Flow structure modification and drag reduction induced by sediment stratification in coastal tidal bottom boundary layers

2020 ◽  
Vol 241 ◽  
pp. 106829 ◽  
Author(s):  
Yun Peng ◽  
Qian Yu ◽  
Yang Yang ◽  
Yunwei Wang ◽  
Ya Ping Wang ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Boundary Layers ◽  
Flow Structure ◽  
Structure Modification ◽  
Bottom Boundary ◽  
Bottom Boundary Layers ◽  
Sediment Stratification

Bottom Boundary Layers

2021 ◽  
Author(s):  
Stephen M. Henderson ◽  
Jeffrey R. Nielson
Keyword(s):  
Boundary Layers ◽  
Bottom Boundary ◽  
Bottom Boundary Layers

scholarly journals NUMERICAL MODELING OF A TURBULENT BOTTOM BOUNDARY LAYER UNDER SOLITARY WAVES ON A SMOOTH SURFACE

2018 ◽  
pp. 26
Author(s):  
Ahmad Sana ◽  
Hitoshi Tanaka
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Solitary Waves ◽  
Bottom Boundary Layer ◽  
Stream Velocity ◽  
Bottom Boundary ◽  
Sediment Movement ◽  
Bottom Boundary Layers ◽  
Turbulent Models

A number of studies on bottom boundary layers under sinusoidal and cnoidal waves were carried out in the past owing to the role of bottom shear stress on coastal sediment movement. In recent years, the bottom boundary layers under long waves have attracted considerable attention due to the occurrence of huge tsunamis and corresponding sediment movement. In the present study two-equation turbulent models proposed by Menter(1994) have been applied to a bottom boundary layer under solitary waves. A comparison has been made for cross-stream velocity profile and other turbulence properties in x-direction.

Numerical modeling of larval settlement in turbulent bottom boundary layers

1992 ◽  
Vol 50 (4) ◽  
pp. 611-642 ◽  
Author(s):  
Thomas F. Gross ◽  
Francisco E. Werner ◽  
James E. Eckman
Keyword(s):  
Numerical Modeling ◽  
Boundary Layers ◽  
Larval Settlement ◽  
Bottom Boundary ◽  
Bottom Boundary Layers

scholarly journals Nongeostrophic Baroclinic Instability over Sloping Bathymetry: Buoyant Flow Regime

2020 ◽  
Vol 50 (7) ◽  
pp. 1937-1956
Author(s):  
Lixin Qu ◽  
Robert Hetland
Keyword(s):  
Growth Rate ◽  
Flow Regime ◽  
Boundary Layers ◽  
Baroclinic Instability ◽  
Deep Ocean ◽  
Ocean Bottom ◽  
Coastal Zones ◽  
Buoyant Flow ◽  
Bottom Boundary ◽  
Bottom Boundary Layers

AbstractBaroclinic instabilities are important processes that enhance mixing and dispersion in the ocean. The presence of sloping bathymetry and the nongeostrophic effect influence the formation and evolution of baroclinic instabilities in oceanic bottom boundary layers and in coastal waters. This study explores two nongeostrophic baroclinic instability theories adapted to the scenario with sloping bathymetry and investigates the mechanism of the instability suppression (reduction in growth rate) in the buoyant flow regime. Both the two-layer and continuously stratified models reveal that the suppression is related to a new parameter, slope-relative Burger number Sr ≡ (M2/f2)(α + αp), where M2 is the horizontal buoyancy gradient, α is the bathymetry slope, and αp is the isopycnal slope. In the layer model, the instability growth rate linearly decreases with increasing Sr {the bulk form Sr = [U0/(H0f)](α + αp)}. In the continuously stratified model, the instability suppression intensifies with increasing Sr when the regime shifts from quasigeostrophic to nongeostrophic. The adapted theories are intrinsically applicable to deep ocean bottom boundary layers and could be conditionally applied to coastal buoyancy-driven flow. The slope-relative Burger number is related to the Richardson number by Sr = δrRi−1, where the slope-relative parameter is δr = (α + αp)/αp. Since energetic fronts in coastal zones are often characterized by low Ri, that implies potentially higher values of Sr, which is why baroclinic instabilities may be suppressed in the energetic regions where they would otherwise be expected to be ubiquitous according to the quasigeostrophic theory.

scholarly journals Sensitivities of Bottom Stress Estimation to Sediment Stratification in a Tidal Coastal Bottom Boundary Layer

2020 ◽  
Vol 8 (4) ◽  
pp. 256
Author(s):  
Yun Peng ◽  
Qian Yu ◽  
Yunwei Wang ◽  
Qingguang Zhu ◽  
Ya Ping Wang
Keyword(s):  
Velocity Distribution ◽  
Critical Role ◽  
Sediment Concentration ◽  
Distribution Models ◽  
Bottom Boundary ◽  
Field Investigations ◽  
Bottom Boundary Layers ◽  
Direct Covariance ◽  
Stress Estimation ◽  
Sediment Stratification

The bottom friction velocity (U*), which controls seabed erosion and deposition, plays a critical role in sediment transport in tidal coastal bottom boundary layers. Approaches have been proposed to calculate U*, including the log profile (LP) estimation, the direct covariance (COV) measurement, and the turbulent kinetic energy (TKE) method. However, the LP method assumes homogeneous flow and the effects of stratification need to be taken into account. Here, field investigations of hydrodynamics and sediment dynamics were carried out on the Jiangsu Coast, China. Two acoustic Doppler velocimeters (ADV) velocity measurements at 0.2 and 1 m above the seabed have been used to estimate U*, based on the aforementioned three methods. The COV and TKE methods provided reasonable estimations of U*, while a pronounced overestimation was identified when using the LP method. This overestimation can be attributed to the stratification effects associated with the vertical suspended sediment concentration (SSC) gradient near the bottom. Then, three models were utilized to correct the overestimation, in which the gradient/flux Richardson number was modified with empirical constants α, β, and A to parameterize the stratification effects in the logarithmic velocity distribution. The values of α, β, and A derived from the observation are smaller than the results from previous investigations. These modified logarithmic velocity distribution models can be applied in numerical simulations when sediment stratification is important.

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