Plume Axis Research Articles

The behavior of a two-dimensional dual forced plume

The behavior of two plumes ejected into a thin water tank is investigated experimentally. As the time elapses, the plume axes deflect towards each other. Time evolution of this two-dimensional, dual forced plume is found to be similar to that of a two-dimensional, single plume ejected near a vertical wall. The symmetric plane of the two plumes in the former case plays the role of the vertical wall. The time required for the dual plume to attain a quasi-steady state is shorter than that for the single plume. The deflection angles of the plume axes are smaller for the dual plume, and the plume water remains near the free water surface in a quasi-steady state. Water circulation in a triangular region surrounded by the free water surface, the side of the plume and the symmetric plane (or the vertical wall for the single plume case) may account for this difference; the circulation is much more pronounced in the single plume case.

The Use of an AIG-Analyzer for the Investigation of SO2-Dispersion Problems

Modern large coal-fired power plants of the GDR are built with 300 m chimneys. Investigations of the spreading of power plant plumes have been made in many countries, but not for sources with heal emission rates greater than 400 M J/s. In 1970 we started field experiments by means of an instrumental aircraft. On board the Interflung aircraft, a single engine AN-2, an SO2, gas analyzer (AIG) and a CO2, analyzer (Infralyt) were installed to characterize the plume at discrete distances down wind. The results of more than 40 flights encompassing a wide range of meteorological conditions (2 – 20 m/s wind speed) were compared with theoretical values. By estimating the plume axis (effective source height) and σ-parameters new knowledge was obtained.

The effects of pheromone concentration on the flight behaviour of the oriental fruit moth, Grapholitha molesta

ABSTRACT. Male oriental fruit moths, Grapholitha molesta (Busck) (Tortricidae), flew at lower overall and net ground velocities when they flew toward higher concentration pheromone sources. Turning frequency was greater with increased pheromone concentration, while the distance of turns from the plume axis back towards the axis decreased. Turning magnitude and inter‐reversal track angles remained constant at all concentrations tested. Concomitant with the changes in ground velocity but constant inter‐reversal angles, were decreases in airspeed, decreases in the moths' course angles and increases in their drift angles. The significance of these changes is discussed in relation to their possible role in a longitudinal chemoklinotactic programme of turning operating in conjunction with anemotaxis to allow location of a pheromone source in wind.

Flow induced by jets and plumes

The order of magnitude of the flow velocity due to the entrainment into an axisymmetric, laminar or turbulent jet and an axisymmetric laminar plume, respectively, indicates that viscosity and non-slip of the fluid at solid walls are essential effects even for large Reynolds numbers of the jet or plume. An exact similarity solution of the Navier-Stokes equations is determined such that both the non-slip condition at circular-conical walls (including a plane wall) and the entrainment condition at the jet (or plume) axis are satisfied. A uniformly valid solution for large Reynolds numbers, describing the flow in the laminar jet region as well as in the outer region, is also given. Comparisons show that neither potential flow theory (Taylor 1958) nor viscous flow theories that disregard the non-slip condition (Squire 1952; Morgan 1956) provide correct results if the flow is bounded by solid walls.

Frequency distribution of the concentration on the center of mean plume axis in the surface layer.

Concentration of NOx was measured several tens of meters downwind from a continuous NOx source by the fast respondent analyzer. Horizontal and vertical distributions of averaged NOx concentration were also measured in the same periods using bag samplers. The frequency distribution of instananeous concentration observed on the mean plume axis agrees well with the sharp cut off power low given by Gifford's fluctuating plume model. But the discontinuity of the frequency distribution at the maximum concentration is not sharp. It was confirmed that the frequency distribution of concentration averaged over a short period within 200 sec also followed Gifford's model. The ratio of the maximum short period concentration to the long period (2,700 sec) concentration was about 5 to 1 when the averaging time of the short period was 4 sec. The ratio descreases with the averaging time until about 100 sec. It becomes almost independent of the averaging time and not so different from 1 when the averaging time is longer than 100 sec.

