Molecular Dynamics Simulations on Internal Structures of Normal Shock Waves in Lennard-Jones Liquids

1995 ◽  
Vol 117 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Akira Satoh
Keyword(s):  
Molecular Dynamics ◽  
Boundary Condition ◽  
Mach Number ◽  
Shock Waves ◽  
Molecular Dynamics Simulations ◽  
Normal Shock ◽  
Lennard Jones ◽  
Internal Structures ◽  
Dynamics Simulations ◽  
Shock Fronts

The present paper describes a highly efficient method for simulating the generation of shock waves in liquids by using the periodic-shell boundary condition, which is an outer boundary condition for molecular dynamics simulations. This method is used to simulate normal shock waves in Lennard-Jones liquids, clarifying the internal structures of shock fronts and the dependence of shock thicknesses on the shock Mach number. The present method significantly decreases computation times because it enables us to simulate only the shock fronts. Some of the main results derived by these simulations of molecular dynamics are that an overshoot in the profile of longitudinal temperature arises in liquid shock waves as well as in gas shock waves, that the thickness of shock front decreases with increasing Mach number, and that this thickness is about two times the diameter of molecules when the Mach number is 4.

Rankine-Hugoniot Relations for Lennard-Jones Liquids

1994 ◽  
Vol 116 (3) ◽  
pp. 625-630 ◽  
Author(s):  
Akira Satoh
Keyword(s):  
Shock Waves ◽  
Ideal Gas ◽  
The State ◽  
Lennard Jones ◽  
Internal Structures ◽  
Shock Mach Number ◽  
Basic Equations ◽  
Dynamics Simulations ◽  
Approximate Expressions ◽  
Shock Fronts

The purpose of the present study is to clarify the Rankine-Hugoniot relations for Lennard-Jones liquids. First, Monte Carlo simulations are conducted to evaluate the state quantities such as the pressures, the internal energies, and the sound velocities. These computed values are used to obtain the approximate expressions for the state quantities by the method of least squares. The Rankine-Hugoniot relations are then clarified numerically as a function of the shock Mach number by solving the basic equations together with those approximate expressions. For liquid shock waves, not only the pressure but also the temperature increases much larger than those for an ideal gas. The results obtained here enable us to conduct more efficient molecular dynamics simulations such as simulating shock fronts alone for the investigation of the internal structures of liquid shock waves.

scholarly journals Shear-rate dependence of thermodynamic properties of the Lennard-Jones truncated and shifted fluid by molecular dynamics simulations

2021 ◽  
Author(s):  
Martin P. Lautenschlaeger ◽  
Hans Hasse
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Shear Rate ◽  
Molecular Dynamics Simulations ◽  
Local Structure ◽  
Rate Dependence ◽  
Lennard Jones ◽  
Fluid Properties ◽  
Dynamics Simulations ◽  
Shear Rate Dependence

It was shown recently that using the two-gradient method, thermal, caloric, and transport properties of fluids under quasi-equilibrium conditions can be determined simultaneously from nonequilibrium molecular dynamics simulations. It is shown here that the influence of shear stresses on these properties can also be studied using the same method. The studied fluid is described by the Lennard-Jones truncated and shifted potential with the cut-off radius r*c = 2.5σ. For a given temperature T and density ρ, the influence of the shear rate on the following fluid properties is determined: pressure p, internal energy u, enthalpy h, isobaric heat capacity cp, thermal expansion coefficient αp, shear viscosity η, and self-diffusion coefficient D. Data for 27 state points in the range of T ∈ [0.7, 8.0] and ρ ∈ [0.3, 1.0] are reported for five different shear rates (γ ̇ ∈ [0.1,1.0]). Correlations for all properties are provided and compared with literature data. An influence of the shear stress on the fluid properties was found only for states with low temperature and high density. The shear-rate dependence is caused by changes in the local structure of the fluid which were also investigated in the present work. A criterion for identifying the regions in which a given shear stress has an influence on the fluid properties was developed. It is based on information on the local structure of the fluid. For the self-diffusivity, shear-induced anisotropic effects were observed and are discussed.

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