Effect of Low Frequency Oscillation on Heat Transfer Characteristics from Tandem Cylinders
Project/Area Number  02650154 
Research Category 
GrantinAid for Scientific Research (C).

Research Field 
Thermal engineering

Research Institution  Gifu University 
Principal Investigator 
桧和田 宗彦 岐阜大学, 工学部, 助教授
HIWADA Munehiko Gifu University, Faculty of Eng., Associate Professor, 工学部, 助教授 (60021622)

CoInvestigator(Kenkyūbuntansha) 
MIMATSU Jyunichi Gifu University, Faculty of Eng., Research Associate, 工学部, 助手 (20202351)

Project Fiscal Year 
1990 – 1991

Project Status 
Completed(Fiscal Year 1991)

Budget Amount *help 
¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1991 : ¥400,000 (Direct Cost : ¥400,000)

Keywords  Forced Convection / Two Circular Cylinder / Low Frequency Oscillation / Unsteady Fluid Forces / Phaseaveraged Fluid Forces / Different Diameter / 強制対流熱伝達 / 2円柱 / 低周波脈動 / 非定常流体力 / 位相平均流体力 / 異径 / 強制対流 
Research Abstract 
The following conditions for vibration experiments have been decided taking account for the first year's results which the upstream circular cylinder was stationary and was set off from the axial line ; Reynolds number Re=5X10^4 (const.), diameter ratios d_1/d_2=5/30 (const.), nondimensional amplitude of upstream cylinder A/d_2=00.25 and forced oscillating frequencies fc=0.12511.08 Hz which is smaller than the natural frequency of a single circular cylinder. Under these experimental conditions, mass transfer characteristics have been examined by naphthalene sublimation methods, and several fluid flow behaviors have been clarified using the phaseaveraged methods, such as, pressure distributions around a downstream cylinder, timeaveraged and fluctuating lift and drag forces and velocity flow field between two cylinders. The instant flow pattern have also been photographed by smokewire methods and so no. The main results are as follows : (1) Stationary offsetting the upstream cylinde
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r produced the marked effect on timeaveraged drag and lift coefficients and Strouhal number under the offset ratio Y^*/d_2=0.5, especially, the drag force had the minimum and lift force had the maximum in the case of Y^*/d_2=0.25. (2) Under the offset conditions, the fluctuating drag coefficients remained constant(C_Drms=0.1) in spite of the variations of Y^*/d_2 and the fluctuating lift coefficients had the maximum value and had the magnitude of timeaveraged drag coefficient at Y^*/d_2=0.65. (3) When upstream cylinder had a simple harmonic oscillation normal to the main flow, so called "dynamic characteri stics", the oscillation frequency in this experimental range had not an influence on the mass (heat) transfer characteristics around a downstream cylinder in both cases of two gaps between cylinders, X^*/d_1=5.0 and 7.9. Local and peripherally averaged mass (heat) transfer coefficients could be estimated by the linearsuperposed technique using the stationary offset data. (4) Phaseaveraged fluid forces and pressure distribution were given as a period variation of upstream cylinder's vibration and phase shift phenomena for lift and drag forces was discovered. Less

Report
(4results)
Research Output
(7results)