Spelling suggestions: "subject:"hydrodynamic.""
361 |
Smooth Particle Hydrodynamics Applied to Fracture MechanicsSticko, Simon January 2013 (has links)
A numerical method commonly referred to as smooth particle hydrodynamics (SPH) is implemented in two dimensions for solid mechanics in general and fracture mechanics in particular. The implementation is tested against a few analytical cases: a vibrating plate, a bending plate, a modus I crack and a modus II crack. A conclusion of these tests is that a better way of treating a shortcoming of SPH called tensile instability is needed. A study is made on the best choice of a vital parameter called the smoothing radius, and it is found that a good choice of the smoothing radius is roughly 1.5 times the initial particle spacing.
|
362 |
Investigation of the Wake Flow behind a stepped circular Cylinder using Particle Image VelocimetryTeutsch, Ina January 2012 (has links)
Subject of the present study was the investigation of the wake behind stepped circular cylinders. Experiments were performed using particle image velocimetry (PIV). Cylinder models with diameter ratios D/d=1, D/d=6/5 and D/d=2 were investigated at Reynolds numbers Re_{D}=2243.6, Re_{D}=12820.5 and Re_{D}=51282.1 with respect to the large diameter. Of main interest were the influences of step size and Reynolds number on the formation of vortex shedding cells. Mean flow characteristics and instantaneous captures of the flow field were analyzed in order to gain insight into vortex development in the wake. Spectral analysis was applied to obtain information on the number of forming vortex shedding cells.It was found that an increase in Re_D leads to a decrease in eddy formation length $L_f$. At the largest investigated Reynolds number, turbulence gained strong influence on the flow characteristics. An increase in stepsize leads to the development of a large and a small diameter wake with distinct eddy formation lengths L_{f,L} and L_{f,S}.Due to a mismatch in vortex shedding frequencies in the two wakes, vortices that come out of phase connect to subsequent vortices on the same side of the step. This occurs more frequently for a higher diameter ratio.Several vortex shedding cells were found in the wake of the step cylinders, their number increasing with the step size and differing for different Reynolds numbers.The wake behind step cylinders was discovered to be strongly three-dimensional. I order to complete the information about flow characteristics, measurements were performed in several parallel vertical and horizontal planes along the cylinder.PIV proved to be a good method for the investigation of flow features in the wake of step cylinders for the chosen model dimensions and Reynolds numbers.
|
363 |
The Hydrodynamics of Pool-Riffle Sequences with Changing Bedform LengthObach, Lana M. January 2011 (has links)
Previous research has demonstrated that pool-riffle bedforms play a critical role in channel stability and ecosystem health in many natural gravel-bed channels. Although the bedform length is known to scale with channel width, no experimental research has yet isolated the effect of bedform length on pool-riffle hydrodynamics. To improve the understanding of the hydrodynamics of these bedforms so that they can be better incorporated in restoration practices, flume experiments were conducted testing the flow at seven different bedform lengths.
Velocity profiles are measured in a 17 m flume with movable PVC bedforms using ultrasonic velocity profilers (UVPs). Smooth two-dimensional (no sinuosity) bedforms are used in order to isolate the key dynamics in convective acceleration and deceleration. The angle of transition between pool and riffle heights was 7°, so that permanent flow separation did not occur. Parameters calculated from the velocity and turbulence profiles include the Coles’ wake parameter (a measure of the deviation from the log law), shear stress estimated from the velocity profile, shear stress estimated from the Reynolds shear stress, and vertical velocity. From the individual velocity time series, the integral length scale and the integral time scales are also calculated.
Overall, the length of riffles and pools exert a fundamental control on the distribution of flow and turbulence within a channel. In the pool, energy is dissipated both through turbulence and as the flow is redistributed to uniform flow conditions. In the riffle, kinetic energy increases as the flow velocity increases, and as the length increases, the flow moves towards a new uniform flow condition. The results start to explain the reasons behind the persistent scaling relation between width and bedform length. It can be concluded that uniform flow conditions exist at the end of the pool when the bedform length ratio is greater than approximately 1:5.0 when the riffle length is held constant, and that uniform flow conditions are no longer observed at the end of the pool when the bedform length ratio exceeds 1:7.0 when the pool length is held constant.
Future research should concentrate on extending the results to include three-dimensional pool-riffle configurations, repeating bedform configurations, internal scaling parameters, and sediment transport. Ultimately, as the hydrodynamics of pool-riffle sequences are better understood, better bedform designs can be implemented in restoration projects.
|
364 |
The hydrodynamic properties of alditol oligosaccharidesTostevin, James Earle 01 January 1966 (has links)
No description available.
