Measurement and numerical modeling studies of the highest bottom shear stress in the Randle Reef area

2014 ◽  
Vol 41 (9) ◽  
pp. 828-838 ◽  
Author(s):  
Cheng He ◽  
Eric Scott ◽  
Matthew Graham ◽  
Andrew Binns
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Open Water ◽  
Bottom Layer ◽  
Velocity Profiles ◽  
Flow Speed ◽  
Model Verification ◽  
Bottom Shear Stress ◽  
Study Region ◽  
Quadratic Formula

The purpose of this study was to investigate the highest bottom shear stress, induced by wind in an area of Hamilton Harbour, Ontario, Canada known as Randle Reef. The study was conducted in support of a component of a contaminated sediment remediation plan utilizing a thin layer of sand to manage contaminated sediments. Toward this end, four acoustic Doppler current profilers (ADCPs) were deployed at two locations in the study region to measure velocity profiles for the purpose of indirectly measuring bottom shear stress (BSS) and model verification. There is no easy way to directly measure BSS in the field. As a result, the use of the logarithmic-profile method from the ADCP measured high resolution velocity profiles in the bottom layer was explored. This approach, according to our best knowledge, has not been published for a wind driven flow in a small open water body. To use the indirectly measured BSS to estimate the highest BSS in the study area, a three-dimensional hydrodynamic model was adopted to provide the spatial and temporal information of the bottom flow. The results showed that the modeled and measured flow velocity components agreed reasonably well at most of the water depths with the correlation coefficients being greater than 0.6. However, agreements between the modeled and measured bottom flow speeds were worse than expected due to the error contributions from both the modeled velocity components. Therefore, the modeled flow speed required rescaling based on ADCP velocity measurements before it could be deemed reliable. This is especially important in estimation of the BSS with a quadratic formula because the calculated BSS is proportional to the square of the speed.

scholarly journals EROSION AROUND A PILE DUE TO CURRENT AND BREAKING WAVES

1988 ◽  
Vol 1 (21) ◽  
pp. 102 ◽  
Author(s):  
E.W. Bijker ◽  
C.A. De Bruyn
Keyword(s):  
Shear Stress ◽  
Breaking Waves ◽  
Velocity Profiles ◽  
Long Waves ◽  
Orbital Velocity ◽  
Bottom Shear Stress ◽  
Normal Waves ◽  
Short Waves ◽  
A Current

Tests have been performed on a vertical pile subject to current only and to a combination of current with normal waves and current with breaking waves. The scour around the pile produced by current only is decreased by normal short waves superimposed upon that current and increased when breaking waves are superimposed upon the current. After analysis of the velocity profiles in the undisturbed area upstream of the pile and next to the pile, the following explanation is found for this phenomenon. When normal short waves are superimposed upon a current, the bottom shear stress of the combination of current with waves is increased more in the undisturbed area than next to the pile in the scour area. This results in a decrease of the scour around the pile. Due to the large values of the orbital velocity under breaking waves this effect is reversed for the combination of a current with breaking and relatively long waves. This results in an increase of the scour around the pile.

Three-Dimensional Turbulent Boundary Layer in a Rotating Helical Channel

1975 ◽  
Vol 97 (2) ◽  
pp. 197-210 ◽  
Author(s):  
A. K. Anand ◽  
B. Lakshminarayana
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Three Dimensional ◽  
Velocity Profiles ◽  
Layer Growth ◽  
Viscous Effects ◽  
Helical Channel ◽  
Wall Shear

An analytical and experimental investigation of the characteristics of a three-dimensional turbulent boundary layer in a rotating helical channel is reported in this paper. Expressions are developed for the velocity profiles in the inner layer, where the viscous effects dominate, and the outer layer, where the viscous effects are small. The prediction of boundary layer growth is based on the momentum integral technique. The analysis is valid for incompressible flow through a rotor blade row with small camber. The velocity profiles, wall shear stress and limiting streamline angles are measured inside the passages of a flat plate inducer at various radial and chordwise locations using rotating probes. The measurements are in general agreement with the predictions. Flow near the blade tip is found to be highly complex due to interaction of blade boundary layers and the annulus wall, resulting in appreciable radial inward flow as well as a defect in mainstream velocity near the midpassage. A wall shear stress correlation, which includes the effect of both Reynolds number and rotation parameter, is derived from the measured data.

