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Three-Dimensional Building-Cube Method for Inviscid Compressible Flow Computations
김래성,Kazuhiro Nakahashi,Zhe-Zhu Xu,Hong Xiao,류성기 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.13
In this study, the Building-Cube method (BCM) devised for calculating large-scale flows and getting rid of the grid dependencies of computational results is extended to perform 3D inviscid compressible fluid flow simulations. The proposed scheme divides a computational domain into a large number of cubes with different sizes, and each individual cube is a sub-flow field simulated with a Cartesian grid of uniform spacing and an equal number of cells and nodes. Through the proposed scheme, we determine the geometric size of individual cube by Adapting the flow characteristics and geometrical shapes using an adaptively refining Cartesian grid approaches. The uniform spacing and equal number of cells and nodes in the Cartesian grid of individual cubes ensure a good performance for parallel computations; large result data can be handled efficiently. Further, an algorithm to solve the inviscid flow equations on the Building-Cube mesh for three-dimensional (3D) geometries is presented. The validation and performance of the proposed 3D BCM are demonstrated through comparisons of the computed results with the experimental data for the ONERA M6 wing and ONERA M5 wing-fuselage configurations.
A Study on the Comparison of Transmission Error Prediction for a Helical Gear Pair
김래성,장기,최창,양용군,류성기 한국기계가공학회 2015 한국기계가공학회지 Vol.14 No.2
In recent years, world is faced with a transportation energy dilemma, and the transportation is almost dependent on a single fuel – petroleum. However, Hybrid Electric Vehicle (HEV) technology holds more advantages to reduce the demand for petroleum in the transportation by efficiency improvements of petroleum consumption. Therefore, there is a trend that lower gear noise levels are demanded in HEV for drivers to avoid annoyance and fatigue during operation. And meshing transmission error (T.E.) is the excitation that leads to the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. In this paper, the analysis of gear tooth profile and lead modification is firstly presented, and then, the different transmission error of no mesh misalignment and mesh misalignment under one loaded torque for the 1st gear pair of HEV gearbox was investigated and compared. At last, the appropriate tooth modification was used to minimize and compare the transmission error of the gear pair with mesh misalignment under the loaded torque.
김래성,양휘주,하만영,Zhe-Zhu Xu,Hong Xiao,류성기 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.8
In this study, the immersed boundary-finite difference lattice Boltzmann method (IB-FDLBM) using the feedback momentum forcing scheme is proposed and implemented to simulate 2-D incompressible flows. IB-FBLBM incorporates the immersed boundary method (IBM) into the finite difference lattice Boltzmann method (FDLBM) devised to alleviate shortcomings by using the uniform Cartesian grid of the standard lattice Boltzmann method (LBM). In order to obtain numerical stability while combining IBM with FDLBM, this method utilizes feedback momentum forcing scheme and equilibrium velocity approach to take into account the change of momentum induced by a body force on the immersed boundaries. This approach has the advantages of being simple and easy to implement, and does not require modification of the original governing equations. In order to confirm the applicability and validation of IB-FDLBM, the lid-driven cavity flow with a circular cylinder, the external steady flows around a circular cylinder and external steady flows around a circular cylinder near a plane wall are simulated with a range of Reynolds numbers. The current numerical results are consistent with those of existing researches.
김래성,김종인,최창,양용군,류성기 한국기계가공학회 2015 한국기계가공학회지 Vol.14 No.2
Gears are produced through a variety of methods. In general, a metal piece is formed into the general shape of a gear through rough cuts. The gear then moves on to a more precise machine that removes more material. Grinders work via abrasion, rubbing a rough surface against a work piece at such high speeds that it literally scrapes unwanted material away from the item. Since the grinder is spinning so fast, the material is removed very quickly. This allows a grinder to remove a very small amount without taking any unwanted material with it. This study investigates the effect of grinding process parameters like grinding spindle speed and table transfer speed on the gear grade and grinding efficiency.