Comparative study of a turbulent wall-attaching offset jet and a plane wall jet

KSME Journal ◽  
1993 ◽  
Vol 7 (2) ◽  
pp. 101-112 ◽  
Author(s):  
Soon Hyun Yoon ◽  
Kyung Chun Kim ◽  
Dae Seong Kim ◽  
Myung Kyoon Chung
Keyword(s):  
Comparative Study ◽  
Plane Wall ◽  
Wall Jet ◽  
Turbulent Wall ◽  
Offset Jet

Enhancement of heat transfer using turbulent wall jet

2019 ◽  
Vol 234 (1) ◽  
pp. 123-136
Author(s):  
Tej Pratap Singh ◽  
Amitesh Kumar ◽  
Ashok Kumar Satapathy
Keyword(s):  
Heat Transfer ◽  
Goodness Of Fit ◽  
Stokes Equations ◽  
Cooling System ◽  
Plane Wall ◽  
The Self ◽  
Wall Jet ◽  
Enhancement Of Heat Transfer ◽  
Self Similar ◽  
Turbulent Wall

Enhancement of heat transfer is very important in many engineering applications. The present study explores one of such possibilities by increasing the surface area of a plane wall. The effect of wavy wall on thermal and flow characteristics of a turbulent wall jet is studied in detail. The amplitude of the wavy surface is varied between 0.1 and 0.7 with an interval of 0.1. The Reynolds number is set to 15,000. The Reynolds averaged Navier Stokes equations are solved using the finite volume approach. The semi-implicit pressure linked equation algorithm is used to couple the pressure and velocity. A new scale, other than the traditional outer scaling, is defined for carrying out the self-similar behavior of the flow. Unlike the plane wall case, the self-similar characteristic is obtained at the respective crests and the troughs. However, it is also noticed that the two characteristics differ significantly with each other. Even, these characteristics are found to differ with each other for different amplitudes. The minimum pressure near the nozzle decreases as the amplitude increases and it is noted to be equal to −0.541 for the highest amplitude, i.e. A = 0.7. It is observed that the strength of convection near the exit of the jet is very high, and it decreases in the downstream direction. This increase in convection augments heat transfer by almost 10% as compared to the plane wall case. Based on the results, a quartic curve is fit for the average Nusselt number with a 99.75% goodness of fit. It is expected that the present study opens a new line in designing a proper cooling system.

Analysis of Conjugate Heat Transfer for a Combined Turbulent Wall Jet and Offset Jet

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Tanmoy Mondal ◽  
Abhijit Guha ◽  
Manab Kumar Das
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Conjugate Heat Transfer ◽  
Wall Jet ◽  
Fluid Interface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
The Mean ◽  
Turbulent Wall ◽  
Offset Jet

This paper presents a study of the conjugate heat transfer, involving conduction through a solid slab and turbulent convection in fluid, for a combined turbulent wall jet and offset jet flow using unsteady Reynolds averaged Navier–Stokes (URANS) equations. The conduction equation for the solid slab and convection equation for the fluid region are solved simultaneously satisfying the equality of temperature and heat flux at the solid–fluid interface. The fluid flow is complex because of the existence of periodically unsteady interaction between the two jets for the chosen ratio of jets separation distance to the jet width (i.e., d/w = 1). The heat transfer characteristics at the solid–fluid interface have been investigated by varying various important parameters within a feasible range: Reynolds number (Re = 10,000–20,000), Prandtl number (Pr = 1–4), solid-to-fluid thermal conductivity ratio (ks/kf = 1000–4000), and nondimensional solid slab thickness (s/w = 1–10). The bottom surface of the solid slab has been maintained at a constant temperature. The mean conjugate heat transfer characteristics indicate that the mean local Nusselt number along the interface is a function of flow (Re) as well as fluid (Pr) properties but is independent of solid properties (ks and s). However, the mean interface temperature and mean local heat flux along the interface always depend on all the aforementioned properties.

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.

Three-Dimensional Wall Jet Originating from a Circular Orifice

1972 ◽  
Vol 23 (3) ◽  
pp. 188-200 ◽  
Author(s):  
B G Newman ◽  
R P Patel ◽  
S B Savage ◽  
H K Tjio
Keyword(s):  
Three Dimensional ◽  
Plane Wall ◽  
Similarity Analysis ◽  
Length Scale ◽  
Wall Jet ◽  
Mean Velocity ◽  
Lateral Direction ◽  
Rate Of Growth ◽  
Circular Orifice ◽  
Turbulent Wall

SummaryAn incompressible three-dimensional turbulent wall jet originating from a circular orifice located adjacent to a plane wall is studied both theoretically and experimentally. An approximate similarity analysis predicts that the two transverse length scales,l0and L0, and the inverse of the mean velocity scale grow linearly with distance downstream x from the orifice. Experimental measurements of mean velocity and longitudinal turbulence intensity profiles were made both in air and water with hot-wire and hot-film anemometers respectively. The behaviour predicted by the similarity analysis was verified. It was found that the rate of growth of the length scale normal to the plane wall, dl0/dx, was somewhat less than that found for a two-dimensional wall jet, whereas the rate of growth of the length scale in the lateral direction, dL0/dx, was about seven times greater than dl0/dx.

CFD MODELING OF THE INTERACTION BETWEEN AN OBLIQUE WALL JET AND A PARALLEL OFFSET JET

2019 ◽  
Vol 46 (2) ◽  
pp. 101-112
Author(s):  
Nidhal Hnaien ◽  
Saloua Marzouk ◽  
Lioua Kolsi ◽  
Hatem Gasmi ◽  
Habib Ben Aissia ◽  
...  
Keyword(s):  
Cfd Modeling ◽  
Wall Jet ◽  
Offset Jet

Experimental investigation of a plane wall jet subjected to an external lateral flow

2015 ◽  
Vol 56 (5) ◽  
Author(s):  
Ahmed Kaffel ◽  
Jean Moureh ◽  
Jean-Luc Harion ◽  
Serge Russeil
Keyword(s):  
Experimental Investigation ◽  
Lateral Flow ◽  
Plane Wall ◽  
Wall Jet
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