Horizontal Buoyant Jet Research Articles

Flow and Heat Transfer Due to a Buoyant Ceiling Jet Turning Downward at a Corner

An experimental investigation has been carried out on the flow and heat transfer characteristics of a horizontal buoyant ceiling jet that turns downward at a corner to yield a vertical negatively buoyant wall flow. Such flow situations are frequently encountered in thermal energy storage, in electronic systems, and in room fires. However, not much work has been done to understand the basic mechanisms governing such flows, particularly the flow near the corner. In this study, a two-dimensional jet of heated air is discharged adjacent to the lower surface of an isothermal horizontal plate. An isothermal vertical plate is attached at the other end of the horizontal surface, making a right angle corner. The vertical penetration distance of the resulting downward flow is measured and is related to the inflow conditions, particularly to the temperature and velocity at the jet discharge. This penetration distance is found to increase as the distance between the discharge location and the corner is reduced and also as the relative buoyancy level in the inlet flow is decreased. Velocity and temperature measurements are also carried out over the flow region. These indicate that the ceiling flow separates from the horizontal surface just before reaching the corner and then reattaches itself to the vertical wall at a finite distance vertically below the corner. The local surface heat flux measurements show a minimum in the heat transfer rate before the turn, along with a recovery in the heat transfer rate after the turn and the existence of a small recirculation zone near the corner. The net entrainment into the flow and heat transfer rate to the solid boundaries are also measured and correlated with the jet discharge conditions.

Modeling Horizontal Round Buoyant Jets in Shallow Water

This paper presents details of an integral-based mathematical model that represents the mixing characteristics produced when a buoyant jet discharges from a round pipe into a shallow body of water. The model consists of a number of submodels that individually account for local effects induced by the presence of bed- and free-surface boundaries. From experimental results, the roles played by these effects are assessed and interactions associated with, for example, the Coanda effect in shallow receiving water are quantified.

Generalized Lagrangian Model for Buoyant Jets in Current

A general Lagrangian jet model formulation is presented for an inclined buoyant jet in a current, with a three‐dimensional trajectory. The shear‐induced entrainment is computed as a function of the local densimetric Froude number and jet orientation, while the forced entrainment is taken as the ambient flow intercepted by the “windward” side of the buoyant jet. Model predictions are compared with both trajectory and tracer concentration data for a wide range of discharge and ambient flow conditions: horizontal buoyant jets in a coflow; vertical jets, oblique jets, and dense plumes in a cross flow; buoyant jets in a stagnant uniform or stratified fluid; and a horizontal buoyant jet in a perpendicular cross flow. The model is also consistent with the concept of asymptotic flow regimes, and reproduces the correct behavior in both the near and far field of a vertical momentum of buoyancy‐dominated jet in a cross flow. The connection of the model with traditional integral jet models is also discussed.

The interaction between a boundary and a horizontal buoyant jet

The standard ocean diffuser consists of a pipe on the ocean ff oor with ports alternately on either side. In New Zealand these ports are often sufficiently spaced such that port interference is small and thus a study of the flow from a single port in a stationary and a moving ambient fluid is relevant. A number of flow regimes occur where the discharge from the single port and the ambient are in opposite directions (a counterflow). This paper presents the results of an extensive experimental study of the possible flow patterns from these outfall ports.

Initial Dilution of Horizontal Jet in Crossflow

Available data on the initial dilution of a horizontal round buoyant jet in a perpendicular crossflow are successfully interpreted using length scales and mathematical models. The database consists of in situ measurements of surface dilution in the sewage boil at a number of sea outfalls in the United Kingdom, as well as limited laboratory experimental data. Simple equations for the prediction of minimum initial dilution in an ambient current are well‐supported by the collective data. The dilution constants obtained are comparable to but greater than those derived from previous laboratory experiments of a vertical negatively buoyant jet in a crossflow. A correlation for the downstream location of minimum dilution is also provided. The results reported herein can be readily used in outfall design.

コンピュータ・グラフィックスによる３次元水平噴流シミュレーションの可視化

With the recent rapid development of super computers, we are now able to perform large-scale computation of fluid. But, as the results are of such a large scale, techniques for visualization of the results of fluid simulation have become one of the most important problems for the researcher and engineer.In this film, we tried some experiences on the visualization. The main objects of this film are (1) investigation of visualization techniques, (2) particularly, evaluation of different expressions of fluid or flow images, (3) estimation and prediction of application fields including not only tools for analyzing fluid simulation but also design, advertisement and education.To accomplish these objects, we selected 3D horizontal buoyant jet, performed its numerical simulation, then prepared the five-minute film Flow Fantasia'85 by using computer graphic techniques.

