Radial Wall Jet Flow Over Sigmoidal Surfaces

2020 ◽  
Author(s):  
Leonard F. Pease ◽  
Michael J. Minette ◽  
Judith Ann Bamberger
Keyword(s):  
Velocity Profile ◽  
Jet Flows ◽  
Wall Jet ◽  
Radial Wall ◽  
Modest Contribution ◽  
Velocity Decay ◽  
Conservation Of Momentum ◽  
Fixed Beds ◽  
Wall Jet Flow ◽  
Particle Bed

Abstract Radial wall jet flows across flat smooth surfaces have been studied for decades. These studies show that the radial velocity of these jets decays inversely with distance from the nozzle with modest contribution from friction (Poreh, et al., 1967; Rajaratnam, 1976). However, the extent to which flat surface results apply to curved surfaces remains unclear. In this paper we explore the influence of settled particle bed slope on radial wall jet velocity profiles. Jet flows over particle beds often introduce curvature in the particle bed profile, but the influence of the developed curvature on the velocity profile has not been explored. We model the step change in thickness as a sigmoidal curve of variable steepness and use conservation of momentum to evaluate the velocity profile for steady fixed beds. We find that surface curvature has a significant influence on the velocity decay coefficients, provided there is a slip velocity in the vicinity of the particle bed interface, which is strictly true for particle surfaces. We show that the velocity profile attenuates because of curvature. Indeed, conservation of momentum predicts conditions where the forward momentum of the flow is directed completely upward. The solution identifies two new dimensionless groups that determine whether a curved surface is sufficient to block radial flow and force flow vertically.

scholarly journals Numerical Study on Plane and Radial Wall Jets to Validate the 2D Assumption for an Idealized Downburst Outflow

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Yongli Zhong ◽  
Zhitao Yan ◽  
Yan Li ◽  
Jie Luo ◽  
Hua Zhang
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Critical Value ◽  
Plane Wall ◽  
Cloud Base ◽  
Jet Flows ◽  
Wall Jet ◽  
Wall Jets ◽  
Radial Wall ◽  
Velocity Decay

Turbulent radial and plane wall jets have been extensively investigated both experimentally and numerically over the past few decades. Previous studies mostly focused on the heat and mass transfers involved in jet flows. In this study, a comprehensive investigation was conducted on turbulent radial and plane wall jets, considering both jet spread and velocity decay for different parameters. The numerical results were compared with existing experimental measurements. The comparison focused on the velocity profile, jet spread, and velocity decay, and revealed that the Reynolds stress model (RSM) performs well in the simulation of both radial and plane wall jets. The results show that with a typical ratio of cloud base height to diameter for most downburst events, the effects of nozzle height and Reynolds number on the evolution of the radial wall jet are not significant. Both the jet spread and velocity decay exhibit a clear dependence on the Reynolds number below a critical value. Above this critical value, the plane wall jet becomes asymptotically independent of the Reynolds number. The co-flow was found to have a significant influence on the evolution of the plane wall jet. Comparatively, the jet spread and velocity of the radial wall jet were faster than those of the plane jet. For applications in civil engineering, it is valid to approximate the downburst outflow with a two-dimensional (2D) assumption from the perspective of longitudinal evolution of the flows.

scholarly journals Flow Analysis of Laminar Wall Jet over Curved Cavity with a Channel Mounted Fin

2019 ◽  
Vol 8 (3) ◽  
pp. 1876-1882 ◽  
Keyword(s):  
Flow Analysis ◽  
Flow Characteristics ◽  
Circuit Board ◽  
Momentum Balance ◽  
Jet Flows ◽  
Wall Jet ◽  
Fluid Flow Characteristics ◽  
Wall Jet Flow ◽  
Jet Characteristics ◽  
Fin Length

Wall jet flow is used for industrial cooling process, cooling of electronic component mounted on circuit board etc. Numerical simulations have been carried out for laminar two dimensional wall jet flows along curved cavity having a channel mounted thin fin. The commercial finite volume code FLUENT is chosen to resolve the mass balance and momentum balance equations. Fluid flow characteristics are investigated for different Reynolds number (Re=100 to 600) and for different fin geometry. The results are plotted in the form of velocity profiles and streamline contours. The effect of fin length on the laminar wall jet characteristics is also investigated.

