Download or read book Visualization of Turbulence Modulation with Large Particles written by Franz Demetrius Davis and published by . This book was released on 1993 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book TURBULENCE MODULATION UNDER LARGE PARTICLE LOADING written by Aidan Stephen Cronin and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Particle-laden turbulence is important to a diverse range of topics: from aerosol transport in the atmosphere to flocculation techniques treating our drinking water. Often the particles in flows of interest are large and non-spherical, making them difficult to study, and so simplified cases are considered to quantify turbulent behaviors. Experimental laboratory research has provided insight into the quantifiable behavior of these simplified particle-laden flows, notably in cases of homogeneous and isotropic (H.I) turbulence. For this research, we designed and constructed a novel laboratory turbulence tank for the study of particle-laden flows that could create a region of H.I turbulence at its center. To do so, we incorporated random, symmetric forcing on a completely new geometry (a modified icosahedron) intending to maintain the properties of H.I. turbulence while increasing the size of the region of the tank in which it is contained. This facility will provide a unique testbed for studies of particle-laden turbulence.

Download or read book Study of Turbulence Modulation by Finite size Solid Particles with the Lattice Boltzmann Method written by Cheng Peng and published by . This book was released on 2018 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent flows laden with finite-size solid particles are found in a variety of natural and engineering processes. However, the overall understanding of how the flow properties, such as turbulent intensity and flow drag, are modified by the addition of the particles is still limited. So far, the only rigorous approach to investigate the modulation mechanisms at the particle scale is to numerically solve the disturbance flow around each particle, known as the interface-resolved simulations (IRS). However, the application of IRS in the turbulent particle-laden flow is particularly challenging due to the requirements of resolving all the length and time scales in the turbulent flow, as well as the need to realize the no-slip boundary condition on the moving particle surfaces. ☐ In recent years, the lattice Boltzmann method (LBM) has emerged as an efficient and accurate numerical approach for computational fluid dynamics. Compared to the conventional approaches of directly solving the Navier-Stokes equations, LBM is simple to code, easy to parallelize, and flexible in treating boundary conditions. In particular, the no-slip boundary treatment based on bounce-back scheme and mesoscopic momentum exchange in LBM take full advantage of the gas kinetic description. However, the realization of these treatments in particle-laden turbulent flow simulations is still rare. So far, the majority of the particle-laden turbulent flow simulations relies on the smoothed-boundary treatments, such as the immersed boundary methods, which tends to induce artificial dissipation. In this dissertation, LBM with a sharp-interface treatment is developed to investigate turbulence modulation by finite-size solid particles. ☐ After a thorough validation, the method is applied to the simulations of a turbulent channel flow laden with both fixed and moving particles. The interactions between the dispersed particles and carrier turbulent flows, especially the modulation induced by the particles on the turbulence intensity and its parameter dependence are examined. The addition of particles is found to result in a more homogeneous distribution of turbulent kinetic energy (TKE) in the wall normal direction and a more isotropic TKE distribution among different spatial directions, comparing to the single-phase turbulent channel flow. To gain further insight, the budget equations of both the total TKE and component-wise TKE in the particle-laden turbulent flows are derived and analyzed using the simulation data. The budget analysis of the total TKE shows that the production rate of TKE from the mean flow is modified to become more uniform in the wall-normal direction by the presence of particles, which is responsible for the more homogeneous distribution of TKE. Specifically, in the buffer region where the TKE source is maximized in the single-phase flow, the TKE source due to the mean shear is reduced since both the mean flow velocity gradient and the Reynolds stress are reduced by the presence of particles. This reduction is found to be related to the particle inertia, where particles with larger inertia result in greater reduction of the TKE source. On the other hand, particles pump energy to turbulent fluctuations by doing work directly (moving particles) or inducing disturbances to the mean flow (fixed particles), converting more mechanical energy from the mean flow to the turbulent motion. The strength of this extra TKE source is related to the dynamics of the wake developed behind particles and therefore is particle-Reynolds-number dependent. The relative strength of the above two mechanisms determines whether the turbulence intensity of a turbulent channel flow is augmented or attenuated by the presence of particles. The budget analysis of component-wise TKE reveals that the more isotropic distribution of TKE among different spatial directions results from the enhanced inter-components transfer of TKE. This enhancement is found to originate from the spherical shape of the particles and particle rotation. ☐ In summary, the improved LBM simulation method based on the sharp-interface treatment provides a better alternative for particle-laden turbulent flow simulations than the commonly used smoothed-interface treatments. The physical results from this dissertation research advance our understanding of flow modulation induced by finite-size solid particles in turbulent flows, particularly in wall-bounded turbulent flows.

