scholarly journals MACRO-TURBULENCE FROM WIND WAVES

1970 ◽  
Vol 1 (12) ◽  
pp. 14 ◽  
Author(s):  
Chin-Yuan Lee ◽  
Frank D. Masch
Keyword(s):  
Energy Dissipation ◽  
Wave Height ◽  
Wind Waves ◽  
Wave Energy Dissipation ◽  
Wave Flume ◽  
Wind Speeds ◽  
Macro Scale ◽  
Scale Turbulence ◽  
Almost All ◽  
Hot Film

Laboratory studies m a wind wave flume were carried out to investigate the macro-scale turbulence associated with wind waves and white cap conditions Velocity fluctuations m water were measured with a hot film anemometer and parametric correlations between wind waves and turbulence characteristics were established Measured data were recorded m analog form, digitized and stored on magnetic tape Auto - covanance functions and power spectral density functions were then obtained for all sample records Results showed that the depth of the penetration of the macro-scale turbulence increased rapidly with wind speed but the rate of penetration diminished at the higher wind speeds This rate of macro-turbulence penetration was found to vary inversely with wave height and wave steepness Most turbulent fluctuations having frequencies equal to or higher than the frequency of the ambient surface waves were confined to the zone of macro-turbulence penetration although some disturbances such as vortex rings and other turbulence associated with white cap wave conditions occasionally penetrated to greater depths It was found that the energy dissipation increased with wave height and that almost all wave energy dissipation was concentrated near the water surface.

Wind-induced growth of water waves

1982 ◽  
Vol 123 ◽  
pp. 425-442 ◽  
Author(s):  
H. Mitsuyasu ◽  
T. Honda
Keyword(s):  
Growth Rate ◽  
Water Waves ◽  
Friction Velocity ◽  
Wind Wave ◽  
Wind Waves ◽  
Pure Water ◽  
Wave Flume ◽  
Wind Speeds ◽  
Wind Profiles ◽  
The Waves

Spatial growth of mechanically generated water waves under the action of wind has been measured in a laboratory wind-wave flume both for pure water and for water containing a surfactant (sodium lauryl sulphate, concentration 2.6 × 10−2%). I n the latter case, no wind waves develop on the surface of the mechanically generated waves as well as on the still water surface for wind speeds up to U10≈ 15 m/s, where U10 is the wind velocity at the height Z = 10 m. Therefore we can study the wind-induced growth of monochromatic waves without the effects of co-existing short wind waves. The mechanically generated waves grew exponentially under the action of the wind, with fetch in both cases. The measured growth rate β for the pure water can be fitted by β/f = 0.34(U*/C)2 0.1 [lsime ] U*/C [lsime ] 1.0, where f is the frequency of the waves, C is the corresponding phase velocity, and U, is the friction velocity obtained from vertical wind profiles. The effect of the wave steepness H/L on the dimensionless growth rate β/f is not clear, but seems to be small. For water containing the surfactant, the measured growth rate is smaller than that for pure water, but the friction velocity of the wind is also small, and the above relation between β/f and U*/C holds approximately if the measured friction velocity U* is used for the relation.

scholarly journals ABOUT THE ENERGY DISSIPATION OVER BARRED BEACH

1988 ◽  
Vol 1 (21) ◽  
pp. 20
Author(s):  
Johannes Oelerich ◽  
Hans-Henning Dette
Keyword(s):  
Stochastic Process ◽  
Energy Dissipation ◽  
Surf Zone ◽  
Field Measurements ◽  
The West ◽  
Wave Energy Dissipation ◽  
Wave Flume ◽  
Moderate Energy ◽  
Empirical Approaches ◽  
Spilling Breaker

Since wave energy dissipation in the surf zone is a stochastic process closed mathematical formulations cannot be expected. The dissipation was computed using several analytical and/or empirical approaches and compared with prototype measurements in the Big Wave Flume (GWK) in Hannover as well as with field measurements from the west coast, of the Island of Sylt/North Sea. Generally good agreements were found for moderate energy dissipation conditions (spilling-breaker), whereas in the case of plunging breakers, however, the fitting is not solved satisfactory.

Wave Height Variation Across Surf Zone of Bar Type Profile

2009 ◽  
Author(s):  
Tai-Wen Hsu ◽  
Kun-Sian Lai
Keyword(s):  
Energy Dissipation ◽  
Wave Height ◽  
Analytical Solutions ◽  
Wave Energy ◽  
Hydraulic Jump ◽  
Surf Zone ◽  
Wave Transformation ◽  
Height Variation ◽  
Wave Energy Dissipation ◽  
Theoretical Results

Analytical solutions for wave height decay due to shoaling and breaking on a bar type profile are presented. A macroscopic analogy between an idealized surf zone and a hydraulic jump are incorporated in the theory to account for wave transformation and energy dissipation in the surf zone. The theoretical results are fairly compared with laboratory observations. Key parameters that influence wave energy dissipation in the surf zone are investigated.

