The purpose of air distribution systems for HVAC is tocreate proper air quality and thermal conditions in an occupiedzone. In mixing type air distribution systems air is suppliedinto a room through various types of outlets and distributed byturbulent air jets. These air jets are the primary factorsaffecting room air motion. The ASHRAE handbook recognises fourmajor zones of maximum velocity decay along a jet. Although numerous theoretical and experimental studies havebeen conducted to develop turbulent air jet theory from the1930's, air jet performance in the further field from theoutlet is still not well understood. Many studies were therefore carried out, and the followingconclusions can be drawn from them:     The end centerline velocities of zone 3 for both "free"jet and wall jet could strongly depend on the outletvelocities and room size.     TheK-value of wall jets could be a function of bothoutlet velocities and outlet size.     It is very important to choose suitable sampling time toevaluate jet performance.     CFD can not always be used to predict jet behaviour,especially for the jet with low outlet velocity and in thearea far away from the outlet. However, for a two-dimensionwall jet, CFD could be a powerful tool for designers. <b>KEYWORDS</b>: air jet, centerline velocity,K-velocity, air diffuser, ventilation, measurement,CFD

Controlled cooling is an important part of steel production industry that affects the properties of the outcome steel. Many of the researches done in controlled cooling are experimental. Due to progress in the numerical techniques and high cost of experimental works in this field the numerical work seems more feasible. Heat transfer analysis is the necessary element of successful controlled cooling and ultimately achievement of novel properties in steel. Heat transfer on the surface of the plate normally contains different regimes such as film boiling, nucleate boiling, transition boiling and radiation heat transfer. This makes the analysis more complicated. In order to perform the heat transfer analysis often empirical correlations are being used. In these correlations the velocity and pressure within the fluid domain is involved. Therefore in order to obtain a better understanding of heat transfer process, study of hydrodynamics of the fluid becomes necessary. Circular jet due to its high efficiency has been used vastly in the industry. Although some experimental studies of round jet arrays have been done, yet the characteristics of a single jet with industrial geometric and flow parameters on the surface of a flat plate is not fully understood. Study of hydrodynamics of the jet impingement is the first step to achieve better understanding of heat transfer process. Finite element method as a popular numerical method has been used vastly to simulate different domains. Traditional approaches of finite element method, Lagrangian and Eulerian, each has its own benefits and drawbacks. Lagrangian approach has been used widely in solid domains and Eulerian approach has been widely used in fluid fields. Jet impingement problem, due to its unknown free surface and the change in the boundary, falls in the category of special problems and none of the traditional approaches is suitable for this application. The Arbitrary Lagrangian Eulerian (ALE) formulation has emerged as a technique that can alleviate many of the shortcomings of the traditional Lagrangian and Eulerian formulations in handling these types of problems. Using the ALE formulation the computational grid need not adhere to the material (Lagrangian) nor be fixed in space (Eulerian) but can be moved arbitrarily. Two distinct techniques are being used to implement the ALE formulation, namely the operator split approach and the fully coupled approach. This thesis presents a fully coupled ALE formulation for the simulation of flow field. ALE form of Navier-Stokes equations are derived from the basic principles of continuum mechanics and conservation laws in the fluid. These formulations are then converted in to ALE finite element equations for the fluid flow. The axi-symmetric form of these equations are then derived in order to be used for jet impingement application. In the ALE Formulation as the mesh or the computational grid can move independent of the material and space, an additional set of unknowns representing mesh movement appears in the equations. Prescribing a mesh motion scheme in order to define these unknowns is problem-dependent and has not been yet generalized for all applications. After investigating different methods, the Winslow method is chosen for jet impingement application. This method is based on adding a specific set of partial differential Equations(Laplace equations) to the existing equations in order to obtain enough equations for the unknowns. Then these set of PDEs are converted to finite element equations and derived in axi-symmetric form to be used in jet impingement application. These equations together with the field equations are then applied to jet impingement problem. Due to the number of equations and nonlinearity of the field equations the solution of the problem faces some challenges in terms of convergence characteristics and modeling strategies. Some suggestions are made to deal with these challenges and convergence problems. Finally the numerical treatment and results of analyzing hydrodynamics of the Jet Impingement is presented. The work in this thesis is confined to the numerical simulation of the jet impingement and the specifications of an industrial test setup only have been used in order to obtain the parameters of the numerical model.

