Major research outcome

Major research outcome

  • KNGPDL develops a second-order spatio-temporal accurate Fokker-Planck model for diatomic gas flows
  • 관리자 |
  • 2025-11-13 17:09:13|
  • 262

With the advent of the New Space era, reentry vehicles are launched more frequently. Accurate prediction of aerothermal properties is critical to the success of reentry. Since the atmospheric density at high altitudes is low, the Navier-Stokes equation based on the continuum assumption is no longer valid. To accurately describe these rarefied gas flows, the direct simulation Monte Carlo (DSMC) method based on the Boltzmann equation is widely used. The DSMC method describes gas flows through the transport and stochastic collisions of computational particles. The DSMC method is valid from the rarefied regime to the continuum regime. However, as the gas density increases, the computational cost of the DSMC method increases dramatically due to frequent particle collisions. To solve this problem, the Fokker-Planck (FP) model has been proposed. The FP method approximates particle collisions as the Brownian motion of each particle. Since the FP model does not consider particle collisions, its grid and time step sizes are not constrained by the mean free path or mean collision time. However, the conventional FP model has only first-order accuracy in both time and space, leading to increased numerical error as the grid and time step sizes increase. Recently, research has been conducted to achieve second-order spat-temporal accuracy for the FP model, aiming to minimize numerical error and enhance computational efficiency by using larger grid and time step sizes. However, this studies have been limited to monatomic gases.
 
In the KAIST Non-Equilibrium Gas and Plasma Dynamics Laboratory (KNGPDL) of the Department of Aerospace Engineering, master’s student Joonbeom Kim and Professor Eunji Jun have developed a Unified stochastic particle Fokker-Planck-Master (USP-FPM) method. The USP-FPM method achieves second-order accuracy in both time and space. Second-order temporal accuracy is attained by reproducing second-order accurate moment relaxations of energy, viscous stress, and heat flux. Second-order spatial accuracy is achieved by employing the polynomial reconstruction method. To validate the accuracy and efficiency of the USP-FPM method, a hypersonic flow around a cylinder is performed The USP-FPM method with a coarse resolution is validated against the DSMC method with a fine resolution. Figure 1 illustrates the translational, rotational, and vibrational temperature contours around a cylinder. The USP-FPM method with the coarse resolution shows good agreement with the DSMC method with the fine resolution.
 
This research has been published in Volume 37 of the Physics of Fluids (POF) journal. Physics of Fluids is a leading journal in fluid mechanics, known for publishing high-quality research across the field of flow dynamics (IF: 4.3, top 6.1% in JCR).
 
Title: A second-order particle Fokker–Planck–Master method for diatomic gas flows
DOI: 10.1063/5.0292414
 
 
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