Katsumi Miyakoshi

Fluctuating Lift Acting on a Square Prism with Attacking Angle Commencing Its Motion in Still Water : Suppression of Nonrepeatability in Fluctuating Lift Produced by Vortex Formation(Fluids Engineering)

静水 中で移動 を開始する迎え角のある正方形角柱 に作用する変動揚力* (渦形成に基づいて生じる変動揚力の非再現性の抑制) 羽二 生 博 之*1, 呉 平*2 宮 越 勝 美*1, 鈴 木 聡 一郎*1 Fluctuating Lift Acting on a Square Prism with Attacking Angle Commencing Its Motion in Still Water (Suppression of Nonrepeatability in Fluctuating Lift Produced by Vortex Formation) Hiroyuki HANIU*3, Ping WU, Katsumi MIYAKOSHI and Soichiro SUZUKI *3 Department of Mechanical Engineering, Kitami Institute of Technology, 165 Koen-cho, Kitami-shi, Hokkaido, 090-8507 Japan

Vortical Structures in a Two-Dimensional Jet Under Flapping Motion Generated by a Wake of a Cylinder Installed in a Nozzle Contraction (2nd Report, Flow Visualization and Image Correlatioin Analysis)

When a plane jet exhibits flapping motion, two distinctive peaks, f1 and f2, appear in the spectrum of fluctuating velocity. The mean frequency is half of the frequency, fv, of vortices shedding from a two-dimensional body that is installed in a jet nozzle contraction. Jet mixing has been enhanced by the flapping motion with a low frequency, f3=f1-f2, which is considered to be caused by an inharmonic excitation. Vortical structures in the flapping jet are investigated by using flow visualization, image correlation and laser Doppler velocimetry. Vortices are seen to roll up asymmetrically at the jet nozzle exit, at a double frequency of that of the vortex shedding from the cylinder. Two types of vortices are formed by coalescence between these vortices and the vortices shedding from the cylinder. The periodicities of these two types of vortices are found to be equal. It is noted that vortices with f1 or f2 do not exist in the flow. The f1 and f2 are caused by the modulation of amplitude of the coalesced vortical structures with half of the flapping frequency, f3.

Development of Analyzing Technique for Ice Movements in Okhotsuk Sea Using Satellites' Millimeter Radar Images

In this study, method of correlation PIV is applied to the ice movement of Okhotsuk Sea using millimeter radar images of DMSP and ADEOSE-II satellites with 12.5km resolution that can penetrate thick clouds usually covering over the Okhotsuk Sea and prevents us from seeing the sea ice via visible light. PIV method in present research emploies very standard correlation algorithm using 15×15 matrix which shows motion of ice properly. With the PIV, movements of sea ice are analysed to investigate the growth of ice.

Vortex Structure in a Two-Dimensional Jet Under Flapping motion Generated by Wake of a Cylinder Installed in Nozzle Contraction

It is possible to control the spread of a plane jet passively by the vortices from a two-dimensional cylinder installed in the nozzle contraction. In a particular condition of cylinder placement, two distinctive spectral peaks at frequencies f1 and f2 with their averaged frequency at 1/2 the vortex shedding frequency fv were observed, where the jet exhibits flapping motion at low frequency f3 (= f1-f2).The vortex structures in a plane jet under inharmonic excitation were studied by means of hot-wire and phase ensemble-averaging techniques. The phase ensemble-averaging results show that the vortex street shed at frequency. fυ/2 was formed in the jet under inharmonic excitation, and similar vorticity distributions appeared in the upper and lower shear-layers alternately at frequency f3. As the result, within the duration of one flapping motion, successive nine vortices were formed at shedding frequency fv/2 to complete their one cycle of evolution.