|
365 |
Stokesian dynamic simulations and analyses of interfacial and bulk colloidal fluidsAnekal, Samartha Guha 30 October 2006 (has links)
Understanding dynamics of colloidal dispersions is important for several
applications ranging from coatings such as paints to growing colloidal crystals for
photonic bandgap materials. The research outlined in this dissertation describes the use
of Monte Carlo and Stokesian Dynamic simulations to model colloidal dispersions, and
the development of theoretical expressions to quantify and predict dynamics of colloidal
dispersions. The emphasis is on accurately modeling conservative, Brownian, and
hydrodynamic forces to model dynamics of colloidal dispersions. In addition, we
develop theoretical expressions for quantifying self-diffusion in colloids interacting via
different particle-particle and particle-wall potentials. Specifically, we have used
simulations to quantitatively explain the observation of anomalous attraction between
like-charged colloids, develop a new criterion for percolation in attractive colloidal
fluids, and validate the use of analytical expressions for quantifying diffusion in
interfacial colloidal fluids. The results of this work contribute to understanding
dynamics in interfacial and bulk colloidal fluids.
|
366 |
Fluid and suspension hydrodynamics in the impeller discharge flow of stirred tanksYu, Ziyun January 2004 (has links)
<p>The hydrodynamics of an agitated tank have been studied byphase-Doppler anemometry. The focus is on the impeller anddischarge region of a 45o pitched blade turbine (PBT). Thestudy includes agitation of pure water as well as of a dilutesuspension of process particles. A three-dimensionalphase-Doppler anemometer is used to measure local,instantaneous, three-dimensional velocities of the fluid and ofthe suspended particles. A shaft encoding technique is used toresolve the turbulent fluctuations from the periodic velocityfluctuation due to the impeller blades, and to provide moredetailed information about the variations relative to theimpeller blade. Velocity bias is corrected for by the total3-dimensional velocity.</p><p>The mean flow field, the fluctuating velocities, and thecomplete Reynolds stress tensor, are reported for the liquidphase flow. The periodic fluctuations in the flow that aregenerated by the impeller blades are eliminated in theexamination of the turbulence. The anisotropy of the turbulenceis assessed by the invariants of the anisotropy tensor. Thetrailing vortex structure is demonstrated to be associated withhigh kinetic energy and strong anisotropy of the turbulence.The vortex is still observable 130-140 degrees behind theblade. It gradually moves down from the impeller blade but thelocation in radial direction remains essentially unchanged. Theinfluence of the periodic fluctuations is examined and it isshown that the turbulence appears more isotropic when theperiodic fluctuations are not eliminated.</p><p>The solid particle concentration is low below the impellerand is high above the impeller tip. The particles diverge fromthe liquid flow mean direction, especially below the agitatorclose to the tip where the strongest turbulence is found.Periodic fluctuations in the particle concentration relate tothe variations found in the angle-resolved mean velocity andfluctuating velocity. The ratio of the maximum to the minimumconcentration is about 2.0 in the present study.</p><p>The baffles influence on the conditions in the impellerregion, and this influence can be observed on the fluid meanvelocity field, the angle-resolved velocities, the kineticenergy, and on the behavior of larger process particles. In theimpeller region the highest kinetic energies are about 15%higher upstream of the baffle than at the middle plane betweenthe baffles. The highest energy level in the middle plane isactually the lowest value and is therefore not representativewhen rotation symmetry is assumed.</p><p>Local energy dissipation rates have been investigated, andthe integration of the local energy dissipation rates overdifferent control volumes has been compared with macroscopicenergy balance calculations. The discrepancy is significant.Different reasons have been analyzed and recommendations forfurther investigation are given. I</p><p>n the outflow region there is a significant variation alsoin the direction of the instantaneous velocity, which may leadto direction bias in the case of non-spherical measurementvolume. In order to account for this direction bias, amathematical model is developed to estimate the projected areaof the measurement volume in LDA or PDA. It is shown that theprojected area variation can lead to a significant directionbias in determination of time averaged values and localparticle concentration in a highly turbulent stirred tank flow.This bias is however negligible for an orthogonal optical setup, as is used in the present study.</p><p><b>Keywords:</b>Hydrodynamics, phase-Doppler anemometer,suspension, pitched-blade turbine, anisotropy, turbulence,Reynolds stresses, trailing vortex, kinetic energy, stirredtank</p>
|
367 |
Essai théorique et appliqué sur le mouvement des liquides Sur une transformation des coordonnées curvilignes orthogonales et sur les coordonnées curvilignes comprenant une famille quelconque de surfaces du second ordre /Lévy, Maurice January 1900 (has links)
Thèse de doctorat : Sciences : Paris, Faculté des sciences : 1867. / Titre provenant de l'écran-titre.
|
368 |
Identification of the hydrodynamic model of an underwater robotic vehicle heaving and pitching near the sea surface using its measured response /Mahfouz, Ayman B., January 2001 (has links)
Thesis (Ph.D.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 187-194.
|
369 |
Corrections to the tra[n]sverse force for superfluid vortices /Rhee, Sung Wu. January 2003 (has links)
Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 73-77).
|
370 |
BGK kinetic scheme for the shallow-water equations /Que, Yin Tik. January 2003 (has links)
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 108-109). Also available in electronic version. Access restricted to campus users.
|
Page generated in 8.1695 seconds