Parametric Analysis of Turbulent Wall Jet in Still Air Over a Transitional Rough, With Asymptotes of Fully Rough and Fully Smooth Wall Jets

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Noor Afzal ◽  
Abu Seena
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Rough Surfaces ◽  
Flow Direction ◽  
Wall Jet ◽  
Functional Forms ◽  
Jet Velocity ◽  
Turbulent Wall ◽  
Momentum Integral ◽  
Power Law Index

The novel scalings for streamwise variations of the flow in a turbulent wall jet over a fully smooth, transitional, and fully rough surfaces have been analyzed. The universal scaling for arbitrary wall roughness is considered in terms of the roughness friction Reynolds number (that arises from the stream wise variations of roughness in the flow direction) and roughness Reynolds number at the nozzle jet exit. The transitional rough wall jet functional forms have been proposed, whose numerical constants power law index and prefactor are estimated from best fit to the data for several variables, like, maximum wall jet velocity, boundary layer thickness at maxima of wall jet velocity, the jet half width, the friction factor and momentum integral, which are supported by the experimental data. The data shows that the two asymptotes of fully rough and fully smooth surfaces are co-linear with transitional rough surface, predicting same constants for any variable of flow for full smooth, fully rough and transitional rough surfaces. There is no universality of scalings in terms of traditional variables as different expressions are needed for each stage of the transitional roughness. The experimental data provides very good support to our universal relations.

Analysis of a Power Law and Log Law for a Turbulent Wall Jet Over a Transitional Rough Surface: Universal Relations

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
Noor Afzal ◽  
Abu Seena
Keyword(s):  
Experimental Data ◽  
Rough Surface ◽  
Power Law ◽  
Power Laws ◽  
Velocity Profiles ◽  
Wall Jet ◽  
Log Law ◽  
Jet Velocity ◽  
Turbulent Wall ◽  
Momentum Integral

The power law and log law velocity profiles and an integral analysis in a turbulent wall jet over a transitional rough surface have been proposed. Based on open mean momentum Reynolds equations, a two layer theory for large Reynolds numbers is presented and the matching in the overlap region is carried out by the Izakson-Millikan-Kolmogorov hypothesis. The velocity profiles and skin friction are shown to be governed by universal log laws as well as by universal power laws, explicitly independent of surface roughness, having the same constants as a fully smooth surface wall jet (or fully rough surface wall jet, as appropriate). The novel scalings for stream-wise variations of the flow over a rough wall jet have been analyzed, and best fit relations for maximum wall jet velocity, boundary layer thickness at maxima of wall jet velocity, the jet half width, the friction factor, and momentum integral are supported by the experimental data. There is no universality of scalings in traditional variables, and different expressions are needed for transitional roughness. The experimental data provides very good support to our universal relations proposed in terms of alternate variables.

Comparison of 2-D Turbulent Particle Laden Density Current and Wall Jets

2006 ◽  
Author(s):  
S. Hormozi ◽  
B. Firoozabadi ◽  
H. Ghasvari Jahromi ◽  
H. Afshin
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Suspended Solids ◽  
Turbidity Currents ◽  
Density Current ◽  
Wall Jet ◽  
Density Currents ◽  
Ambient Water ◽  
Wall Jets ◽  
Good Agreement

Dense underflows are continuous currents, which move down the slope due to the fact that, their density are heavier than ambient water. In turbidity currents the density differences arises from suspended solids. Vicinity of the wall make density currents and wall jets similar in some sense but Variation of density cause this flows more complex than wall jets. An improved form of ‘near-wall’ k-ε turbulence model is chosen which preserve all characteristics of both density and wall jet currents and a compression is made between them. Then the outcomes from low Reynolds number k-ε model is compared with v2–f model which show similarity. Also results show good agreement with experimental data.

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.

Experimental Investigation of the Effect of Free Stream Flow on the Thermal Behavior of a Turbulent Wall Jet

2014 ◽  
Author(s):  
Johnny Issa ◽  
Alfonso Ortega
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Stream Flow ◽  
Free Stream ◽  
Flow Characteristics ◽  
Thermal Characteristics ◽  
Wall Jet ◽  
Reynolds Analogy ◽  
Turbulent Wall

A systematic experimental investigation is conducted to understand of the effect of the free stream flow on the thermal characteristics of the turbulent wall jet. The jet Reynolds number varies between 6000 and 10000. The effect of the free stream flow on heat transfer and flow characteristics of the wall jet is investigated for blowing ratio varying between 2.4 to infinity. In the absence of free stream flow, Nusselt number data showed a very good agreement with published correlations. The free stream flow reduced Nusselt number in the region close to the jet exit and increased it in the region far downstream, a behavior explained using Reynolds analogy. The local Nusselt number dependence on Reynolds number and on the downstream location is identified and the obtained experimental results are correlated for the various considered blowing ratios.

