Time: 9:30 am, May 19, 2014

Address: F310, School of Mechanical Engineering 

Speaker: Prof. Samir Ziada (McMaster University)

Inviter: Prof. Liu Yingzheng and Prof. Li Dayong

Abstract:
This report focuses on the phenomenon of vorticity shedding in tube bundles and its relation to the acoustic resonance mechanism and the dynamic fluid forces exerted on the tubes. These phenomena are investigated by means of velocity, pressure and force measurements, as well as with the aid of extensive visualization of the unsteady flow structure at the presence and absence of acoustic resonance. Vorticity shedding excitation is shown to be generated by either jet, wake, or shear layer instabilities. The tube layout pattern (in-line or staggered), the spacing ratio, and Reynolds number determine which instability mechanism will prevail, and thereby the relevant Strouhal number for design against vorticity shedding excitation. Strouhal number design charts for vortex shedding in tube bundles are presented for a wide range of tube patterns and spacing ratios. With respect to the acoustic resonance mechanism, it is shown that the natural vorticity shedding, which prevails before the onset of resonance, is not always the source exciting acoustic resonance. This is especially the case for in-line tube bundles. This finding leads to the conclusion that separate "acoustic" Strouhal number charts must be developed to improve our ability to avoid acoustic resonances in new designs. To this end, the most recently developed charts of acoustic Strouhal numbers are provided. Finally, design charts of dynamic lift coefficients and bound spectra of turbulent fluid forces acting on the tubes are also presented.

Introduction of Speaker:
Prof. Samir Ziada received his B.S. from Cairo University (Egypt) in 1972; M. Eng. from McMaster University (Canada) in 1977, and Ph.D. from Lehigh University (USA) in 1981. He worked as: Research Engineer, Leader of Flow-Induced Vibration Group and Expert/Leader of Fluid-Structure-Sound Interaction Group at Sulzer Innotec Limited, Switzerland (81-97); Guest Scientist Karlsruhe University, Germany (87-88); Professor of Mechanical Engineering at McMaster University, Canada (98-present); Dept Chair of Mechanical Engineering at McMaster University (03-08). Prof. Ziada has also been the visiting professor at Trinity College, Ireland (08); Ecole Centrale de Lyon, France (09); Technical University of Vienna, Austria (09); Applied Dynamics Laboratory, Portugal (10); CNRS/EDF Research and Development, France (12). Prof. Ziada has carried out consultation work for ABB and Alstom (Switzerland), Gentilly Nuclear Power Plant (Quebec), Rolls Royce Defence Division (England), US Nuclear Regulatory Commission, Argonne National Laboratory, Structural Integrity Associates, Control Components Inc (USA), Bombardier, Babcock & Wilcox Ltd, Foster Wheeler Co., Hatch Mott MacDonald, M&I Air Moving Systems, Braon, Kvaerner Chemetics (Ontario, Canada), and other companies. Prof. Ziada has received 4 awards, including: Canadian Foundation of Innovation (CFI), 1998; Best Paper Award in100th Galvanizer's Association Meeting, Baltimore, 2008; Merit Award for Excellence in Teaching granted by McMaster Student Union, 2000, and Premier’s Research Excellence Award granted by the Ministry of Energy, Science and Technology, 1999 to 2003.Prof. Ziada holds 2 U.S. Patents. He has published 8 books & approximately 190 technical papers.