scholarly journals MODELING OF THE REYNOLDS STRESS IN THE BURSTING LAYER AFFECTED BY TYPHOON

2011 ◽  
Vol 1 (32) ◽  
pp. 35
Author(s):  
Tomokazu Murakami ◽  
Jun Yoshino ◽  
Takashi Yasuda
Keyword(s):  
Water Level ◽  
Reynolds Stress ◽  
Trough Level ◽  
Wind Waves ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Wave Trough ◽  
Mean Water Level ◽  
The Mean ◽  
Particle Velocities

When large and intensive water surface displacements are caused by developed wind waves due to a typhoon, it is impossible in the Eulerian coordinate system to measure water particle velocities continuously in a domain between the wave trough level and the mean water level. Consequently, the domain between the wave trough level and the mean water level becomes a void zone where the Reynolds stress cannot be described. By treating the sea surface boundary layer including the void zone as a bursting layer, we modeled the Reynolds stress in the bursting layer. Validity of that modeling was verified by performing comparisons with experimentally obtained results.

scholarly journals Bursting-Layer Modeling Based on the Assumption of the Averaged Sea Surface for Strong Wind-Driven Currents

2008 ◽  
Vol 38 (4) ◽  
pp. 896-908 ◽  
Author(s):  
Tomokazu Murakami ◽  
Takashi Yasuda
Keyword(s):  
Vertical Distribution ◽  
Wind Wave ◽  
Trough Level ◽  
Sea Surface ◽  
Strong Wind ◽  
Wave Trough ◽  
Mean Water Level ◽  
The Mean ◽  
Wind Driven Currents ◽  
The Vertical Distribution

Abstract In the sea, which is affected by strong winds that cover the water surface with wind-wave breakers, the sea surface layer, called the bursting layer by authors, is generated immediately below the mean water level. For treatment of strong wind-driven currents, it is necessary to model the bursting layer correctly based on observed data. However, an essential difficulty occurs in that, because of large water surface displacement caused by developed wind waves, water particle velocities above the wave trough level cannot be measured continuously in the Eulerian coordinates when measuring the velocity of strong wind-driven currents. Consequently, it is impossible to apply the Reynolds average rule to the velocity field above the wave trough level. In this study, an experiment that uses a wind-wave tank with a double bottom is performed to measure the horizontal velocity of currents driven only by the wind stress. The vertical distribution up to the mean water level is determined to make its vertically integrated value agree with the total mass flux of the wind-driven currents. Furthermore, the vertical distribution of the Reynolds stress is derived by solving a Reynolds equation; its solution agrees with the given velocity distribution. Numerical simulation was performed to reproduce the strong wind-driven currents. Results showed that the bursting-layer model can correctly calculate the steep vertical distribution of the current velocity in the bursting layer.

scholarly journals Aerodynamics of smooth and rough square-section prisms at incidence in very high Reynolds-number cross-flows

2021 ◽  
Vol 62 (3) ◽  
Author(s):  
Nils Paul van Hinsberg
Keyword(s):  
Reynolds Number ◽  
Cross Sections ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Surface Boundary ◽  
Experimental Proof ◽  
Surface Boundary Layer ◽  
Pitch Moment ◽  
The Mean ◽  
High Reynolds

Abstract The aerodynamics of smooth and slightly rough prisms with square cross-sections and sharp edges is investigated through wind tunnel experiments. Mean and fluctuating forces, the mean pitch moment, Strouhal numbers, the mean surface pressures and the mean wake profiles in the mid-span cross-section of the prism are recorded simultaneously for Reynolds numbers between 1$$\times$$ × 10$$^{5}$$ 5 $$\le$$ ≤ Re$$_{D}$$ D $$\le$$ ≤ 1$$\times$$ × 10$$^{7}$$ 7 . For the smooth prism with $$k_s$$ k s /D = 4$$\times$$ × 10$$^{-5}$$ - 5 , tests were performed at three angles of incidence, i.e. $$\alpha$$ α = 0$$^{\circ }$$ ∘ , −22.5$$^{\circ }$$ ∘ and −45$$^{\circ }$$ ∘ , whereas only both “symmetric” angles were studied for its slightly rough counterpart with $$k_s$$ k s /D = 1$$\times$$ × 10$$^{-3}$$ - 3 . First-time experimental proof is given that, within the accuracy of the data, no significant variation with Reynolds number occurs for all mean and fluctuating aerodynamic coefficients of smooth square prisms up to Reynolds numbers as high as $$\mathcal {O}$$ O (10$$^{7}$$ 7 ). This Reynolds-number independent behaviour applies to the Strouhal number and the wake profile as well. In contrast to what is known from square prisms with rounded edges and circular cylinders, an increase in surface roughness height by a factor 25 on the current sharp-edged square prism does not lead to any notable effects on the surface boundary layer and thus on the prism’s aerodynamics. For both prisms, distinct changes in the aerostatics between the various angles of incidence are seen to take place though. Graphic abstract