Numerical Investigation of Impact of Pile Space on Flow around Two Vertical Cylindrical Piles

2012 ◽  
Vol 212-213 ◽  
pp. 1103-1107
Author(s):  
Jian Wen Qi ◽  
Cui Ping Kuang ◽  
Jie Gu ◽  
Jing Huang
Keyword(s):  
Shear Stress ◽  
Current Velocity ◽  
Three Dimensional ◽  
Horseshoe Vortex ◽  
Wake Vortex ◽  
Physical Factors ◽  
Bottom Shear Stress ◽  
Steady Current ◽  
Maximum Current ◽  
Cylindrical Piles

The flow around two vertical cylindrical piles exposed to a steady current is studied numerically by a three-dimensional hydrodynamic model, which is closured with a k-ε turbulence model. This model is firstly validated by experimental data obtained from a labortory experiment for a steady flow through a circular pile. Then this validated model is used to study flow pattern around two cylindrical piles. Finally, four key physical factors of the size of the horseshoe vortex and lee wake vortex, the maximum current velocity and bottom shear stress are analyzed under the different pile spaces. The main conclusions are: i) the size of the horseshoe vortex increases with the increase of the two pile space, while the size of the lee wake vortex changes slightly; ii) the maximum current velocity and the maximum bottom shear stress decrease with the increase of two pile space, and reach steady after the two pile space larger than six times of cylindrical pile diameter.

Impact of the Level of Approximation on Modeling Flushing Waves

2007 ◽  
Vol 2 (2) ◽  
Author(s):  
P. Staufer ◽  
J. Dettmar ◽  
J. Pinnekamp
Keyword(s):  
Shear Stress ◽  
Numerical Models ◽  
Three Dimensional ◽  
Shear Stresses ◽  
Bottom Shear Stress ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Successful Operation ◽  
One Dimensional ◽  
The One

Sewer cleaning with the means of flushing offers the possibility to place sewers free of deposit if flushing waves are generated continuously or quasi-continuously by suitable flushing devices. Numerical investigations should be carried out regarding different hydraulic circumstances because sewer networks consist of various compounds with complex geometries e.g. cross-section alignment or special structures. To accomplish a stable and successful operation of flushing devices it seems necessary to use different level of approximation on modelling flushing waves. Thereby both accuracy and running-time of simulations with numerical models will be optimized. This paper presents differences and similarities of the simulation results of a one-dimensional and a three-dimensional model of flushing wave within a big sized sewer. As assumed the one-dimensional model becomes less accurate when the complexity of the geometry increases. The three-dimensional model shows an underestimation of velocity and bottom shear-stress at the flushing head due to energy losses within the water body. Contrary, the one-dimensional model overestimates bottom shear-stress at the flushing head because of a stationary basic approach which is used. However, real highly resolved measurements of bottom shear-stresses are required to confirm the results in detail.

A Three-Dimensional Numerical Modelling Study of the Sound Velocity Profiles in the Persian Gulf

2008 ◽  
Author(s):  
Masoud Sadrinasab ◽  
Karim Kenarkoohi
Keyword(s):  
Sound Velocity ◽  
Persian Gulf ◽  
Three Dimensional ◽  
Bottom Layer ◽  
Velocity Profiles ◽  
The North ◽  
Strait Of Hormuz ◽  
Inverse Estuary ◽  
The Persian Gulf ◽  
Autumn And Winter

The Persian Gulf connects to the Indian Ocean via the Strait of Hormuz. In this study, a three-dimensional hydrodynamic model (COHERENS) is employed in a fully prognostic mode to derive sound velocity profiles in the Persian Gulf, an evaporation-driven inverse estuary that is governed by import of surface water from the adjacent ocean and export of saline bottom gulf water through the Strait of Hormuz. During spring and summer, a cyclonic overturning circulation establishes along the full length of the Gulf. During autumn and winter, this circulation breaks up into mesoscale eddies, laterally stirring most of the Gulf’s surface waters. Output of the model shows that sound velocity in the Persian Gulf depends mainly on the temperature in the surface layer whereas the bottom layer as well as the southern part of the Gulf depends on temperature and salinity. Maximum sound velocity occurs during summer in the Persian Gulf which decreases gradually moving from Strait of Hormuz to the north western part of the Gulf. A gradual decrease in sound velocity profiles with depth was commonly observed almost at all stations in the Gulf. However, an exception occurred in Strait of Hormuz during winter. The results of the model are very close to previous observations.

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