Velocity Coefficients For Free Jets From Sharp-Edged Orifices

1984 ◽  
Vol 106 (1) ◽  
pp. 13-17 ◽  
Author(s):  
J. H. Lienhard ◽  
J. H. Lienhard
Keyword(s):  
Boundary Layer ◽  
Surface Tension ◽  
Orifice Plate ◽  
Liquid Jet ◽  
Free Jets ◽  
Dissipation Of Energy ◽  
Direct Measurements ◽  
Velocity Coefficient ◽  
Viscosity Dependence

The viscosity-dependence of the velocity coefficient for a free liquid jet, issuing from a sharp-edged orifice, is predicted by computing the dissipation of energy in the boundary layer on the back of the orifice plate. The prediction is upheld by the only known direct measurements of velocity coefficients. The resulting coefficients are much closer to unity for large orifices than they are generally assumed to be. The influence of surface tension on small jets is also explained.

Stagnation-Point Heat Transfer During Impingement of Laminar Liquid Jets: Analysis Including Surface Tension

1993 ◽  
Vol 115 (1) ◽  
pp. 99-105 ◽  
Author(s):  
Xin Liu ◽  
L. A. Gabour ◽  
J. H. Lienhard
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Tension ◽  
Stagnation Point ◽  
Potential Flow ◽  
Weber Number ◽  
Liquid Jet ◽  
Legendre Functions ◽  
Stagnation Zone ◽  
Maximum Heat

The stagnation-zone characteristics of an impinging liquid jet are of great interest because the maximum heat transfer coefficient occurs in that region. This paper is an analytical study of the fluid flow and heat transfer in the stagnation zone of an unsubmerged liquid jet. The role of surface tension is emphasized. Stagnation-zone transport is strongly dependent on the potential flow above the boundary layer. Only a few studies have examined the potential flow of an unsubmerged jet, each using approximate potential flow theory and neglecting surface tension. In this paper, numerical solutions for a laminar unsubmerged jet are obtained, using a simulation method for steady, inviscid, incompressible flow with surface tension. A series solution that satisfies the boundary conditions in an approximate manner is constructed in terms of Legendre functions. Numerical solution of the momentum equation shows that surface tension has an effect on the stagnation-point flow field when the Weber number is small. Solutions of the associated boundary layer problem are used to obtain predictions of the influence of Weber number on the stagnation-zone heat transfer. The results are validated by comparison to measurements at high Weber number.

Direct measurements of drag of ribbon-type manipulators in a turbulent boundary layer

AIAA Journal ◽  
1987 ◽  
Vol 25 (3) ◽  
pp. 388-394 ◽  
Author(s):  
S. P. Govindaraju ◽  
F. W. Chambers
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Direct Measurements

On the reverse swing of a cricket ball—modelling and measurements

2001 ◽  
Vol 215 (1) ◽  
pp. 45-55 ◽  
Author(s):  
A T Sayers
Keyword(s):  
Boundary Layer ◽  
Flow Visualization ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
Drag Forces ◽  
Cricket Ball ◽  
Direct Measurements ◽  
Scale Ratio ◽  
Lift And Drag ◽  
At Will

The phenomenon of reverse swing of the ball in a game of cricket is achieved by very few bowlers, and then only by those who seem able to bowl at speeds in excess of 85 mile/h. It also seems that reverse swing cannot be achieved at will. Rather, it is obtained perhaps by accident as much as by design, its inception being as much of a surprise to the bowler as to the batsman. This would suggest that the flow conditions pertaining to reverse swing are extremely marginal at best. This paper investigates the flow conditions required for reverse swing to occur and presents data describing the lift and drag on the ball. While some direct measurements are made on a cricket ball for comparison purposes, the flow over the ball is modelled through a 2.7:1 scale ratio sphere. This permitted relatively large lift and drag forces to be measured. The results define the range of Reynolds numbers and seam angles over which reverse swing will occur, as well as the corresponding forces on the cricket ball. Flow visualization is used to indicate the state of the boundary layer.

scholarly journals Shear instability of an axisymmetric air–water coaxial jet

2018 ◽  
Vol 843 ◽  
pp. 575-600 ◽  
Author(s):  
Jean-Philippe Matas ◽  
Antoine Delon ◽  
Alain Cartellier
Keyword(s):  
Surface Tension ◽  
Stability Analysis ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Convective Instability ◽  
Scaling Laws ◽  
Shear Instability ◽  
Liquid Jet ◽  
Absolute Instability ◽  
Instability Waves

We study the destabilization of a round liquid jet by a fast annular gas stream. We measure the frequency of the shear instability waves for several geometries and air/water velocities. We then carry out a linear stability analysis, and show that there are three competing mechanisms for the destabilization: a convective instability, an absolute instability driven by surface tension and an absolute instability driven by confinement. We compare the predictions of this analysis with experimental results, and propose scaling laws for wave frequency in each regime. We finally introduce criteria to predict the boundaries between these three regimes.

scholarly journals On the deflection of a liquid jet by an air-cushioning layer

2018 ◽  
Vol 846 ◽  
pp. 711-751 ◽  
Author(s):  
M. R. Moore ◽  
J. P. Whiteley ◽  
J. M. Oliver
Keyword(s):  
Surface Tension ◽  
Equations Of Motion ◽  
Constant Thickness ◽  
Liquid Jet ◽  
Pressure Jump ◽  
Length Scales ◽  
Small Surface ◽  
Numerical Studies ◽  
Impact Problems ◽  
Systematic Derivation

A hierarchy of models is formulated for the deflection of a thin two-dimensional liquid jet as it passes over a thin air-cushioning layer above a rigid flat impermeable substrate. We perform a systematic derivation of the leading-order equations of motion for the jet in the distinguished limit in which the air pressure jump, surface tension and gravity affect the displacement of the centreline of the jet, but not its thickness or velocity. We identify thereby the axial length scales for centreline deflection in regimes in which the air layer is dominated by viscous or inertial effects. The derived length scales and reduced equations aim to expand the suite of tools available for future analyses of the evolution of lamellae and ejecta in impact problems. Assuming that the jet is sufficiently long that tip and entry effects can be neglected, we demonstrate that the centreline of a constant-thickness jet moving with constant axial speed is destabilised by the air layer for sufficiently small surface tension. Expressions for the fastest-growing modes are obtained in both the viscous-dominated air and inertia-dominated air regimes. For a finite-length jet emanating from a nozzle, we show that, in one particular asymptotic limit, the evolution of the jet centreline is akin to the flapping of an unfurling flag above a thin air layer. We discuss the distinguished limit in which tip retraction can be neglected and perform numerical investigations into the resulting model. We show that the cushioning layer causes the jet centreline to bend, leading to rupture of the air layer. We discuss how our toolbox of models can be adapted and utilised in the context of recent experimental and numerical studies of splash dynamics.

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