scholarly journals Analytical approach for determining the mean water level profile in an estuary with substantial fresh water discharge

2016 ◽  
Vol 20 (3) ◽  
pp. 1177-1195 ◽  
Author(s):  
Huayang Cai ◽  
Hubert H. G. Savenije ◽  
Chenjuan Jiang ◽  
Lili Zhao ◽  
Qingshu Yang
Keyword(s):  
Water Level ◽  
Fresh Water ◽  
River Discharge ◽  
River Flow ◽  
Water Discharge ◽  
Value Theory ◽  
Velocity Amplitude ◽  
Mean Water Level ◽  
The Mean ◽  
Fresh Water Discharge

Abstract. The mean water level in estuaries rises in the landward direction due to a combination of the density gradient, the tidal asymmetry, and the backwater effect. This phenomenon is more prominent under an increase of the fresh water discharge, which strongly intensifies both the tidal asymmetry and the backwater effect. However, the interactions between tide and river flow and their individual contributions to the rise of the mean water level along the estuary are not yet completely understood. In this study, we adopt an analytical approach to describe the tidal wave propagation under the influence of substantial fresh water discharge, where the analytical solutions are obtained by solving a set of four implicit equations for the tidal damping, the velocity amplitude, the wave celerity, and the phase lag. The analytical model is used to quantify the contributions made by tide, river, and tide–river interaction to the water level slope along the estuary, which sheds new light on the generation of backwater due to tide–river interaction. Subsequently, the method is applied to the Yangtze estuary under a wide range of river discharge conditions where the influence of both tidal amplitude and fresh water discharge on the longitudinal variation of the mean tidal water level is explored. Analytical model results show that in the tide-dominated region the mean water level is mainly controlled by the tide–river interaction, while it is primarily determined by the river flow in the river-dominated region, which is in agreement with previous studies. Interestingly, we demonstrate that the effect of the tide alone is most important in the transitional zone, where the ratio of velocity amplitude to river flow velocity approaches unity. This has to do with the fact that the contribution of tidal flow, river flow, and tide–river interaction to the residual water level slope are all proportional to the square of the velocity scale. Finally, we show that, in combination with extreme-value theory (e.g. generalized extreme-value theory), the method may be used to obtain a first-order estimation of the frequency of extreme water levels relevant for water management and flood control. By presenting these analytical relations, we provide direct insight into the interaction between tide and river flow, which will be useful for the study of other estuaries that experience substantial river discharge in a tidal region.

scholarly journals Dynamics of fortnightly water level variations along a tide-dominated estuary with negligible river discharge

2021 ◽  
Author(s):  
Erwan Garel ◽  
Ping Zhang ◽  
Huayang Cai
Keyword(s):  
Water Level ◽  
Phase Difference ◽  
River Discharge ◽  
Water Levels ◽  
Level Increase ◽  
Upstream Direction ◽  
Water Level Variations ◽  
Mean Water Level ◽  
The Mean ◽  
Guadiana Estuary

