SCALING BEHAVIOUR OF A MULTIPLY CONNECTED FLUCTUATING INTERFACE IN TWO DIMENSIONS

Fractals ◽  
2003 ◽  
Vol 11 (supp01) ◽  
pp. 227-232
Author(s):  
AYŞE ERZAN ◽  
HÜSEY.IN KAYA ◽  
ALKAN KABAKÇIOĞLU
Keyword(s):  
Kinetic Model ◽  
Numerical Simulations ◽  
Average Velocity ◽  
Two Dimensions ◽  
Scaling Exponents ◽  
Multiply Connected ◽  
Fractal Set ◽  
Scaling Behaviour ◽  
Infinite String

We consider a one-parameter kinetic model for a fluctuating interface which can be thought of as an infinite string decorated with infinitely many closed strings. Numerical simulations show that a number of scaling exponents describing this string system may be related to the Kardar-Parisi-Zhang exponents. However, as the average velocity of the infinite string is taken to zero, and the string system becomes an isotropic fractal set, we also find new exponents which cannot be reduced to previously known ones.

Direct numerical simulations of Rayleigh–Bénard convection in water with non-Oberbeck–Boussinesq effects

2019 ◽  
Vol 881 ◽  
pp. 1073-1096 ◽  
Author(s):  
Andreas D. Demou ◽  
Dimokratis G. E. Grigoriadis
Keyword(s):  
Numerical Simulations ◽  
Two Dimensions ◽  
Direct Numerical Simulations ◽  
Wall Region ◽  
Number Range ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Near Wall

Rayleigh–Bénard convection in water is studied by means of direct numerical simulations, taking into account the variation of properties. The simulations considered a three-dimensional (3-D) cavity with a square cross-section and its two-dimensional (2-D) equivalent, covering a Rayleigh number range of $10^{6}\leqslant Ra\leqslant 10^{9}$ and using temperature differences up to 60 K. The main objectives of this study are (i) to investigate and report differences obtained by 2-D and 3-D simulations and (ii) to provide a first appreciation of the non-Oberbeck–Boussinesq (NOB) effects on the near-wall time-averaged and root-mean-squared (r.m.s.) temperature fields. The Nusselt number and the thermal boundary layer thickness exhibit the most pronounced differences when calculated in two dimensions and three dimensions, even though the $Ra$ scaling exponents are similar. These differences are closely related to the modification of the large-scale circulation pattern and become less pronounced when the NOB values are normalised with the respective Oberbeck–Boussinesq (OB) values. It is also demonstrated that NOB effects modify the near-wall temperature statistics, promoting the breaking of the top–bottom symmetry which characterises the OB approximation. The most prominent NOB effect in the near-wall region is the modification of the maximum r.m.s. values of temperature, which are found to increase at the top and decrease at the bottom of the cavity.

SPH Numerical Simulations of the Deformation of a Liquid Surface in Two Dimensions

2019 ◽  
pp. 63-75
Author(s):  
Cristian Cáliz-Reyes ◽  
Laura A. Ibarra-Bracamontes ◽  
Rosanna Bonasia ◽  
Gonzalo Viramontes-Gamboa
Keyword(s):  
Numerical Simulations ◽  
Liquid Surface ◽  
Two Dimensions

scholarly journals Seismic stimulation for enhanced oil recovery

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. O23-O35 ◽  
Author(s):  
Steven R. Pride ◽  
Eirik G. Flekkøy ◽  
Olav Aursjø
Keyword(s):  
Pressure Gradient ◽  
Numerical Simulations ◽  
Oil Recovery ◽  
Scale Effects ◽  
Fluid Pressure ◽  
Oil Production ◽  
Two Dimensions ◽  
Lattice Boltzmann Model ◽  
Pore Scale ◽  
Capillary Barriers

The pore-scale effects of seismic stimulation on two-phase flow are modeled numerically in random 2D grain-pack geometries. Seismic stimulation aims to enhance oil production by sending seismic waves across a reservoir to liberate immobile patches of oil. For seismic amplitudes above a well-defined (analytically expressed) dimensionless criterion, the force perturbation associated with the waves indeed can liberate oil trapped on capillary barriers and get it flowing again under the background pressure gradient. Subsequent coalescence of the freed oil droplets acts to enhance oil movement further because longer bubbles overcome capillary barriers more efficiently than shorter bubbles do. Poroelasticity theory defines the effective force that a seismic wave adds to the background fluid-pressure gradient. The lattice-Boltzmann model in two dimensions is used to perform pore-scale numerical simulations. Dimensionless numbers (groups of material and force parameters) involved in seismic stimulation were defined carefully so that numerical simulations could be applied to field-scale conditions. Using defined analytical criteria, there is a significant range of reservoir conditions over which seismic stimulation can be expected to enhance oil production.

