Determining flow patterns and the distribution of chemical constituents in the environment is critical to understanding and solving problems in freshwater, estuarine, and coastal environments. Computer models describing flows in the environment usually use empirical estimates of key parameters and are difficult to validate. The objective of this research was to develop a method to trace flows in surface waters by directly measuring existing conditions. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to establish elemental “fingerprints” for water sources, and fractions of “fingerprinted” waters in a sample containing these source waters were estimated. Two different, complex systems were studied: the Sacramento-San Joaquin Delta and the near-coastal environment of Oahu, Hawaii. If the method could be successfully used in these highly complicated environments, it should be applicable in almost any other natural environment. Successful application in three smaller, simpler systems supports this conclusion.
Within the Delta, source “fingerprints” were established, and their variation both temporally and spatially was determined. Elemental behavior was determined by laboratory work and field studies, and a simple mathematical model was used to calculate the fraction of source water in samples collected throughout the system. Mixing was consistently determined for most flow conditions using the tracer elements sodium, magnesium, calcium, and strontium. The method was used to establish the sources of water pumped from the Delta into major aqueducts and the effects of various operational changes.
Because of Hawaii’s uniform geology and difficulties measuring trace elements in saline waters, the method was significantly less successful in Hawaii. Concentrations of major ions were used to estimate dilution for stream and wastewater flows to 25:1 in receiving waters; rare earth elements (lanthanum, praseodymium, and neodymium) were added to a wastewater flow to qualitatively determine mixing at dilution levels of about 300:1.
The procedures for ICP-MS analysis developed for this study are presented, as are the criteria for selecting and using elemental tracers in freshwater, estuarine, and certain saltwater environments. The method can be used to directly determine mixing levels and the distribution of chemical constituents, to validate computer models, and to address a variety of specific environmental issues.
}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, } @phdthesis{10.7907/1jmz-kj71, author = {Dugan, Regina E.}, title = {Axisymmetric Buoyant Jets in a Cross Flow with Shear: Transition and Mixing}, school = {California Institute of Technology}, year = {1993}, doi = {10.7907/1jmz-kj71}, url = {https://resolver.caltech.edu/CaltechETD:etd-08272007-090225}, abstract = {It has been proposed that axisymmetric buoyant jets discharged vertically into a horizontal turbulent boundary layer flow undergo a transition from self-induced mixing to an ultimate state where mixing is dominated by the shear-flow turbulence. Both plume mixing and ambient shear-flow mixing have been separately well characterized by many previous studies and can be thought of as asymptotic mixing regimes. This investigation focuses on the transition between the two asymptotic regimes that is not well understood and that is often of particular engineering interest.
In this work, we present the results of a detailed experimental analysis of buoyant jet mixing in a turbulent shear flow. Our purpose is to obtain a detailed picture of the turbulent velocity field and the concentration distributions throughout the various mixing regimes in order to discern the effects of changes in various flow parameters on the predominant mixing mechanisms. The experimental technique employs buoyant jets whose fluid is optically homogeneous with that of the ambient shear flow. This enables the combined use of laser-Doppler velocimetry and laser-induced fluorescence to measure the velocity and concentration profiles, respectively.
Dimensional analysis indicates that the cross-flow shear velocity and the plume specific buoyancy flux are the parameters controlling the transition from plume mixing to diffusion mixing. Quantitative analysis of the experimental results indicates that the mixing is dominated entirely by diffusion, or shear-flow mixing, even close to the point of discharge. Further, we observe that within the diffusive mixing regime, a transition occurs from a region where the turbulent mixing coefficient is proportional to the local elevation to a region where the turbulent mixing coefficient is proportional to the boundary layer thickness. Detailed instantaneous spatial concentration distributions indicate that regions of dilution far below mean values persist well into the mixing regime dominated by shear-flow turbulence. This indicates that both plume mixing and diffusion-type mixing models may provide a false sense of security with regard to the absolute minimum dilutions observed in actual flow situations since both methods focus on the minimum average dilution.
}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, } @phdthesis{10.7907/2s6d-kv47, author = {Rasi, Marco}, title = {Mixing in Density-Stratified Conjugate Flows}, school = {California Institute of Technology}, year = {1989}, doi = {10.7907/2s6d-kv47}, url = {https://resolver.caltech.edu/CaltechETD:etd-02152007-155510}, abstract = {Two-layer stratified shear flows have been studied in the laboratory using combined laser-induced fluorescence and laser-Doppler velocimetry. Use of this high resolution, non-intrusive instrumentation has enabled new insight on the entraining characteristics of supercritical two-layer flows and the phenomenon known as an internal hydraulic jump.