In this study, the effects of submergence on local scour in a uniform cohesionless sediment bed by a plane turbulent wall jet and the resulting flow field were investigated experimentally. Here, submergence is defined as the ratio of the tailwater depth to the thickness of the jet at its origin. The main focus was to determine scour dimensions at an asymptotic state, examine whether there was similarity in the velocity profiles for the flow in the scour hole, and to determine the growth of the length scales and decay of the maximum velocity of the jet. Also examined were the relationships between the scales for the velocity field in the scour hole and the scour hole size.<p>In the experiments, the range of submergence was varied from 3-17.5, whereas the range of densimetric Froude number and the ratio of the boundary roughness to the gate opening (relative boundary roughness) were varied from 4.4-6.9 and 0.085-0.137 respectively. The velocity field in the scour hole at asymptotic state was measured using a SonTek 16-MHz MicroADV. Time development of the characteristic dimensions of the scour hole was also measured.<p>The dimensions of the scour hole were found to increase with increasing submergence for all experiments with a bed-jet flow regime. In the bed-jet flow regime, the jet remains near the bed throughout the scouring process. Further, the time development of the scour hole dimensions were observed to increase approximately linearly with the logarithm of time up to a certain time before the beginning of asymptotic state for experiments with either the bed-jet or surface-jet flow regimes.<p> The flow field results showed that the velocity profiles in the region of forward flow and the recirculating region above the jet were similar in shape up to about the location of the maximum scour depth. Relationships describing this velocity profile, including its velocity and length scales, were formulated. The decay rate of the maximum velocity, the growth of the jet half-width, and the boundary layer thickness were also studied. The decay and the growth rate of the jet length scales were found to be influenced by the submergence ratio, densimetric Froude number, and the relative boundary roughness.<p>Two distinct stages in the decay of the maximum streamwise velocity, with distance along the direction of flow, were observed for the jet flows having a bed-jet flow regime. The first stage of velocity decay was characterized by a curvilinear decay of velocity, which followed that of a wall jet on a smooth, rigid bed for streamwise distance approximately equal to 2L. For the surface-jet flow regime, the decay of velocity was observed to be similar to that of a free-jump on a smooth, rigid bed for a streamwise distance approximately equal to L. Here, L is defined as the streamwise distance measured from the end of the rigid apron to where the maximum streamwise velocity in the jet is half the velocity of the jet at the end of apron. The streamwise maximum velocity of the jet was then seen to increase in what was called the recovery zone.<p>A relationship for the streamwise decay of the maximum velocity within the scour hole is proposed. Moreover, other scales representing the flow inside the scour hole such as the streamwise distance from the end of the apron to where the streamwise maximum velocity starts to deviate from curvilinear to linear decay and the streamwise distance to where maximum streamwise velocity starts to increase are suggested. Some new results on the velocity distribution for the reverse flow for a bed-jet flow regime are also presented. Finally, some dimensionless empirical equations describing the relationship between the jet scales for the jet flow in a scour hole and the scour hole size are given.

