Measurements and Analysis of Flow Velocity and Sediment Concentration at the Seabed

A review of flow velocity and sediment concentration measurements on field sites is given, but the main emphasis is on the data analysis results of near-bottom measurements of flow velocities and suspended sediment concentrations over a sandy bottom during four storms in the central North Sea. The water depth was 70 meters and the seafloor consisted of fine sand of 0.20 mm average diameter. The measurements included sediment concentrations, flow velocity in the boundary layer on the seafloor, steady current over the water column, wave heights, and photographs of the seafloor. The paper presents the variation of the sediment concentrations, waves and currents during the storms. Results from the logarithmic boundary layer flow model fit to the current measurements using the roughness (z0) and friction velocity (u*) as fitting parameters are also given. It also gives limited comparisons of model predictions with the data. The predictions are obtained from a wave-current interaction model combined with three different moveable bed models, which predict ripple size and sediment transport effects on the bed roughness.

Download Full-text

A One-Dimensional Viscous-Inviscid Strong Interaction Model for Flow in Indented Channels With Separation and Reattachment

Journal of Biomechanical Engineering ◽

10.1115/1.1580524 ◽

2003 ◽

Vol 125 (3) ◽

pp. 355-362 ◽

Cited By ~ 7

Author(s):

S. G. C. Kalse ◽

H. Bijl ◽

B. W. van Oudheusden

Keyword(s):

Boundary Layer ◽

Boundary Layers ◽

Present Model ◽

Interaction Model ◽

Dimensional Model ◽

One Dimensional ◽

Flow Models ◽

Flow Through ◽

Layer Flow ◽

Semi Empirical

A new one-dimensional model is presented for the calculation of steady and unsteady flow through an indented two-dimensional channel with separation and reattachment. It is based on an interactive boundary layer approach, where the equations for the boundary layer flow near the channel walls and for an inviscid core flow are solved simultaneously. This approach requires no semi-empirical inputs, such as the location of separation and reattachment, which is an advantage over other existing one-dimensional models. Because of the need of an inviscid core alongside the boundary layers, the type of inflow as well as the length of the channel and the value of the Reynolds number poses some limitations on the use of the new model. Results have been obtained for steady flow through the indented channel of Ikeda and Matsuzaki. In further perspective, it is discussed how the present model, in contrast to other one-dimensional flow models, can be extended to calculate the flow in nonsymmetrical channels, by considering different boundary layers on each of the walls.

Download Full-text

Homotopy Solution for Non-Similarity Boundary-Layer Flow near a Stagnation Point

Zeitschrift für Naturforschung A ◽

10.1515/zna-2010-0303 ◽

2010 ◽

Vol 65 (3) ◽

pp. 161-172 ◽

Cited By ~ 1

Author(s):

Xiangcheng You ◽

Hang Xu

Keyword(s):

Boundary Layer ◽

Flow Velocity ◽

Stagnation Point ◽

Boundary Layer Flow ◽

Nonlinear Partial Differential Equation ◽

Variable Coefficients ◽

External Flow ◽

Linear Ordinary Differential Equations ◽

Analytical Approximations ◽

Layer Flow

In this paper, non-similarity boundary-layer flow of a Newtonian fluid near an asymmetric plane stagnation point with a dimensionless external flow velocity ue = x/(x+1) is studied. The original boundary-layer equations are transferred into a nonlinear partial differential equation (PDE) with variable coefficients. An analytic technique for strongly nonlinear equations, namely the homotopy analysis method (HAM), is applied to replace the nonlinear PDE by an infinite number of linear ordinary differential equations (ODEs) with constant coefficients. An artificial parameter, called the convergence-control parameter, is introduced to ensure the convergence of solution series. Accurate analytical approximations of skin friction and boundary-layer thickness are obtained, and the effect of the external flow velocity on the non-similarity flows is investigated. This approach has general meanings and can be applied to many other non-similarity boundary-layer flows.

Download Full-text

Micro-Optical Sensors for Boundary Layer Flow Studies

Volume 2: Fora ◽

10.1115/fedsm2006-98556 ◽

2006 ◽

Cited By ~ 3

Author(s):

Darius Modarress ◽

Pavle Svitek ◽

Katy Modarress ◽

Daniel Wilson

Keyword(s):

Boundary Layer ◽

Flow Velocity ◽

Optical Sensors ◽

Boundary Layer Flow ◽

Single Mode ◽

Field Analysis ◽

Optical Mems ◽

Optical Elements ◽

Wall Boundary Layer ◽

Layer Flow

This manuscript describes optical MEMS (or MOEMS)-based microsensors for near wall boundary layer flow and particle field analysis. The sensors have been developed to measure a variety of parameters including flow velocity, surface speed, skin friction, and particle sizing. The surface mounted sensors measure flow velocity and/or flow velocity gradients as close as 70 microns from the wall. The sensors have been successfully used in a number of filed tests and flow facilities at different Reynolds numbers. They have also been used on-board full-scale vehicles. These compact and embeddable sensors incorporate specially designed diffractive optical elements and use single-mode optical fiber or integrated diode lasers for illumination.

Download Full-text