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DSMC Simulation of Vapor Transport Near an Evaporating Liquid Vapor Interface

Institute
Lehrstuhl für Thermodynamik (TUM-ED)
Type
Master's Thesis /
Content
 
Description

Background

Where do molecules go after leaving an evaporating liquid surface? This simple question is at the heart of many evaporation processes, but it is difficult to answer experimentally.

Under reduced pressure, vapor molecules may travel a relatively long distance before colliding with other molecules. In this case, the vapor near the interface may no longer behave like a simple continuum gas. Instead, molecular motion, collisions, and nonequilibrium effects can influence the local temperature, density, velocity distribution, and heat flux.

Understanding this process is important for both fundamental research and engineering applications. It helps explain how evaporation really occurs at the molecular scale, while also supporting the development of technologies involving phase change, such as advanced cooling, water purification, steam generation, and vacuum based thermal systems. Direct Simulation Monte Carlo (DSMC) provides a suitable numerical approach to investigate this molecular vapor transport and to support the interpretation of evaporation experiments.

 

Objectives

This project aims to perform systematic DSMC simulations of vapor transport near an evaporating liquid vapor interface to:

  • Build a simplified DSMC model of the vapor region above an evaporating liquid surface.
  • Simulate vapor transport under selected pressure, temperature, and evaporation conditions.
  • Calculate vapor temperature, density, velocity distribution, and heat flux profiles near the interface.
  • Evaluate the characteristic length scale of nonequilibrium effects near the liquid vapor interface.
  • Investigate how vapor side transport affects the interpretation of experimentally measured temperature profiles.
  • Compare DSMC simulation trends with available experimental observations.
  • Assess the sensitivity of the vapor side transport behavior to pressure, boundary conditions, and evaporation rate.

 

Methods

  • Primary software: SPARTA DSMC simulator.
  • Alternative tools: Python or MATLAB for preprocessing, postprocessing, and visualization.

The project will start from a simplified one dimensional or two dimensional vapor domain. Basic evaporation boundary conditions will be tested first, followed by selected cases based on experimental pressure and temperature conditions.

Depending on the progress of the project, AI assisted postprocessing or simple surrogate modeling may be explored to identify dominant trends, smooth statistical fluctuations in DSMC data, and accelerate selected parameter studies.

 

References

  • Evaporation kinetics and engineering relevance:
  1. Lu, Z., Kinefuchi, I., Wilke, K. L., Vaartstra, G., & Wang, E. N. (2019). A unified relationship for evaporation kinetics at low Mach numbers. Nature Communications, 10, 2368. doi.org/10.1038/s41467-019-10209-w
  • Experimental observation of temperature jump during evaporation:
  1. Badam, V. K., Kumar, V., Durst, F., & Danov, K. (2007). Experimental and theoretical investigations on interfacial temperature jumps during evaporation. Experimental Thermal and Fluid Science, 32(1), 276–292. doi.org/10.1016/j.expthermflusci.2007.04.006
  2. Gatapova, E. Y. (2024). Evaporation into half-space: Experiments with water at the molecular mean free path scale. Physics of Fluids, 36(9), 091707. doi.org/10.1063/5.0228893
  • DSMC simulation of liquid vapor transport:
  1. Frezzotti, A., Barbante, P., & Gibelli, L. (2019). Direct simulation Monte Carlo applications to liquid-vapor flows. Physics of Fluids, 31, 062103. https://doi.org/10.1063/1.5097738
  2. Graur, I. A., Gatapova, E. Y., Wolf, M. C. W., & Batueva, M. A. (2021). Non-equilibrium evaporation: 1D benchmark problem for single gas. International Journal of Heat and Mass Transfer, 181, 121997. https://doi.org/10.1016/j.ijheatmasstransfer.2021.121997
Requirements
  • MSc student in Mechanical Engineering, Physics, Aerospace Engineering, Energy Engineering, or related field
  • Basic familiarity with thermodynamics, kinetic theory, or gas dynamics
  • Strong interest in interfacial evaporation, molecular transport, and heat and mass transfer
  • Experience with Linux, WSL, Python, MATLAB, or similar tools
  • Prior exposure to DSMC, molecular simulation, numerical methods, or data analysis is a plus, but not required
Possible start
immediately
Contact
M.Sc. Wenxuan Pu
Room: 5507.EG.703
Phone: +49 89 289 16242
wx.putum.de