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An Immersed-Boundary Finite-Volume Method for Simulation of Heat Transfer in Complex Geometries
Kim, Jungwoo,Park, Haecheon The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.6
An immersed boundary method for solving the Navier-Stokes and thermal energy equations is developed to compute the heat transfer over or inside the complex geometries in the Cartesian or cylindrical coordinates by introducing the momentum forcing, mass source/sink, and heat source/sink. The present method is based on the finite volume approach on a staggered mesh together with a fractional step method. The method of applying the momentum forcing and mass source/sink to satisfy the no-slip condition on the body surface is explained in detail in Kim, Kim and Choi (2001, Journal of Computational Physics). In this paper, the heat source/sink is introduced on the body surface or inside the body to satisfy the iso-thermal or iso-heat-flux condition on the immersed boundary. The present method is applied to three different problems : forced convection around a circular cylinder, mixed convection around a pair of circular cylinders, and forced convection around a main cylinder with a secondary small cylinder. The results show good agreements with those obtained by previous experiments and numerical simulations, verifying the accuracy of the present method.
An Immersed-Boundary Finite-Volume Method for Simulation of Heat Transfer in Complex Geometries
Jungwoo Kim,Haecheon Choi 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.6
An immersed boundary method for solving the Navier-Stokes and thermal energy equations is developed to compute the heat transfer over or inside the complex geometries in the Cartesian or cylindrical coordinates by introducing the momentum forcing, mass source/sink, and heat source/sink. The present method is based on the finite volume approach on a staggered mesh together with a fractional step method. The method of applying the momentum forcing and mass source/sink to satisfy the no-slip condition on the body surface is explained in detail in Kim, Kim and Choi (2001, Journal of Computational Physics). In this paper, the heat source/sink is introduced on the body surface or inside the body to satisfy the iso-thermal or iso-heat-flux condition on the immersed boundary. The present method is applied to three different problems: forced convection around a circular cylinder, mixed convection around a pair of circular cylinders, and forced convection around a main cylinder with a secondary small cylinder. The results show good agreements with those obtained by previous experiments and numerical simulations, verifying the accuracy of the present method.
복잡한 형상에서의 열유동장 해석을 위한 가상 경계 방법
김정우(Jungwoo Kim),최해천(Haecheon Choi) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.9
A new immersed boundary method for solving the Navier-Stokes and thermal energy equations is developed to compute the flow and temperature fields over or inside complex geometries by introducing momentum forcing, mass source/sink, and heat source. The present method is based on a finite volume approach on a staggered mesh. The method of applying momentum forcing and mass source/sink is explained in detail in Kim, Kim and Choi (2001, Journal of Computational Physics). The heat source is applied on the body surface or inside the body to satisfy the constant temperature or the constant heat flux condition on the immersed body. This method is applied to the problems such as oscillatory flow with heat transfer in a square cavity, forced convection from a circular cylinder, and heat transfer by a pair of circular cylinders under the influence of buoyancy, resulting in good agreements with the existing results obtained by experiments and numerical simulations.
A 20~32 GHz GaN Power Amplifier MMIC Using Lange Couplers for Wideband Operation
Woojin Chang,Haecheon Kim,Byoung-Gyu Min,Ho-Kyun Ahn,Jae-Won Do,Kyu Jun Cho,Dong-Min Kang,Hong-Gu Ji,Sung-Il Kim,Sang-Heung Lee,Jong-Min Lee,Dong-Young Kim,Hyung-Sup Yoon,Sung-Jae Chang,Yoo-Jin Jang,J 대한전자공학회 2018 대한전자공학회 학술대회 Vol.2018 No.6
In this paper, we demonstrated a K-/Ka-band monolithic microwave integrated circuit (MMIC) power amplifier (PA) designed and fabricated using a AlGaN/GaN 0.15 μm hetero-structure field effect transistor (HFET) on SiC technology. Lange couplers and 2-way combiners were used for combining GaN HFETs and stages of the PA circuit. Especially, six Lange couplers in the PA MMIC were applied for wideband amplification of the PA MMIC. Microstriplines and open-stubs were used for matching circuits, except for MIM capacitors acting as DC blocks in the PA MMIC. In each bias circuit of the PA, two MIM capacitors were used for less vulnerable characteristics of the PA to lengths and diameters of bonding wires. The PA has been achieved a 3 dB bandwidth of 12 GHz, a gain, S21, of 7.8~10.7 dB, an input reflection coefficient, S11, of - 22~-10 dB and an output reflection coefficient, S22, of -41~-12 dB for 20~32 GHz. And also a saturated output power of 31.2 dBm was achieved at 28 GHz.