In this thesis the critical parameters involved in the dislodgement and deformation of microbubbles in laminar channel flow, are determined and evaluated. Experimentally the effects of surface tension, viscosity, fluid flow rate, density, and bubble diameter on bubble dislodgement were evaluated. A theoretical scale analysis was performed which provided a general relationship between the parameters. Experimental results provided reasonable comparisons with values calculated from the scale analysis. Non-dimensional plots were generated of Weber number, at bubble dislodgement, versus Reynolds number and Weber number as a function of a non-dimensional bubble diameter. A calculated velocity detachment equation was also produced. This work is applicable to many areas of science and industry, particularly in the field of ink-jet printing. / Graduation date: 1992

QCD es una teoría que gobierna la interacción fuerte entre quarks y gluones dentro de los hadrones, por ejemplo, protones y neutrones. Esta teoría tiene dos características: libertad asintótica y color confinamiento. La dependencia de la constante de acoplamiento con la escala es tal que esta decrece con la distancia entre partones. Esto permite realizar precisos cálculos teóricos a una gran escala de energía usando teoría de perturbaciones (pQCD). Además, la fuerza de la interacción incrementa con la distancia entre partones y gluones obligando que estos estén confinados en hadrones.En el acelerador Tevatron, protones y antiprotones colisionan a una alta energía. En estas colisiones se producen jets de hadrones colimados en la misma dirección de los quarks y gluones que han colisionado. La medida de la sección eficaz de producción de jets centrales constituye una prueba de las predicciones de pQCD en más de ocho órdenes de magnitud. Además la medida también es sensible a la distribución de los partones dentro del proton (PDFs). Medidas de la producción de jets a grandes rapidititis son importantes porque ayudan a restringir la incertidumbre en esas distribuciones de los partones en una región donde no se espera señal de nueva física. Esta tesis presenta la medida de producción de jets usando datos recogidos por el experimento CDF, uno de los detectores que estudia las colisiones en Tevatron. La medida esta hecha con un algoritmo muy preciso para buscar jets, relativamente nuevo en colisionadores hadrónicos. La medida esta comparada con predicciones de pQCD, donde los efectos de efectos no-perturbativos han sido incluidos. Los resultados demuestran que hay un excelente acuerdo entre la medida y la teoría, no mostrando señal de nueva física. Además, las incertidumbre es la medida son mas pequeñas que la teoría, cosa que indica que estas medidas pueden ser usadas para restringir las PDFs. / QCD is the gauge theory that governs the strong interactions between quarks and gluons inside hadrons like, for example, protons and neutrons. It shows two well established characteristics, related to the non-abelian nature of the theory, that dominate its phenomenology: asymptotic freedom and color confinement. The dependence of the strong coupling with the hard scale is such that it decreases with decreasing the distance between partons. This allows performing precise theoretical calculations at large energy transfer using perturbative QCD (pQCD). In the other hand, the strength of the interaction increases with the distance between partons and thus colored quarks and gluons are forced to be confined inside colorless hadrons.At the Tevatron at Fermilab, protons and antiprotons collide at very high energy. In those collisions, collimated jets of hadrons are produced along the direction of struck quarks and gluons in the final state. The measurement of the inclusive jet production cross section provides a stringent test of pQCD predictions over almost nine orders of magnitude. In addition, the measurement is sensitive to the parton distribution in the proton (PDFs). Jet measurements at large rapidities are important because they constrain the gluon density in a region where no effect from new physics is expected.This PhD. Thesis presents a measurement of the inclusive jet production cross section using the new data collected by the CDF experiment in Run II, one of the detectors at Tevatron. The longitudinally invariant kT algorithm has been used in order to search for jets in the final state. The measurement is compared to pQCD NLO calculations where non-perturbative effects from the underlying event and the fragmentation of partons into jets of hadrons have been taken into account. The results show an excellent agreement between the measurements and the theory, without presenting signal for new physics. In addition the systematic uncertainties in the measurements are smaller than in the theory, indicating that these measurements can be used to constrain the PDFs.

