Real-coded Lattice Gas Research Articles

A floor field real-coded lattice gas model for crowd evacuation

In this paper we present a modified real-coded lattice gas (RLG) model in which the floor field is introduced. The floor field is calculated on finer lattices in order to determine the pedestrians' direction accurately. Thus, the pedestrian's motion has many more degrees of freedom compared with existing discrete models. Furthermore, the walking speed is determined by the available space ahead of the pedestrians in a multi-step way. Therefore, the model can precisely describe the pedestrians' motion. Then, we calibrate model parameters by comparing with the existing measured data. Finally, we employ this model to investigate normal evacuation from a room. The conclusions are as follows: 1) In the single-exit room, for a given exit width larger than 0.6 m, the average specific flow increases with the initial number of pedestrians. For a given initial number of pedestrians, the specific flow increases first and then decreases when the width of the exit increases. 2) The evacuation time of the two-exit room is less than that of the single-exit room only when the total width is greater than 1.6 m.

Simulation for pedestrian dynamics by real-coded cellular automata (RCA)

In this paper, we propose a new approach for pedestrian dynamics. We call it a real-coded cellular automata (RCA). The scheme is based on the real-coded lattice gas (RLG), which has been developed for fluid simulation. Similar to RLG, the position and velocity can be freely given, independent of grid points. Our strategy including the procedure for updating the position of each pedestrian is explained. It is shown that the movement of pedestrians in an oblique direction to the grid is successfully simulated by RCA, which was not taken into account in the previous CA models. Moreover, from simulations of evacuation from a room with an exit of various widths, we obtain the critical number of people beyond which the clogging appears at the exit.

The modeling of colloidal fluids by the real-coded lattice gas

We model colloid-dispersed fluids using the real-coded lattice gas, in which colloidal particles are treated as hard spheres interacting with solvents of the lattice gas particles. We simulate the Brownian motion of a colloidal particle and compare its velocity distribution with that from the theoretical prediction. Both agree well showing that thermal fluctuation is naturally incorporated. We also measured the drag force acting on a colloidal particle and compare the drag coefficient with existing data. It is found that higher space and time resolutions are required in order to model the correct colloidal fluids interactions.

A mesoscopic simulation model for immiscible multiphase fluids

We introduce a new scheme for real-coded lattice gas to the numerical simulation of immiscible multiphase fluids. This scheme is based on a minimization principle. A numerical example demonstrates the spontaneous segregation of N-phase in two dimensions. Numerical studies on the surface tension between two fluids show a good agreement with Laplace’s law. The reproduction of Brownian motion for single droplet was verified through Maxwell–Boltzmann distribution of its velocity. A preliminary application illustrates a simulation of many immiscible droplets dispersed in another fluid.

実数型格子ガス法による直角分岐部におけるベシクル流れのシミュレーション(S24-2 バイオ・ナノ流動ダイナミクス(2),S24 バイオ・ナノ流動ダイナミクス)

実数型格子ガス法による直角分岐部におけるベシクル流れのシミュレーション(S24-2 バイオ・ナノ流動ダイナミクス(2),S24 バイオ・ナノ流動ダイナミクス)

On the density correlation of the spontaneous fluctuation in a real-coded lattice gas

We investigate the spontaneous fluctuation in a real-coded lattice gas (RLG) model by studying the density correlation function. In particular, the dynamic structure factor obtained from RLG is in agreement with the Rayleigh–Brillouin spectrum, a spectrum which can also be measured from a real fluid at the continuum limit. We also work out the analytic form of the static structure factor for the RLG model, which is supported by the numerical results.

217 実数格子ガス法を用いたコロイド流動系の数値解析

217 実数格子ガス法を用いたコロイド流動系の数値解析

Real-coded lattice gas model for ternary amphiphilic fluids.

We have developed an amphiphilic surfactant model in the framework of the real-coded lattice gas (RLG), in order to analyze the dynamics and structure of ternary fluids. Formation of both the oil-in-water and the bicontinuous microemulsion phases, as well as the reduction of surface tension by adsorption of surfactant at interface are successfully reproduced in numerical simulations. Our model is simple in terms of description and implementation, however, complex structures and dynamic behavior of the ternary fluids emerge from the collective dynamics of the RLG and surfactant particles.

