scholarly journals Hydrodynamic and Thermodynamic Nonequilibrium Effects around Shock Waves: Based on a Discrete Boltzmann Method

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1397
Author(s):  
Chuandong Lin ◽  
Xianli Su ◽  
Yudong Zhang
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Local Equilibrium ◽  
Nonequilibrium Statistical Mechanics ◽  
Three Dimensional ◽  
Distribution Functions ◽  
Velocity Distribution Functions ◽  
Nonequilibrium Effects ◽  
Boltzmann Method ◽  
Boltzmann Model

A shock wave that is characterized by sharp physical gradients always draws the medium out of equilibrium. In this work, both hydrodynamic and thermodynamic nonequilibrium effects around the shock wave are investigated using a discrete Boltzmann model. Via Chapman–Enskog analysis, the local equilibrium and nonequilibrium velocity distribution functions in one-, two-, and three-dimensional velocity space are recovered across the shock wave. Besides, the absolute and relative deviation degrees are defined in order to describe the departure of the fluid system from the equilibrium state. The local and global nonequilibrium effects, nonorganized energy, and nonorganized energy flux are also investigated. Moreover, the impacts of the relaxation frequency, Mach number, thermal conductivity, viscosity, and the specific heat ratio on the nonequilibrium behaviours around shock waves are studied. This work is helpful for a deeper understanding of the fine structures of shock wave and nonequilibrium statistical mechanics.

Modeling of collapsing cavitation bubble near solid wall by 3D pseudopotential multi-relaxation-time lattice Boltzmann method

2017 ◽  
Vol 232 (3) ◽  
pp. 445-456 ◽  
Author(s):  
Minglei Shan ◽  
Yu Yang ◽  
Hao Peng ◽  
Qingbang Han ◽  
Changping Zhu
Keyword(s):  
Relaxation Time ◽  
Lattice Boltzmann ◽  
Cavitation Bubble ◽  
Solid Wall ◽  
Three Dimensional ◽  
Lattice Boltzmann Model ◽  
Bubble Collapse ◽  
Lattice Boltzmann Simulation ◽  
Boltzmann Method ◽  
Boltzmann Model

Understanding the dynamic characteristic of the cavitation bubble near a solid wall is a fundamental issue for the bubble collapse application and prevention. In the present work, an improved three-dimensional multi-relaxation-time pseudopotential lattice Boltzmann model is adopted to investigate the cavitation bubble collapse near the solid wall. With respect to thermodynamic consistency, Laplace law verification, the three-dimensional pseudopotential multi-relaxation-time lattice Boltzmann model is investigated. By the theoretical analysis, it is proved that the model can be regarded as a solver of the Rayleigh–Plesset equation, and confirmed by comparing the results of the lattice Boltzmann simulation and the Rayleigh–Plesset equation calculation for the case of cavitation bubble collapse in the infinite medium field. The bubble collapse near the solid wall is modeled using the improved pseudopotential multi-relaxation-time lattice Boltzmann model. We find the lattice Boltzmann simulation and the experimental results have the same dynamic process by comparing the bubble profiles evolution. Form the pressure field and the velocity field evolution it is found that the tapered higher pressure region formed near the top of the bubble is a crucial driving force inducing the bubble collapse. This exploratory research demonstrates that the lattice Boltzmann method is an alternative tool for the study of the interaction between collapsing cavitation bubble and matter.

scholarly journals Observations of diffusion in the electron halo and strahl

2016 ◽  
Vol 34 (12) ◽  
pp. 1175-1189 ◽  
Author(s):  
Chris Gurgiolo ◽  
Melvyn L. Goldstein
Keyword(s):  
Magnetic Field ◽  
Energy Range ◽  
Lower Energy ◽  
Three Dimensional ◽  
Distribution Functions ◽  
Electron Velocity ◽  
Electron Velocity Distribution ◽  
Velocity Distribution Functions ◽  
The Magnetic Field ◽  
Solar Wind Electron

Abstract. Observations of the three-dimensional solar wind electron velocity distribution functions (VDF) using ϕ–θ plots often show a tongue of electrons that begins at the strahl and stretches toward a new population of electrons, termed the proto-halo, that exists near the projection of the magnetic field opposite that associated with the strahl. The energy range in which the tongue and proto-halo are observed forms a “diffusion zone”. The tongue first appears in energy generally near the lower-energy range of the strahl and in the absence of any clear core/halo signature. While the ϕ–θ plots give the appearance that the tongue and proto-halo are derived from the strahl, a close examination of their density suggests that their source is probably the upper-energy core/halo electrons which have been scattered by one or more processes into these populations.

