Search results for "Fluid Dynamic"
showing 10 items of 1034 documents
Lagrangian finite element modelling of dam–fluid interaction: Accurate absorbing boundary conditions
2007
The dynamic dam-fluid interaction is considered via a Lagrangian approach, based on a fluid finite element (FE) model under the assumption of small displacement and inviscid fluid. The fluid domain is discretized by enhanced displacement-based finite elements, which can be considered an evolution of those derived from the pioneering works of Bathe and Hahn [Bathe KJ, Hahn WF. On transient analysis of fluid-structure system. Comp Struct 1979;10:383-93] and of Wilson and Khalvati [Wilson EL, Khalvati M. Finite element for the dynamic analysis of fluid-solid system. Int J Numer Methods Eng 1983;19:1657-68]. The irrotational condition for inviscid fluids is imposed by the penalty method and con…
Generalized Fatigue Criterion of maximum shear and normal strains on the fracture plane for materials under multiaxial random loadings
1991
A generalized fatigue criterion for materials under multiaxial random loadings is presented. The criterion is based on the assumption that shear and normal strain on the expected fracture plane – shear strain in one direction on this plane is considered – determine the fracture plane. It has been shown that the well known fatigue criteria of maximum normal strain, maximum shear strain and the criterion of maximum shear and normal strains on the critical shear plane result from the newly formulated criterion.
Residence Time Analysis in the Albufera of Valencia, a Mediterranean Coastal Lagoon, Spain
2021
The Albufera of Valencia is a coastal lagoon located in the western area of the Mediterranean Sea, in the Iberian Peninsula. It has an area of 23.1 km2 and an average depth of only 1 m, with a maximum depth of 1.6 m. This lagoon is the remnants of an original and more extensive wetland of about 220 km2 which is now mostly dedicated to rice cultivation. Surface water is supplied through several main and many secondary canals for a total of 64 water entry points and three exit points to the sea. It is difficult to evaluate the residence time due to the lack of reliable measurements of the inflow or outflow, as well as continuous measurements. Between 1988 and 2018, several procedures were use…
Evidence of thin-film precursors formation in hydrokinetic and atomistic simulations of nano-channel capillary filling
2008
We present hydrokinetic Lattice Boltzmann and Molecular Dynamics simulations of capillary filling of high-wetting fluids in nano-channels, which provide clear evidence of the formation of thin precursor films, moving ahead of the main capillary front. The dynamics of the precursor films is found to obey the Lucas-Washburn law as the main capillary front, z2(t) proportional to t, although with a larger prefactor, which we find to take the same value for both geometries under inspection. Both hydrokinetic and Molecular Dynamics approaches indicate a precursor film thickness of the order of one tenth of the capillary diameter. The quantitative agreement between the hydrokinetic and atomistic m…
Large-Eddy Simulation of Turbulent Flow and Heat Transfer in Plane and Rib-Roughened Channels
1992
Large-eddy simulation results are presented and discussed for turbulent flow and heat transfer in a plane channel with and without transverse square ribs on one of the walls. They were obtained with the finite-difference code Harwell-FLOW3D, Release 2, by using the PISOC pressure-velocity coupling algorithm, central differencing in space, and Crank-Nicolson time stepping. A simple Smagorinsky model, with van Driest damping near the walls, was implemented to model subgrid scale effects. Periodic boundary conditions were imposed in the streamwise and spanwise directions. The Reynolds number based on hydraulic diameter (twice the channel height) ranged from 10 000 to 40 000. Results are compar…
Experimental analysis of cross-sectional flow motion in a large amplitude meandering bend
2010
Flow in meandering bends is characterized by the formation of a large cross-sectional central-region circulation cell. The width-to-depth ratio is one of the most important parameters affecting the entity of the cross-circulation motion. In steep outside bends, beside the central-region cell, a counter-rotating circulation cell often forms in the upper part of the outer-bank. In spite of its practical importance, the evolving mechanisms of both the circulation cells and their role on boundary shear stress distribution in bends are not yet fully understood. The aim of the present paper is to gain some insight into how cross-sectional flow motion evolves along meandering bends. Experiments ha…
Experimental Analysis of Horizontal Turbulence of Flow over Flat and Deformed Beds
2015
Abstract Laboratory experiments in a straight flume were carried out to examine the evolution of large-scale horizontal turbulent structures under flat-bed and deformed-bed conditions. In this paper, the horizontal turbulence of flow under these conditions is analyzed and compared. The conditioned quadrant method is applied to verify the occurrence of turbulent events. The distributions of horizontal Reynolds shear stress and turbulent kinetic energy are also presented and discussed. Results show the occurrence of an “initial” sequence of horizontal vortices whose average spatial length scales with the channel width. Under deformed-bed conditions, this spatial length does not change.
Computational modeling and experimental characterization of fluid dynamics in micro-CT scanned scaffolds within a multiple-sample airlift perfusion b…
2023
The perfusion of flow during cell culture induces cell proliferation and enhances cellular activity. Perfusion bioreactors offer a controlled dynamic environment for reliable in vitro applications in the tissue engineering field. In this work, to evaluate the effects of the operating parameters of a custom-made bioreactor, numerical simulations were performed to solve the fluid velocity profile inside the bioreactor containing multi-grid support that allows allocating of multiple seeded scaffolds at the same time. The perfusion system exhibited a uniform distribution of liquid velocities within the regions, suitable for cell growth on seeded scaffolds. The effects of the porous microstructu…
Magnetic wire-based sensors for the micro-rheology of complex fluids
2013
We propose a simple micro-rheology technique to evaluate the viscoelastic properties of complex fluids. The method is based on the use of magnetic wires of a few microns in length submitted to a rotational magnetic field. In this work, the method is implemented on a surfactant wormlike micellar solution that behaves as an ideal Maxwell fluid. With increasing frequency, the wires undergo a transition between a steady and a hindered rotation regime. The study shows that the average rotational velocity and the amplitudes of the oscillations obey scaling laws with well-defined exponents. From a comparison between model predictions and experiments, the rheological parameters of the fluid are det…
An efficient dissipative particle dynamics-based algorithm for simulating electrolyte solutions
2015
We propose an efficient simulation algorithm based on the dissipative particle dynamics (DPD) method for studying electrohydrodynamic phenomena in electrolyte fluids. The fluid flow is mimicked with DPD particles while the evolution of the concentration of the ionic species is described using Brownian pseudo particles. The method is designed especially for systems with high salt concentrations, as explicit treatment of the salt ions becomes computationally expensive. For illustration, we apply the method to electro-osmotic flow over patterned, superhydrophobic surfaces. The results are in good agreement with recent theoretical predictions.