Download or read book Dense Spray Properties Structure and Turbulence Modulation written by G. A. Ruff and published by . This book was released on 1989 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: A theoretical and experimental study of aspects of dense sprays is described, considering: the structure and mixing properties of the near-injector, dense-spray region of pressure-atomized sprays; and the direct effect of particle (drop) motion on the turbulence properties of multiphase flows (which is often called turbulence modulation). The structure of dense sprays was studied using large-scale (9.5 and 19.1 mm jet exit diameters) water sprays in still air. Measurements included: flow visualization using flash photography; liquid volume fractions using gamma-ray absorption; streamwise mean and fluctuating velocities at the injector exit, and entrainment velocities, using laser velocimetry; and dispersed-phase properties using single- and double-flash holography. Predictions based on the locally-homogeneous flow (LHF) approximation of multiphase flow theory were evaluated using the measurements. Measurements showed that mixing was strongly influenced by the degree of flow development at the injector exit and the breakup regime: fully-developed flow and atomization breakup yielded the fastest mixing rates. Turbulence modulation was studied by considering nearly monodisperse spherical glass particles falling in a stagnant water bath, where effects of turbulence modulation were responsible for the entire turbulence field. Measurements included phase velocities, as well as the temporal and spatial correlations of continuous-phase velocities, using a two-point phase-discriminating laser velocimeter; and calibration of particle motion properties using motion-picture shadowgraphs. (JHD).

Download or read book Turbulence Modulation in Gas particle Flows a Comparison of Selected Models written by Sarah M. Hodgson and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The problem of turbulence modulation, the process whereby the gas-phase turbulence is modified by the presence of particles, is investigated. Experimental trends are examined and parameters affecting turbulence modulation and the mechanisms by which turbulence modulation occurs are identified. A new model that accounts for the crossing trajectory effect is presented. This model and the turbulence modulation models of Chen and Wood [4], Tu and Fletcher [45], and Mostafa and Mongia [30] are investigated using the TASCflow CFD code. The models are compared with the experimental results of Tsuji et al [44]. The model of Tu and Fletcher is not able to reproduce either general experimental trends or the experimental results, while the other three models can predict the general experimental trends but cannot reproduce the experimental results. Analysis shows that the turbulent viscosity, [mu]'t', plays an important role in modifying the turbulence intensity profiles. The new model was not able to capture the crossing trajectory effect for the flow considered.

Download or read book Turbulence Structure and Modulation written by Alfredo Soldati and published by Springer. This book was released on 2014-05-04 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlling turbulence is an important issue for a number of technological applications. Several methods to modulate turbulence are currently being investigated. This book describes various aspects of turbulence structure and modulation, and explains and discusses the most promising techniques in detail.

Download or read book Preprints for the Symposium on Turbulence written by and published by . This book was released on 1992 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence Modulation in Particle laden Flows written by John D. Schwarzkopf and published by . This book was released on 2008 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Study of Turbulence Modulation in Gas particulate Flows written by Abhishek Shrivastava and published by . This book was released on 2006 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence Modulation in Gas particle Flows a Comparison of Selected Models written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence Modulation of Carrier phase in Fluid particle Flows written by Pengfei Wang and published by . This book was released on 2000 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence Modulation in Particle Laden Flow with Mono Dispersed Droplets written by 呂偉福 and published by . This book was released on 2010 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence in Open Channels and River Flows written by Michio Sanjou and published by CRC Press. This book was released on 2022-07-20 with total page 303 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence in Open Channel and River Flows covers turbulence and related fluid mechanics in open-channel flows, addressing both basic mechanisms and their applications. It helps readers understand the organized motion involved in turbulent flow and apply this understanding to the practice of hydraulic engineering, including mass and sediment transport. Chapters cover mathematical expansion procedures and basic fluid mechanics to help readers understand essentially physical phenomena, and present special techniques for measurement and accurate direct observation of open-channel turbulence in laboratory flumes or natural rivers. Topics related to environmental management and turbulence-related disasters are addressed. Includes detailed mathematical expansions and supporting supplements in an appendix Presents the mathematics and fluid mechanics needed to understand turbulence in open channels Includes experimental topics from the author’s research, encouraging readers to measure and accurately observe turbulence in laboratories and rivers The book is ideal for graduate students, researchers and engineers in hydraulics and hydromechanics.

Download or read book Fundamentals of Turbulence Modulation in Fluid Particle Systems written by C. T. Crowe and published by . This book was released on 1998 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Visualizing Turbulent Mixing of Gases and Particles written by Kwan-Liu Ma and published by . This book was released on 1995 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gas liquid Flows written by and published by . This book was released on 1995 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gas Liquid Flows 1995 written by and published by . This book was released on 1995 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: