Jun Zhang
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  1. Multiscale Simulation of Hypersonic Gas Flows

The development of near-space hypersonic vehicles toward faster and farther directions poses challenges to the study of aerothermodynamics. To caputure the multiscale characteristics of hypersonic nonequilibirum gas flows in the whole flow regimes, we proposed a unified stochastic particle (USP) method by coupling molecular motions and collisions [1], as shown in Fig. 1. Recently, the open-source software based on the USP method within the framework of SPARTA has been released, and it is referred to as SPARTACUS (SPARTA Combined with USP) [2], as shown in Fig. 2. We have employed SPARTACUS to simulate a variety of multiscale gas flows involving internal energy exchange [3].


Fig. 1. Comparison of DSMC and USP methods.

Fig. 2. The application of SPARTACUS to hypersonic flows.

[1] F. Fei, J. Zhang*, J. Li, and Z. H. Liu*, "A unified stochastic particle Bhatnagar-Gross-Krook method for multiscale gas flows," Journal of Computational Physics 400, 108972 (2020).

[2] K. Feng, P. Tian, J. Zhang*, F. Fei, and D. Wen, "SPARTACUS: An open-source unified stochastic particle solver for the simulation of multiscale nonequilibrium gas flows," Comput. Phys. Commun. 108607 (2023).

[3] P. Tian, K. Feng, Q. Ma, Z. Li, J. Zhang*, "Unified stochastic particle simulation of polyatomic gas flows using SPARTACUS," Computers & Fluids 265, 105987 (2023).


  2.   Gas-Surface Interactions and Three Phase Moving Contact Line

Considering the complex physical and chemical process of gas-surface interactions in hypersonic flows, we conducted researches starting from microscopic molecular dynamics (MD), developed mesoscopic gas-solid interaction models, and then deduced macroscopic slip boundary conditions with the help of molecular kinetic theory [4, 5], as shown in Fig. 3. For dynamic wetting involving three phase moving contact line, we developed multiscale modelling method by coupling CFD and MD simulations [6, 7], as shown in Fig. 4.

GSI-English.jpg

Fig. 3. Multiscale simulation of GSI for hypersonic flows.

dynamic wetting.jpg

Fig. 4. Multiscale simulation of dynamic wetting.

[4] J. Zhang*, P. Luan, J. Deng, P. Tian, and T. Liang, "Theoretical derivation of slip boundary conditions for single-species gas and binary gas mixture," Physical Review E 104, 055103 (2021).

[5] J. Deng, J. Zhang*, T. Liang, J. Zhao, Z. Li, and D. Wen, "A modified Cercignani–Lampis model with independent momentum and thermal accommodation coefficients for gas molecules scattering on surfaces," Physics of Fluids 34, 107108 (2022).

[6] J. Zhang*, M. K. Borg, and J. M. Reese, "Multiscale simulation of dynamic wetting," International Journal of Heat and Mass Transfer 115, 886 (2017).

[7] H. Liu, J. Zhang*, P. Capobianchi, M. K. Borg, Y. Zhang, and D. Wen, "A multiscale volume of fluid method with self-consistent boundary conditions derived from molecular dynamics," Physics of Fluids 33, 062004 (2021).

  3.  Multiscale Modelling and Machine Learning

The discovery of governing equations from data is revolutionizing the development of some research fields, where the scientific data are abundant, but the well-characterized quantitative descriptions are probably scarce. We proposed to combine molecular simulations and machine learning to discover the governing equations for fluid dynamics [8], as shown in Fig 5. The prediction from data-driven discovery not only provides the right form of governing equation, but also determines the accurate values of transport coefficients such as viscosity and diffusion. This strategy is expected to help discover constitutive relationships and establish governing equations for nonequilibrium flows and complex fluids.

data-driven.png

Fig. 5. Data-driven discovery of governing equations based on molecular simulations.

[8] J. Zhang*, and W. Ma, "Data-driven discovery of governing equations for fluid dynamics based on molecular simulation," Journal of Fluid Mechanics 892, A5 (2020).


Personal information

Professor
Supervisor of Doctorate Candidates
Supervisor of Master's Candidates

E-Mail:

Date of Employment:2017-02-01

School/Department:航空科学与工程学院

Gender:Male

Contact Information:jun.zhang@buaa.edu.cn

Status:Employed

Discipline:Mechanics
Aeronautical and Astronautical Science and Technology

Honors and Titles:

国家级青年人才  2018

中科院青年创新促进会会员  2012

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