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Journal ArticleDOI

Dynamic pressure distribution on large circular cylinders caused by wind generated random waves

01 Jan 1983-Ocean Engineering (Pergamon)-Vol. 10, Iss: 4, pp 235-260

AbstractA technique has been developed to evaluate the dynamic pressures on cylindrical structures due to irregular waves based on McCamy and Fuchs linear diffraction theory and principle of superposition. Experiments have been conducted in Hydraulic Engineering Laboratory, Indian Institute of Technology, Madras to examine the dynamic pressures excited by irregular waves on circular cylinders of large diameter. The pressures around the cylinder at representative locations were measured and compared with calculated pressures. The spectral density functions computed from pressure time series measured in the laboratory agree well with the calculated pressure spectral densities. The agreement is good and encouraging. more

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Journal ArticleDOI
Abstract: Construction cofferdams for sea-crossing bridges can be damaged or even collapsed due to extreme wave loads under tropical cyclones. To enhance a better understanding of the random wave pressure on the cofferdam, wave gauges and pressure transducers were installed on a real cofferdam for sea-crossing bridge to measure the random wave pressure during Typhoon Dujuan in 2015. The first order diffraction theory was used to calculate the wave pressure numerically. The measured and numerical results were compared in the frequency domain and discussed in terms of pressure spectrum, pressure spectral characteristics, transfer function and maximum wave pressure. The main conclusions are: (1) the wave diffraction and water depth affect the dominant frequency range, zeroth moments and peak spectral value of wave pressure spectrums on the cofferdam; (2) the maximum wave pressure on the up-wave side of the cofferdam is up to 2.2 times that on the down-wave side; (3) the secondary peaks were observed in pressure spectrums under tropical cyclone; and (4) the numerical model based on the first order diffraction theory could not capture the secondary peaks and overestimate the wave pressure energy near the primary peak frequency.

7 citations

Journal ArticleDOI
Abstract: Investigations on the hydrodynamic pressures due to regular and random waves exerted on a large vertical cylinder in a constant water depth are reported in this paper. In the experimental investigation, the test cylinder embedded with diaphragm-type pressure transducers at nine different elevations was rotated about its axis to measure the dynamic pressure around its circumference. The wave field in the neighbourhood of the cylinder was measured at six different locations. The results of the experiments are compared with the linear diffraction theory of MacCamy, R. C. and Fuchs, R. A. [(1954) Wave forces on piles: a diffraction theory. U.S. Army Beach Erosion Board, Technical Memorandum No. 69]. In general, the agreement between the theoretical and experimental results is found to be satisfactory. A comparison between the regular and random wave test results is also presented and discussed.

6 citations

Journal ArticleDOI
Abstract: The hydrodynamic pressures due to random waves on a large vertical cylinder, resting on a flume bed and piercing above the free surface has been investigated experimentally in constant water depth. The test cylinder was fixed with diaphragm-type pressure transducers at nine different pressure ports with one of them at the still water level (S.W.L.) itself. The cylinder was rotated about its own axis to study the pressure distribution around its circumference. The time histories of the water surface elevation and the corresponding dynamic pressures exerted on the cylinder have been analysed in the frequency domain. The experimental results are compared with the theoretical results based on the linear diffraction theory of MacCamy and Fuchs and the agreement is satisfactory. Finally, the hydrodynamic pressure coefficients obtained from random wave tests are compared with those from regular wave tests.

3 citations

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01 Jan 1971
Abstract: From the Publisher: A revised and expanded edition of this classic reference/text, covering the latest techniques for the analysis and measurement of stationary and nonstationary random data passing through physical systems. With more than 100,000 copies in print and six foreign translations, the first edition standardized the methodology in this field. This new edition covers all new procedures developed since 1971 and extends the application of random data analysis to aerospace and automotive research; digital data analysis; dynamic test programs; fluid turbulence analysis; industrial noise control; oceanographic data analysis; system identification problems; and many other fields. Includes new formulas for statistical error analysis of desired estimates, new examples and problem sets.

6,669 citations

01 Dec 1954
Abstract: : Although circular piling is a much-used structural element in shore protection, harbor, and other maritime structures, only recently have significant advances been made toward gaining a quantitative understanding of the forces developed by wave action against piling. The present report deals with this subject.

481 citations

Journal ArticleDOI
Abstract: Simulation procedures have not been used extensively in coastal engineering and ocean wave problems although several oil companies have used these techniques The following study was undertaken to make the procedures more available to the engineer working with ocean wave problems and to investigate possible ways of increasing the efficiency and the realism of the ocean wave and force simulations produced Techniques for simulating ocean waves are most applicable when the response of the structure is complicated and perhaps involves other random environmental factors which may be introduced by concurrent simulations The accuracy of the wave simulation is greatest for low amplitude waves and decreases for large steep waves The degree of loss in accuracy for the higher and steeper waves deserves further research Simulation techniques have the disadvantage of being time consuming and usually requiring the use of computers Analytic solutions are to be preferred if feasible Sometimes part of a problem can be solved analytically and then the intractable parts processed by simulation A detailed search for shortcuts and approximations before proceeding with the actual simulation will often result in sizeable savings of computer time

210 citations

Journal ArticleDOI
Abstract: The results of calculations of the pressure distribution on the surface of a stationary rigid sphere and a stationary rigid circular cylinder of infinite length, when exposed to a plane progressive sound wave, are compared with experiment. A small probe microphone was used to measure the sound pressures on the surface of the obstacles in a room essentially free from acoustic wall reflections under a variety of experimental conditions. The sound pressures p on the surface are conveniently expressed relative to the free‐field pressure p0 in the undisturbed incident wave.In the case of the sphere, reasonably good agreement was obtained between theory and experiment in the range of 13

51 citations

Book ChapterDOI
01 Jan 1978
Abstract: Observations of the wave elevation, pressure and three components of velocity have been made at different depths from a tower in the Adriatic Sea near Venice in a water depth of 16 m. The spectral analysis of the pressure measurements show significant differences from linear wave theory which depend on the wavelength and depth of the transducer. The velocity field was measured with two electromagnetic current meters in the same vertical line. The amplitudes of the vertical and horizontal velocities were about 10% less than expected on the basis of linear wave theory. The downward transport of horizontal momentum, estimated from the co-spectrum of the vertical and horizontal velocities, was found to be much greater than the total atmospheric stress. The large values of the momentum flux are associated with deviations in the phase of the horizontal velocity component with respect to the wave elevation from the value expected using linear wave theory.

28 citations