In the experiments, salt water was discharged at a steady flowrate from a rectangular slot located at the bottom of the upstream end of a horizontal channel containing fresh water. The flow of the dense bottom layer was controlled at the downstream end of the channel by either a free overfall or a broad-crested weir. The transition between the wall-jet-like flow near the source and the subcritical downstream counterflow took place through an internal hydraulic jump, characterized by a steep interfacial slope and a local recirculating flow region.
A one-dimensional theory based on the assumptions of uniformity of velocity and density distributions downstream of the mixing region was discussed and extended to predict the overall internal flow geometry and the dilution attained by the source fluid across the mixing region. The analysis, which applies to the general case of a mixing channel of finite depth and length, was carried out in three stages. First, the flow at the upstream end of the channel was considered, and a conservation of flow force in the total channel depth across the jump was hypothesized. Second, the gradually-varied counterflow, governed by boundary shear and interfacial momentum transfer, as well as by the critical flow condition at the channel end, was studied by applying the momentum principle to both layers. Finally, the upstream and downstream equations were combined to obtain hydraulic solutions, in a way that clearly establishes that the overall problem can only be solved if the importance of the interplay between source and control is recognized.
An extensive series of experiments confirmed the general predictions of the one-dimensional theory. Four predicted mixing modes (free internal hydraulic jump, flooded jump, upstream-controlled instability, and downstream-controlled instability) were all observed in the experiments. The dependence of the entrainment rate, both on the depth of the ambient water and on the control establishing the critical flow at the end of the channel, has been documented with comprehensive experimental data.
The non-intrusive laser-based instrumentation used has enabled a detailed experimental description of the density and velocity distributions at several locations in the flow field and has pointed out some inaccuracies in the one-dimensional approach. A procedure to overcome these inaccuracies has been proposed.
The ideas developed and the experimental results obtained from this work can be readily extended to further the understanding of many of the two-layer stratified shear flows of interest to engineers and geophysicists.
}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, } @phdthesis{10.7907/N4NS-MP03, author = {Hannoun, Imad A.}, title = {Turbulent Mixing in Stably-Stratified Fluids Subjected to Zero-Mean Shear}, school = {California Institute of Technology}, year = {1987}, doi = {10.7907/N4NS-MP03}, url = {https://resolver.caltech.edu/CaltechETD:etd-03032008-132151}, abstract = {The interaction of a sharp density interface with oscillating grid induced shear-free turbulence was experimentally investigated. A linear photodiode array was used in conjunction with laser-induced fluorescence to measure the concentration of a tracer that was initially located in the less dense layer. A laser-Doppler velocimeter was used to measure the vertical component and a horizontal component of velocity near the interface, and also at a point where tracer concentration was measured. Potential refractive index fluctuation problems were avoided using solutes that provided a homogeneous optical environment. The study consists of two major parts.
In the first part of the investigation, energy spectra, velocity correlations, and kinetic energy fluxes were measured. Amplification of the horizontal turbulent velocity fluctuations, coupled with a sharp reduction in the vertical velocity fluctuation level, was observed near the density interface. Moreover, the experiments indicate that the density interface acts in a manner qualitatively similar to a rigid flat plate inserted in the flow. These findings are in agreement with previous results pertaining to shear-free turbulence near rigid walls (Hunt and Graham 1978).
In the second part of the investigation, internal wave spectra, wave amplitudes and velocities, and the interfacial mixing layer thickness were measured. The results indicate that mixing occurs in intermittent bursts and that the local gradient Richardson number J remains constant for a certain range of the overall Richardson number Rj. The spectra of the internal waves decay as f-3 at frequencies below the maximum Brunt-Väisälä frequency. These findings give support to a model of oceanic turbulence proposed by Phillips (1977) in which the internal waves are limited in their spectral density by sporadic local instabilities and breakdown to turbulence. The results also indicate that, for a certain Rj range, the thickness of the interfacial layer (normalized by the integral lengths scale of the turbulence)is a decreasing function of Rj. At sufficiently high Rj the interfacial thickness becomes limited by diffusive effects. A simple model for entrainment at a density interface in the presence of shear-free turbulence is presented and compared with the observations.
