Reattachment Flow Issuing from a Finite Width Nozzle : Report 3. Effects of Inclinations of Reattachment Wall

Nozaki, Tsutomu; Hatta, Keiji; Nakashima, Masahiro

doi:10.1299/jsme1958.25.196

Cited by 3 publications

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“…Friction factor, C f , has been correlated with Reynolds number based on inner layer thickness by analogy with classical boundary layer. Nozaki et al (1982) have applied a control volume model for approximate calculation of offset jet flow with various offsets and inclination of the reattachment wall. The calculation predicted that the maximum inclination which maintains the reattachment is 608 and independent of both initial turbulence intensity and the offset.…”

Section: Computational Studymentioning

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: Computational Studymentioning

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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“…They presented the mean velocity field and turbulent parameters such as turbulent intensity, Reynolds shear stresses, triple velocity products, and two point velocity correlations at some sections in reattachment and wall jet regions. Some experimental studies were also performed on inclined offset jets (Nozaki et al 1982;Nasr and Lai 2000;Song et al 2000). In addition, it was shown that by increasing the inclined wall angle, the size of recirculation region and the reattachment length increase (Nasr and Lai 2000).…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Nozzle Geometry Effect on Turbulent 3-D Water Offset Jet Flows

Aliha¹,

Afshin²,

Farhanieh³

2016

JAFM

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Using the Yang-Shih low Reynolds k-ε turbulence model, the mean flow field of a turbulent offset jet issuing from a long circular pipe was numerically investigated. The experimental results were used to verify the numerical results such as decay rate of streamwise velocity, locus of maximum streamwise velocity, jet half width in the wall normal and lateral directions, and jet velocity profiles. The present study focused attention on the influence of nozzle geometry on the evolution of a 3D incompressible turbulent offset jet. Circular, square-shaped, and rectangular nozzles were considered here. A comparison between the mean flow characteristics of offset jets issuing from circular and square-shaped nozzles, which had equal area and mean exit velocity, were made numerically. Moreover, the effect of aspect ratio of rectangular nozzles on the main features of the flow was investigated. It was shown that the spread rate, flow entrainment, and mixing rate of an offset jet issuing from circular nozzle are lower than square-shaped one. In addition, it was demonstrated that the aspect ratio of the rectangular nozzles only affects the mean flow field of the offset jet in the near field (up to 15 times greater than equivalent diameter of the nozzles). Furthermore, other parameters including the wall shear stress, flow entrainment and the length of potential core were also investigated.

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Numerical characterization of a planar turbulent offset jet over an oblique wall

Pramanik

Das

2013

Computers & Fluids

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Reattachment Flow Issuing from a Finite Width Nozzle : Report 3. Effects of Inclinations of Reattachment Wall

Cited by 3 publications

References 0 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

Numerical Investigation of Nozzle Geometry Effect on Turbulent 3-D Water Offset Jet Flows

Numerical characterization of a planar turbulent offset jet over an oblique wall

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