Pitt mechanical engineering researcher receives NSF award to better describe how liquids interact within solid structures

PITTSBURGH (September 19, 2016) … The infamous collapse of Washington State’s Tacoma Narrows Bridge in 1940 is a textbook example of how harmonic resonance can cause structural failure. Likewise, in principle, similar phenomena could occur in the delicate vessels and arteries in the human body. Researchers at the University of Pittsburgh’s Swanson School of Engineering are utilizing a $121,027 National Science Foundation award to study the interaction of a viscous liquid within a solid body and investigate which mathematical models best describe the phenomena.

Principal investigator of the three-year study, “On the Occurrence of Resonance in Elastic-Dissipative Coupled Systems,” is Giovanni P. Galdi, PhD, the Leighton E. and Mary N. Orr Professor of Mechanical Engineering and Professor of Mathematics. Dr. Galdi, a world-renowned expert within the field of mathematical fluid mechanics and editor-in-chief of the Journal of Mathematical Fluid Mechanics, has been sole PI in seven NSF grants over 20 years.

“The study of the motion of a viscous liquid in the presence of rigid or deformable bodies has become one of the main focuses of applied research. However, there is a lack of a rigorous explanation of the phenomena and identify the good versus bad mathematical models,” Dr. Galdi said. “Our first goal is to study the blood flow model, and then to examine when a liquid is impinging on an elastic framework.”

Dr. Galdi explained that in the context of modeling of arterial blood flow, it is important to determine whether, for a given model, the pulsatile action of the heart pumping blood would produce an unrealistic high-amplitude oscillation of the arterial wall. While under normal circumstances such a condition would not occur, Dr. Galdi said that better understanding the models would give researchers a better understanding of how the circulatory system operates.

The second goal will examine the vortex-induced oscillations of a structure in the uniform stream of a viscous liquid. Dr. Galdi references the Tacoma Narrows Bridge event to explain how this phenomenon plays a major role in the collapse of structures such as chimneys and bridges under wind load. “Just like blood flowing through an artery, wind acts like a fluid when it impacts a solid structure. For example, you can see it in action when a flag waves in a strong wind. We utilize mathematical models to determine the quantitative relation between magnitude of upstream velocity and frequency of oscillation, which are critical when designing larger structures like bridges and office towers.

“Fluid mechanics plays such an important role in everything from the human body to construction to even the potential for nano-sized robots, so this research can help to identify the most appropriate models to use.”

###