Study on Circumferential and Meridional Modes of Free Vibration Response for Fixed Base and Column-Supported Cooling Tower Shell

Abstract

Axisymmetric shell structures are generated by rotating plane curve around its axis of rotation to form a circumferentially closed surface and are generally used for hyperbolic cooling towers. These are thin shell structures possessing adequate strength and aesthetically pleasing. Considerable research on the behavior of cooling towers is available in the literature since the development in the finite element method. The present work investigates the free vibration analysis of shell on fixed base and column-supported cooling tower shell using ANSYS software. The study on modes of vibration (first lateral mode, torsion mode) and behavior of tower shell in circumferential mode (n) 1, 2, 3, 4, 5, and 6 for Meridional Mode (m) 1, 2, and 3 are observed for shell on fixed base and column supported shell for different uniform shell thicknesses. The analysis results revealed that natural frequency of the first lateral mode is unaffected by change in the shell thicknesses, but it occurs earliest in the thickest shell. Influence of shell thickness on torsion mode was observed to have no significant change except change in mode number. The study of circumferential mode (n = 1, 2, 3, 4, 5, 6) for Meridional mode (m = 1, 2, 3) for shell on fixed base with varying different uniform shell thicknesses (Uniform along the height) revealed that the frequency values alter for circumferential mode (n ≥ 4) greater than or equal to 4. The study of circumferential mode (n = 1, 2, 3, 4, 5, 6) for the Meridional modes (m = 1, 2) for column supported shell with varying different shell thicknesses (Uniform along the height) revealed that the frequency values alter for circumferential mode (n ≥ 1) greater than or equal to 1.