Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 99 for “"Eddy Viscosity"”.
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Eddy viscosity models for pure waves over large roughness elements
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1997.
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Development of a One-Equation Eddy Viscosity Turbulence Model for Application to Complex Turbulent Flows
… The goal of this research has been to develop an eddy viscosity type turbulence model to increase the accuracy of flow simulations for mildly separated flows, flows with rotation and curvature effects, and flows with surface roughness. It is accomplished by developing a new zonal one-equation …
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A theoretical investigation of an averaged-structure eddy viscosity model applied to turbulent shear flows
The project is concerned with the study of a new mathematical model in which the structure of turbulence is described by averaging the effects of the eddies of various scales over the whole volume of flow. The model assumes that the turbulent stresses can be presented in a way analogous to the …
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Implementation of a non-linear eddy viscosity turbulence model into Hydra-TH for fuel related applications
A quadratic [kappa]-[epsilon]non-linear eddy viscosity model (NLEVM) has been implemented into Hydra-TH, a Computational Fluid Dynamics (CFD) software being developed to support the nuclear reactor thermal-hydraulics modeling and simulation needs of the CASL program. This model adopts a non-linear …
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Adjoint-based optimization of U-bend channel flow using a multi-fidelity eddy viscosity turbulence model
… RANS and high-fidelity wall-resolved Large Eddy Simulation (LES) models. The LES solution is shown to match experimental results, whereas the RANS solution is not sufficiently accurate. A process for training a RANS eddy viscosity field using the LES solution is provided. This approach is …
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THE VERTICAL STRUCTURE OF ESTUARINE TIDAL CURRENTS
… estuary. The theory focuses on the use of eddy viscosity models. Surface slope estimates based on tide predictions, current velocity profile measurements, and stress estimates from near bottom turbulence measurements are used to investigate the dynamic balance in the tidal channel, and to …
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A numerical analysis of turbulent flow along an abruptly rotated cylinder
… empirical foundation of the mixing length and eddy viscosity "theories" of turbulence. The term mathematical model may more aptly describe the mixing length/eddy viscosity approach to turbulence than the word theory, for these concepts take into account little of the basic dynamics of …
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An experimental study of a three-dimensional pressure-driven turbulent boundary layer
… interferometer technique. The data show that the eddy viscosity of the flow is not isotropic, but the ratio of eddy viscosities perpendicular and parallel to the direction of the mean velocity vector component parallel to the wall at the point in the layer where u²¯ is maximum is close to unity, …
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Study of two-way coupled particle laden turbulent flow over a backward-facing step using large-eddy simulation
Large-eddy simulation (LES) is a computationally viable strategy to study particle-laden turbulent flows in practically relevant configurations, although modeling challenges need to be addressed for improved predictive capabilities. In this study, we perform a comprehensive assessment of …
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Influence of initial turbulence intensity on the heat and moisture transfer through a recirculated air curtain
… describes the development and verification of an eddy viscosity model which accounts for the influence of the initial turbulence intensity on the transfer of heat and moisture across a recirculated air curtain. The control of the turbulence intensity at the nozzle exit of an air curtain permits …
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Finite element solution of the Navier-Stokes equations for 3-D turbulent free shear flows
… turbulence has been developed to described the eddy viscosity distribution of two and three-dimensional turbulent free shear flows. The model is derived by integrating the parabolized transport equation for the turbulence kinetic energy over the cross section of the flow. The Prandtl-Kolmogrov …
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Observations of interaction between the internal wavefield and low frequency flows in the North Atlantic
… moorings, indicating that the magnitude of the eddy viscosity was under 200 cm2/sec, with the sign of the energy transfer uncertain. This is considerably below the 0(4500 cm2/sec) predicted by Müller (1976). An extensive error analysis indicates that the large wave stress predicted by the theory …
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Experimental and theoretical study of turbulent oscillatory boundary layers
… with the temporal variation of the turbulent eddy viscosity. This, together with some other experimental evidence, motivates the development of a new theoretical model which adopts a rigorous way to account for a time-varying turbulent eddy viscosity. The model accurately predicts the mean and …
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Wall-modeled Large-eddy Simulation Based on Building-block Flows
… flow model (BFM) — for wall modeled large-eddy simulation (WMLES) is proposed by devising the flow as a collection of building blocks that enables the prediction of the eddy viscosity. The core assumption of the model is that simple canonical flows contain the essential physics to provide …
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Hilbert Space Projections and the Navier-Stokes Equation
… with these measures is carried out and an eddy viscosity is calculated.
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New integral and differential computational procedures for incompressible wall-bounded turbulent flows
… modeled using the Boussinesq assumption, and the eddy viscosity is defined explicitly as in differential methods. The turbulence modeling is not hidden in opaque empirical correlations as in conventional integral methods. A practical four-parameter velocity profile has been established based on …
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Assessment of RANS Turbulence Models for Hypersonic Flat Plates
… Navier-Stokes approaches using linear eddy viscosity models for turbulence were not designed and optimized with hypersonic flow problems in mind, and thus have weaknesses that are continuously being studied and addressed. This study evaluates the performance of the Menter Shear Stress …
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Learning Nonlinear Dynamics: Methods and Applications
… problem, which involves modeling the unobserved eddy viscosity field. We tackle two interconnected inverse problems: reconstructing the eddy viscosity from flow data and discovering its governing partial differential equations (PDEs), thereby proposing a new pathway to uncover new or refined RANS …
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The hydrodynamic modelling of an evolving sea
… is simulated by a horizontally varying eddy viscosity.
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ΜΑΘΗΜΑΤΙΚΗ ΠΕΡΙΓΡΑΦΗ ΤΗΣ ΔΙΑΔΟΣΗΣ ΤΩΝ ΜΗ ΓΡΑΜΜΙΚΩΝ ΔΙΑΣΠΕΙΡΟΜΕΝΩΝ ΚΥΜΑΤΙΣΩΝ ΣΤΟΝ ΠΑΡΑΚΤΙΟ ΧΩΡΟ
… THE BOUSSINESQ EQUATIONS IN THE SURF ZONE. THE EDDY VISCOSITY COEFFICIENT IS CALCULATED FROM THE SOLUTION OF THE TURBULENCE TRANSPORT EQUATION (K-MODEL). BASED ON A POWER SERIES EXPANSION FOR THE DISTRIBUTION OVER THE DEPTH OF THE VERTICAL VELOCITY WE PROPOSE AN EXTENSION OF THE EQUATIONS IN …
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