6 2 / J . C o m p u t . F l u i d s E n g . V o l . 2 3 , N o . 3 , p p . 6 2 - 7 1 , 2 0 1 8 . 9 COMPUTATIONAL STUDY OF RAREFIED FLOW INSIDE A LID DRIVEN CAVITY USING A MIXED MODAL DISCONTINUOUS GALERKIN METHOD T. Chourushi, 1 S. Singh 1 and R.S. Myong *1,2 1 Graduate School of Mechanical and Aerospace Engineering, Gyeongsang National University 2 Dept. of Aerospace and Software Engineering & ReCAPT, Gyeongsang National University 혼 합 Modal 불 연 속 Galerkin 기 법 을 이 용 한 Lid-Driven Cavity 내 의 희 박 유 동 전 산 연 구 투샬 초루시, 1 사티비르 싱, 1 명 노 신 *1,2 1 경상대학교 대학원 기계항공공학부 2 경상대학교 항공우주및SW공학전공 및 항공기부품기술연구소 With the advancement of fabrication technology and miniaturization, fluid flows at micro- and nano- scales has received considerable attention. Flow characteristics in these systems significantly vary from those of macro- scale devices, due to geometric restrictions. In such cases, Navier-Stokes-Fourier(NSF) equations with no-slip condition may not be valid for studying gas flows inside a micro- cavity. This article therefore investigates the cavity flows using modified NSF equations with velocity slip and temperature jump conditions. In the present case, a monatomic gas is considered for modelling gas flows. To accurately predict the flow physics, mixed modal discontinuous Galerkin(DG) method is being developed. The flow characteristics of monatomic gas is studied by varying the Reynolds number(Re) and Knudsen number(Kn), respectively. Results obtained are compared with the previous results and are found to be in good agreement with them. Key Words : Micro-fluidics, cavity flows, discontinuous Galerkin method, rarefied gas Received: August 10, 2018, Revised: September 25, 2018, Accepted: September 25, 2018. * Corresponding author, E-mail: myong@gnu.ac.kr DOI http://dx.doi.org/10.6112/kscfe.2018.23.3.062 KSCFE 2018 1. Introduction Industrial, commercial and governmental research organizations are constantly working on miniaturization of devices to satisfy the consumer needs. These devices include hard-disk drive heads, ink-jet printer heads, micro heat-exchangers, micro pumps, and turbines. The gas flow under these micro-systems significantly varies from that of conventional (macro-systems) devices, as the characteristic length reduces to few microns. Under such circumstances, Navier-Stokes-Fourier(NSF) equations with no-slip boundary conditions may not remain valid, as the flow enters into non-equilibrium conditions[1,2]. In the past, several studies have been conducted to prove the inability of NSF equations with no-slip boundary conditions to study micro- fluids[3-5]. At micro scales, number of intermolecular collisions are significantly reduced, and thus non-equilibrium effects start to dominate[4]. This degree of rarefaction of a gas is defined with the Knudsen number( ). To describe the rarefied gas, the Boltzmann transport equation(BTE) is consequently considered as the fundamental equation. In the past, several methods have been devised to solve these equations, out of which Direct Simulation of Monte Carlo (DSMC) method is often used for numerical simulation of BTE[6]. However, DSMC is subject to high statistical noise at low flow speeds, which is a typical situation for micro gases. Also, DSMC is computationally expensive in