In this study, the effects of submergence on local scour in a uniform cohesionless sediment bed by a plane turbulent wall jet and the resulting flow field were investigated experimentally. Here, submergence is defined as the ratio of the tailwater depth to the thickness of the jet at its origin. The main focus was to determine scour dimensions at an asymptotic state, examine whether there was similarity in the velocity profiles for the flow in the scour hole, and to determine the growth of the length scales and decay of the maximum velocity of the jet. Also examined were the relationships between the scales for the velocity field in the scour hole and the scour hole size.<p>In the experiments, the range of submergence was varied from 3-17.5, whereas the range of densimetric Froude number and the ratio of the boundary roughness to the gate opening (relative boundary roughness) were varied from 4.4-6.9 and 0.085-0.137 respectively. The velocity field in the scour hole at asymptotic state was measured using a SonTek 16-MHz MicroADV. Time development of the characteristic dimensions of the scour hole was also measured.<p>The dimensions of the scour hole were found to increase with increasing submergence for all experiments with a bed-jet flow regime. In the bed-jet flow regime, the jet remains near the bed throughout the scouring process. Further, the time development of the scour hole dimensions were observed to increase approximately linearly with the logarithm of time up to a certain time before the beginning of asymptotic state for experiments with either the bed-jet or surface-jet flow regimes.<p> The flow field results showed that the velocity profiles in the region of forward flow and the recirculating region above the jet were similar in shape up to about the location of the maximum scour depth. Relationships describing this velocity profile, including its velocity and length scales, were formulated. The decay rate of the maximum velocity, the growth of the jet half-width, and the boundary layer thickness were also studied. The decay and the growth rate of the jet length scales were found to be influenced by the submergence ratio, densimetric Froude number, and the relative boundary roughness.<p>Two distinct stages in the decay of the maximum streamwise velocity, with distance along the direction of flow, were observed for the jet flows having a bed-jet flow regime. The first stage of velocity decay was characterized by a curvilinear decay of velocity, which followed that of a wall jet on a smooth, rigid bed for streamwise distance approximately equal to 2L. For the surface-jet flow regime, the decay of velocity was observed to be similar to that of a free-jump on a smooth, rigid bed for a streamwise distance approximately equal to L. Here, L is defined as the streamwise distance measured from the end of the rigid apron to where the maximum streamwise velocity in the jet is half the velocity of the jet at the end of apron. The streamwise maximum velocity of the jet was then seen to increase in what was called the recovery zone.<p>A relationship for the streamwise decay of the maximum velocity within the scour hole is proposed. Moreover, other scales representing the flow inside the scour hole such as the streamwise distance from the end of the apron to where the streamwise maximum velocity starts to deviate from curvilinear to linear decay and the streamwise distance to where maximum streamwise velocity starts to increase are suggested. Some new results on the velocity distribution for the reverse flow for a bed-jet flow regime are also presented. Finally, some dimensionless empirical equations describing the relationship between the jet scales for the jet flow in a scour hole and the scour hole size are given.

Magnetohydrodynamic (MHD) investigations of decaying isotropic turbulence and rectangular jets (RJ) are carried out. A novel MHD lattice Boltzmann scheme that combines multiple relaxation time (MRT) parameters for the velocity field with a single relaxation time (SRT) parameter for the Maxwell’s stress tensor is developed for this study. In the MHD homogeneous turbulence studies, the kinetic/magnetic energy and enstrophy decays, kinetic enstrophy evolution, and vorticity alignment with the strain-rate tensor are evaluated to assess the key physical MHD turbulence mechanisms. The magnetic and kinetic energies interact and exchange through the influence of the Lorentz force work. An initial random fluctuating magnetic field increases the vortex stretching and forward cascade mechanisms. A strong uniform mean magnetic field increases the anisotropy of the turbulent flow field and causes inverse cascading. In the RJ studies, an investigation into the MHD effects on velocity, instability, and the axis-switching phenomena is performed at various magnetic field strengths and Magnetic Reynolds Numbers. The magnetic field is found to decelerate the jet core, inhibit instability, and prevent axis-switching. The key physical mechanisms are: (i) the exchange of energy between kinetic and magnetic modes and (ii) the magnetic field effect on the vorticity evolution. From these studies, it is found that magnetic field influences momentum, vorticity, and energy evolution and the degree of modification depends on the field strength. This interaction changes vortex evolution, and alters turbulence processes and rectangular jet flow characteristics. Overall, this study provides more insight into the physics of MHD flows, which suggests possible applications of MHD Flow Control.

