Calculating High-Pressure PAO4 Viscosity with Equilibrium Molecular Dynamics Simulations

IF 2.9 3区工程技术 Q2 ENGINEERING, CHEMICAL Tribology Letters Pub Date : 2024-03-12 DOI:10.1007/s11249-024-01835-7

Lars B. Kruse, Kerstin Falk, Michael Moseler

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Abstract

The development of optimized lubricants is hindered by missing knowledge of fluid properties, in particular the viscosity, in the range of extreme pressures and temperatures relevant for application. Molecular dynamics simulations can be used to calculate viscosity, but the necessary computational effort imposes practical limits for high viscosities. In this study, the viscosity of PAO4 oil was extracted from equilibrium molecular dynamics simulations as a function of pressure and temperature reaching viscosities up to 20 Pas. Three calculation methods based on different microscopic expressions for the viscosity were used. The methods exhibit considerably different performance with respect to preciseness and computational efficiency. The highest viscosities were found to be calculated most efficiently via the Stokes–Einstein relation, by computing the diffusion coefficient from the velocity correlation function. This offers a new, more effective route to push viscosity calculations in equilibrium molecular dynamics simulations to higher pressure systems.

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利用平衡分子动力学模拟计算高压 PAO4 粘度

由于缺乏与应用相关的极端压力和温度范围内的流体特性，特别是粘度方面的知识，优化润滑剂的开发工作受到了阻碍。分子动力学模拟可用于计算粘度，但对于高粘度而言，必要的计算量会造成实际限制。在本研究中，从平衡分子动力学模拟中提取了 PAO4 油的粘度与压力和温度的函数关系，粘度最高可达 20 Pas。使用了三种基于不同粘度微观表达式的计算方法。这些方法在精确度和计算效率方面表现出相当大的差异。通过速度相关函数计算扩散系数，发现通过斯托克斯-爱因斯坦关系计算最高粘度最有效。这为将平衡分子动力学模拟中的粘度计算推向更高的压力系统提供了一条新的、更有效的途径。

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来源期刊

Tribology Letters 工程技术-工程：化工

CiteScore

5.30

自引率

9.40%

发文量

116

审稿时长

2.5 months

期刊介绍： Tribology Letters is devoted to the development of the science of tribology and its applications, particularly focusing on publishing high-quality papers at the forefront of tribological science and that address the fundamentals of friction, lubrication, wear, or adhesion. The journal facilitates communication and exchange of seminal ideas among thousands of practitioners who are engaged worldwide in the pursuit of tribology-based science and technology.