scholarly journals Turbulent Diffusion of Three-Dimensional Wall Jet Issuing from Semi-Circular Tube : Time-Mean Velocity and Concentration Field

1978 ◽  
Vol 44 (380) ◽  
pp. 1266-1274 ◽  
Author(s):  
Toru KOSO ◽  
Hideo OHASHI
Keyword(s):  
Turbulent Diffusion ◽  
Circular Tube ◽  
Three Dimensional ◽  
Concentration Field ◽  
Wall Jet ◽  
Mean Velocity

Turbulent Vorticity Diffusion in the Stronger Wall Jet Managed by a Flat Plate Wing in the Outer Layer

2015 ◽  
Author(s):  
Takuma Katayama ◽  
Shinsuke Mochizuki
Keyword(s):  
Shear Stress ◽  
Flat Plate ◽  
Outer Layer ◽  
Large Scale ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Quantitative Relationship ◽  
Wall Jet ◽  
Mean Velocity ◽  
The Mean

The present experiment focuses on the vorticity diffusion in a stronger wall jet managed by a three-dimensional flat plate wing in the outer layer. Measurement of the fluctuating velocities and vorticity correlation has been carried out with 4-wire vorticity probe. The turbulent vorticity diffusion due to the large scale eddies in the outer layer is quantitatively examined by using the 4-wire vorticity probe. Quantitative relationship between vortex structure and Reynolds shear stress is revealed by means of directly measured experimental evidence which explains vorticity diffusion process and influence of the manipulating wing. It is expected that the three-dimensional outer layer manipulator contributes to keep convex profile of the mean velocity, namely, suppression of the turbulent diffusion and entrainment.

Reynolds-Stress Modeling of Three-Dimensional Secondary Flows With Emphasis on Turbulent Diffusion Closure

2007 ◽  
Vol 74 (6) ◽  
pp. 1142-1156 ◽  
Author(s):  
I. Vallet
Keyword(s):  
Reynolds Stress ◽  
Turbulent Diffusion ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Reynolds Stress Model ◽  
Secondary Flows ◽  
Velocity Correlation ◽  
Mean Velocity ◽  
Diffusion Term ◽  
Spatial Gradients

The purpose of this paper is to assess the importance of the explicit dependence of turbulent diffusion on the gradients of mean-velocity modeling in second moment closures on three-dimensional (3D) detached and secondary flows prediction. Following recent theoretical work of Younis, Gatski, and Speziale, 2000, [Proc. Royal Society Lon. A, 456, pp. 909–920], we propose a triple-velocity correlation model, including the effects of the spatial gradients of mean velocity. A model for both the slow and rapid parts of the pressure-diffusion term was also developed and added to a wall-normal-free Reynolds-stress model. The present model is validated against 3D detached and secondary flows. Further developments, especially on the echo terms (which should appear in the formulation of pressure-velocity correlation), are discussed.

scholarly journals Experimental Investigation on Mean Flow Development of a Three-Dimensional Wall Jet Confined by a Vertical Baffle

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 237
Author(s):  
Ming Chen ◽  
Haijin Huang ◽  
Xingxing Zhang ◽  
Senpeng Lv ◽  
Rengmin Li
Keyword(s):  
Three Dimensional ◽  
Wall Jet ◽  
Lateral Growth ◽  
Mean Flow ◽  
Particle Image Velocimetry Technique ◽  
Mean Velocity ◽  
Flow Development ◽  
Velocity Decay ◽  
The Mean ◽  
Vertical Baffle