}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, } @phdthesis{10.7907/SX4D-3555, author = {Papantoniou, Dimitris Antony}, title = {Observations in Turbulent Buoyant Jets by Use of Laser-Induced Fluorescence}, school = {California Institute of Technology}, year = {1986}, doi = {10.7907/SX4D-3555}, url = {https://resolver.caltech.edu/CaltechETD:etd-03142008-142149}, abstract = {The entrainment mechanism and mixing process are investigated in the far field of a liquid phase buoyant jet issuing into an unconfined, quiescent medium, by an experimental technique based on laser-induced fluorescence (LIF). Visualization experiments show the existence of a large scale organization in the far field, with structures spanning the radial extent of the conical flow region. Quantitative, high-resolution measurements of scalar concentration were performed along the radial direction in the far field region. For each data set, a large number of successive instantaneous concentration profiles were obtained by combining LIF techniques with linear photodiode array imaging and high speed data acquisition. The measurements revealed that the instantaneous profile bears no resemblance to the time-averaged profile. The flow interior is characterized by large spatial gradients of concentration, associated with interfaces between mixed jet fluid and fresh, entrained ambient fluid transported to regions deep into the flow. This is inconsistent with the description of transport by gradient diffusion concepts. The probability of finding unmixed ambient fluid and the concentration variance are greatly increased under the action of buoyancy. At any axial location, the arrival of a structure front is marked by a spatially coherent (along the radial direction) increase in the local concentration level. It is found that, within the structure, values of the concentration are generally decreasing in the upstream direction; substantial uniformity within the mixed fluid portion is observed along the radial direction. In the conical flow field of the momentum jet, a central region (in fixed spatial coordinates) may be identified within which the local mixed fluid composition is relatively uniform. This is not the case for the buoyancy driven plume, due to a greater variance in the position of the large structure and the high value of the intermittency. It is suggested that fluid is entrained by vortical motions mainly from the back and side regions of the large structure. Flow visualization reveals vorticity in the axial direction which enhances the mixing process; this vorticity appears stronger in the buoyancy driven flow. The results of these experiments are interpreted through a simple conceptual model of entrainment and mixing that encompasses the observed large scale organization of the buoyant jet flow.
}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, } @phdthesis{10.7907/6khx-sv30, author = {Papanicolaou, Panayiotis Nikolas}, title = {Mass and Momentum Transport in a Turbulent Buoyant Vertical Axisymmetric Jet}, school = {California Institute of Technology}, year = {1985}, doi = {10.7907/6khx-sv30}, url = {https://resolver.caltech.edu/CaltechTHESIS:02202019-095834395}, abstract = {The entrainment and mixing processes in an axisymmetric vertical turbulent buoyant jet and its transition from a jet to a plume have been studied. The ambient fluid is of uniform density and calm except for the flow induced by the jet, and the density variations are assumed small.
A systematic set of experiments was carried out to examine turbulent buoyant jet behavior over a wide range or initial jet Richardson numbers. All experiments were performed in a glass wall tank with dimensions 1.15 m x 1.15 m x 3.30 m deep, equipped with a jet flow source and an instrument carriage to enable velocity and concentration measurements in the entire jet flow field.
The axial and radial velocity components and the concentration of a Rhodamine 6G dye were measured simultaneously at the same point of the jet flow field using a two - reference beam laser - Doppler velocimeter combined with a laser induced fluorescence measuring device. From the time signals of the axial and radial velocity components (w) and (u) and the concentration (c) of a Rhodamine 6G dye, information was obtained concerning the mean values, turbulent fluctuations and correlations between w, u and c, up to 100 jet and 80 plume diameters downstream of the jet exit.
More specifically, the mean flow (including the spreading rate of the mean velocity and tracer concentration profiles and distribution along the jet axis) and the turbulent structure (including the profile of turbulence intensity, turbulent mass flux of a tracer and turbulent momentum flux) were investigated as a function of distance from jet origin made dimensionless by a characteristic length scale based on jet buoyancy and momentum fluxes. The results from a detailed dimensional analysis were verified experimentally. It was determined that the turbulent flux of a tracer (or buoyancy) varied from 6-10% for jets and was 15-20% of the total for plumes. The turbulent momentum flux was found to be 15% of the local momentum flux transported by the mean flow.
While the profiles of w and c and the turbulent velocity profiles are found to be much the same tor both jets and plumes, the turbulence intensity profiles of the concentration take higher values in plumes than in jets. More rapid dilutions were obtained in buoyancy driven plumes than in momentum driven jets.
Useful information concerning engineering applications is provided from the experimental constants derived.