Strong Turbulent Buoyant Plumes. I. Similarity

Abstract It is shown that similarity solutions in strong buoyant plumes (plane or axisymmctric) exist if a local characteristic turbulent diffusion coefficient varies inversely proportional to the square of the local gas density in the plume. The similarity formulation implies that the proper dependent variable for the temperature (density) defect is ΔT/0(Δρ/ρ), where ΔT( Δρ) is the temperature (density) defect from the ambient temperature (density), T0(ρ0), and ρ is the local density in the plume. The same variable is applicable further downstream from the source when the plume becomes weak. The form of the variable, ΔT/T0, proposed for both strong and weak plumes is different from the form of the variable, ΔT/T( Δρ/ρ0), previously used for weak plumes. Long experience with strong plumes from fires and recent experimental results of temperature variations along the plume axis support the use of the variable ΔT/T0. The similarity solution is consistent with Morton's (1965) model of strong plumes and the form of the entrainment function for strong density variations in plumes or jets proposed by Ricou and Spalding (1961). In a subsequent paper, a simple model will be presented, based on the similarity solutions, to predict flame heights and the location of the virtual source in turbulent diffusion flames (momentum or buoyancy controlled). The model is similar to Steward's (1970), developed for buoyancy controlled flames.

Nearshore current pattern off south texas: an interpretation from aerial photographs

Current patterns in a 4-km-wide zone along the south Texas coast were interpreted from patterns of water turbidity visible in aerial photographs taken during a winter day of moderate northerly winds. Features of the turbidity pattern remained recognizable on photographs taken 25 min apart. Currents measured from the movements of these features were southward and nearly parallel to shore, increasing from about 17 cm/sec in an offshore zone to about 40 cm/sec at the line of breaking waves. The shoreward increase in velocity was probably a manifestation of wave-driven longshore currents. Rip-current plumes were drifting with this longshore current and during their drift were deformed by the horizontal shear of the current. As a result of the shear, the plume axes trended seaward in an obliquely updrift direction. Much of the turbidity visible in the photographs was caused by suspended sediment apparently supplied to the Gulf of Mexico through Aransas Pass, a tidal inlet from which a large ebb-tidal plume of turbid water was issuing at the time of the photography. Another discrete mass of turbid water along the coast to the south was probably the preceding ebb-tidal plume, which had become separated from the inlet and was drifting with the shore-parallel shelf current. Still farther south, a linear pattern of turbid and less turbid bands in the offshore zone suggested the development of Langmoir circulation having cell axes parallel to the shelf current. The turbid bands probably marked the zones of surface divergence and upwelling of the Langmuir circulation. The spacing between the turbid bands averaged about ten times the water depth, and thus the cells were much flatter than Langmuir cells that have been observed in deeper water.

Experimental study on radiative ignition of polymethylmethacrylate

An experimental study has been conducted to explore the behavior of the radiative ignition of polymethylmethacrylate (PMMA) by examining in detail the ignition delay and the temperature and fuel concentration distributions in the gas phase during ignition. The ignition delay of the transition ignition is found to change discontinuously at a certain radiant flux, which is about 60 J/(cm 2 sec) in the present case. For a radiant flux above this critical value, ignition is observed to occur at the plume axis away from the PMMA surface, and for a radiant flux below the critical value, it is observed to occur near the PMMA surface close to the plume boundary. It is shown that ignition occurs at a point where both the temperature and fuel concentration are in the proper range. Based on the present experimental results, the criterion of ignition is discussed.

Nature and Field Application of Plumose Structures: ABSTRACT

Development of plumose structures in brittle rocks has been investigated by analogy to fracturing experiments on glass and ceramic bodies. Plume morphology shows that structures commonly lumped as plumose are a composite of discrete features, formed at all scales, during fracture propagation. Inclusion hackle forms when an advancing planar fracture front becomes locally distorted at an inhomogeneity. The planar fracture, locally split by the inclusion, does not rejoin in a single plane behind the inclusion. This causes the lagging fracture portion to curve into the leading one forming a steplike tail elongate in the propagation direction. Twist hackle forms when a fracture front abruptly encounters changed stress directions along an extended frontal section. The entire fracture front breaks into individually advancing en echelon twist-hackle faces, each face perpendicular to the new resultant principal tension. Faces diverge and are elongate in the propagation direction. The faces form hackle steps by curving into each other to complete separation. Velocity hackle, uncommo in rocks, forms at a limiting propagation velocity. Plume axes mark areas of greatest tensile stress and lightest propagation velocities. Plume asymmetry indicates intrastratum fracturing stress distributions. Axes consistently at the top or bottom of each stratum in a layered sequence indicate overall downward and upward (perhaps basement induced) propagation directions respectively. Recognizing twist-hackle faces and steps as differently oriented planes produced by a single fracture event eliminates identification and misinterpretation of false fracture sets. End_of_Article - Last_Page 482------------

An Assessment of Plume Dispersion Parameters Measured in Fall and Winter at a Tar-Sands Refinery Complex

