Three-Dimensional Buoyant Wall Jets Released Into a Coflowing Turbulent Boundary Layer

1990 ◽  
Vol 112 (2) ◽  
pp. 356-362 ◽  
Author(s):  
J. R. Sinclair ◽  
P. R. Slawson ◽  
G. A. Davidson
Keyword(s):  
Three Dimensional ◽  
Ground Level ◽  
Turbulent Shear ◽  
Wall Jet ◽  
Turbulent Shear Flow ◽  
Streamwise Vorticity ◽  
Buoyant Jet ◽  
Buoyant Jets ◽  
Jet Trajectory ◽  
Model Predictions

Experiments have been conducted in a water flume to simulate finite-length line sources of heat that issue horizontally at ground level into a coflowing turbulent shear flow. The downstream development of each buoyant jet is documented by detailed mean temperature measurements, which are analyzed to determine the jet trajectory, spread rates, and distance to the point of liftoff from the surface. In addition, a three-dimensional, parabolic, numerical model based on the fundamental conservation equations is developed. Model predictions of several buoyant jets compare reasonably with the experimental data and suggest that the strength of the streamwise vorticity plays an important role in governing liftoff of a buoyant wall jet from the surface.

scholarly journals Nonlinear spectral model for rotating sheared turbulence

2019 ◽  
Vol 866 ◽  
pp. 5-32 ◽  
Author(s):  
Ying Zhu ◽  
C. Cambon ◽  
F. S. Godeferd ◽  
A. Salhi
Keyword(s):  
Turbulent Shear ◽  
Finite Difference Schemes ◽  
Turbulent Shear Flow ◽  
Third Order ◽  
Mean Velocity ◽  
Coupled Equations ◽  
Velocity Gradients ◽  
Model Predictions ◽  
Pseudo Scalar ◽  
High Order Finite Difference

We propose a statistical model for homogeneous turbulence undergoing distortions, which improves and extends the MCS model by Mons, Cambon & Sagaut (J. Fluid Mech., vol. 788, 2016, 147–182). The spectral tensor of two-point second-order velocity correlations is predicted in the presence of arbitrary mean-velocity gradients and in a rotating frame. For this, we numerically solve coupled equations for the angle-dependent energy spectrum${\mathcal{E}}(\boldsymbol{k},t)$that includes directional anisotropy, and for the deviatoric pseudo-scalar $Z(\boldsymbol{k},t)$, that underlies polarization anisotropy ($\boldsymbol{k}$ is the wavevector,$t$the time). These equations include two parts: (i) exact linear terms representing the viscous spectral linear theory (SLT) when considered alone; (ii) generalized transfer terms mediated by two-point third-order correlations. In contrast with MCS, our model retains the complete angular dependence of the linear terms, whereas the nonlinear transfer terms are closed by a reduced anisotropic eddy damped quasi-normal Markovian (EDQNM) technique similar to MCS, based on truncated angular harmonics expansions. And in contrast with most spectral approaches based on characteristic methods to represent mean-velocity gradient terms, we use high-order finite-difference schemes (FDSs). The resulting model is applied to homogeneous rotating turbulent shear flow with several Coriolis parameters and constant mean shear rate. First, we assess the validity of the model in the linear limit. We observe satisfactory agreement with existing numerical SLT results and with theoretical results for flows without rotation. Second, fully nonlinear results are obtained, which compare well to existing direct numerical simulation (DNS) results. In both regimes, the new model improves significantly the MCS model predictions. However, in the non-rotating shear case, the expected exponential growth of turbulent kinetic energy is found only with a hybrid model for nonlinear terms combining the anisotropic EDQNM closure and Weinstock’s return-to-isotropy model.

Non-Boussinesq Integral Model for Horizontal Turbulent Strongly Buoyant Plane Jets

2008 ◽  
Author(s):  
Jianjun Xiao ◽  
John R. Travis ◽  
Wolfgang Breitung
Keyword(s):  
Power Plants ◽  
Boussinesq Approximation ◽  
Density Variation ◽  
Integral Model ◽  
Buoyant Jet ◽  
Boussinesq Model ◽  
Buoyant Jets ◽  
Jet Trajectory ◽  
Plane Jets ◽  
Hydrogen Safety

