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 64 for “"Direct Numerical Simulation (DNS)"”.
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Improved turbulent lift momentum closure for multiphase computational fluid dynamics
… turbulent lift force utilizing a combination of direct numerical simulation (DNS) data and a numerical optimization of the lift coefficient using experimental data [3].
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Toward Ideal Large-Eddy Simulation
… that there is a subgrid model for large-eddy simulation (LES) of turbulence that is provably ideal in at least two important senses: a simulation using the ideal model matches all spatial statistics and minimizes error in the large-scale dynamics. However, the ideal model embodies a tremendous …
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Multidimensional and multivariate empirical mode decomposition
… through the current study, when applied to the Direct Numerical Simulation (DNS) of a flat-plate boundary layer (a large dataset), revealed the desired scale separation behaviour across multiple data channels. This proves that the algorithm could be useful for a broad range of future problems.
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LAMINAR TURBULENT TRANSITION - SPECTRAL ANALYSIS AND COHERENT STRUCTURES OF DNS WAVEPACKETS
This thesis concerns a direct numerical simulation (DNS) of wavepackets undergoing laminar turbulent transition in a Blasius boundary layer. A fully crossed factorial simulation design is used, in which 18 different wavepackets are analyzed to determine the combined effects of frequency, bandwidth …
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Modeling of laminar-to-turbulent transition using a hybrid multi-scale simulation strategy
… of transition and the associated flow dynamics. Direct numerical simulation (DNS), although suitable for fundamental studies, tends to be computationally expensive, thus making large-eddy simulations (LES) a viable strategy. In LES, large scales of the flow field are computed, and the effects of …
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A numerical study of flow-structure interactions with application to flow past a pair of cylinders
… of marine risers and cables. In this thesis a Direct Numerical Simulation (DNS) approach based on spectral/hp elements is employed. Structural motion implies changes on the boundaries of the flow domain. An Arbitrary Lagrangian Eulerian (ALE) scheme is incorporated to efficiently move the mesh …
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Combining In Situ Measurements and Advanced Catalyst Layer Modeling in PEM Fuel Cells
… a useful tool for fuel cell design. By comparing numerical results to experimental results, numerical models can provide a better understanding of the physical processes occurring within the fuel cell catalyst layer. This can lead to design optimization and cost reduction. The purpose of this …
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Drag Reduction by Polymeric Additive Solutions
… model. To evaluate its accuracy, multiple simulation scenarios were benchmarked against Direct Numerical Simulation (DNS) data. Results indicated, that the viscoelastic RANS turbulence model shows a high accuracy against DNS percentages of drag reduced when dealing with higher solvent …
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A DNS capability for obtaining underwater light field and retrieving upper ocean conditions via in-water light measurements
… military applications. This thesis presents a direct numerical simulation (DNS) capability of solving complicated natural light field patterns in the ocean-atmosphere system. The DNS is applied by means of Monte Carlo method to solve radiative transfer for both unpolarized and polarized natural …
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Implementation and Verification of a Synthetic Eddy Method (SEM) in the Eagle3d Compressible Flow Solver
… Non-Oscillatory (WENO) approximation to reduce numerical dissipation. SEM is a modern synthetic turbulence method able to reproduce an arbitrary Reynolds stresses specification on discretionary geometries while keeping computational costs low. The Large-Eddy Simulation (LES) capability of …
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Direct Numerical Simulation of Flow Over Circular Cylinders for Large -Eddy Simulation Modeling
… of 1500 is studied using a three-dimensional direct numerical simulation (DNS). At this condition, the shear layer is unstable. However, previous direct numerical simulations of this flow have been limited to Reynolds numbers of 1000 or less, where the shear layer is stable or only weakly …
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Numerical simulations of vortices near free and solid surfaces
… free and solid surfaces has been examined using direct numerical simulation (DNS). A computer code was developed which solves the unsteady, three-dimensional Navier-Stokes equations for incompressible flow. A critical element of the numerical scheme is the efficient solution of Poisson's …
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Assessment of RANS Turbulence Models for Hypersonic Flat Plates
… of hypersonic flat plate cases from a recent direct numerical simulation (DNS) database. Quantities of interest examined include velocity, temperature, turbulent kinetic energy, modeled turbulent kinetic energy budget terms, eddy viscosity, Reynolds stresses, heat fluxes, wall skin friction, …
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Droplet Drag Modeling on Spray Conditions
Numerical approaches have been conducted to investigate the effect of droplet deformation and internal circulation on droplet dynamics. Although droplet drag is a classical area of study, there are still theoretical gaps in understanding the motion of large droplets. In applications such as spray …
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Numerical study of mach number effects in compressible wall-bounded turbulence
… compressible flows has been investigated using direct numerical simulation (DNS). The research is divided into two aspects: a study of the intrinsic compressibility effects in isothermal-wall channel flow and a study of the impinging shock/turbulent boundary-layer interaction. For the channel …
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Application of hybrid Computational Fluid Dynamics turbulence model, STRUCT-[epsilon], on heated flow cases
… Fluid Dynamics (CFD) modeling is a powerful numerical method that can be used to characterize fluid flow, pressure drop, and thermal transient behavior in complex flow geometries. However, with current CFD simulation techniques, the accurate modeling of turbulence structures is often …
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Hydraulic Characterization of Mounded Gravel Fish Nests: Incipient Motion Criteria and Despiking Acoustic Doppler Velocimeter Data
… methods are evaluated using field ADV and direct numerical simulation (DNS) data of a turbulent boundary layer. Visual assessment of despiked velocity time series and power spectra and corresponding changes in statistical moments, as well as response to arti- ficial spiking of DNS data, …
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Optimal Large -Eddy Simulation of Turbulent Channel Flow
… model are computed from realizations of a direct numerical simulation (DNS) of a plane channel at a friction Reynolds number of 587. Due to the limited number of realizations, estimates of the model term are global only in the streamwise and spanwise directions and local in the wall-normal …
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Toward a theory of diffuse energy transport in large irregular structures
… over short-time intervals. Though not based directly on an assumption of diffusion, the ansatz contains the same phase-neglecting principle as SEA and implies a diffusion limit equivalent to SEA. In this thesis, the concatenation ansatz is tested on various benchmark systems, some typically …
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Evaluation of RANS-Based Turbulence Models for the Propagation of Stratified Fronts in Buoyancy-Driven Flow
… to high resolution results from HiRJet and direct numerical simulation (DNS). Sources of inaccuracy were identified through evaluation of separate components such as treatment of turbulence production due to buoyancy and modeling of anisotropic turblence. The STRUCT-ϵ model was adopted to …
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