}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, } @phdthesis{10.7907/w0ax-hs27, author = {Valioulis, Iraklis Anestis}, title = {Particle Collisions and Coalescence in Fluids}, school = {California Institute of Technology}, year = {1983}, doi = {10.7907/w0ax-hs27}, url = {https://resolver.caltech.edu/CaltechETD:etd-11082005-142054}, abstract = {
Coagulation, in the physical context, is looked upon here first from the fundamental perspective of collision and coalescence of individual particles. A Monte Carlo technique is used to investigate the particle size distribution in a suspension of coagulating particles when one or more collision mechanisms operate. The effect of interparticle forces - hydrodynamic, van der Waals’ and electrostatic - on the collision probability of the particles is examined. The results obtained are used to evaluate the well-known dynamic equilibrium hypothesis according to which an equilibrium particle size distribution is assumed to exist under the action of a given collision mechanism. It is shown that dimensional analysis cannot, in general, be used to predict steady state particle size distributions, mainly because of the strong dependence of the interparticle forces on the sizes of the interacting particles.
The insight into particle kinetics thus gained from the Monte Carlo simulation of collision processes is used to develop a numerical simulation of a rectangular settling basin. The computer model follows the spatial and temporal development of the influent particle size distribution towards the outlet of the tank, accounting for all of the basic kinetics of particle collision and coalescence processes and including transport processes such as particle settling, advection, resuspension and turbulent mixing. The influence of the particle size-density relationship and floc deaggregation by turbulent shearing are also modeled. Of necessity, modeling of some of these processes has been somewhat empirical since the physical and biochemical nature of the flocs are unique to a particular suspension and their determination requires experimental work. The results of the simulations performed indicate that the particle size-density relationship, the collision efficiencies between flocs and the influent particle size distribution are of major importance to the performance of the sedimentation basin. Clearly, further modifications, improvements and trials are needed in order to use the model for the design of new facilities. Nevertheless, the computer model may serve as a guide for selection of several design and operation variables for the successful treatment of a particular waste or the selective removal of pollutants whose concentration depends the shape of the effluent particle size distribution.
}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, } @phdthesis{10.7907/16RG-AZ72, author = {Chen, Jing-Chang}, title = {Studies on gravitational spreading currents}, school = {California Institute of Technology}, year = {1980}, doi = {10.7907/16RG-AZ72}, url = {https://resolver.caltech.edu/CaltechTHESIS:09302010-090407312}, abstract = {The objective of this investigation is to examine the buoyancy-driven gravitational spreading currents, especially as applied to ocean disposal of wastewater and the accidental release of hazardous fluids.
A series of asymptotic solutions are used to describe the displacement of a gravitationally driven spreading front during an inertial phase of motion and the subsequent viscous phase. Solutions are derived by a force scale analysis and a self-similar technique for flows in stagnant, homogeneous, or linearly density-stratified environments. The self-similar solutions for inertial-buoyancy currents are found using an analogy to the well-known shallow-water wave propagation equations and also to those applicable to a blast wave in gasdynamics. For the viscous-buoyancy currents the analogy is to the viscous long wave approximation to a nonlinear diffusive wave, or thermal wave propagation. Other similarity solutions describing the initial stage of motion of the flow formed by the collapse of a finite volume fluid are developed by analogy to the expansion of a gas cloud into a vacuum. For the case of a continuous discharge there is initially a starting jet flow followed by the buoyancy-driven spreading flow. The jet mixing zone in such flows is described using Prandtl’s mixing length theory. Dimensional analysis is used to derive the relevant scaling factors describing these flows.
}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, } @phdthesis{10.7907/JBRN-V548, author = {Kotsovinos, Nikolas Evangelos}, title = {A study of the entrainment and turbulence in a plane bouyant jet}, school = {California Institute of Technology}, year = {1975}, doi = {10.7907/JBRN-V548}, url = {https://resolver.caltech.edu/CaltechETD:etd-05162007-081622}, abstract = {The entrainment and mixing processes in a two-dimensional vertical turbulent buoyant (heated) jet in its transition state from a pure jet to a pure plume have been studied. The ambient fluid is of uniform density and non-flowing except for the flow induced by the jet. Density variations are assumed small.
The equations of motion integrated across the jet have been carefully examined and it has been found that the kinematic buoyancy flux of a heated plume and the kinematic momentum flux of a pure jet are not in general conserved. It has been proven that the flow in a two-dimensional pure jet is not self-preserving.