Abstract. Observations indicate that the fortnightly fluctuations in mean water level increase in amplitude along the lower half of a tide-dominated estuary (The Guadiana estuary) with negligible river discharge but remain constant upstream. Analytical solutions reproducing the semi-diurnal wave propagation shows that this pattern results from reflection effects at the estuary head. The phase difference between velocity and elevation increases from the mouth to the head (where the wave has a standing nature) as the high and low water levels get progressively closer to slack water. Thus, the tidal (flood-ebb) asymmetry in discharge is reduced in the upstream direction. It becomes negligible along the upper estuary half, as the mean sea level remains constant despite increased friction due to wave shoaling. Observations of a flat mean water level along a significant portion of an upper estuary, easier to obtain than the phase difference, can therefore indicate significant reflection of the propagating semi-diurnal wave at the head. Details of the analytical model shows that changes in the mean depth or length of semi-arid estuaries, in particular for macrotidal locations, affect the fortnightly tide amplitude, and thus the upstream mass transport and inundation regime. This has significant potential impacts on the estuarine environment.

Waves Off Land's End

1965 ◽  
Vol 18 (2) ◽  
pp. 180-187 ◽  
Author(s):  
L. Draper ◽  
H. S. Fricker
Keyword(s):  
Water Level ◽  
First Year ◽  
Zero Crossing ◽  
South West ◽  
Mean Water Level ◽  
The Mean ◽  
Wave Recorder

Since January 1962, waves have been recorded by a shipborne wave recorder (Tucker, 1956) on the Sevenstones light-vessel which is stationed about 20 miles south-west of Land's End in about 200 ft. of water. Records were taken at three-hourly intervals and were mostly of 12 minutes’ duration. The analysis presented here is based on 2920 records taken in the first year of operation; the method of analysis which has been used is that described by Tucker (1961). This gives for each record:(a) H1 = The sum of the distances of the highest crest and the lowest trough from the mean water level.(b) Tz = The mean zero-crossing period.(c) Tc = The mean crest period.

scholarly journals Propagation of bichromatic-bidirectional waves

RBRH ◽  
2019 ◽  
Vol 24 ◽  
Author(s):  
Mario Grüne de Souza e Silva ◽  
Paulo Cesar Colonna Rosman ◽  
Claudio Freitas Neves
Keyword(s):  
Water Level ◽  
Stress Tensor ◽  
Nonlinear Term ◽  
Primary Wave ◽  
Radiation Stress ◽  
Stress Components ◽  
Mean Water Level ◽  
The Mean ◽  
Mohr’S Circles ◽  
Infragravity Wave

ABSTRACT This study aims to investigate the transformations experienced by the mean water level and radiation stress tensor during the propagation of Bichromatic-Bidirectional (Bi-Bi) waves on a slope of 1:22 and water depth varying from 55 cm to 26 cm, simulating laboratory conditions. A computer program written in Python was used to compute those quantities at different combinations of wave angles and periods. The setup and setdown of the mean water level are strongly dependent on the combination of periods and direction of the primary waves, as they propagate along the slope, modifying the bound infragravity wave. Mohr’s circles for the radiation stress tensor showed significant changes of diameter and center at different points along the basin. The radiation stress components for the Bi-Bi waves are the sum of the stresses associated with each primary wave and a nonlinear term which results from the interference between primary waves. Disregarding these nonlinear terms may significantly affect the nearshore hydrodynamics prediction.

Numerical Experiments of Bottom Stress on Wave Setup

2012 ◽  
Vol 212-213 ◽  
pp. 1108-1111
Author(s):  
Shi Chao Liu ◽  
Li Huang
Keyword(s):  
Numerical Experiment ◽  
Water Level ◽  
Numerical Experiments ◽  
Surf Zone ◽  
Current Increase ◽  
Wave Setup ◽  
Bottom Stress ◽  
Mean Water Level ◽  
The Mean ◽  
Wave Induced

Wave-induced setup increases the mean water level in the surf zone and can be influenced by bottom stress in the presence of ambient current. As the numerical experiment shows, the effects of bottom stress on wave setup are associated with wave conditions. An onshore-directed bottom stress caused by offshore ambient current increase the wave setup and an offshore-directed bottom stress caused by onshore ambient current decrease the wave setup. According to the experiment, it is necessary to calculate wave-induced setup including the bottom stress in the presence of ambient current.