Radial Wall Jet Flow Over Sigmoidal Surfaces

2021 ◽  
Author(s):  
Leonard Pease ◽  
Michael Minette ◽  
Judith Bamberger
Keyword(s):  
Jet Flow ◽  
Wall Jet ◽  
Radial Wall ◽  
Wall Jet Flow

Plane Turbulent Wall Jet Flow Development and Friction Factor

1963 ◽  
Vol 85 (1) ◽  
pp. 47-53 ◽  
Author(s):  
G. E. Myers ◽  
J. J. Schauer ◽  
R. H. Eustis
Keyword(s):  
Maximum Velocity ◽  
Velocity Profiles ◽  
Wall Jet ◽  
Shearing Stress ◽  
Integral Methods ◽  
Velocity Decay ◽  
Wall Jet Flow ◽  
Turbulent Wall ◽  
Momentum Integral ◽  
Wall Shearing Stress

An investigation of the jet development, the velocity profiles, and the wall shearing stress in a two-dimensional, incompressible, turbulent wall jet was undertaken. The maximum velocity decay, jet thickness, and the shearing stress are predicted analytically by momentum-integral methods. Experimental data concerning velocity profiles, velocity decay, and jet thickness agree well with previous investigators. The wall shearing stress was measured by a hot-film technique and the results help to resolve a wide divergence between the experimental values of other investigators.

Numerical modeling of Glauert type exponentially decaying wall jet flows of nanofluids using Tiwari and Das’ nanofluid model

2019 ◽  
Vol 29 (3) ◽  
pp. 1010-1038 ◽  
Author(s):  
Amin Jafarimoghaddam ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Numerical Modeling ◽  
Differential Equations ◽  
Design Methodology ◽  
Analytic Solution ◽  
Jet Flows ◽  
Wall Jet ◽  
Content Type ◽  
Flow And Heat Transfer ◽  
Wall Jet Flow

Purpose The purpose of this study is to present a simple analytic solution to wall jet flow of nanofluids. The concept of exponentially decaying wall jet flows proposed by Glauert (1956) is considered. Design/methodology/approach A proper similarity variables are used to transform the system of partial differential equations into a system of ordinary (similarity) differential equations. This system is then solved analytically. Findings Dual solutions are found and a stability analysis has been done. These solutions show that the first solution is physically realizable, whereas the second solution is not practicable. Originality/value The present results are original and new for the study of fluid flow and heat transfer over a static permeable wall, as they successfully extend the problem considered by Glauert (1956) to the case of nanofluids.

Inviscid, Axisymmetric, Annular Wall Jet Impingement As an Idealization of Cascade Thrust Reversers

2019 ◽  
Author(s):  
R. Chilukuri
Keyword(s):  
Velocity Profile ◽  
Internal Flow ◽  
Jet Impingement ◽  
Aircraft Engine ◽  
Wall Jet ◽  
Round Jets ◽  
Constant Vorticity ◽  
Annular Jet ◽  
Wall Jet Flow ◽  
Thrust Reverser

Abstract An analytical solution to inviscid, axisymmetric, impinging wall jet flow is proposed as a limited idealization of internal flow within a cascade thrust reverser of an aircraft engine. Behavior of prior Bessel Series solution for round jets is critically examined, before extending the formulation to an annular jet with non-zero inner wall radius. Behavior and accuracy of prior spectral and finite difference algorithms are examined, leading to an efficient hybrid computational scheme. Jet inflow velocity profile has a deficit as well as non-zero vorticity-function at the inner radial boundary, as is typical in engine fan ducts. Inviscid recirculation appears at the impingement corner, the strength of which is made determinate by assuming locally constant vorticity-function. Results indicate that fan duct velocity profile deficit is a significant contributor to occurrence of a large recirculation zone that is experimentally observed within a fully deployed thrust reverser.

