Mode Characteristics of Thin Cylindrical Shells and Flow near Shell Wall

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This paper describes about the mode characteristics of thin cylindrical shells and the flow near the shell wall. The mode characteristics which are classified into the circumferential direction mode and the longitudinal direction mode are treated as contribution rates. These are defined as the ratio of the numbers of each direction mode and the total mode. In the shell models, the radius and the thickness are changed in order to estimate the mode characteristics systematically. The contribution rate increases with decreasing radius and also increases with increasing thickness. The magnitude is in proportion to κ power of the ratio of the thickness and the radius. The index κ with respect to the circumferential direction mode is greater than the one of the longitudinal direction in the frequency band below the natural frequency of the circumferential direction. Next, a flow near the wall of the thin cylindrical shell under the acoustic excitation is visualized by using the smoke wire method. The characteristic flow patterns are confirmed with each excitation frequency. Although the flow of the circumferential direction is almost dominant, the complicated flow is observed in the frequency band where the contribution of the circumferential direction mode excels. Thus, it is shown that the flow patterns match to a certain degree the mode characteristics of the shell.
東海大学の論文