Three-dimensional (3D) confined wall jets have various engineering applications related to efficient energy dissipation. This paper presents experimental measurements of mean flow development for a 3D rectangular wall jet confined by a vertical baffle with a fixed distance (400 mm) from its surface to the nozzle. Experiments were performed at three different Reynolds numbers of 8333, 10,000 and 11,666 based on jet exit velocity and square root of jet exit area (named as B), with water depth of 100 mm. Detailed measurements of current jet were taken using a particle image velocimetry technique. The results indicate that the confined jet seems to behave like an undisturbed jet until 16B downstream. Beyond this position, however, the mean flow development starts to be gradually affected by the baffle confinement. The baffle increases the decay and spreading of the mean flow from 16B to 23B. The decay rate of 1.11 as well as vertical and lateral growth rates of 0.04 and 0.19, respectively, were obtained for the present study, and also fell well within the range of values which correspond to the results in the radial decay region for the unconfined case. In addition, the measurements of the velocity profiles, spreading rates and velocity decay were also found to be independent of Reynolds number. Therefore, the flow field in this region appears to have fully developed at least 4B earlier than the unconfined case. Further downstream (after 23B), the confinement becomes more pronounced. The vertical spreading of current jet shows a distinct increase, while the lateral growth was found to be decreased significantly. It can be also observed that the maximum mean velocity decreases sharply close to the baffle.

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.

Effect of initial conditions on mean flow characteristics of a three dimensional turbulent wall jet

2021 ◽  
pp. 095440622110149
Author(s):  
Sarvesh Kumar ◽  
Amitesh Kumar
Keyword(s):  
Reynolds Number ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Wall Jet ◽  
Mean Flow ◽  
Mean Velocity ◽  
Nozzle Length ◽  
Number Formula ◽  
Local Reynolds Number

The effect of initial conditions in a [Formula: see text] sidewall enclosure on the mean flow characteristics of a three dimensional turbulent square wall jet has been studied experimentally. The initial conditions are varied by varying the length of the nozzle; it is varied as l/ h = 10, 50, and 90, where l and h indicates the nozzle length and the side of the square nozzle, respectively. The effect of nozzle length on initial velocity profiles, velocity distribution in lateral and wall normal directions, spread rate, decay of maximum mean velocity, local Reynolds number and similarity behaviour has been studied. The wall normal spread width is higher for the nozzle length l/h = 10 in the near field [Formula: see text] but this trend completely changed after [Formula: see text]. The spread rate is found independent of the initial condition of the nozzles in the fully developed region. The decay rate of maximum mean velocity is found higher for l/ h = 10 in the region of ([Formula: see text], whereas decay rate becomes independent of the initial conditions in the fully developed region [Formula: see text]. The local Reynolds number variation is also estimated along the downstream directions for present case and found that the local Reynolds number [Formula: see text] reaches approximately 56% of the jet exit Reynolds number [Formula: see text] at [Formula: see text] for nozzle length l/ h = 10, while it is 57% and 59% of Rejet for the nozzles [Formula: see text] and [Formula: see text] respectively at the same location. The nozzle l/ h = 10 attained self similar behaviour more quickly as compared to the other nozzles. The sidewall played a significant role which pushed the fluid more towards the center resulting in a lower jet half width in the wall normal direction as compared to the corresponding case, without a sidewall. The decay rates of the maximum mean velocity for all the nozzles are estimated to be 1.08 which is in the accepted range found in the literature.

Experimental Study of the Sidewall Effect on Three Dimensional Turbulent Wall Jet

2021 ◽  
Author(s):  
Sarvesh Kumar ◽  
Amitesh Kumar
Keyword(s):  
Experimental Study ◽  
Decay Rate ◽  
Three Dimensional ◽  
Wall Jet ◽  
Mean Velocity ◽  
Self Similar ◽  
The Mean ◽  
Vertical Jet ◽  
H 30 ◽  
Flow Stream