Horizontal buoyant jets are fundamental flow regimes for hydrogen safety analyses in the nuclear power plants. Integral model is an efficient, fast running engineering tool that can be used to obtain the jet trajectory, centerline dilution and other properties of the flow. In the published literature, most of the integral models that are used to predict the horizontal buoyant jet behavior employ the Boussinesq approximation, which limits the density range between the jets and the ambient. CorJet, a long researched, developed, and established commercial model, is such a Boussinesq model, and has proved to be accurate and reliable to predict the certain buoyant jet physics. In this study, Boussinesq and non-Boussinesq integral models with modified entrainment hypothesis were developed for modeling horizontal turbulent strongly buoyant plane jets. All the results and data where the Boussinesq model is valid will collapse to CorJet when they are properly normalized, which implies that the calculation is not sensitive to density variations in Boussinesq model. However, non-Boussinesq results will never collapse to CorJet analyses using the same normalized scaling, and the results are dependent on the density variation. The reason is that CorJet employs the Boussinesq approximation in which density variations are only important in the buoyancy term. For hydrogen safety analyses, the large density variation between hydrogen and the ambient, which is normally the mixture of air and steam, will make the Boussinesq approximation invalid, and the effect of the density variation on the inertial mass of the fluid can not neglected. This study highlights the assumption of the Boussinesq approximation as a limiting, simplified theory for strongly buoyant jets. A generalized scaling theory for horizontal strongly buoyant jet seems not to exist when the Boussinesq approximation is not applicable. This study also reveals that the density variation between jets and the ambient should be less than 10% to accurately model horizontal buoyant jets when the Boussinesq approximation is applied. Verification of this integral model is established with available data and comparisons over a large range of density variations with the CFD codes GASFLOW and Fluent. The model has proved to be an efficient engineering tool for predicting horizontal strongly buoyant plane jets.

Evaluation of fish-injury mechanisms during exposure to turbulent shear flow

2005 ◽  
Vol 62 (7) ◽  
pp. 1513-1522 ◽  
Author(s):  
Zhiqun Deng ◽  
Gregory R Guensch ◽  
Craig A McKinstry ◽  
Robert P Mueller ◽  
Dennis D Dauble ◽  
...  
Keyword(s):  
High Speed ◽  
Motion Tracking ◽  
Oncorhynchus Tshawytscha ◽  
Three Dimensional ◽  
Turbulent Shear ◽  
Control Group ◽  
Similar Data ◽  
Turbulent Shear Flow ◽  
Eye Injuries ◽  
Injury Mechanisms

Understanding the factors that injure or kill turbine-passed fish is important to the operation and design of the turbines. Motion-tracking analysis was performed on high-speed, high-resolution digital videos of juvenile salmonids exposed to a laboratory-generated shear environment to isolate injury mechanisms. Hatchery-reared fall chinook salmon (Oncorhynchus tshawytscha, 93–128 mm in length) were introduced into a submerged, 6.35-cm-diameter water jet at velocities ranging from 12.2 to 19.8 m·s–1, with a reference control group released at 3 m·s–1. Injuries typical of turbine-passed fish were observed and recorded. Three-dimensional trajectories were generated for four locations on each fish released. Time series of velocity, acceleration, force, jerk, and bending angle were computed from the three-dimensional trajectories. The onset of minor, major, and fatal injuries occurred at nozzle velocities of 12.2, 13.7, and 16.8 m·s–1, respectively. Opercle injuries occurred at 12.2 m·s–1 nozzle velocity, while eye injuries, bruising, and loss of equilibrium were common at velocities of 16.8 m·s–1 and above. Of the computed dynamic parameters, acceleration showed the strongest predictive power for eye and opercle injuries and overall injury level, and it may provide the best potential link between laboratory studies of fish injury, field studies designed to collect similar data in situ, and numerical modeling.

Coherent Streamwise Vortex Structures in the Near-Field of the Three-Dimensional Wall Jet

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Lhendup Namgyal ◽  
Joseph W. Hall
Keyword(s):  
Velocity Field ◽  
Near Field ◽  
Three Dimensional ◽  
Vortex Pair ◽  
Streamwise Vortex ◽  
Vortex Structures ◽  
Stereoscopic Particle Image Velocimetry ◽  
Wall Jet ◽  
Streamwise Vorticity ◽  
Low Dimensional

A turbulent three-dimensional wall jet with an exit Reynolds number of 250,000 was investigated using stereoscopic particle image velocimetry (PIV) in the near-field region (x/D = 5). The proper orthogonal decomposition (POD) was applied to all three components of the velocity field to investigate the underlying coherent structures in the flow. A low-dimensional reconstruction of the turbulent velocity field using the first five POD modes showed the presence of coherent streamwise vortex structures formed in the outer shear-layers of the wall jet, not unlike those found in the near-field of free jets. The instantaneous streamwise vorticity reconstructed from the low-dimensional reconstructed velocity field indicates the presence of a persistent vortex pair close to the wall and on either side of the jet centerline that appear similar to the mean streamwise vorticity. These regions do not appear to be directly related to the positioning of the streamwise vortex structures in the outer shear-layer.

