| Co-Investigator(Kenkyū-buntansha) |
KIWATA Takahiro Kanazawa University, Faculty of Technology, Research Associate, 工学部, 助手 (40225107)
UENO Hisanori Kanazawa University, Faculty of Technology, Associate Profssor, 工学部, 助教授 (80019752)
長久 太郎 金沢大学, 工学部, 助教授 (20019706)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1991: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1990: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1989: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
A row of uniformly spaced bluff bodies with a rectangular cross-section placed perpendicularly to an approaching flow like the fin rows of a heat exchanger produces unsteady and non-uniform flow across the row, which consists In separated flow region with an unsteady cell structure. The present study consists of experiments In a wind tunnel and numerical simulations of flow by a finite difference method. Firstly, a simultaneous measurements of pressures around the circumference of a fin row and velocity distribution of a wake In a wind tunnel allow the evaluation of instantaneous drag and lift forces In each mode of two and more flow patterns which appear by unsteadiness of a biased flow formed In the gaps, and In the biased flow, we find good correspondence of pressure distributions and lift and drag forces to wake velocity profiles. It Is concluded that the biased flow is metastable and can switch Intermittently In gaps, and that the nonuniformity of gap and wake flows is significant
… More
in the range of the gap ratio S/H below a critical value. We find also that the uniformity of a wake velocity Is the best at the critical gap for elongated rectangular cylinders, B/H=3, 5 In rows. Next, we have developed the computer-code for computation of flows around rectangular cylinders, to gain a better Insight into the detailed characteristics of the fluld- and thermo-dynamics of bluff bodies. By a finite volume method, both laninar flow and thermal fields around bluff bodies with a rectangular cross section of various B/H ratios and an aerofoil seption haie been computed on body-fitted curvilinear coordinates at a Reynolds number of(1, 4, 7)x1O^3, and we can successfully simulate some Interesting flow and thermal phenomena whereby a flow pattern critically, changes when the B/H ratio Is about 2.5 and 6 ; that Is, a fully separated flow, an alternately reattached one and a stationarily reattached one. It is also clarified that Nusselt number distribution well corresponds with a motion of flow about the body, such as the size of a vortex-formation region and a notion of vortices shed downstream over the side walls. The present computational code Is certified to be suitable as the computed results show a good agreement with the measured results, and the computed results clearly show the effects of a shape of the bluff body on aero- and thermo-dynamic characteristics. The results reveal an interactions between a wake and separation bubbles, also. Furthermore, turbulent flows around rectangular bodies also have been computed by a standard k-epsilon turbulence model. There are, however, some discrepancies between the results from the k-epsilon, turbulence model and experiments for unsteady phenomena. We have reported the results of experiments and numerical simulations on the optimum shapes of cross-section and arrangement of a row of fins, In six papers. Less
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