Calibration of a 58 m wave flume

1981 ◽  
Vol 8 (4) ◽  
pp. 449-455 ◽  
Author(s):  
D. B. Muggeridge ◽  
J. J. Murray
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Random Wave ◽  
Regular Waves ◽  
M Wave ◽  
Wave Flume ◽  
Wind Speeds ◽  
On Line ◽  
Predicted Values ◽  
Good Agreement

A 58.27 × 4.57 × 3.04 m wave flume has been constructed and calibrated. The maximum wave height that can be generated in regular waves is 0.7 m at a water depth of 1.8 m. Random wave spectra have also been modelled in the flume for prototype wind speeds up to 25 m/s. The maximum significant wave height that can be generated at a 1 m water depth is 20 cm.A series of tests performed to verify design curves presented by Gilbert, Thompson, and Brewer show good agreement with the predicted values. The Pierson-Moskowitz spectrum was modelled between wind speeds of 5 and 25 m/s at suitable scale factors ranging from 1:50 to 1:150. All analysis was carried out in real time by means of an on-line computer.

scholarly journals A NUMERICAL MODEL OF WAVE DEFORMATION IN SURF ZONE

1988 ◽  
Vol 1 (21) ◽  
pp. 41 ◽  
Author(s):  
Akira Watanabe ◽  
Mohammad Dibajnia
Keyword(s):  
Energy Dissipation ◽  
Numerical Model ◽  
Potential Energy ◽  
Wave Height ◽  
Wave Energy ◽  
Surf Zone ◽  
Time Dependent ◽  
Wave Energy Dissipation ◽  
Wave Deformation

A numerical model is presented for nearshore wave deformation due to shoaling and breaking, and to decay and recovery in the surf zone. The model is based on a set of time-dependent mild slope equations including a term of wave energy dissipation caused by breaking. Its applicability is demonstrated by comparisons between the computations and the measurements of cross-shore distributions of the wave height and potential energy over typical beach configurations.

RESEARCH OF EXTERNAL MASS TRANSFER PROCESSES FOR ADSORPTION FROM SOLUTIONS IN A APPARATUS WITH STIRRING

2021 ◽  
pp. 11-20
Author(s):  
V. Solovej ◽  
K. Gorbunov ◽  
V. Vereshchak ◽  
O. Gorbunova
Keyword(s):  
Mass Transfer ◽  
Energy Spectrum ◽  
Energy Dissipation ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Wave Number ◽  
Wave Form ◽  
Local Isotropy ◽  
Stirred Vessel ◽  
Almost All

A study has been mode of transport-controlled mass transfer-controlled to particles suspended in a stirred vessel. The motion of particle in a fluid was examined and a method of predicting relative velocities in terms of Kolmogoroff’s theory of local isotropic turbulence for mass transfer was outlined. To provide a more concrete visualization of complex wave form of turbulence, the concepts of eddies, of eddy velocity, scale (or wave number) and energy spectrum, have proved convenient. Large scale motions of scale contain almost all of the energy and they are directly responsible for energy diffusion throughout the stirring vessel by kinetic and pressure energies. However, almost no energy is dissipated by the large-scale energy-containing eddies. A scale of motion less than is responsible for convective energy transfer to even smaller eddy sires. At still smaller eddy scales, close to a characteristic microscale, both viscous energy dissipation and convection are the rule. The last range of eddies has been termed the universal equilibrium range. It has been further divided into a low eddy size region, the viscous dissipation subrange, and a larger eddy size region, the inertial convection subrange. Measurements of energy spectrum in mixing vessel are shown that there is a range, where the so called -(5/3) power law is effective. Accordingly, the theory of local isotropy of Kolmogoroff can be applied because existence of the internal subrange. As the integrated value of local energy dissipation rate agrees with the power per unit mass of liquid from the impeller, almost all energy from the impeller is viscous dissipated in eddies of microscale. The correlation for mass transfer to particles suspended in a stirred vessel is recommended. The results of experimental study are approximately 12 % above the predicted values.

scholarly journals Wave energy dissipation in the mangrove vegetation off Mumbai, India

2017 ◽  
Author(s):  
Samiksha S. Volvaiker ◽  
Ponnumony Vethamony ◽  
Prasad K. Bhaskaran ◽  
Premanand Pednekar ◽  
MHamsa Jishad ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Drag Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Coastal Region ◽  
Measured Data ◽  
Vegetation Density ◽  
Mangrove Vegetation ◽  
Wave Height Attenuation ◽  
Set Up

Abstract. Coastal regions of India are prone to sea level rise, cyclones, storm surges and human induced activities, resulting in flood, erosion, and inundation. The primary aim of the study is to estimate wave attenuation by mangrove vegetation using SWAN model in standalone mode, as well as SWAN nested with WW3 model for the Mumbai coastal region. To substantiate the model results, wave measurements were carried out during 5–8 August 2015 at 3 locations in a transect normal to the coast using surface mounted pressure level sensors under spring tide conditions. The measured data presents wave height attenuation of the order of 52 %. The study shows a linear relationship between wave height attenuation and gradual changes in water level in the nearshore region, in phase with the tides. Model set-up and sensitivity analyses were conducted to understand the model performance to vegetation parameters. It was observed that wave attenuation increased with an increase in drag coefficient (Cd), vegetation density, and stem diameter. For a typical set-up for Mumbai coastal region having vegetation density of 0.175 per m2, stem diameter of 0.3 m and drag coefficient varying from 0.4 to 1.5, the model reproduced attenuation, ranging from 49 to 55 %, which matches well with the measured data. Spectral analysis performed for the cases with and without vegetation very clearly portrays energy dissipation in the vegetation area as well as spectral changes. This study has the potential of improving the quality of wave prediction in vegetation areas, especially during monsoon season and extreme weather events.

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