A Voronoi Cell Material Point Method for Large Deformation Solid Mechanics Problems

2016 ◽  
Vol 846 ◽  
pp. 108-113
Author(s):  
Vinh Phu Nguyen ◽  
Giang Dinh Nguyen
Keyword(s):  
Numerical Simulations ◽  
Solid Mechanics ◽  
Impact Damage ◽  
Voronoi Cell ◽  
Material Point ◽  
Two Dimensions ◽  
Point Method ◽  
Particle Methods ◽  
Contact Impact ◽  
Polygonal Particle

Particle methods have been increasingly used in numerical simulations of complex problemsin both sciences and engineering. A plethora of different particle methods exists of which thematerial point method (MPM) is a promising method that is able to deal with high strain rate problemsthat involve contact, impact, damage and fragmentation. Particle domains in the MPM are currentlyrepresented by quadrilaterals in two dimensions. Extension to polygonal particle domains is presentedbased on a simple sub-division of the polygons into sub-triangles. This allows MPM simulations tobe carried out for structures and materials discretized by Voronoi tessellations. Performances of theproposed method are illustrated by means of numerical simulations.

Two-Dimensional Linear Friction Damper Consisting of Concave Cone and Cylindrical Member (Investigation of Performance by Numerical Simulation and Experiment)

2015 ◽  
Author(s):  
Hideya Yamaguchi ◽  
Hidehisa Yoshida
Keyword(s):  
Numerical Simulations ◽  
Friction Force ◽  
Vibration Isolation ◽  
Two Dimensions ◽  
Resonant Peak ◽  
Friction Damper ◽  
Isolation System ◽  
Friction Forces ◽  
Vibration Isolation System ◽  
Linear Friction

A passive vibration isolation system consisting of a constant friction force has performance limitations; the isolation performance declines and the residual displacement becomes large in the case of the large friction force, while the resonant peak becomes large in the case of the small friction force. It is known that above drawbacks are avoidable when the friction force varies in proportion to the relative displacement. Recently, authors have proposed a simple linear friction damper mechanism that consists of a cylindrical block and a tilt lever supported with a pivot or a leaf spring. Performance of the vibration isolation system equipped with the proposed damper is investigated, and its effectiveness is confirmed by numerical simulations and the experiments. However, the motion of the mechanism is limited to one-dimension. This paper proposes an extended mechanism that can be applied to motion moving in two dimensions by combining the concave cone and the cylindrical member. The concave cone is supported with a universal joint on the apex side and its tilting motion is constrained by the restoring spring. The rounded edge of the cylindrical member is set up to contact the inside flank of the concave cone. When the cylindrical member moves in an arbitrary direction on the planar floor and pushes the concave cone, the normal and friction forces at the contact point vary depending on the displacement of the cylindrical member. The fundamental property and the performance of the proposed mechanism are investigated by numerical simulations and experiments.

scholarly journals Transport of a dilute active suspension in pressure-driven channel flow

2015 ◽  
Vol 777 ◽  
pp. 482-522 ◽  
Author(s):  
Barath Ezhilan ◽  
David Saintillan
Keyword(s):  
Distribution Function ◽  
Kinetic Model ◽  
Numerical Simulations ◽  
Persistence Length ◽  
Conservation Equation ◽  
Depletion Layer ◽  
Hydrodynamic Interactions ◽  
Kinematic Effect ◽  
Flow Limit ◽  
Pressure Driven

Confined suspensions of active particles show peculiar dynamics characterized by wall accumulation, as well as upstream swimming, centreline depletion and shear trapping when a pressure-driven flow is imposed. We use theory and numerical simulations to investigate the effects of confinement and non-uniform shear on the dynamics of a dilute suspension of Brownian active swimmers by incorporating a detailed treatment of boundary conditions within a simple kinetic model where the configuration of the suspension is described using a conservation equation for the probability distribution function of particle positions and orientations, and where particle–particle and particle–wall hydrodynamic interactions are neglected. Based on this model, we first investigate the effects of confinement in the absence of flow, in which case the dynamics is governed by a swimming Péclet number, or ratio of the persistence length of particle trajectories over the channel width, and a second swimmer-specific parameter whose inverse measures the strength of propulsion. In the limit of weak and strong propulsion, asymptotic expressions for the full distribution function are derived. For finite propulsion, analytical expressions for the concentration and polarization profiles are also obtained using a truncated moment expansion of the distribution function. In agreement with experimental observations, the existence of a concentration/polarization boundary layer in wide channels is reported and characterized, suggesting that wall accumulation in active suspensions is primarily a kinematic effect that does not require hydrodynamic interactions. Next, we show that application of a pressure-driven Poiseuille flow leads to net upstream swimming of the particles relative to the flow, and an analytical expression for the mean upstream velocity is derived in the weak-flow limit. In stronger imposed flows, we also predict the formation of a depletion layer near the channel centreline, due to cross-streamline migration of the swimming particles towards high-shear regions where they become trapped, and an asymptotic analysis in the strong-flow limit is used to obtain a scale for the depletion layer thickness and to rationalize the non-monotonic dependence of the intensity of depletion upon flow rate. Our theoretical predictions are all shown to be in excellent agreement with finite-volume numerical simulations of the kinetic model, and are also supported by recent experiments on bacterial suspensions in microfluidic devices.

Sign in / Sign up

Export Citation Format

Share Document