Theories of convection from maintained and instantaneous sources buoyancy are developed, using methods which applicable to stratified body fluids with any variation density height; detailed solutions have been presented for the case a stably fluid linear gradient. The three main assumptions involved (i) that profiles vertical velocity similar at all heights, (ii) rate entrainment height is proportional characteristic height, (iii) incompressible do not change volume on mixing, local...

This paper describes an investigation of the turbulent forced plumes generated by steady release mass, momentum and buoyancy from a source situated in extensive region uniform or stably stratified fluid. The treatment, which is extension earlier work on buoyant plumes, also brings out relationship between jet Plume as special cases plumes.The analysis shows that behaviour plume finite size delivers buoyancy, mass can environment be related to virtual point only, treatment given for latter...

Abstract Vorticity, although not the primary variable of fluid dynamics, is an important derived playing both mathematical and physical roles in solution understanding problems. The following treatment discusses generation vorticity at rigid boundaries its subsequent decay. It intended to provide a consistent very broadly applicable framework within which wide range questions can be answered explicitly. rate shown relative tangential acceleration boundary without taking viscosity into...

The well-known solution for laminar forced convection in a uniformly heated pipe neglects the effect of buoyancy forces caused by temperature variations fluid. This depends on orientation, but horizontal it produces circulation fluid direction normal to axis, with consequent modification main flow. present treatment includes these effects, is restricted small rates heating (which correspond gradients along wall) so that motion due can be regarded as secondary In this way solutions velocity...

This paper describes a simple model which can be used to investigate the transport of water vapour by thermal plumes in atmosphere. For an approximate treatment these plumes, it is assumed (as previous paper) that vertical velocity, temperature and specific humidity are constant across ascending column, inflow velocity due mixing at edge plume proportional within plume. The behaviour rising air then investigated means equations representing conservation mass, momentum, heat vapour, numerical...

An exact solution is presented in this paper for the problem of laminar convective flow under a pressure gradient along vertical pipe, walls which are heated or cooled uniformly; based on assumption that velocity and buoyancy profiles far from pipe entrance do not change with height, entry-lengt effects ignored. Two different types behaviour found accordingly as forces act together opposition near centre pipe. When an upflow (or downflow cooled) increased relatively axis decreased until,...

A wide range of behaviour for turbulent forced plumes generated by vertical emission heated or other buoyant fluid from finite sources in extensive and otherwise still uniform environments can be represented on a single non-dimensional diagram characteristic heights, plotted against parameter Γ, which represents the balance flow conditions imposed at physical source. The set curves presented includes maximum height ascent negatively plumes, transition jet-like to plume-like above emitting...

This note demonstrates the equal importance of viscosity and thermal conductivity (or any equivalent process diffusion) in determining departure from equilibrium continuously stratified layers fluid. The analysis is carried out by an extension previous variational principles, applied to freely bounded horizontal which are thermally stratified; initial rate growth small disturbances shown depend on Rayleigh Prandtl numbers. method gives usual critical number for onset convection unstably with...

The generation of trailing vortices in the wakes surface-mounted obstacles at moderate Reynolds numbers is examined by channel-flow experiments and numerical simulation. A skew-mounted obstacle generates a single concentrated vortex, together with weak streamwise vorticity opposite sense extending to considerable distances on either side zero gross circulation across whole stream. Cross-stream-symmetrical (having plane symmetry normal surface) generate one or more nested vortex pairs,...

A similarity solution is obtained up to the first order in an effective Rayleigh number for behaviour of very weak thermal vortex rings produced by rapid release heat at one point a large region fluid.The laminar pattern flow similar that ordinary rings, but temperature decreases outwards from centre all directions with some asymmetry about horizontal plane through centre, and there no accumulation into ring. The propagates slowly relation its rate growth, process dominated viscous diffusion.

Theories on the behavior of turbulent buoyant plumes generally form three classes: (1) strictly self-similar models valid only in a uniform environment; (2) quasi-similar based flux conservation mass, momentum, and heat; (3) heat, kinetic energy mean motion. Few direct comparisons various numerical solutions for different have been reported; little attempt has made to compare formulation spite fact that such comparison must basis an understanding their differences. The following contribution...

This note presents a discussion of the roles axial momentum flux, flow force, angular flux and circulation in determining strength hence characterizing structure such narrow rotating axisymmetric core flows as swirling jets, vortex sink vortices wakes. The salient (though sometimes neglected) features these are that perturbation pressure plays an essential role both coupling azimuthal velocity fields transmission force along core, is invariant only cores with zero gross circulation. A number...

Many salient features of fully developed turbulent jets, plumes and wakes with steady mean flow are shown clearly by the relationship between momentum flux mass in column moving fluid. Using a simple model for flows, this can be found from solution single ordinary differential equation character many related flows represented immediately (except actual distribution space) on momentummass diagram. In note some approximate solutions based dimensional arguments outlined briefly cases buoyant...

Vortex rings are seen to form when dyed water drops strike a surface and their formation structure depend on height of fall tension. The assumption that vortex sheet envelopes the penetrating drop, frequently stated without explanation in literature, does not explain these factors this paper shows why it is incorrect. Alternative mechanisms have been proposed literature but none explains adequately vorticity generation or restriction ring low Weber numbers. This proposes mechanism based...

Earlier models of fire plumes based on simple entrainment laws and neglecting dynamic pressure have failed to produce the relatively shallow inflow over perimeter known as wind. This is prime importance in modelling it normally provides much air required for combustion; this reason we carried out a very numerical experiment two-dimensional natural convection above strip heat source with intention simulating those aspects behaviour involved generation wind without attempting formidably...

Investigations are conducted into situations where flow recirculation occurs in laminar combined convection flows vertical circular tubes. Particular attention is given to which finite sections of the tube wall maintained at constant temperatures, may be either hotter or colder than temperature fluid entrance tube. A numerical study carried out governing elliptic partial differential equations expressed difference form and solved using a relaxation technique. The values parameters, namely...

Abstract A study defining the occurrence, structure and evolution of “maritime continent” island thunderstorms over Bathurst Melville Islands near Darwin, Australia is presented. Satellite data for November‐December pre‐monsoon transition season show unambiguous records on at least 65% days period 1978‐1986. Storms develop most commonly between 1230LST 1530LST radar indicate a mean lifetime 2.5 h. Non‐occurrence was found only 7% examined associated with return to dry flow typical early...

A numerical and experimental study is described for the two-dimensional steady flow through a uniform cascade of normal flat plates. The Navier–Stokes equations are written in terms stream function vorticity solved using second-order-accurate finite-difference scheme which based on modified procedure to preserve accuracy iterative convergence at higher Reynolds numbers. upstream downstream boundary conditions discussed an asymptotic solution employed both downstream. frequently used method...

Entrainment models are developed for laminar axisymmetric flow in viscous jets, plumes, and wakes, an application is made to the ascent of plumes a stably stratified environment. The entrainment flux scale obtained using order-of-magnitude arguments, each case shown be proportional kinematic viscosity ν with exception thermal at Prandtl numbers less than unity when it thermometric conductivity κ.