Vibration measurements on a 32,000 ton d.w. super tanker

The present report deals with the results of the vibration measurements of a 32,000 ton d.w. super tanker on trial trips. All the natural frequencies of the flexural and torsional vibrations up to the blade frequency were observed involving those of small amplitude measured by Geiger vibrographs and by the optical one which was made on trial. Since the measured critical frequencies of the flexural vibration of the hull are almost proportional to the number of nodes in both the ballast and loaded conditions, it is pointed out that the higher modes of hull vibration are considered to be of shearing vibration. The details of the theoretical investigations on the present observations are not presented except that one of the computed results of the vibration profile of the higher mode of shearing vibration of the hull is quoted as an example.