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Author: Young Ro Yi Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Global and regional ocean simulations rely on eddy viscosities and diffusivities to represent the unresolved turbulent mixing of momentum and scalars. The simulated flow and the transport of quantities such as heat and carbon are quite sensitive to how the turbulence is modeled. Particularly, the eddy diffusivity model of Osborn (1980) is widely used to represent the vertical buoyancy flux, which requires accurate knowledge of the mixing coefficient--defined as the ratio of the dissipation rates of available turbulent potential energy (TPE) and turbulent kinetic energy (TKE). While a constant value of 0.2 is often prescribed for the mixing coefficient, there is significant evidence for parameterizing it as a function of dimensionless numbers that characterize the state of the turbulence. Using direct numerical simulations, we studied stably stratified turbulence under three different sets of forcing: (i) linear axisymmetric forcing; (ii) three types of shear forcing; and (iii) combined momentum and buoyancy forcing. By analyzing the budgets of the normal Reynolds stresses and the vertical buoyancy flux, we observed that terms involving the pressure field (i.e., pressure-strain correlations and pressure scrambling) exhibited significant changes as the turbulent mixing became more efficient. Each of these three sets of flows exhibited quantitative physical differences in their mixing characteristics. Our findings suggested the need for improved models of the turbulent mixing in stratified flows, which we achieved by revising existing scaling relationships for the mixing coefficient and exploring anisotropic model forms for the turbulent momentum and scalar fluxes.
Author: Young Ro Yi Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Global and regional ocean simulations rely on eddy viscosities and diffusivities to represent the unresolved turbulent mixing of momentum and scalars. The simulated flow and the transport of quantities such as heat and carbon are quite sensitive to how the turbulence is modeled. Particularly, the eddy diffusivity model of Osborn (1980) is widely used to represent the vertical buoyancy flux, which requires accurate knowledge of the mixing coefficient--defined as the ratio of the dissipation rates of available turbulent potential energy (TPE) and turbulent kinetic energy (TKE). While a constant value of 0.2 is often prescribed for the mixing coefficient, there is significant evidence for parameterizing it as a function of dimensionless numbers that characterize the state of the turbulence. Using direct numerical simulations, we studied stably stratified turbulence under three different sets of forcing: (i) linear axisymmetric forcing; (ii) three types of shear forcing; and (iii) combined momentum and buoyancy forcing. By analyzing the budgets of the normal Reynolds stresses and the vertical buoyancy flux, we observed that terms involving the pressure field (i.e., pressure-strain correlations and pressure scrambling) exhibited significant changes as the turbulent mixing became more efficient. Each of these three sets of flows exhibited quantitative physical differences in their mixing characteristics. Our findings suggested the need for improved models of the turbulent mixing in stratified flows, which we achieved by revising existing scaling relationships for the mixing coefficient and exploring anisotropic model forms for the turbulent momentum and scalar fluxes.
Author: Michael Meredith Publisher: Elsevier ISBN: 0128215135 Category : Science Languages : en Pages : 386
Book Description
Ocean Mixing: Drivers, Mechanisms and Impacts presents a broad panorama of one of the most rapidly-developing areas of marine science. It highlights the state-of-the-art concerning knowledge of the causes of ocean mixing, and a perspective on the implications for ocean circulation, climate, biogeochemistry and the marine ecosystem. This edited volume places a particular emphasis on elucidating the key future questions relating to ocean mixing, and emerging ideas and activities to address them, including innovative technology developments and advances in methodology. Ocean Mixing is a key reference for those entering the field, and for those seeking a comprehensive overview of how the key current issues are being addressed and what the priorities for future research are. Each chapter is written by established leaders in ocean mixing research; the volume is thus suitable for those seeking specific detailed information on sub-topics, as well as those seeking a broad synopsis of current understanding. It provides useful ammunition for those pursuing funding for specific future research campaigns, by being an authoritative source concerning key scientific goals in the short, medium and long term. Additionally, the chapters contain bespoke and informative graphics that can be used in teaching and science communication to convey the complex concepts and phenomena in easily accessible ways. - Presents a coherent overview of the state-of-the-art research concerning ocean mixing - Provides an in-depth discussion of how ocean mixing impacts all scales of the planetary system - Includes elucidation of the grand challenges in ocean mixing, and how they might be addressed
Author: Herman J.H. Clercx Publisher: Springer ISBN: 3319668870 Category : Technology & Engineering Languages : en Pages : 225
Book Description
The book presents a state-of-the-art overview of current developments in the field in a way accessible to attendees coming from a variety of fields. Relevant examples are turbulence research, (environmental) fluid mechanics, lake hydrodynamics and atmospheric physics. Topics discussed range from the fundamentals of rotating and stratified flows, mixing and transport in stratified or rotating turbulence, transport in the atmospheric boundary layer, the dynamics of gravity and turbidity currents eventually with effects of background rotation or stratification, mixing in (stratified) lakes, and the Lagrangian approach in the analysis of transport processes in geophysical and environmental flows. The topics are discussed from fundamental, experimental and numerical points of view. Some contributions cover fundamental aspects including a number of the basic dynamical properties of rotating and or stratified (turbulent) flows, the mathematical description of these flows, some applications in the natural environment, and the Lagrangian statistical analysis of turbulent transport processes and turbulent transport of material particles (including, for example, inertial and finite-size effects). Four papers are dedicated to specific topics such as transport in (stratified) lakes, transport and mixing in the atmospheric boundary layer, mixing in stratified fluids and dynamics of turbidity currents. The book is addressed to doctoral students and postdoctoral researchers, but also to academic and industrial researchers and practicing engineers, with a background in mechanical engineering, applied physics, civil engineering, applied mathematics, meteorology, physical oceanography or physical limnology.
