City Research Online

Abstract

The problem of linear wave diffraction by a vertical circular cylinder was studied both numerically and experimentally. The accuracy of the indirect boundary element method was improved by placing the source intensity distribution on a separate fictituous boundary outside the fluid domain. This method was demonstrated for the problem of steady flow past an infinite circular cylinder near a plane boundary, using a linear interpolation of source intensity. Reliable estimates of the force on the cylinder were obtained, provided that the gap between the cylinder and the plane was more than one tenth of the diameter.

The three dimensional problem of wave diffraction by a vertical circular cylinder was solved using a quadratic variation of source intensity. It was possible to use the series form of the Green's function throughout. Good agreement with the exact solution for both the pressure and the total in-line force, was obtained with only twelve elements. This corresponds to fifty-six complex equations.

Experimental measurements of pressure were taken on a vertical circular cylinder in regular waves in the inertia/diffraction regime. The amplitudes of these pressures were consistently higher than the linear theory. The discrepancies did not appear to correlate with wave steepness except at high frequencies. The phase angles were closer to the theoretical predictions. These discrepancies were caused by the effects of finite wave height but a more complete explanation awaits a successful second order theory.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > T Technology (General) T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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