Large-Aspect-Ratio Structures in Simulated Ocean Surface Boundary Layer Turbulence under a Hurricane

2020 ◽  
Vol 50 (12) ◽  
pp. 3561-3584
Author(s):  
Clifford Watkins ◽  
Daniel B. Whitt
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Aspect Ratio ◽  
Prandtl Number ◽  
Ocean Surface ◽  
Surface Boundary ◽  
Large Aspect Ratio ◽  
Surface Boundary Layer ◽  
Velocity Magnitude ◽  
The Mean

AbstractA large-eddy simulation (LES) initialized and forced using observations is used to conduct a process study of ocean surface boundary layer (OSBL) turbulence in a 2-km box of ocean nominally under Hurricane Irene (2011) in 35 m of water on the New Jersey shelf. The LES captures the observed deepening, cooling, and persistent stratification of the OSBL as the storm approaches and passes. As the storm approaches, surface-intensified Ekman-layer rolls, with horizontal wavelengths of about 200 m and horizontal-to-vertical aspect and velocity magnitude ratios of about 20, dominate the kinetic energy and increase the turbulent Prandtl number from about 1 to 1.5 due partially to their restratifying vertical buoyancy flux. However, as the storm passes, these rolls are washed away in a few hours due to the rapid rotation of the wind. In the bulk OSBL, the gradient Richardson number of the mean profiles remains just above (just below) 1/4 as the storm approaches (passes). At the base of the OSBL, large-aspect-ratio Kelvin–Helmholtz billows, with Prandtl number below 1, intermittently dominate the kinetic energy. Overall, large-aspect-ratio covariance modifies the net vertical fluxes of buoyancy and momentum by about 10%, but these fluxes and the analogous diffusivity and viscosity still approximately collapse to time-independent dimensionless profiles, despite rapid changes in the forcing and the large structures. That is, the evolutions of the mean temperature and momentum profiles, which are driven by the net vertical flux convergences, mainly reflect the evolution of the wind and the initial ocean temperature profile.

scholarly journals Primary and secondary vortices in oscillating fluids: their connection with skin friction

1926 ◽  
Vol 113 (763) ◽  
pp. 44-45 ◽  
Keyword(s):  
Water Level ◽  
Skin Friction ◽  
Clear Water ◽  
Free Communication ◽  
Water Colour ◽  
Aluminium Powder ◽  
Mean Water Level ◽  
The Mean ◽  
Secondary Vortices

The first three instantaneous photographs (figs. 1, a and b , and fig. 2) relate to the pressure conditions existing at the end of a tank in which water is caused to oscillate by moving the tank to and fro horizontally on rollers ; the tank was provided with an artificial end having a cavity in free communication with the water in the tank through a horizontal slot near the upper end of the cavity. Figs. 3 to 8 are instantaneous photographs of jets and vortices formed in oscillating water under various conditions ; figs. 4 a , 5, 6 and 8 were obtained by mixing aluminium powder with the water and allowing all but the finest particles to settle. For figs. 3 and 4 b water-colour paint was smeared on the end of the tank just above the mean water-level, whilst for fig. 7 such paint was squirted on the bottom of the trough after the clear water had been poured in and come to rest.

scholarly journals FIELD STUDY OF WIND TIDE IN SEMI-ENCLOSED SHALLOW BASINS

2020 ◽  
pp. 27
Author(s):  
Caroline Paugam ◽  
Damien Sous ◽  
Vincent Rey ◽  
Samuel Meule
Keyword(s):  
Water Level ◽  
Water Surface ◽  
Physical Phenomenon ◽  
Relative Effect ◽  
Wind Effect ◽  
Strong Wind ◽  
Level Variation ◽  
Water Level Variation ◽  
Mean Water Level ◽  
The Mean

The aim of the study is to understand the wind effect on mean water level variation in semi-enclosed shallow basins. The studied physical phenomenon is nearly steady water surface tilting due to wind stress, the so-called wind tide (Platzman (1963)). During strong wind conditions, wind tides can have significant consequences on low-lying areas such as submersion and flooding. Two field sites are monitored in the S-E of France to characterize wind tides and more specifically to understand the relative effect of wind magnitude and depth on the mean water level dynamics.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/Q30I0taty9w

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