Author: Jorg Imberger Publisher: Academic Press ISBN: 0120885719 Category : Science Languages : en Pages : 446
Book Description
A broad cross-section of scientists working in aquatic environments will enjoy this treatment of environmental fluid dynamics, a foundation for elucidating the importance of hydrodynamics and hydrology in the regulation of energy.
Author: M. Lesieur Publisher: Cambridge University Press ISBN: 9780521781244 Category : Mathematics Languages : en Pages : 240
Book Description
Large-Eddy Simulations of Turbulence is a reference for LES, direct numerical simulation and Reynolds-averaged Navier-Stokes simulation.
Author: Eric P. Chassignet Publisher: Cambridge University Press ISBN: 1107079993 Category : Science Languages : en Pages : 445
Book Description
Buoyancy is one of the main forces driving flows on our planet, especially in the oceans and atmosphere. These flows range from buoyant coastal currents to dense overflows in the ocean, and from avalanches to volcanic pyroclastic flows on the Earth's surface. This book brings together contributions by leading world scientists to summarize our present theoretical, observational, experimental and modeling understanding of buoyancy-driven flows. Buoyancy-driven currents play a key role in the global ocean circulation and in climate variability through their impact on deep-water formation. Buoyancy-driven currents are also primarily responsible for the redistribution of fresh water throughout the world's oceans. This book is an invaluable resource for advanced students and researchers in oceanography, geophysical fluid dynamics, atmospheric science and the wider Earth sciences who need a state-of-the-art reference on buoyancy-driven flows.
Author: Guenther Wolfgang Ebert Publisher: ISBN: Category : Languages : en Pages : 138
Book Description
Mixing is a common feature of stratified fluids. In stratified fluids the density varies with the height. This is true for the most fluids in geophysical environments, like lakes, the atmosphere or the ocean. Turbulent mixing plays a crucial role for the overall energy budget of the earth and has therefore an huge impact on the global climate. By introducing the mixing efficiency, it is possible to quantify mixing. It is defined as the ratio of gain of potential energy to the injection of mechanical energy. In the ocean energy provided by tidal forces leads to turbulence and thus highly dense water is lifted up from the deep sea to the surface. For this process, a mixing efficiency of 0.2 is estimated. Until now it is not completely understood how this high value can be achieved. Thus we measured the mixing efficiency by using a Couette-Taylor system, which can produce steady-state homogeneous turbulence. This is similar to what we find in the ocean. The Couette-Taylor system consists of two concentric cylinders that can be rotated independently. In between a stratified fluid is filled using salt as a stratifying agent. In the laboratory experiment, we obtained mixing efficiencies in the order of 0.001 as a result. Moreover we found that the mixing efficiency decreases with decreasing stratification like previous laboratory experiments have shown. As this value is two orders of magnitude smaller than what we find in the ocean, further studies will be necessary.
Author: S. A. Thorpe Publisher: Cambridge University Press ISBN: 9781139445795 Category : Science Languages : en Pages : 496
Book Description
The subject of ocean turbulence is in a state of discovery and development with many intellectual challenges. This book describes the principal dynamic processes that control the distribution of turbulence, its dissipation of kinetic energy and its effects on the dispersion of properties such as heat, salinity, and dissolved or suspended matter in the deep ocean, the shallow coastal and the continental shelf seas. It focuses on the measurement of turbulence, and the consequences of turbulent motion in the oceanic boundary layers at the sea surface and near the seabed. Processes are illustrated by examples of laboratory experiments and field observations. The Turbulent Ocean provides an excellent resource for senior undergraduate and graduate courses, as well as an introduction and general overview for researchers. It will be of interest to all those involved in the study of fluid motion, in particular geophysical fluid mechanics, meteorology and the dynamics of lakes.
Author: Young Ro Yi
Author: Young Ro Yi
Author: Robert Sugden Rogallo
Author: Michael Meredith
Author: Herman J.H. Clercx
Author: Jorg Imberger
Author: M. Lesieur
Author: Eric P. Chassignet
Author: Guenther Wolfgang Ebert
Author: A. A. R. Townsend
Author: S. A. Thorpe