Incomplete similarity of a plane turbulent wall jet on smooth and transitionally rough surfaces

2015 ◽  
Vol 16 (11) ◽  
pp. 1076-1090 ◽  
Author(s):  
Z. Tang ◽  
N. Rostamy ◽  
D.J. Bergstrom ◽  
J.D. Bugg ◽  
D. Sumner
Keyword(s):  
Rough Surfaces ◽  
Wall Jet ◽  
Incomplete Similarity ◽  
Turbulent Wall

The asymptotic downstream flow of plane turbulent wall jets without external stream

2015 ◽  
Vol 779 ◽  
pp. 351-370 ◽  
Author(s):  
Klaus Gersten
Keyword(s):  
Experimental Data ◽  
Momentum Flux ◽  
Maximum Velocity ◽  
Jet Flow ◽  
Plane Wall ◽  
Wall Jet ◽  
Free Jet ◽  
Wall Distance ◽  
Wall Jet Flow ◽  
Turbulent Wall

The plane turbulent wall-jet flow without externally imposed stream is considered. It is assumed that the wall jet does not emerge from a second wall perpendicular to the velocity vector of the initial wall jet. The (kinematic) momentum flux $K(x)$ of the wall jet decreases downstream owing to the shear stress at the wall. This investigation is based on the hypothesis that the total friction force on the wall is smaller than the total inflow momentum flux. In other words, the turbulent wall jet tends to a turbulent ‘half-free jet’ with a non-zero momentum flux $K_{\infty }\;(\text{m}^{3}~\text{s}^{-2})$ far downstream. The fact that the turbulent half-free jet is the asymptotic form of a turbulent wall jet is the basis for a singular perturbation method by which the wall-jet flow is determined. It turns out that the ratio between the wall distance $y_{m}$ of the maximum velocity and the wall distance $y_{0.5}$ of half the maximum velocity decreases downstream to zero. Dimensional analysis leads immediately to a universal function of the dimensionless momentum flux $K(\mathit{Re}_{x})/K_{\infty }$ that depends asymptotically only on the local Reynolds number $\mathit{Re}_{x}=\sqrt{(x-x_{0})K_{\infty }}/{\it\nu}$, where $x_{0}$ denotes the coordinate of the virtual origin. When the values $K$ and ${\it\nu}$ at the position $x-x_{0}$ are known, the asymptotic momentum flux $K_{\infty }$ can be determined. Experimental data on all turbulent plane wall jets (except those emerging from a second plane wall) collapse to a single universal curve. Comparisons between available experimental data and the analysis make the hypothesis $K_{\infty }\neq 0$ plausible. A convincing verification, however, will be possible in the future, preferably by direct numerical simulations.

scholarly journals Reynolds Number Effects on Statistics and Structure of an Isothermal Reacting Turbulent Wall-Jet

2014 ◽  
Vol 92 (4) ◽  
pp. 931-945 ◽  
Author(s):  
Zeinab Pouransari ◽  
Luc Vervisch ◽  
Arne V. Johansson
Keyword(s):  
Reynolds Number ◽  
Wall Jet ◽  
Reynolds Number Effects ◽  
Turbulent Wall

PIV Study of Three-Dimensional Wall Jet Over Smooth and Rough Surfaces

2007 ◽  
Author(s):  
Martin Agelinchaab ◽  
Mark F. Tachie
Keyword(s):  
Open Channel ◽  
Rough Surfaces ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Jet Flows ◽  
Wall Jet ◽  
Image Velocimetry ◽  
The Mean ◽  
Turbulent Wall ◽  
Insight Into

This paper reports experimental study of three-dimensional turbulent wall jet over smooth and rough surfaces. The wall jet was created using a square nozzle of size 6 mm and flow into an open channel. The experiments were performed at a Reynolds number based on the nozzle size and jet exit velocity of 4800. A particle image velocimetry was used to conduct detailed measurements over the smooth and rough surfaces at various streamwise-transverse and streamwise-spanwise planes. From these measurements, mean velocities and turbulent quantities were extracted at selected locations. The distributions of the mean velocities, turbulent intensities and Reynolds shear stress were used to provide insight into the characteristics of three-dimensional wall jet flows over smooth and rough surface.

Numerical investigation of turbulent offset jet flow over a moving flat plate using low-Reynolds number turbulence model

2021 ◽  
pp. 1-32
Author(s):  
Vishwa Mohan Behera ◽  
Sushil Rathore
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Jet Flow ◽  
Wall Jet ◽  
Plate Velocity ◽  
Self Similar ◽  
Jet Velocity ◽  
Low Reynolds ◽  
Offset Jet ◽  
Stationary Plate

Abstract The present study reports the numerical simulation of turbulent plane offset jet flow over a moving plate. The effect of plate velocity on various flow characteristics are discussed in detail including the special case of a stationary plate. For turbulence closure, low-Reynolds number (LRN) model proposed by Yang and Shih (YS) is applied because it is computationally robust and reported to perform well in many complex flow situations. The computations have been carried out with a Reynolds number of 15000 for various offset ratios (OR=3, 7 and 11) for plate to jet velocity ratios in the range 0-2. Finite volume method with a staggered grid arrangement has been used to solve the transport equations. The application of LRN model along with integration to wall approach enables to capture one closed loop of Moffatt vortex near the left corner of the wall for the stationary plate case. The spreading of jet has been found to reduce with increase in the plate velocity. The jet half-width lies very close to the wall for the plate to jet velocity 1.5 and 2. For two extreme limits of plate velocity i.e. Uplate = 0 and 2, the nearly self-similar profiles are observed at different axial locations in the wall jet region. Also, the flow is observed to exhibit nearly self-similar behavior when velocity profiles are plotted for various offset ratios at a given axial location in the wall jet region for Uplate = 0 and 2.

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