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AERODYNAMIC CHARACTERISTICS OF MIRA FASTBACK MODEL IN EXPERIMENT AND CFD
Yingchao Zhang,Jintao Zhang,Kaiguang Wu,Zijie Wang,Zhe Zhang 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.4
The lasting high fuel cost has recently inspired the resurgence in drag reduction research for vehicles, which calls for a thorough understanding of the vehicle wake. The acknowledged MIRA fastback vehicle model is characterized by similar real vehicle geometry, thus it is especially suitable for the above purpose. In spite of a considerable number of previous investigations, our knowledge of flow around this model remains incomplete. This paper aims to visit turbulent flow structure behind this model. An investigation has been conducted to measure the near wake flow structure of the MIRA 1/8 scale mode, using both Particle Image Velocimetry (PIV) experimental method and Computational Fluid Dynamics (CFD) simulation method. In order to capture the flow structure accurately, PIV measurement was performed in different sections along three orthogonal directions, and the CFD method acquired additional simulation results to catch the better flow status. Through the maps of the time-averaged vorticity, the instantaneous vorticity and the handled velocity vector from the PIV and CFD methods, we found out the formation mechanism of the transient flow of fastback model and summed up the schematic of flow structure. This study not only analyzed the vortex shedding characteristics of turbulent near wake, but more importantly provided insight into the complex three-dimensional features of the flow structure in the wakes of MIRA fastback model.
Shengyan Shang,Anil Kunwar,Yanfeng Wang,Jinye Yao,Yingchao Wu,Haitao Ma,Yunpeng Wang 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.2
Solder ball of initial diameter 1.4 mm, was refl ow soldered with Cu substrate at 523.15 K using fl ux doped with Cu@Agcore–shell nanoparticles (NPs) in the proportion 0–2 wt%. The solders were then air cooled to room temperature. The use ofNPs, by reducing the base height (H) of the solder and enhanced the diameter (W) of the solder, caused an overall increase inthe spread ratio of the solder. The altered magnitudes of heat and mass transfer in these geometrically diff erent but constantvolume specimens were analyzed using fi nite element method. The occurrence of diff erential concentration gradient, radialthermal gradient and velocity magnitudes, in solders with diff ering geometry were numerically elaborated. The Cu6Sn5 intermetalliccompound (IMC) formed at the Cu/Sn interface, was obtained to be the thickest for the specimen using undopedfl ux, whereas it was found to be smallest for the sample processed with fl ux containing 0.5% NPs. From the growth kineticsstudy, it has been inferred that IMC thickness is linearly proportional to the geometrical parameter H and Wb , with b < 1.