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Aerodynamic Sound Radiated from longitudinal and Transverse vortex Systems Generated around the Leading Edge of Delta Wings

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Open Journal of Fluid Dynamics 2016年第2期6卷 101-118页

作者： Shigeru Ogawa Jumpei Takeda Taiki Kawate Keita Yano Department of Mechanical Engineering National Institute of Technology Kure College Hiroshima Japan

Flow around the front pillar of an automobile is typical of a flow field with separated and reattached flow by a vortex system. It is known that the vortex system causes the greatest aerodynamic sound around a vehicle. The objective of the present study is to clarify the relationship between vortical structures and aerodynamic sound by the vortex system generated around the front pillar. The vortex system consists of the longitudinal and the transverse system. The characteristics of the longitudinal vortex system were investigated in comparison with the transverse one. Two vortex systems were reproduced by three-dimensional delta wings. The flow visualization experiment and the computational fluid dynamics (CFD) captured well the characteristics of the flow structure of the two vortex systems. These results showed that the longitudinal with the rotating axis along mean flow direction had cone-shaped configuration whereas the transverse with the rotating axis vertical to mean flow direction had elliptic one. Increasing the tip angles of the wings from 40 to 140 degrees, there first exists the longitudinal vortex system less than 110 degrees, with the transition region ranging from 110 to 120 degrees, and finally over 120 degrees the transverse appears. The characteristics of aerodynamic sound radiated from the two vortex systems were investigated in low Mach numbers, high Reynolds number turbulent flows in the lownoise wind tunnel. As a result, it was found that the aerodynamic sound radiated from both the longitudinal and the transverse vortex system was proportional to the fifth from sixth power of mean flow velocity, and that the longitudinal vortex generated the aerodynamic sound larger than the transverse.

关键词： Aerodynamic Noise Delta Wing longitudinal vortex Transverse vortex CFD

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Synchronal Measurement of Flow Structure and Heat Transfer of Impingement Jet

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Journal of Thermal Science 2010年第3期19卷 228-233页

作者： Shoichi MATSUDA Naomichi SAJI Minoru YAGA Masaaki ISHIKAWA Kenyu OYAKAWA Dept.Mech.Systems Eng. Univ.of the RyukyusSenbaru 1NishiharaOkinawaJapan903-0213 Graduate student Faculty of Eng.Univ.of the RyukyusSenbaru 1NishiharaOkinawaJapan903-0213

This paper will present the characteristics of flow behavior and thermal field of both free and impingement jet issued from a circular orifice nozzle at Re=*** flow behavior of a single round jet and impingement jet was observed by smoke flow visualization recorded by a high speed camera using 5000 frame per *** transfer coefficient on the impingement surface was measured by means of infrared camera (TVS-8500,Avio) with a two-dimensional array of Indeum-Antimony (In Sb) sensors varying in the separation distance between the nozzle and the target *** heat transfer coefficient changes in time and ***,the root mean square distribution of the heat transfer was obtained from the *** a result,it was confirmed that the longitudinal vortex was observed outside of the ring vortex,and then the longitudinal vortex was penetrated in the jet ***,the high value of root mean square of the heat transfer coefficient has spread radially in stripy manner,which is caused as the results of the longitudinal vortexes flowing in the radial direction on the impingement plate.

关键词： Impingement jet Forced convection Heat transfer Ring vortex longitudinal vortex

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Experimental study by PIV of swirling flow induced by trapezoid-winglets

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Journal of Hydrodynamics 2013年第6期25卷 919-928页