Increased energy processing activity in the north has resulted in a demand for measured data on plume dispersion that is relevant to this particular region. The north was, therefore, selected for study in a comprehensive government/industry research program. The objective of these studies was to assess the behavior of plumes in various geographic areas in Canada. The program utilizes airborne and automobile-mounted probes to determine SO/sub 2/ and temperature profiles within stock-emitted plumes as well as meteorological data on local atmospheric structure. The data are then analyzed numerically to obtain plume axis elevations and standard deviations of spread and these results are compared to accepted predictive methods. Good agreement with the analysis of Briggs was observed for predicting the location of the plume axis in neutral conditions; some deviations were noted in stable conditions. Values of the measured product (sigma y-sigma z) were generally larger than those of Pasquill, particularly for those values close to the source. A difference between the measured values of (sigma y-sigma z) in fall and winter was observed in stable conditions.

Visual impact of plumes from power plants: A theoretical model

Theoretical relationships have been derived and transformed into a computer model to describe plume visual impact at various observer vantage points resulting from power plant boiler operation. Plume visual impact results from a reduction in visual range (visibility) and plume coloration. The model considers plume transport and diffusion, light scattering and absorption by aerosols and gases, and chemical transformation in the plume of nitric oxide to nitrogen dioxide, sulfur dioxide to sulfates, and nitrogen oxides to nitrates. The model is applied in a parametric study to explore the effect of emissions and environmental conditions on plume visual impact. The case selected is a hypothetical 1500 Mwe coal-fired power plant equipped with efficient particulate abatement equipment. The results establish that visual range is not significantly affected unless the observer is viewing along the plume axis or unless significant amounts of secondary particles are formed in the plume. Yellow-brown plume coloration is shown to result from the net production of nitrogen dioxide gas in the plume. The coloration is most apparent during stable and clear atmospheric conditions and effectively masked for elevated concentrations of background or plume aerosol.

Plume Dispersion in a Mountainous River Valley during Spring

The dispersion of hot plumes emitted from a smelter complex located In the Columbia River Valley, British Columbia, was evaluated under stable and neutral conditions during two mornings In spring. Spatial measurements of SO2 and temperature within the plume were obtained by immersion probing using fast response helicopter and automobile mounted Instrumentation. In addition, meteorological measurements of vertical wind and temperature profiles at, and downwind from, the smelter were obtained from minisonde balloon releases. With weak down-valley winds, it was found that the plume axis elevations were generally lower during both stable and neutral conditions than would be predicted by Briggs plume-rise formulae. In contrast, plume dispersion, although confined in the horizontal by the steep valley walls during both stability regimes, was significantly enhanced by exceptionally good lateral mixing, particularly close to the source.

Observations of the motion field of the Connecticut River plume

Observations of the motion field associated with the plume formed by the outflow of the Connecticut River into the coastal seawater of Long Island Sound are presented. Approximately 35 drogues and drifters were tracked for each of three experiments using an airborne camera. The trajectories and the Eulerian velocity field deduced from them are presented. The offshore boundary of the plume was formed by a front where there was a strong discontinuity at the surface in both the velocity and density fields. In addition to a vigorous outflow of plume surface water away from the river mouth and parallel to the plume axis, the observations showed a pronounced surface flow toward the front and normal to the axis which was consistent with frontal convergence. The speed of plume water was found to be highly supercritical. The motion of nearby ambient seawater appeared to be little affected by the plume.

Sampling of Variable, Waste‐Migration Patterns in Ground Watera

ABSTRACTA survey of waste‐migration patterns from septic‐tank/ tile‐field systems surrounding Houghton Lake, Michigan indicates that sampling plans designed to detect and quantify waste migration in ground water should be predicated on the concept that the waste plume may be complex and that the plume may not follow regional, ground‐water flow. The waste‐migration plumes at Houghton Lake range from simple, multichemical plumes that move with regional flow to complex plumes that bifurcate, that show different migration patterns for different chemicals, and that move up the regional gradient for short distances. The complexity of these patterns is attributed to a combination of the following system properties: loading rate and recharge at the waste source, local hydrology, chemical‐adsorption capacity of the soil, soil microbiology, regolith texture and fabric, and proximity to other waste sources. Based on the observed patterns, it is suggested that observation wells be placed so that an in‐depth, 3‐dimensional array of samples can be obtained. The wells should be of sufficient depth to insure that deep‐moving plumes can be detected and, if the actual, vertical‐migration pattern is of importance, the wells should allow collection of water samples at a number of depths. The waste‐migration pattern should be monitored throughout the year in anticipation of vertical movement of the plume axis during periods of surface recharge. If more than one chemical is of interest, then it is unsafe to assume that an index chemical, such as chlorides, demonstrates the migration of the other chemicals and analyses must be run for the other chemicals.

