An experimental investigation of the effect of varying dimensions of a ring bluff body on the frequency stability of vortices

Mark L. Gamis

Date

3-2005

Degree

Bachelor of Science in Applied Physics

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Nelio C. Altoveros

Abstract

This study investigated experimentally the effects of the dimensions of a ring bluff body on the stability of the vortex frequency formed behind the ring, specifically the parameter D/W where D is the average diameter of the ring and W is the width of the ring. Ten ring samples were fabricated from washers and welded inside a 3.175-cm stainless steel pipe sample holder. This sample holder was housed between two long pipes, an upstream straight pipe run and a downstream straight pipe run which also housed an externally-mounted pressure sensor through an L-shaped metal tube. Water was made to flow through the pipe assembly from a reservoir tank and the vortex fluctuations behind the ring were observed through pressure fluctuations sensed by the sensor. The analog data was digitized and transferred to a computer using a ZF642 Microcontroller. Using FFT, the frequency content of the signals was extracted. Results showed that for ring samples with D/W less than 7, vortices shed irregularly so the frequency extracted from the signal has no definite peak. Rings with D/W values of 7,9,10 an 11 were observed to have a relatively more stable frequency of vortex fluctuations. Since regular vortex shedding was observed on these ring samples, a vortex shedding flow meter can therefore be fabricated using a ring bluff body with the same dimensions. (D/W = 6 to 10)

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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