作者：车翠翠田茂诚张冠敏冷学礼 School of Energy and Power Engineering Shandong University

The characteristics of the longitudinal vortex induced by trapezoid-winglets in a circular tube are investigated by the Particle Image Velocimetry （PIV） Technique with flow Reynolds number in the range of 500-13 000. In the experimental test section, four trapezoid-winglets are fixed symmetrically on the tube wall in two different ways： up-flow and down-flow. The results show that a counter-rotating vortex pair is formed behind each winglet and they distribute as a symmetrical vortex array in the transverse section. Between the two vortexes in a vortex pair the fluid flows towards the wall in the up-flow winglet case and away from the wall in the down-flow winglet case, corresponding also to the regions of peak values of the velocity components normal to the mainstream. Both of the flow patterns enhance the velocity in the near wall region, leading to the intensification of the transverse mixing and the mass transfer in the tube. With Reynolds number increasing, the flow maintains the vortex pattern in the case of the up-flow winglets, indicating better persistence of the longitudinal vortex, while the vortexes in the case of the down-flow winglets are more scattered and tend to breaking into small eddies. The trapezoid winglet shows the preferable turbulent disturbance characteristics in the tube and the experimental results provide benchmark data for further CFD studies.

关键词： longitudinal vortex Particle Image Velocimetry (PIV) trapezoid-winglets circular tube

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Local heat transfer enhancement induced by a piezoelectric fan in a channel with axial flow

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2020年第12期21卷 1008-1022页

作者： Yun-long QIU Chang-ju WU Wei-fang CHEN School of Aeronautics and Astronautics Zhejiang UniversityHangzhou 310027China

The present work experimentally and numerically investigates the local heat transfer enhancement induced by a piezoelectric fan interacting with a cross flow in a local heated *** piezoelectric fan is placed along the flow direction and tested under different amplitudes and flow *** the simulations,a spring-based smoothing method and a local remeshing technique are used to handle the moving boundary *** mesh is used to reduce the size of dynamic mesh domain and to improve computational *** experimental and numerical values of the time-averaged mean Nusselt number are found to be in good agreement,with deviations of less than 10%.The experimental result shows that the heat transfer performance of the heated surfaces is substantially enhanced with a vibrating piezoelectric *** numerical result shows that the heat transfer enhancement comes from the strong longitudinal vortex pairs generated by the piezoelectric fan,which significantly promote heat exchange between the main flow and the near-wall *** the case of a=0.66(a is the dimensionless amplitude)and Re=1820,the enhancement ratio of the time-averaged mean Nusselt number reaches 119.9%.

关键词： Piezoelectric fan Local heat transfer enhancement Forced convection longitudinal vortex Pressure drop

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Experimental Study on Aerodynamic Noise Radiated from Delta Wing

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Journal of Mechanics Engineering and Automation 2020年第6期10卷 161-169页

作者： H.Honda S.Ogawa K.Suzuki National Institute of Technology(KOSEN) Kure College2-2-11 AgaminamiKure CityHiroshima Prefecture 737-8506Japan Department of Mechanical Engineering National Institute of Technology(KOSEN)Kure College2-2-11 AgaminamiKure CityHiroshima Prefecture 737-8506Japan

Aerodynamic noise has been impairing the comfort of passengers in *** have shown that the aerodynamic noise is generated by the separation of the flow and the generation of the longitudinal vortex at the front pillar(A-pillar)and the door *** remove the effects of the door mirror and extract the longitudinal vortex from A-pillar,studies employ the delta wing *** research also employed the model and observed relations between the generated sound from the vortex at the A-pillar and the surface pressure fluctuation of the *** experiment was carried out in a wind tunnel of the Japan Aerospace Exploration Agency(JAXA)wind tunnel using the delta wing *** radiated sound was measured using a far-field microphone to characterize the sound,and microphone array to conduct sound source *** of surface pressure fluctuation was measured using electret condenser *** showed that the radiated sound has a characteristic of dipole sound,and broadband sound from 1 kHz is radiated from the apex of the *** indicate that sound generated from the apex of the delta wing was scattered at the surface of the delta wing,which follows the Lighthill-Curle *** pressure fluctuation with high fluctuation was distributed following the cone-like shape of the longitudinal *** peaks moved to the apex with the frequency *** between far-field sound and surface pressure fluctuation was *** point which is 70 mm inward from the apex showed higher value than those at the *** the diameter of the longitudinal vortex grows at the downstream,it is considered that a certain vortex scale radiates the most noise.

关键词： Aerodynamic noise longitudinal vortex delta wing experiment.

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