1006 The influence of an accelerated boundary layer on a liquid-jet free surface

Shear instabilities induced by the relaxation of laminar boundary layer at the free surface of a high speed liquid jet are investigated experimentally. Physical insights into these instabilities and the resulting capillary wave growth are gained by performing non-intrusive measurements of flow structure in the direct vicinity of the surface. The experimental results are a combination of surface visualization, planar laser induced fluorescence (PLIF), particle image velocimetry (PIV), and particle tracking velocimetry (PTV). They suggest that 2D spanwise vortices in the shear layer play a major role in these instabilities by triggering 2D waves on the free surface as predicted by linear stability analysis. These vortices, however, are found to travel at a different speed than the capillary waves they initially created resulting in interference with the waves and wave growth. A new experimental facility was built; it consists of a 20.3 × 146.mm rectangular water wall jet with Reynolds number based on channel depth between 3.13 × 104 to 1.65 × 105 and 115. to 264. based on boundary layer momentum thickness.

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Heat transfer in the seabed boundary layer

Journal of Fluid Mechanics ◽

10.1017/jfm.2021.842 ◽

2021 ◽

Vol 928 ◽

Author(s):

S. Michele ◽

R. Stuhlmeier ◽

A.G.L. Borthwick

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Free Surface ◽

Surface Waves ◽

Multiple Scales ◽

Perturbation Expansion ◽

Phase Speed ◽

Maximum Heat ◽

Practical Applications ◽

Free Surface Waves

We present a theoretical model of the temperature distribution in the boundary layer region close to the seabed. Using a perturbation expansion, multiple scales and similarity variables, we show how free-surface waves enhance heat transfer between seawater and a seabed with a solid, horizontal, smooth surface. Maximum heat exchange occurs at a fixed frequency depending on ocean depth, and does not increase monotonically with the length and phase speed of propagating free-surface waves. Close agreement is found between predictions by the analytical model and a finite-difference scheme. It is found that free-surface waves can substantially affect the spatial evolution of temperature in the seabed boundary layer. This suggests a need to extend existing models that neglect the effects of a wave field, especially in view of practical applications in engineering and oceanography.

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A Bypass Scenario of Laminarturbulent Transition in the Wind-Driven Free-Surface Boundary Layer

Fluid Mechanics and its Applications - IUTAM Symposium on Laminar-Turbulent Transition and Finite Amplitude Solutions ◽

10.1007/1-4020-4049-0_15 ◽

2005 ◽

pp. 267-288

Author(s):

Victor I. Shrira ◽

Guillemette Caulliez ◽

Dmitry V. Ivonin

Keyword(s):

Boundary Layer ◽

Free Surface ◽

Surface Boundary ◽

Surface Boundary Layer

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Jet Impingement of a Non-Newtonian Fluid

Fluids Engineering ◽

10.1115/imece2006-15993 ◽

2006 ◽

Author(s):

Jiangang Zhao ◽

Roger E. Khayat

Keyword(s):

Boundary Layer ◽

Free Surface ◽

Hydraulic Jump ◽

Similarity Solutions ◽

Surface Velocity ◽

Free Surface Velocity ◽

Viscous Boundary Layer ◽

Boundary Layer Region ◽

Layer Region ◽

Viscous Boundary

The similarity solutions are presented for the wall flow which is formed when a smooth planar jet of power-law fluids impinges vertically on to a horizontal plate, and spreads out in a thin layer bounded by a hydraulic jump. This problem is formulated analogous to radial jet flow problem and the solution procedure is accounted for by means of similarity solution of the boundary-layer equation [1] for Newtonian fluids. For the convenience of analysis, the flow may be divided into three regions, namely a developing boundary-layer region, a fully viscous boundary-layer region, and a hydraulic jump region. The similarity solutions of the film thickness and free surface velocity in fully viscous boundary-layer region include unknown constant L, which is solved numerically and approximately in the developing boundary-layer flow region. Comparison between the numerical and approximate solutions leads generally to good agreement, except for severely shear-thinning fluids. The boundary-layer solution depends on two parameters: power-law index n and α, the dimensionless flow parameters. The effect of α on film thickness and free surface velocity is investigated. The relations between the position of the hydraulic jump and dimensionless flow parameter are obtained and the effect of α on the position of the jump is presented.

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Acoustic prediction of flowrate: varying liquid jet stream onto a free surface

2020 International Conference on Signal Processing and Communications (SPCOM) ◽

10.1109/spcom50965.2020.9179604 ◽

2020 ◽

Author(s):

B T Balamurali ◽

Edwin Jonathan Aslim ◽

Yun Shu Lynn Ng ◽

Tricia Li Chuen Kuo ◽

Jacob Shihang Chen ◽

...

Keyword(s):

Free Surface ◽

Liquid Jet ◽

Jet Stream

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Mass transport in water waves over an elastic bed

Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences ◽

10.1098/rspa.1995.0090 ◽

1995 ◽

Vol 450 (1939) ◽

pp. 371-390 ◽

Cited By ~ 5

Keyword(s):

Boundary Layer ◽

Free Surface ◽

Mass Transport ◽

Water Waves ◽

Viscous Boundary Layer ◽

Curvilinear Coordinate ◽

Transport Velocity ◽

Mass Transport Velocity ◽

Orthogonal Curvilinear Coordinate System ◽

Viscous Boundary

The mass transport velocity in water waves propagating over an elastic bed is investigated. Water is assumed to be incompressible and slightly viscous. The elastic bed is also incompressible and satisfies the Hooke’s law. For a small amplitude progressive wave perturbation solutions via a boundary-layer approach are obtained. Because the wave amplitude is usually larger than the viscous boundary layer thickness and because the free surface and the interface between water and the elastic bed are moving, an orthogonal curvilinear coordinate system (Longuet-Higgins 1953) is used in the analysis of free surface and interfacial boundary layers so that boundary conditions can be applied on the actual moving surfaces. Analytical solutions for the mass transport velocity inside the boundary layer adjacent to the elastic seabed and in the core region of the water column are obtained. The mass transport velocity above a soft elastic bed could be twice of that over a rigid bed in the shallow water.

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