Effect of wall inclination on the mean flow and turbulence characteristics in a two-dimensional wall jet

Lai, J.C.S.; Lu, Daogang

doi:10.1016/0142-727x(95)00017-k

Cited by 35 publications

(23 citation statements)

References 13 publications

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“…Near-wall turbulent shear stress data is in good agreement with previous hot-wire data, but in the outer region Reynolds stresses data shows relatively higher values. Lai and Lu (1996) have experimentally studied mean velocity and turbulence characteristics of a two-dimensional wall jet for different angle HFF 24,2 of inclination of the wall (b), at a nozzle exit Reynolds number of 10,000. It has been reported by the author that in the range of 08 , b , 458, as the angle of inclination increases, the centerline velocity decays faster, and the jet spreads faster resulting in a shorter potential core and increased jet volume entrainment.…”

Section: Introductionmentioning

confidence: 99%

Computational study of a turbulent wall jet flow on an oblique surface

Pramanik

Das

2014

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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Purpose – The purpose of the present study is to investigate the flow and turbulence characteristics of a turbulent wall jet flowing over a surface inclined with the horizontal and to investigate the effect of variation of the angle of inclination of the wall on the flow structure of the wall jet. Design/methodology/approach – The high Reynolds number two-equation κ− model with standard wall function is used as the turbulence model. The Reynolds number considered for the present study is 10,000. The Reynolds averaged Navier-Stokes (RANS) equations are used for predicting the turbulent flow. A staggered differencing technique employing both contravariant and Cartesian components of velocity has been applied. Results for distribution of wall static pressure and skin friction, decay of maximum streamwise velocity, streamwise variation of integral momentum and energy flux have been compared for the cases of α=0°, 5°, and 10°. Findings – Flow field has been represented in terms of streamwise and lateral velocity contours, static pressure contour, vorticity contour and streamwise velocity and static pressure profiles at different locations along the oblique offset plate. Distribution of Reynolds stresses in terms of spanwise, lateral and turbulent shear stresses, and turbulent kinetic energy and its dissipation rate have been presented to describe the turbulent characteristics. Similarity of streamwise velocity and the velocity parallel to the oblique wall has been observed in the developed region of the wall jet flow. A decaying trend is observed in the variation of total integral momentum flux in the developed region of the wall jet which becomes more evident with increase in oblique angle. Developed flow region has indicated trend of similarity in profiles of streamwise velocity as well as velocity component parallel to the oblique wall. A depression in wall static pressure has been observed near the nozzle exit when the wall is inclined and the depression increases with increase in inclination. Effect of variation of oblique angles on skin friction coefficient has indicated that it decreases with increase in oblique angle. Growth of the outer and inner shear layers and spread of the jet shows linear variation with distance along the oblique wall. Decay of maximum streamwise velocity is found to be unaffected by variation in oblique angle except in the far downstream region. The streamwise variation of spanwise integral energy shows increase in oblique angle and decreases the magnitude of energy flux through the domain. In the developed flow region, streamwise variation of centreline turbulent intensities shows increased values with increase in oblique angle, while turbulence intensities along the jet centreline in the region X<12 remain unaffected by change in oblique angles. Normalized turbulent kinetic energy distribution highlights the difference in turbulence characteristics between the wall jet and reattached offset jet flow. Near wall velocity distribution shows that the inner region of boundary layer of the developed oblique wall jet follows a logarithmic profile, but it shows some difference from the standard logarithmic curve of turbulent boundary layers which can be attributed to an increase in skin friction coefficient and a decrease in thickness of the wall attached layer. Originality/value – The study presents an in-depth investigation of the interaction between the jet and the inclined wall. It is shown that due to the Coanda effect, the jet follows the nearby wall. The findings will be useful in the study of combined flow of wall jet and offset jet and dual offset jet on oblique surfaces leading to a better design of some mechanical jet flow devices.

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Section: Introductionmentioning

confidence: 99%

Computational study of a turbulent wall jet flow on an oblique surface

Pramanik

Das

2014

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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“…Another study of a flow on an inclined wall jet was conducted by the same authors Lai & Lu in 2000 by a new measure technology using a two -component laser Doppler anemometer (LDA) [13].…”

Section: The Bistable Fluidic Power Element Using the Coanda Effectmentioning

confidence: 99%

“…Experiments in this field were made by Lai & Lu (1996) for a wall angle between 15°and 45° and a nozzle exit Reynolds number of 10,000, using constant temperature hotwire anemometry. Another study of a flow on an inclined wall jet was conducted by the same authors Lai & Lu in 2000 by a new measure technology using a two -component laser Doppler anemometer (LDA) [13].…”

Section: The Bistable Fluidic Power Element Using the Coanda Effectmentioning

confidence: 99%

Fluidic Elements based on Coanda Effect

Constantin¹

2010

INCAS BULLETIN

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“…Design optimization is the only possible solution nowadays, as there is no proper theory to predict the CE. Finding universal description for such extensive problem cannot be expected, but there are some expectations to discover basic principles [1]. Our department is mainly focused on reduction of energy demand and improvement of functionality in devices for air conditioning and ventilation in buildings and vehicles.…”

mentioning

confidence: 99%

Comparison of CFD simulations and measurements of flow affected by coanda effect

Fišer

Jedelský

Vach

et al. 2012

EPJ Web of Conferences

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Simple example of CE is a jet blowing over convex surface. The jet could attach to the surface depending on geometrical configuration and character of the flow. Many practical applications involve near wall flows, and often in these applications of wall jets, the jet is injected at an angle to a solid boundary. Such examples can be seen in aircraft industry, energy devices (film cooling of turbine blades, gas turbine combustion chamber walls, jet exhausters, spraying devices, etc.) and many other areas. All of these devices have something in common; they were created using experimental research to assure their functionality. Design optimization is the only possible solution nowadays, as there is no proper theory to predict the CE. Finding universal description for such extensive problem cannot be expected, but there are some expectations to discover basic principles [1]. Our department is mainly focused on reduction of energy demand and improvement of functionality in devices for air conditioning and ventilation in buildings and vehicles. Particularly local ventilation in small spaces can be unpredictable because of air jet interaction with surfaces. Improvement and better control of CE for better distribution of air into the room can be made based on an analysis of wall jet physics character. Enhanced interior aerodynamics in vehicle cabs is important motivation for study of effect of different factors on the CE. This article is focused on experimental and CFD investigation of behaviour of a jet which is travelling around surface. The main goal was describe the influence of surface geometry and properties of jet on Coanda effect formation.

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Effect of wall inclination on the mean flow and turbulence characteristics in a two-dimensional wall jet

Cited by 35 publications

References 13 publications

Computational study of a turbulent wall jet flow on an oblique surface

Computational study of a turbulent wall jet flow on an oblique surface

Fluidic Elements based on Coanda Effect

Comparison of CFD simulations and measurements of flow affected by coanda effect

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