scholarly journals BUOYANT DISCHARGES FROM SUBMERGED MULTIPORT DIFFUSERS

1974 ◽  
Vol 1 (14) ◽  
pp. 126
Author(s):  
Donald R.F. Harleman ◽  
Gerhard H. Jirka
Keyword(s):  
Channel Model ◽  
Coastal Zone Management ◽  
Three Dimensional ◽  
Cooling Water ◽  
Frictional Resistance ◽  
Two Dimensional ◽  
Buoyant Jet ◽  
Buoyant Jets ◽  
Dimensional Flow ◽  
Zone Management

The application of submerged multiport diffusers for the discharge of degradable liquid wastes and of heated cooling water from electric power generation forms an important aspect of coastal zone management. Previous buoyant jet models for submerged diffuser discharge have been developed for the limiting case of discharge in unconfined deep water in the form of rising buoyant jets. These models can be used for sewage diffusers, but are not applicable for diffusers in shallow receiving water with low buoyancy, the type used for thermal discharges ("thermal diffusers"). A multiport diffuser will produce a general three-dimensional flow. Yet the predominantly two dimensional flow which exists in the center portion of the three-dimensional diffuser can be analyzed as a two-dimensional "channel model". Theoretical solutions for diffuser-induced dilutions are derived for the two-dimensional case and verified experimentally. Furthermore, the theory can be applied to the three-dimensional situation by requiring equivalency of far-field effects, that is the frictional resistance governing the diffuser-induced motion at larger distances from the diffuser line.

Boundary Effects on Dilution of Buoyant Jets

1973 ◽  
Vol 8 (1) ◽  
pp. 168-177
Author(s):  
James J. Sharp ◽  
Chung-su Wang
Keyword(s):  
Experimental Study ◽  
Boundary Effects ◽  
Shear Stresses ◽  
Wall Jet ◽  
Practical Case ◽  
Buoyant Jet ◽  
Momentum Exchange ◽  
Buoyant Jets ◽  
Free Jet ◽  
Analytical Studies

Abstract Most studies of buoyant jet phenomena have been conducted with the outfall pipe remote from the bed. This situation idealises the practical case because, over a period of time, it is likely that the diffuser pipeline will settle some way into the bed due to the scour action of prevailing currents. Thus, the dilution achieved in the rising jet may be affected to some extent by the proximity of the ocean bed. This paper describes an experimental study conducted to determine the effect of a bed immediately below the outfall mozzle. The results indicated generally that the effect of the floor was to considerably increase the surface dilution above the value predicted by current theories and other experiments, in which the nozzle is remote from the floor. The magnitude of the increase varied but could be as high as 1000%. Although no analytical studies were undertaken visual observations indicated some reasons for the increase of dilution. As the jet was discharged shear stresses between the floor and the jet caused the effluent to cling to the floor in a manner somewhat similar to that of a wall jet. This caused greater momentum exchange at the interface between the jet and receiving fluid and thereby increased dilution beyond that obtained with a free jet. It has been known for some time that studies of buoyant jets undertaken in quiescent homogeneous receiving fluid considerably underestimate the dilution which will be achieved in practice because of prevailing currents at the outfall site and the possibility of stratification in the receiving fluid. This study indicates that existing theories for buoyant jet dilution may be even more conservative than was previously thought.

scholarly journals Variations on Kolmogorov flow: turbulent energy dissipation and mean flow profiles

2011 ◽  
Vol 670 ◽  
pp. 204-213 ◽  
Author(s):  
B. ROLLIN ◽  
Y. DUBIEF ◽  
C. R. DOERING
Keyword(s):  
Reynolds Number ◽  
Stokes Flow ◽  
Three Dimensional ◽  
Turbulent Energy ◽  
Dissipation Factor ◽  
Turbulent Shear ◽  
Flow Profile ◽  
Turbulent Shear Flow ◽  
Mean Flow ◽  
Flow Profiles

The relation between the form of a body force driving a turbulent shear flow and the dissipation factor β = ϵℓ/U3 is investigated by means of rigorous upper bound analysis and direct numerical simulation. We consider unidirectional steady forcing functions in a three-dimensional periodic domain and observe that a rigorous infinite Reynolds number bound on β displays the same qualitative behaviour as the computationally measured dissipation factor at finite Reynolds number as the force profile is varied. We also compare the measured mean flow profiles with the Stokes flow profile for the same forcing. The mean and Stokes flow profiles are strikingly similar at the Reynolds numbers obtained in the numerical simulations, lending quantitative credence to the notion of a turbulent eddy viscosity.

Sign in / Sign up

Export Citation Format

Share Document