Normal modes of a coupled fluid-shell system

Conference · Thu Jan 01 04:00:00 EST 1981 · HTD (Publ.) (Am. Soc. Mech. Eng.); (United States)

OSTI ID:5617383

Au-Yang, M K

The coupled normal modes of a finite fluid-cylindrical shell system are studied in a general sense to include frequencies above the coincidence frequency. It was found that the effect of fluid on the shell is always that of an added mass. Above the coincidence frequency, the added mass can be positive or negative. In the latter case, the effect of the fluid on the shell is springlike. The added mass approaches infinity at the hardwall acoustic resonant frequencies of the fluid, representing infinitely large pressure induced on the fluid as a result of the shell motion. Coupled normal modes of a finite fluid-shell system always exist. The number of coupled normal modes of the system is equal to the number of hardwall acoustic modes of the fluid plus the number of in-vacuum shell modes. The fundamental mode of the system has a frequency that is equal to or less than the lowest of the acoustic or in-vacuum shell mode frequencies; this is usually referred to as the ''in-fluid'' shell mode. The higher coupled modes have frequencies close to the hardwall acoustic modal frequencies and are usually referred to as acoustic modes. Just as a light fluid does not affect the modal frequencies of the shell, so the shell flexibility does not affect the acoustic modal frequencies of a light fluid. This last statement is verified by experimental observation. A numerical example is given for the coupled oscillation of the internal component of a pressurized water reactor and the coolant surrounding it. 6 refs.

• Research Organization: Babcock and Wilcox Co, Lynchburg, Va
• OSTI ID: 5617383
• Report Number(s): CONF-810625-
• Conference Information: Journal Name: HTD (Publ.) (Am. Soc. Mech. Eng.); (United States) Journal Volume: 46
• Country of Publication: United States
• Language: English

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