A systematic set of experiments was carried out to examine turbulent buoyant jet behavior for a wide range of initial Richardson numbers (or densimetric Froude numbers). Values of the Richardson number, which describes the relative importance of buoyancy in a jet, extended from the value appropriate for a pure jet (zero) to that appropriate for a plume (approximately 0.6). The buoyant jet temperature and velocity fields were measured using calibrated fast response thermistors and a Laser Doppler velocimeter respectively. The velocity and temperature data obtained were recorded magnetically in digital form and subsequently processed to extract both mean and fluctuating values of temperature and velocity.
The structure of the mean flow (including the spreading rate of the mean velocity and temperature profiles, velocity and temperature distribution along jet axis, and the heat flux profile), the turbulence structure (including the profile of turbulence intensity and turbulent heat transfer, probability density distribution of temperature and velocity, skewness and flatness factor of temperature fluctuations) and the large scale motions (intermittency, profile of maximum and minimum temperature, frequency of crossing of hot/cold, cold/hot interface) of a buoyant jet were investigated as a function of the jet Richardson number. It was determined that the turbulent heat transfer and the turbulent intensity increase with increasing the Richardson number. The spreading rate of the transverse mean velocity and temperature profiles were found to be independent of the Richardson number. The turbulent buoyancy flux in a fully developed buoyant jet has been found to be a significant fraction (38%) of the axial buoyancy flux.}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, } @phdthesis{10.7907/hxbp-pc89, author = {Trijonis, John Charles}, title = {An economic air pollution control model-application : photochemical smog in Los Angeles County in 1975}, school = {California Institute of Technology}, year = {1972}, doi = {10.7907/hxbp-pc89}, url = {https://resolver.caltech.edu/CaltechTHESIS:06262014-113258422}, abstract = {An economic air pollution control model, which determines the least cost of reaching various air quality levels, is formulated. The model takes the form of a general, nonlinear, mathematical programming problem. Primary contaminant emission levels are the independent variables. The objective function is the cost of attaining various emission levels and is to be minimized subject to constraints that given air quality levels be attained.
The model is applied to a simplified statement of the photochemical smog problem in Los Angeles County in 1975 with emissions specified by a two-dimensional vector, total reactive hydrocarbon, (RHC), and nitrogen oxide, (NOx), emissions. Air quality, also two-dimensional, is measured by the expected number of days per year that nitrogen dioxide, (NO2), and mid-day ozone, (O3), exceed standards in Central Los Angeles.
The minimum cost of reaching various emission levels is found by a linear programming model. The base or “uncontrolled” emission levels are those that will exist in 1975 with the present new car control program and with the degree of stationary source control existing in 1971. Controls, basically “add-on devices”, are considered here for used cars, aircraft, and existing stationary sources. It is found that with these added controls, Los Angeles County emission levels [(1300 tons/day RHC, 1000 tons /day NOx) in 1969] and [(670 tons/day RHC, 790 tons/day NOx) at the base 1975 level], can be reduced to 260 tons/day RHC (minimum RHC program) and 460 tons/day NOx (minimum NOx program).
“Phenomenological” or statistical air quality models provide the relationship between air quality and emissions. These models estimate the relationship by using atmospheric monitoring data taken at one (yearly) emission level and by using certain simple physical assumptions, (e. g., that emissions are reduced proportionately at all points in space and time). For NO2, (concentrations assumed proportional to NOx emissions), it is found that standard violations in Central Los Angeles, (55 in 1969), can be reduced to 25, 5, and 0 days per year by controlling emissions to 800, 550, and 300 tons /day, respectively. A probabilistic model reveals that RHC control is much more effective than NOx control in reducing Central Los Angeles ozone. The 150 days per year ozone violations in 1969 can be reduced to 75, 30, 10, and 0 days per year by abating RHC emissions to 700, 450, 300, and 150 tons/day, respectively, (at the 1969 NOx emission level).
The control cost-emission level and air quality-emission level relationships are combined in a graphical solution of the complete model to find the cost of various air quality levels. Best possible air quality levels with the controls considered here are 8 O3 and 10 NO2 violations per year (minimum ozone program) or 25 O3 and 3 NO2 violations per year (minimum NO2 program) with an annualized cost of $230,000,000 (above the estimated $150,000,000 per year for the new car control program for Los Angeles County motor vehicles in 1975).
}, address = {1200 East California Boulevard, Pasadena, California 91125}, advisor = {List, E. John}, }