Search results for "Fluid Dynamic"
showing 10 items of 1034 documents
Oscillations in the dynamics of temperature-driven phase separation
1997
We examine the dynamics of the phase separation of a single phase of water-in-oil microemulsion droplets towards a phase of smaller droplets coexisting with a water-rich phase. Oscillations are observed in the turbidity of the mixture and in the specific heat, when this transition is induced by a continuous temperature increase. The oscillations indicate an unusual type of dynamics which involves an energy barrier only to be overcome by a large number of droplets collectively. It is due to the spontaneous curvature of the water-oil-interface, and conservation of volumes.
Solution properties of the incompressible Euler system with rough path advection
2021
The present paper aims to establish the local well-posedness of Euler's fluid equations on geometric rough paths. In particular, we consider the Euler equations for the incompressible flow of an ideal fluid whose Lagrangian transport velocity possesses an additional rough-in-time, divergence-free vector field. In recent work, we have demonstrated that this system can be derived from Clebsch and Hamilton-Pontryagin variational principles that possess a perturbative geometric rough path Lie-advection constraint. In this paper, we prove the local well-posedness of the system in $L^2$-Sobolev spaces $H^m$ with integer regularity $m\ge \lfloor d/2\rfloor+2$ and establish a Beale-Kato-Majda (BKM)…
Navier-Stokes equations : unpredictability even without butterfiles?
2018
Mathematically, the motion of a fluid is described by the so-called Navier-Stokes equations. In the spirit of Newtonian mechanics, these equations should determine the future motion of the fluid out of its initial state. However, despite the significant effort made for more than a century, this determinism has not yet been mathematically proved nor disproved. This paper offers a general perspective on the Navier-Stokes equations, the fourth millennium problem.
Molecular dynamics study of phase separation kinetics in thin films.
2005
We use molecular dynamics to simulate experiments where a symmetric binary fluid mixture (AB), confined between walls that preferentially attract one component (A), is quenched from the one-phase region into the miscibility gap. Surface enrichment occurs during the early stages, yielding a B-rich mixture in the film center with well-defined A-rich droplets. The droplet size grows with time as l(t) proportional t(2/3) after a transient regime. The present atomistic model is also compared to mesoscopic coarse-grained models for this problem.
How large is the Knudsen number reached in fluid dynamical simulations of ultrarelativistic heavy ion collisions?
2014
We investigate the applicability of fluid dynamics in ultrarelativistic heavy ion (AA) collisions and high multiplicity proton nucleus (pA) collisions. In order for fluid dynamics to be applicable the microscopic and macroscopic distance/time scales of the system have to be sufficiently separated. The degree of separation is quantified by the ratio between these scales, usually referred to as the Knudsen number. In this work, we calculate the Knudsen numbers reached in fluid dynamical simulations of AA and pA collisions at RHIC and LHC energies. For this purpose, we consider different choices of shear viscosity parametrizations, initial states and initialization times. We then estimate the …
Statistical Modeling for the Flow of Short Fibers Composites
1994
Numerical results are given for the flow of fiber composites modelled as suspensions of non spherical particles. In this framework, because the many particles rotate, their state of orientation is described with a statistical approach. We used these methods to compute coupled solutions in which the orientation of the particles is affected by the flow and the flow itself depends on the orientation of the particles. The computation methods involve an augmented lagrangian approach and a streamline upwind petrov galerkin formulation to solve the convective orientation equation.
Application of the image processing methods for analysis of two-phase flow in turbomachinery
2007
The aim of this research is an application of digital image analysis for working out the method, which will allow to evaluate irregularity rate of two-phase flow across various geometry of tube bundle in aspect of the shell - and - tube heat exchanger optimization. Visualization of liquid flow in the shell — side enables an analysis of flow parameters by the use of image processing and analysis methods.
Equivalent continuum-based upscaling of flow in discrete fracture networks: The fracture-and-pipe model
2021
Abstract. Predicting effective permeabilities of fractured rock masses is a key component of reservoir modelling. This is often realized with the discrete fracture network (DFN) method, where single-phase incompressible fluid flow is modelled in discrete representations of individual fractures in a network. Depending on the overall number of fractures, this can result in significant computational costs. Equivalent continuum models (ECM) provide an alternative approach by subdividing the fracture network into a grid of continuous medium cells, over which hydraulic properties are averaged for fluid flow simulations. While this has the advantage of lower computational costs and the possibility…
Permeability and effective porosity of porous media
1997
The concept of permeability of porous media is discussed, and a modification of Kozeny’s permeability equation to include the effect of effective porosity is introduced. An analytical expression for the specific surface area of a system constructed of randomly placed identical obstacles with unrestricted overlap is derived, and a lattice-gas cellular automaton method is then used to simulate the dependence on porosity of permeability, tortuosity, and effective porosity for a flow of Newtonian uncompressible fluid in this two-dimensional porous substance. The simulated permeabilities can well be explained by the concept of effective porosity, and the exact form of the specific surface area. …
Neues zur Optomotorik der Insekten
1952
(1) It was shown that the optomotoric reaction of the ColeopteraCalandra oryzae is influenced by the existence of a stationary striped cylinder, placed inside the rotated cylinder.