Natural Frequencies of a Short Circular Cylinder, Including the Effects of Entrained Mass

摘要

The paper contains a summary of recent research work that has been undertaken to quantify the effects of entrained mass on the natural frequencies of oscillation of a short-chord circular cylinder. A brief summary is given of existing exact methods for the prediction of natural vibrational modes of rings and partial rings in air, and of a semi-empirical method which allows for the effect of entrained mass. A short critique of the latter leads directly to the suggestion of a new and perhaps more accurate method of prediction. There then follows a description of the design of an experimental ring in which the circular cylinder may be clamped in several different configurations and subjected to an external periodic force. A description of the tests in air and water is then followed by an examination of the test results and a detailed appraisal of the accuracy of the suggested calculation method. The examination shows that the semi-empirical formulae, incorporating appropriate attenuation factors, may be used to predict the natural vibrational modes with a high degree of accuracy. Finally, there are suggestions for further experimental research and calculations.