Vibration analysis of cylindrical shells in contact with an annular fluid region

An experimental and numerical investigation of the vibratory modal characteristics of a vertical thin-walled cylindrical shell containing water, or oil, in an adjacent coaxial region is presented. A system of two fluid-coupled cylindrical shells is studied. In addition to the effect of increasing liquid level in the shell, the effects of the thickness of the liquid layer in the annular region between the vibrating outer shell and another coaxial rigid cylinder, or between two thin coaxial cylindrical shells, are studied. Experimental results were obtained using the standard modal analysis technique and the time average holographic method. In parallel, computation of natural frequencies and mode shapes of the coupled fluid-structural vibrations were carried out by means of the finite element method operated within the framework of the ANSYS program package. The comparison between experimental results and finite element results was found to be reasonable in most of the cases studied. The fundamental influence of the viscosity of the fluid in the narrow annulus upon the dynamic behaviour of the shell is discussed.