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										<p>We all want to know what happens in the heart of an important person, and never more than on Valentine's Day.</p><p>Well, here's one way to look at it.</p><p>This view inside a beating heart hasn't been seen, or even been seen, until now, according to Rice University mechanical engineer Tayfun Tezduyar, who says such visualizations can help clinicians understand the mechanisms that they push blood through the body and fix things when they go wrong.  .</p><p>Tezduyar, the James F. Barbour Professor of Mechanical Engineering at Rice's George R. Brown School of Engineering, is an expert in fluid-structure interaction modeling whose work spans biomechanics, including the circulatory system, and large-scale systems. such as parachutes, wind turbines and ground vehicles. </p><p>In this research, Tezduyar and colleagues at Waseda University in Japan tackled what he said is one of the most difficult problems in biomechanics: a way to accurately characterize blood flow around and through the heart's valves, taking into account the details of the flow near the surfaces of the three valve leaflets along the way.</p><p>The amazing simulation of a working ventricle-valve-aorta represents calculations first presented by Tezduyar and his Waseda colleagues in 2020. Project leader Kenji Takizawa, a professor in the Waseda School of Creative Sciences and Engineering, was research associate at Rice beginning in 2007, establishing an ongoing collaboration with Tezduyar.  His research associate, Takuya Terahara, who also spent time at Rice as a visiting Ph.D.  student in 2018, produced the animation.</p><p>The animation shows two views of the ventricle-valve-aorta, top and side, and reveals in great detail how the ventricle fills with blood, how quickly the three-leaf valve opens to relieve pressure, and the turbulent flow of blood through as you push through. </p><p>"This is computational technology that no one else in the world currently has with this level of precision near the surfaces of brochures," Tezduyar said.  “We recently became aware that folks at the Texas Medical Center are requesting CFD (computational fluid dynamics) simulations of the cardiovascular system.  I think maybe they were referring to what happens only in the aorta, and that would have been much easier.  But we went a little further."</p><p>Tezduyar said the simulation incorporates the valve mechanism and fluid flow through the aorta and its three arterial branches.  "That's a very difficult calculation," he said.  “When someone needs to make decisions based on a simulation, the main issue is how accurate and reliable it is.  The opening and closing of valves makes it extremely complex, and in general, the more complex a simulation becomes, the less reliable it might be. </p><p>"What we've done is maintain both complexity and precision," he said.  “It was a painstaking job.  Modeling three-leaflet valves that touch each other, completely shut off blood flow, and then open again, and to do so with an accurate representation of flow patterns near the leaflets, is a challenging new class of problems in fluid mechanics".</p><p>He said the model is detailed enough to capture the spiraling motion of blood in the aorta.  “We need to represent the flow patterns in these walls correctly to assess shear stress in arterial walls, which is related to aneurysm risk,” said Tezduyar, who co-leads the Advanced Flow Modeling and Simulation Team with Takizawa.</p><p>"This is valuable information for clinicians looking for ways to cure heart disease," he said.  "For example, the model would help them evaluate replacement valves, including geometry, thickness and material."</p><p>Tezduyar said he and Takizawa are open to discussing long-term collaborative work on patient-specific simulations with clinicians.</p> 									</div>
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