end of October that year when the cable suffered severe damage which could not easily be repaired. Because of the high cost of cable and the fact that a good series of records had already been obtained for a rough time of year, the instrument was recovered and used elsewhere. Records were taken every two hours and each has a useable length of twelve minutes. Most of the waves arriving at Sekondi are in the form of swell which has been generated by storms in the southern hemisphere; consequently wave conditions do not change very quickly, and it was found unnecessary to analyse every record except during rough conditions. The method of analysis used is that described in the associated paper "The Analysis and Presentation of Wave Data - a Plea for Uniformity".

scholarly journals APPLICATIONS ON NONLINEAR WAVE COMBINATION

1986 ◽  
Vol 1 (20) ◽  
pp. 26
Author(s):  
J.T. Juang
Keyword(s):  
Wave Height ◽  
Taiwan Strait ◽  
Western Coast ◽  
Linear Wave ◽  
Wave System ◽  
Height Distribution ◽  
Wave Height Distribution ◽  
Local Wave ◽  
Source Wave ◽  
The Waves

Due to the special bathymetry in Taiwan Strait, the waves off the western coast of Taiwan are considered to be composed of two-source wave system. One propagates from the central part of the Strait named main wave, and the other is generated by the local wind known as local wave which occurs along the shore. After the combination and the transformation procedure from these two-nonlinear-source wave system, the wave height distribution in Taiwan Strait should be modified. A comparison of the wave height distributions based on the present proposed method with the field data indicates that the present method yields a better result than other theorems. Furthermore, the result of application of two non-linear wave theorem to wave prediction are also presented.

scholarly journals MACH-REFLECTION AS A DIFFRACTION PROBLEM

1976 ◽  
Vol 1 (15) ◽  
pp. 45 ◽  
Author(s):  
Udo Berger ◽  
Soren Kohlhase
Keyword(s):  
Wave Height ◽  
Incident Wave ◽  
Water Waves ◽  
Gas Dynamics ◽  
Mach Reflection ◽  
Diffraction Problem ◽  
Vertical Wall ◽  
Oblique Wave ◽  
Wave Heights ◽  
The Waves

As under oblique wave approach water waves are reflected by a vertical wall, a wave branching effect (stem) develops normal to the reflecting wall. The waves progressing along the wall will steep up. The wave heights increase up to more than twice the incident wave height. The £jtudy has pointed out that this effect, which is usually called MACH-REFLECTION, is not to be taken as an analogy to gas dynamics, but should be interpreted as a diffraction problem.

scholarly journals STATISTICAL PROPERTIES OF THE MAXIMUM RUN OF IRREGULAR SEA WAVES

1988 ◽  
Vol 1 (21) ◽  
pp. 48 ◽  
Author(s):  
Akira Kimura
Keyword(s):  
Probability Distribution ◽  
Wave Height ◽  
Probability Distributions ◽  
Confidence Regions ◽  
Statistical Properties ◽  
Irregular Waves ◽  
Sea Waves ◽  
Sea State ◽  
Irregular Wave ◽  
Distribution Of The Maximum

The probability distribution of the maximum run of irregular wave height is introduced theoretically. Probability distributions for the 2nd maximum, 3rd maximum and further maximum runs are also introduced. Their statistical properties, including the means and their confidence regions, are applied to the verification of experiments with irregular waves in the realization of a "severe sea state" in the test.

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