The derivation of plume dispersion parameters from measured three-dimensional data

The method of finite differences is used to determine the plume axis and the S.D. of plume spread from three-dimensional data acquired by aerial probing. Comparisons are also made with corresponding values estimated by accepted empirical methods. The derivation of reliable values for critical plume dispersion parameters, that are applicable to a given geographic region, significantly improves the precision of computations for specifying stack heights, selecting plant sites, and predicting ground-level pollutant concentrations.

WAVE EFFECTS ON BUOYANT PLUMES

When a buoyant plume is discharged into water where wave motions exist, the axis of plume is "bent over and horizontally fluctuated. The dilution rate of the plume is affected by this motion. Experiments are carried out to investigate the dilution rate of plumes when they arrive at the free surface. An analogy to the case of buoyant plumes discharged into uniform steady cross streams is applied to analyse the experimental data. Within the experimental range, it is found that the dilution rate is inversely proportional to the square of the ratio of the water depth to the diameter of outlet and is proportional to the ratio of the discbarge velocity to a characteristic horizontal velocity of the ambient fluid. The entrainment coefficient is given as a function of a densimetric Eroude number for small Eroude number and is a constant, 0.28, for bigger Eroude number than 4.3.

Concentration fluctuations and peak-to-mean concentration ratios in plumes from a ground-level continuous point source

Diffusion data collected by 63 incremental samplers during four short duration, continuous releases of 85Kr are used to examine concentration fluctuations and peak-to-mean concentration ratios in the atmosphere. Cumulative frequency distributions and the intensity of short-term concentrations are shown to be a function of the relative crosswind position within the mean plume. Peak-to-mean concentration ratios are shown as a function of relative crosswind position within the plume and the ratio of the durations of the mean and the peak (time ratio). The relationship between the intensity of concentration fluctuations and the relative crosswind position is similar to that reported for laboratory data. The relationship between peak-to-mean ratios and the time-ratio was found to differ from the simple power law relationship suggested by several workers. Previous estimates of the peak-to-mean/time ratio relationship for positions near the mean plume axis are shown to be too low.

Preliminary Hot-Wire Measurements on Free-Convection Zones Over Model Fires

Abstract As part of a research program on the spread of forest fires, an investigation was carried out to determine to what extent a high-temperature hot-wire probe could be used to study the turbulent flow field in the free-convection zone above a model fire. A method has been proposed for obtaining the mean values of the vertical plume velocity U, the temperature and the turbulent quantities from nine successive measurements made with a single hot-wire sensor. Measurements made along the axis of the buoyant plume over circular arrays of burning wicks releasing from 48,000 to 180,000 Btu/hr, as well as line arrays releasing 9300 and 33,500 Btu/hr ft, indicate that the method yields reasonable values for U, and T 1 and on the plume axis as well as U and off-axis, but that the values of are unreliable, probably since the plumes studied exhibited inherent unsteadiness and were susceptible to external disturbances because of their low momentum.

Concerning the effect of terrain configuration on smoke dispersal

Wind velocity, wind direction and wind lateral gustiness measured in the Weisseritz valley at Tharandt and on the surrounding plateau are compared. For dynamic and thermal reasons the lateral gustiness is generally reduced in the valley, particularly when the winds are blowing parallel with the valley. With very strong winds, however, lateral gustiness is increased, particularly when the air flow is oblique to the valley. The reasons for this are discussed and conclusions are drawn regarding smoke dispersal. In addition, the effect of wooded belts on smoke dispersal is considered. It is only when the wooded belt is above the plume axis that the increased turbulence can favourably affect smoke dispersal. Finally, the dispersal of smoke towards the Erzgebirge with its heavy smoke damage is discussed.

Turbulent dispersion in a pipe flow

AbstractThe nearly homogeneous, isotropic turbulence field in the core of a fully developed pipe flow was chosen as the medium for turbulent dispersion of a smoke tracer injected from a point on the centerline. By using the optical probe technique the fields of the mean and fluctuating point concentration were mapped at several Reynolds numbers, and spectral analyses made of concentration fluctuations on the plume axis. With the use of sheet illumination, the mean and fluctuating components of the integral material concentration in a plume cross section were measured and the fluctuating component was spectrally analyzed. The maximum Reynolds number was 684,000, the maximum ratio of root‐mean‐square concentration fluctuation to mean concentration exceeded 100% for points and 40% for sheets, and the turbulent Peclet number was found to equal 850. The existence of standard flow conditions was confirmed by measurement of the frictional drag coefficient and the mean concentration field.