Origins and Evolution of the Electron and Ion Populations of the Magnetopause’s Boundary Layers

2020 ◽  
Author(s):  
Jean Berchem ◽  
Giovanni Lapenta ◽  
Robert Richard ◽  
William Paterson ◽  
C. Philippe Escoubet
Keyword(s):  
Boundary Layers ◽  
Three Dimensional ◽  
Distribution Functions ◽  
Current Layer ◽  
Filamentary Structure ◽  
Particle In Cell ◽  
Reconnection Region ◽  
Dayside Magnetopause ◽  
Velocity Distribution Functions ◽  
Multiscale Structures

<p>Increasingly sophisticated instruments and simulations have revealed a wide variety of plasma processes and multiscale structures at the dayside magnetopause. In this presentation, we focus on the origins and evolution of the plasma populations observed in the magnetopause boundary layers. We present the results of Particle-In-Cell (PIC) simulations encompassing large volumes of the dayside magnetosphere. The implicit 3D PIC code used in the study was initialized from a global MHD state of the magnetosphere for southward interplanetary field conditions.  Three-dimensional plots of the perpendicular slippage indicates that reconnection occurs over most of the dayside magnetopause. However, the simulation reveals that the reconnection region has a much more filamentary structure than the X-line expected from the extrapolation of 2D models and that multiscale structures thread the reconnection outflow. In particular, the simulation indicates the formation of multiple layers of electrons with significant field-aligned velocities along the main magnetopause current layer. We use velocity distribution functions at different locations in the reconnection outflow to characterize the origins and evolution of the electron and ionpopulations of the magnetosheath and magnetospheric boundary layers and compare them with observations from the MMS and Cluster spacecraft.</p>

SLIP ON CURVED BOUNDARIES IN THE LATTICE BOLTZMANN MODEL

2007 ◽  
Vol 18 (01) ◽  
pp. 15-24 ◽  
Author(s):  
LAJOS SZALMÁS
Keyword(s):  
Couette Flow ◽  
Lattice Boltzmann ◽  
Slip Flow ◽  
Distribution Functions ◽  
Lattice Boltzmann Model ◽  
Momentum Balance ◽  
Curved Boundaries ◽  
Cylindrical Couette Flow ◽  
Boltzmann Method ◽  
Boltzmann Model

We present a new boundary condition in the lattice Boltzmann method to model slip flow along curved boundaries. A requirement is formulated for the distribution functions based on the tunable momentum balance at the walls, which is shown to be equivalent to the constraint on the second moment. Numerical simulation of plane Couette flow in inclined channels and cylindrical Couette flow shows excellent agreement with the analytical results in the nearly continuum regime. Orientation effects on the velocity field are completely avoided.

SIMULATION OF SHOCK-WAVE PROPAGATION WITH FINITE VOLUME LATTICE BOLTZMANN METHOD

2007 ◽  
Vol 18 (04) ◽  
pp. 447-454 ◽  
Author(s):  
KUN QU ◽  
CHANG SHU ◽  
YONG TIAN CHEW
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Lattice Boltzmann Method ◽  
Finite Volume ◽  
Lattice Boltzmann ◽  
Compressible Flows ◽  
Distribution Functions ◽  
Shock Wave Propagation ◽  
Simple Function ◽  
Boltzmann Method

A new approach was recently proposed to construct equilibrium distribution functions [Formula: see text] of the lattice Boltzmann method for simulation of compressible flows. In this approach, the Maxwellian function is replaced by a simple function which satisfies all needed relations to recover compressible Euler equations. With Lagrangian interpolation polynomials, the simple function is discretized onto a fixed velocity pattern to construct [Formula: see text]. In this paper, the finite volume method is combined with the new lattice Boltzmann models to simulate 1D and 2D shock-wave propagation. The numerical results agree well with available data in the literatures.

A numerical study of droplet dynamic behaviors on a micro-structured surface using a three dimensional color-gradient lattice Boltzmann model

Soft Matter ◽  
2018 ◽  
Vol 14 (5) ◽  
pp. 837-847 ◽  
Author(s):  
Zihao Cheng ◽  
Yan Ba ◽  
Jinju Sun ◽  
Chao Wang ◽  
Shengchuan Cai ◽  
...  
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Numerical Study ◽  
Three Dimensional ◽  
Lattice Boltzmann Model ◽  
Dynamic Behaviors ◽  
Structured Surfaces ◽  
Color Gradient ◽  
Boltzmann Method ◽  
Boltzmann Model

Non-circular droplet contact areas on micro-structured surfaces are simulated using the lattice Boltzmann method.

Numerical Simulations on Hydrodynamic Process of Melt Jet Breakup and Fragmentation With the Two-Phase Lattice Boltzmann Method

2018 ◽  
Author(s):  
Shimpei Saito ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Alessandro De Rosis ◽  
Alessio Festuccia ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Lattice Boltzmann ◽  
Present Model ◽  
Three Dimensional ◽  
Lattice Boltzmann Model ◽  
Hydrodynamic Process ◽  
Two Phase ◽  
Jet Breakup ◽  
Boltzmann Method ◽  
Boltzmann Model

Jet breakup and fragmentation are important phenomena to be well understood during a core-disruptive accident of sodium-cooled fast reactors. The three-dimensional two-phase lattice Boltzmann model developed previously by the authors is improved in numerical stability used to simulate the hydrodynamic process of melt jet breakup. Nonorthogonal central moments is successfully introduced into the model. Numerical simulations of FARO-TERMOS experiments demonstrate the enhancements in stability of the present model. The simulations with two types of grid resolutions show the effect of spatial resolution on the results.

Sign in / Sign up

Export Citation Format

Share Document