The exchange flow through tidal inlets generates two-dimensional large coherent vortical structures (2DLCS), that are much broader than the water depth and exist because of the inherent instability of shallow shear flows. These vortical starting jets are critical to the mixing that occurs in the inlet area. Depending on the tidal period T, the width of the inlet W, and the maximum velocity in the inlet UMAX, the mixing will vary from poor exchange to efficient exchange. Here, we present laboratory and numerical experiments that study the formation of the 2DLCS at the mouth of the inlets. Experiments were conducted at large scale, in the shallow flat-bottomed water basin at the Institute of Hydromechanics of the University of Karlsruhe, Germany, which has the capability to generate a sinusoidal flow that simulates a series of tidal cycles. A set of idealized inlets were arranged in the tank, and by varying the tidal period and the maximum velocity, three different types of life-history were obtained (stationary dipole, dipole entrains, and dipole escapes). These types of life-history are defined by the mixing number depending if KW is equal, less or greater than a critical value. The experiments were visualized using color dye tracers. To quantify the shallow water velocity field, the Particle Image Velocimetry (PIV) technique was used. From the PIV data the vorticity field was obtained, and the regions where the vortex formed were identified. Then, a vortex time-evolution analysis was developed using iv physical parameters such as the position on the basin of the vortex, the equivalent diameter, and the maximum vorticity among others. The mixing number accurately predicts the behavior of the vortex for the first cycle on idealized inlets for the subsequent cycles; the structures behave differently than predicted by KW, because the blocking effect of the vortex /formed in the previous cycle. For characteristic times t*  tUWless than about 2, the dipole is attached to the inlet and forms rapidly. For later times, the dipole advects downstream, and slowly dissipates. Numerical experiments are also presented. Comparing the numerical data with the laboratory data, good agreement is reached, but important limitations are identified for the grid resolution and domain size.

The present work investigates the turbulent jet flow mixing of downward impinging jets within a staggered rod bundle based on previous experimental work. The two inlet jets had Reynold's numbers of 11,160 and 6,250 and were chosen to coincide with the available data. Steady state simulations were initially carried out on a semi-structured polyhedral mesh of roughly 13.2 million cells following a sensitivity study over six different discretized meshes. Very large eddy simulations were carried out over the most refined mesh and continuous 1D wavelet transforms were used to analyze the dominant instabilities and how they propagate through the system in an effort to provide some insight into potential problems relating to structural vibrations due to turbulent instabilities. The presence of strong standing horseshoe vorticies near the base of each cylinder adjacent to an inlet jet was noted and is of potential importance in the abrasion wear of the graphite support columns of the VHTR if sufficient wear particles are present in the gas flow.

With the development of urban areas and the constant need to change or improve the existing structures, a need for creative and less destructive soil reinforcement processes has occurred. Jet-grouting is one possible ground improvement technique. The behavior of the soil improved by jet-grouting is still not well understood. In this thesis, the mechanical behavior of the injected soil is modeled in order to determine the different parameters needed for the engineering design of a soil reinforcement based on jet-grouting. At first several models are presented in order to determine the extent of the injected zone within the soil mass, based on engineering parameters (cement poroelastic properties, injection rate). A model based on an energetic balance is proposed to compute the lower bound of the injection radius. The second part of the thesis focuses on the characterization of the uniaxial compressive strength of the soilcrete created in the injected area determined in the first part. Three different methods have been adapted to the problem. A hollow sphere model has been calibrated against published data. After calibration, both Eshelby's and averaging methods proved to provide results close to the reference data. The last part of this report presents numerical studies of the pile and of a group of piles. The study of the group of piles focuses on the effect of arching between soilcrete columns to reduce the vertical settlements due to urban tunneling at the surface. It appears that the values obtained for settlements in the presence of jet-grouted columns are much less important than in usual tunneling problems (with no reinforcement).