Abstract An experimental study on the effect of sidewalls on the flow characteristics of a three-dimensional turbulent square wall jet is carried out at a Reynolds number of 25,000. The sidewalls are defined as the two parallel plates along the vertical jet centerline. Four different sizes of sidewall enclosure (here after referred to as SWE) are placed at the lateral positions (z) of ±3.5h, ±4h, ±4.5h and ±5h from the vertical jet centerline plane, where h is the height of square jet. The mean characteristics of fluid flow in wall normal (y) and lateral (z) directions at different downstream locations (x/h = 0.2 - 45) are measured using a hotwire anemometer. The velocity measurements are also performed in the z ? y lateral plane at four downstream locations (x/h = 30, 35, 40 and 45). Results indicate that the mean velocity profile in lateral and wall normal directions behaves differently depending on the size of SWEs. The decay rate of mean velocity increases with decrease in size of SWEs after the downstream location (x/h ≥ 20). The decay rate of the maximum mean velocity increases about 5% in 140mm SWE as compared to 200mm SWE. It is noted that spread of the jet in wall normal and lateral directions increases with decrease in size of SWEs after the attachment of the flow stream on the sidewalls. In the present case, the smaller size of SWE (140mm SWE) has 14.3% and 26.2% higher spread rate as compared to larger size of SWE (200mm SWE) in wall-normal and lateral directions, respectively. It is also seen that the self similar profile gets delayed in wall normal direction as compared to lateral direction for all the cases. The wall normal self-similar profile is obtained early with increase in the size of SWEs and it is obtained at x/h = 30, 27, 24 and 20 for 140mm ,160mm,180mm and 200mm SWEs respectively. The flow stream seems to climb the sidewall and this tendency increases with increase in size of SWEs.

Mean and Turbulence Characteristics of a Class of Three-Dimensional Wall Jets—Part 1: Mean Flow Characteristics

1991 ◽  
Vol 113 (4) ◽  
pp. 620-628 ◽  
Author(s):  
G. Padmanabham ◽  
B. H. Lakshmana Gowda
Keyword(s):  
Three Dimensional ◽  
Flow Characteristics ◽  
Experimental Investigations ◽  
Wall Jet ◽  
Mean Flow ◽  
Wall Jets ◽  
Mean Velocity ◽  
Turbulence Characteristics ◽  
Turbulent Wall ◽  
And Behavior

This paper reports experimental investigations on mean and turbulence characteristics of three-dimensional, incompressible, isothermal turbulent wall jets generated from orifices having the shapes of various segments of a circle. In Part 1, the mean flow characteristics are presented. The turbulence characteristics are presented in Part 2. The influence of the geometry on the characteristic decay region of the wall jet is brought out and the differences with other shapes are discussed. Mean velocity profiles both in the longitudinal and lateral planes are measured and compared with some of the theoretical profiles. Wall jet expansion rates and behavior of skin-friction are discussed. The influence of the geometry of the orifice on the various wall jet properties is presented and discussed. Particularly the differences between this class of geometry and rectangular geometries are critically discussed.

EXPERIMENTAL INVESTIGATION OF FLOW RESPONSE TO STATIONARY DISTURBANCE IN ROTATING-DISK FLOW

2019 ◽  
Vol XVI (2) ◽  
pp. 13-22
Author(s):  
Muhammad Ehtisham Siddiqui
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Three Dimensional ◽  
Rotating Disk ◽  
Careful Analysis ◽  
Laboratory Frame ◽  
Transition To Turbulence ◽  
Turbulent Regime ◽  
Mean Velocity ◽  
Layer Flow

Three-dimensional boundary-layer flow is well known for its abrupt and sharp transition from laminar to turbulent regime. The presented study is a first attempt to achieve the target of delaying the natural transition to turbulence. The behaviour of two different shaped and sized stationary disturbances (in the laboratory frame) on the rotating-disk boundary layer flow is investigated. These disturbances are placed at dimensionless radial location (Rf = 340) which lies within the convectively unstable zone over a rotating-disk. Mean velocity profiles were measured using constant-temperature hot-wire anemometry. By careful analysis of experimental data, the instability of these disturbance wakes and its estimated orientation within the boundary-layer were investigated.

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