Journal of Japan Society of Fluid Mechanics

[title in Japanese]

[in Japanese], [in Japanese], [in Japanese]

1993 Volume 12 Issue 3 Pages 225-226
Published: September 30, 1993
Released on J-STAGE: March 07, 2011

DOIhttps://doi.org/10.11426/nagare1982.12.225

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[title in Japanese]

Syoten OKA, [in Japanese]

1993 Volume 12 Issue 3 Pages 249-254
Published: September 30, 1993
Released on J-STAGE: March 07, 2011

DOIhttps://doi.org/10.11426/nagare1982.12.249

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[title in Japanese]

[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...

1993 Volume 12 Issue 3 Pages 255-274
Published: September 30, 1993
Released on J-STAGE: March 07, 2011

DOIhttps://doi.org/10.11426/nagare1982.12.255

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Computational Study of Three-dimensional Flow Fields in an Astronomical Observatory Dome

Kazuhiro TSUBOI, Kayo MIYAKOSHI, Mikio NAGASAWA, Norio KAIFU, Kunio KU ...

1993 Volume 12 Issue 3 Pages 275-285
Published: September 30, 1993
Released on J-STAGE: March 07, 2011

DOIhttps://doi.org/10.11426/nagare1982.12.275

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Flow patterns in a dome for an astronomical observatory are investigated numerically based on a finite difference procedure which is characterized by an equi-spaced rectangular grid system and a masking technique. The computed results under various conditions are visualized, by which the structure of the flow field in the enclosure is well understood. This makes some effects to 'flushing characteristics' clear, namely, the inclination angle of the telescope, wind directions and the shape of the enclosure. Furthermore, qualitative estimation of the effect of the incoming flow profile is performed. The results also demonstrate the effectiveness of the present approach.

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Computation of Drag Coefficients of Two-Dimensional Bodies by Modified Oseen's Approximation

Hideo YANO, Tetsuyuki WATANABE, Kenichi IWAKI

1993 Volume 12 Issue 3 Pages 286-292
Published: September 30, 1993
Released on J-STAGE: March 07, 2011

DOIhttps://doi.org/10.11426/nagare1982.12.286

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The present paper proposes a modified version of the Oseen's linearized equations with an empirical parameter to obtain approximately the drag coefficients of two-dimensional bodies symmetrical to the uniform-flow axis, which are placed in a uniform flow field in the Reynolds-number range of 0<Re_??_R_c (where Rc, is the critical Reynolds number for vortex shedding). To verify the validity of the proposed equations, we computed the drag coefficients of simple bodies such as a circular cylinder, a square prism and a flat plate on the basis of discrete singularity method. As a result, it was confirmed that the computed drag coefficients of these bodies agree very well with the known experimental results and the computational results by a finite difference method.

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Fluid Force Measurements for a Circular Cylinder with a Slit

Naoki IZUTSU

1993 Volume 12 Issue 3 Pages 293-301
Published: September 30, 1993
Released on J-STAGE: March 07, 2011

DOIhttps://doi.org/10.11426/nagare1982.12.293

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The drag and lift acting on a circular cylinder with a slit were measured in uniform flows. In subcritical Reynolds numbers, the fluid passing through the slit functions as a wake splitter plate which reduces the mean drag coefficient. The wake Strouhal number declines, and the fluctuating drag and lift decrease sharply. The slit is active for the suppression of the fluid force on the cylinder in a wide range of attack angles. A narrowed slit reduces the minimum drag coefficient, and a slight attack angle can suppress the fluctuating lift by stabilizing the flow behind the cylinder.

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Instabillity of Swirling Flow in an Elliptical Cylinder

Resonance between Reciprocating Motion of a Piston and Swirl Rotation

Katsushi SAKUMA, Takeshi IMAI, Takeshi MIYAZAKI

1993 Volume 12 Issue 3 Pages 302-313
Published: September 30, 1993
Released on J-STAGE: March 07, 2011

DOIhttps://doi.org/10.11426/nagare1982.12.302

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The linear short-wave instability of swirling flow in an elliptical cylinder is investigated in the low Mach number limit. The swirl is subjected to time oscillating axial strain due to piston oscillation. Although the perturbation equations in general have coefficients that are doubly time-periodic, the Floquet theory can provide an easy way to evaluate instability growth rate if the ratio between the two periods (swirl ratio) is a rational number. The instability (for a fixed compression ratio) is enhanced as the ellipticity of cylinder increases and as the swirl becomes stronger, which is in accordance with the nature of elliptical instability. The instability in a 2 : 1 elliptical cylinder is enhanced (suppressed) as the compression ratio is increased, if the swirl ratio is small (large).

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[title in Japanese]

[in Japanese]

1993 Volume 12 Issue 3 Pages 314-318
Published: September 30, 1993
Released on J-STAGE: March 07, 2011

DOIhttps://doi.org/10.11426/nagare1982.12.314

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[title in Japanese]

[in Japanese], [in Japanese], [in Japanese]

1993 Volume 12 Issue 3 Pages 319-321
Published: September 30, 1993
Released on J-STAGE: March 07, 2011

DOIhttps://doi.org/10.11426/nagare1982.12.319

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