Numerical Simulation of Two-Dimensional Laminar Incompressible Wall Jet Flow Under Backward-Facing Step

2006 ◽  
Vol 128 (5) ◽  
pp. 1023-1035 ◽  
Author(s):  
P. Rajesh Kanna ◽  
Manab Kumar Das
Keyword(s):  
Linear Trend ◽  
Step Length ◽  
Jet Flow ◽  
Step Height ◽  
Jet Flows ◽  
Wall Jet ◽  
Two Dimensional ◽  
Backward Facing Step ◽  
Navier Stokes Equation ◽  
Wall Jet Flow

Two-dimensional laminar incompressible wall jet flow over a backward-facing step is solved numerically to gain insight into the expansion and recirculation of flow processes. Transient streamfunction vorticity formulation of the Navier-Stokes equation is solved with clustered grids on the physical domain. The behavior of the jet has been studied for different step geometry (step length, l, step height, s) and Reynolds number (Re). It is found that the presence of a step in the wall jet flow creates recirculation and the reattachment length follows an almost linear trend within the range considered for both parameters Re and step geometry. Simulations are made to show the effect of entrainment on recirculation eddy. Detailed study of u velocity decay is reported. The velocity profile in the wall jet region shows good agreement with experimental as well as similarity results. The distance where the similarity profile forms is reduced by increasing the step geometry whereas an increment in Re increases this distance. The effects of Re, step length, and step height on wall vorticity are presented. The parametric study is helpful to predict the reattachment location for wall jet flows over step.

Three-Dimensional Curved Wall Jets

1972 ◽  
Vol 94 (2) ◽  
pp. 339-344 ◽  
Author(s):  
U. M. Patankar ◽  
K. Sridhar
Keyword(s):  
Aspect Ratio ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Ambient Air ◽  
Jet Flow ◽  
Jet Flows ◽  
Wall Jet ◽  
Wall Jets ◽  
Potential Core ◽  
Velocity Decay

This paper presents an experimental investigation of mean velocities of turbulent, three-dimensional incompressible air jets from various rectangular orifices issuing tangentially to and flowing along the surface of a curved wall into quiescent ambient air. An experimental study of the jet separation is also presented. The three-dimensional curved wall jet is found to be drastically different in its mean property behavior from its so-called two-dimensional counterpart. Velocity contour plots show the resultant effect on the jet flow of two diverging tendencies—the free jet flow and the Coanda flow. This effect is found to occur earlier with smaller aspect-ratio orifices. Within the range of variables studied, three-dimensional curved wall jets may be characterized by three regions of maximum velocity decay. The rate of maximum velocity decay is dependent on orifice aspect ratio, except in the potential core region. Further, the curved wall jet differs from other three-dimensional jet flows in its growth behavior.

Complete Velocity Profile and “Optimum” Skin Friction Formulas for the Plane Wall-Jet

1982 ◽  
Vol 104 (1) ◽  
pp. 59-65 ◽  
Author(s):  
G. P. Hammond
Keyword(s):  
Velocity Profile ◽  
Skin Friction ◽  
Initial Conditions ◽  
Jet Flows ◽  
Wall Jet ◽  
Wall Region ◽  
Law Of The Wall ◽  
Single Formula ◽  
Turbulent Wall ◽  
Good Agreement

An analytic expression for the complete velocity profile of a plane, turbulent wall-jet in “stagnant” surroundings is obtained by coupling Spalding’s single formula for the inner layer with a sine function for the “wake component.” This expression is transformed at the velocity maxima to yield an “optimum log-law” for skin friction. An approximate skin friction formula based on the “initial conditions” of the wall-jet is also presented. The formulas are generally in good agreement with experimental data. The complete velocity profile does not exhibit the conventional “law of the wall” behavior and modifications are consequently recommended to the usual treatment of the near-wall region in numerical calculation procedures for wall-jet flows. The use of the “Clauser plot” method of skin friction measurement is similarly shown to be in error when applied to wall-jets.

PIV Study of Laminar Wall Jets of Non-Newtonian Fluids

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
K. F. K. Adane ◽  
M. F. Tachie
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Newtonian Fluids ◽  
Jet Flows ◽  
Wall Jet ◽  
Fluid Type ◽  
Particle Image Velocimetry Technique ◽  
Velocity Decay

Three-dimensional laminar wall jet flows of shear-thinning non-Newtonian fluids have been studied using a particle image velocimetry technique. The non-Newtonian fluids were prepared from xanthan gum solutions of various concentrations. The velocity measurements were performed in various streamwise-transverse and streamwise-spanwise planes at various inlet Reynolds numbers. From these measurements, the maximum velocity decay, jet half-widths, and velocity profiles were obtained to study the effects of Reynolds number and fluid type on the characteristics of the wall jet flows. It was observed that the maximum velocity decay and jet half-widths depend on inlet Reynolds number and fluid but the similarity velocities profiles are independent of both Reynolds number and specific fluid type.

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