Three-dimensional analyses of fluids with surfactants using the real-coded lattice gas method

We established a simulation model for the fluid-surfactant system, by introducing dumbbell-structured particles into the Real-Coded Lattice Gas (RLG), an efficient particle-based model for fluctuating hydrodynamics. Numerical simulations in 3D geometries were carried out. In particular, we successfully reproduced the spontaneous assembling of spherical micelles in an aqueous environment and the formation of bicontinuous phase in a water/oil/surfactant ternary fluid.

Single Phase and Binary Immiscible Fluid Flow in Porous Media Using the Real-coded Lattice Gas.

I have developed a model for porous media suitably implemented to the Real-coded Lattice Gas. In order to accurately detect collisions between moving particles and solid matrices, my model investigates the entire trajectories of moving particles. Behaviour of single phase fluids have been validated by the Darcy's Law. For binary immiscible fluids, the simulation results are in good agreement with the generalised Darcy's Law and the conventional LGA studies.

Development of a Simulation Model for Solid Objects Suspended in a Fluctuating Fluid

We introduce a new scheme for the future application of Real-coded Lattice Gas (RLG) to the numerical simulation of suspended solid objects in a fluctuating fluid environment. The reproduction of Brownian motion for a single solid object is verified through the Gaussian distribution of its displacements. The effectiveness of the solid–solid interaction model is also confirmed in an N-body simulation.

Development of a simulation model for solid objects suspended in a fluctuating fluid

We have been developing a new lattice gas model, a Real-coded Lattice Gas (RLG) method, in order to study complex fluid flows. In this study, we extend the RLG method in order to perform of the simulation of blood flows with individual descriptions of red blood cells. These topics are strongly related to clinical and medical engineering problems.

Equilibrium and Non-Equilibrium Analyses of Fluids with Surfactants: Real-Coded Lattice Gas Approach.

We modeled a surfactant by newly introducing a surfactant particle which represents amphiphilic interactions and incorporated it into the Real-Coded Lattice Gas (RLG 1)), a continuous lattice gas model for hydrodynamics in order to investigate equilibrium and non-equilibrium properties of fluids involving surfactants. We simulated formations of micelles in an aqueous environment and bicontinuous states in a water/oil/surfactant ternary environment. Simulations of a basic washing process are finally demonstrated to show the applicability of the model to analyses under non-equilibrium conditions.

Formation of micelle in the real-coded lattice gas

We extend the Real-Coded Lattice Gas (RLG), which is a continuous lattice gas model for hydrodynamics (Malevanets, 1997), to simulate a multi-phase system with surfactants. We modeled the surfactant as a dumbbell-shaped particle, consisting of a set of hydrophilic and hydrophobic ends, and a rigid rod connecting in between. Based on this model, we carried out simulations of micelle formations in an aqueous environment.

Immiscible real-coded lattice gas

The real-coded lattice gas method was proposed by Malevanets (1997). In this new lattice gas model, particles have continuous velocity distributions, which would yield to Maxwell–Boltzmann distribution in the equilibrium state. Furthermore, collision and streaming schemes do not depend on the explicit lattice structure. Extension to the three-dimensional calculation becomes straightforward both conceptually and practically. We extended this innovative model to the modeling of immiscible binary fluids by introducing colored particles and their interactions. Benchmark calculations show that Laplace law is satisfied in both 2D and 3D spaces. Simulations of phenomena occurring in the realistic immiscible binary fluids were carried out successfully. The model worked stably, and the qualitative agreement with the well-known droplet behavior has been observed.

548 実数格子ガス法を用いた界面活性剤による構造形成の数値解析

548 実数格子ガス法を用いた界面活性剤による構造形成の数値解析

界面活性剤を含む多相系の実数速度格子ガスモデル

We have developed an extended version of the Real-Coded Lattice Gas Method, in order to simulate behaviors of multi-phase systems with surfactants. We characterized surfactants by dumbbell-shaped particles, composed by sets of hydrophilic ends and hydrophobic ends connected by rigid rods. By adopting our model, we conducted simulations of micelle formations by surfactants in an aqueous environment. In the simulations, our model provided significant results which reflect some of the properties of actual micelle structures.