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 16 of 16 for “"slip length"”.
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Measurement and Control of Slip-Flow Boundary Conditions at Solid-Gas Interfaces
… similar to the mean free path, and thus partial slip is expected. This regime has become more important with increased focus on nano-scale devices, but there is currently no consensus on how the slip length should vary for different solids and gases, or whether it can be controlled. In this …
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Skin friction drag reduction in turbulent flows using superhydrophobic surfaces
… which allows the external fluid to partially slip over the boundary, decreasing the net frictional shear stress on the wall. Five prototype drag-reducing surfaces were evaluated experimentally as possible candidates for turbulent drag reduction applications, using a combination of flow tests, …
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Exploring plastron stability and fluid friction reduction on robust micro-textured non-wetting surfaces
… Reynolds numbers Re << 1, the effective Navier slip length is evaluated using torque measurements in a parallel plate rheometer resulting in a measured Navier slip length in laminar flow of b ~~ 39 [mu]m, comparable to the mean periodicity of the microstructure evaluated from confocal …
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Analysis of Interfacial Processes on Non-Wetting Surfaces
… analytical solution is developed for effective slip length and, in turn, drag reduction and friction factor on structured non-wetting surfaces. Secondly, by combining the solution for effective slip length on structured non-wetting surfaces and the fractal characterization of generic multiscale …
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The influence of superhydrophobic surfaces on near-wall turbulence
… due to the overlying flow being able to locally slip over the gas pockets, resulting in a mean slip at the surface. This thesis investigates the different effects that slip and the texturing of the surface have on turbulence over superhydrophobic surfaces. It is shown that, after filtering out …
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Surfactants at fluid interfaces: molecular modeling and deep learning
… of sur factants. The first study investigates slippage modulation at brine–oil interfaces by surfactants, which is relevant to enhanced oil recovery operations. We identified a slip length of 1.2 nm at clean decane-brine interfaces. Introducing surfactants to the interface leads to an initial …
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Scaling laws for stress and energy for interface with strong rate-weakening friction
… surface. Both the statistical properties of slip, pulling force and average rupture stress are studied with varying the constitutive parameters characterizing the model: the stiffness ratio and strength of the velocity-weakening. Longtime investigations suggest that firstly, a pulse- like …
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Molecular dynamics-based approaches for mesoscale lubrication
… stress-strain rate relationship and b) the no-slip boundary condition. In this thesis, we present a methodology for deriving a modified Reynolds equation (referred to as the Molecular Dynamics-based Equation for Lubrication, or the MODEL) which overcomes these limitations by introducing a …
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The effect of texture granularity on turbulence
… for the case of textures made of an alternating slip/no-slip pattern, a common model for super- hydrophobic surfaces. For texture sizes L⁺ ≤ 20, it has been previously discussed that turbulence remains smooth-wall-like, other than experiencing an apparent origin offset for different flow …
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Swimming at low Reynolds number slip boundaries and interacting filaments
… hydrodynamically with a fluid through slip boundary conditions or with other filaments and is composed of two separate parts. The first part of the thesis focuses on a single filament characterised by a slip boundary condition, which is a property displayed by many non-Newtonian fluids. …
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Passive and active approaches to sustained turbulent hydrodynamic drag reduction using superhydrophobic surfaces
… rough texture when submerged in water. A partial slip condition is created at the interface between the water and the submerged body, allowing for a reduction in skin friction drag. I begin by identifying and fabricating several superhydrophobic surfaces, and testing their ability to reduce skin …
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Enhanced Laminar Convective Heat Transfer using Microstructured Superhydrophobic Surfaces
… to the surface. For many cases, the classical no slip boundary condition holds true. However, there are a subset of situations where this assumption is not valid, and slip between the surface and fluid must be considered. One such example is a micropatterned, superhydrophobic surface, which has …
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Numerical Prediction of Drag Reduction and Interfacial Shapes Over Superhydrophobic Surfaces
… interface height $h$ to understand its effect on slip and drag reduction ($DR$). For the laminar Couette flow, the presence of the surface roughness is felt up to $40\%$ of the channel height in the wall-normal direction. The nonlinear dependence of $DR$ on $h$ is observed to have three distinct …
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Structure, property and transport mechanism of water and electrolytes in graphene nanopores
… axial direction of the pore, water viscosity and slip length increase with a decrease in the pore radius, in contrast to water confined in a carbon nanotube. Due to the nanometer dimension of the pore, Reynolds number for pressure-driven water flow through graphene nanopores is very small and a …
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Finite-element simulations of interfacial flows with moving contact lines
… The contact line singularity is removed by the slip boundary condition proposed by Ren and E [Phys. Fluids, vol. 19, p. 022101, 2007], which has two friction coefficients: βN that controls the slip between the bulk fluids and the solid wall and βCL that controls the deviation of the microscopic …
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Control of the buffer and logarithmic layers in wall-bounded turbulent flows
… for all three velocity components using Robin, slip-like boundary conditions. The results of our simulations support the idea that the relevant parameter is the offset between the virtual origins perceived by the mean flow and turbulence. When using Robin, slip-like boundary conditions, the …