Surface Dilution of Round Negative Buoyant Jets–A Comparison with Other Jets

Experimental results, concerning surface dilutions of round turbulent jets with negative buoyancy, are presented and discussed. Fresh water jets, of density ρo, discharging from a vertical pipe, of internal diameter do, placed in the middle of the experimental tank, at a depth H from the free surface of a quiescent ambient liquid, consisting of common salt water solution, of density ρs, slightly larger than ρo, have been studied. Dilution measurements, made with a conductivity probe, have been performed, along radial traverses, at a small depth of 5do, below the free surface. The experimental results were analyzed and presented in terms of dimensionless dilution scale gl versus the dimensionless length scale zl. In this form they are directly compared to axial dilution results of the positive buoyant jet. With the proper definition of length scale, they are expressed satisfactorily by the well established semiem-pirical expressions, concerning the axial dilution of positive buoyant jets. Semiem-pirical relationships, concerning the axial dilution distribution of the horizontal buoyant jet, are also presented. Thus, a direct comparison is made possible for surface dilutions in the three round buoyant jet cases, namely the positive, the negative and the horizontal jet, which will be very useful in engineering design.

Buoyant Jet Discharges into Finite Ambient Waters

The paper presents the results of an experimental study regarding the effect of the lateral dimension of the receiving water on the spreading, mixing, and temperature decay of a horizontal buoyant surface jet. The widths of the ambient water in the experiments have been 240, 120, 90 and 60 times the diameter of the jet nozzle. Based on the experimental data, correlations are carried out and empirical equations for prediction of jet width, thickness in vertical direction and longitudinal temperature decay are obtained. The available data of earlier investigators are included to obtain generalized equations for the spreading and temperature decay. Similarity of temperature profiles in the lateral and vertical directions is observed. The longitudinal temperature decay is found to vary inversely with distance in the flow direction and ¼th power of the densimetric Froude number.

Measurements on horizontal buoyant jet in calm ambient fluid, with theory based on variable coefficient of entrainment determined experimentally

Diverses caracteristiques d'un panache ascendant d'eau chaude injectee horizontalement dans de l'eau plus froide au repos ont ete determinees par l'experience. La valeur du nombre de Froude faisant intervenir la difference de densites et defini par rapport au diametre de la buse d'injection, varie entre 5,8 et 16. Les fluctuations de temperature de nature turbulente sont mesurees durant 70 a 90 s, a la cadence de dix releves par seconde. Ces mesures ont eu lieu dans diverses sections du panache et en divers points de chaque section. La temperature moyenne ainsi que la valeur quadratique moyenne des fluctuations sont determinees a partir des releves. Les resultats montrent que la temperature est normalement distribuee mais que la section du panache n'est circulaire qu'a proximite de la buse ou de la surface libre. On a determine pour diverses sections la distribution de la valeur quadratique moyenne de la temperature. Ces resultats tendent a confirmer la validite de la theorie de similitude proposee. Sont egalement mesurees : la vitesse moyenne le long de la trajectoire et la largeur du panache. Les resultats sont en assez bon accord avec la theorie modifiee fondee sur le panache convectif qui se forme sur une source chaude. Le coefficient d'entrainement a egalement ete determine a partir des mesures. Lorsque la distance a la buse s'accroit, la valeur du coefficient augmente jusqu'a environ 0,082. D'autres experiences sont cependant necessaires pour confirmer cette valeur.

Surface Discharge of Horizontal Buoyant Jets

SYNOPSISThe characteristics of surface discharge of horizontal buoyant jets have received more and more attention as the volume of cooling water discharged from both conventional and nuclear power plants are recently getting larger. Experimental and theoretical works on this problem has been accumulated. A two-dimensional problem has been treated by N. Tamai in the extension of the free turbulent jet and it is shown that the concept of the entrainment constant introduced by G. I. Taylor is very powerful.The purpose of this paper is to investigate the applicability of the method used in a two-dimensional buoyant jet to a three-dimensional problem and to introduce a theoretical and experimental analysis of vertical velocity and density profiles in a two-dimensional channel.The results of numerical calculation for a three-dimensional problem are analogous to those of the theoretical analysis by Hayashi et al. The computed results agree with measured data in case of the temperature variation along the jet axi...