2012 Mechanical Engineering Research Opportunities
Prof. Sheryl M. Gracewski
Department of Mechanical Engineering
grace@me.rochester.edu
Research Project #1: Fluid-Structure Interaction Model of Hair Cells in the Cochlea
Motivation: Hearing loss is usually associated with damage to the hair cells within the cochlea which resides within the cochlear sensori-epithelium. There are two types of hair cells within the cochlea, called the inner and outer hair cells. The hair cells receive mechanical stimuli and turn them into electric (neural) signals. Interestingly the two types of hair cells respond to different mechanical stimuli. Outer hair cells are elastically stimulated through attachment to an external tissue. Inner hair cells are viscously stimulated by the fluid flow around them. Why mammalian cochlea has adopted two distinct stimulation ways is not fully understood yet. We would like to study the fluid-structure interaction of the inner hair cells.
Project Description:A finite element model of an inner hair cell bundle will be developed using COMSOL multiphysics, a commercially available code. One section of a hair cell bundle as shown in Figure 1 will be modeled as solid structures, connected by springs that model the tip links, and surrounded by a fluid. The hair bundle is sandwiched between two plate-like structures (In the figure only bottom plate is shown). The relative motion between the plates makes a shear flow around the hair bundle, which deforms it. We will simulate how hair bundles respond to the realistic stimuli.
Figure 1: Fluid-structure interaction of hair bundle. Left) Some experiments used a fluid-jet to stimulate hair bundle. Center) Other experiments used a micro-probe to stimulate hair bundle. Right) Actual stimulation in vivo is different from most experiments.
Research Project #2: Model of the Basilar Membrane of the Cochlea
Motivation:The mammalian cochlea is a frequency analyzer. External sound stimuli are encoded at different locations along the cochlear coil (35 mm in human cochlea) according to their frequency. The human ear can resolve 3.6 Hz in the frequency range between 1000 and 2000 Hz. Without such remarkable resolution, we could not distinguish our friends' voices over the phone. Interaction between the fluid in the cochlear duct and the basilar membrane is believed to be responsible for the tonotopy— the relation between the frequency and the location of maximum basilar membrane response. The goal is to develop a more realistic model of the fluid-structure interaction between the basilar membrane and the intra-cochlear fluid.
Project Description: During the summer of 2011, a Xerox Fellow developed time and frequency domain models of the cochlear duct and basilar membrane within the cochlea. In these models, the basilar membrane was modeled by a series of unconnected springs with varying stiffness. For the current project, these passive springs will be replaced with active, connected components that should predict higher local sensitivity to frequency. These models will be incorporated into a more detailed finite element model of the organ of Corti (the isolated piece in Fig. 1).
Figure 1:Top) The cochlear coil (basilar membrane) has three turns. The sound pressure arrives at the basal (lower, right in the figure) end of the coil. The pressure propagates along the cochlear coil through fluid-structure interaction between the basilar membrane and the fluid filling the cochlear ducts. The color indicates the displacement amplitude of the basilar membrane due to 1 kHz pure tone stimulation. Bottom) The vibration pattern along the midline of the basilar membrane. Three curves are measured at 0.02 ms apart from light to dark lines showing that a wave appears to propagate along the basilar membrane to the location of highest response. This work is done by 2010 Xerox Fellow, Franciscus Wolfs (Mech Eng).
Prof. Paul Funkenbush
Department of Mechanical Engineering
paul.funkenbusch@rochester.edu
Research Project:Using design of experiments methods to understand/control variability in biological systems.
Design of Experiments (DOE) has been extremely successful in better understanding and controlling variability in manufactured products, as part of techniques such as “Taguchi methods” and “Six Sigma”. However, in biological systems variability tends to be much more extreme and is often beyond direct control. For example, the mechanical properties of human bone vary widely among individuals and can’t be selected to control or optimize behavior. What effect does this have on biomechanical analysis of how bones respond to forces? Is it worthwhile (assuming it is even possible) to measure the properties for individuals in order to improve our analyses? In our research we are seeking to adapt and evolve DOE methods to address these types of questions. Work on this project will involve literature (“library”) research to find data, construction of simple models (physical and/or computer), running experiments with these models, analyzing the data produced, and writing-up the results. Students considering this project should be pursuing studies in Mechanical or Biomedical engineering and have an interest in both modeling and biological systems and a desire to work in a new, relatively “uncharted”, area.
Prof. Renato Perucchio
Department of Mechanical Engineering and Biomedical Engineering
rlp@me.rochester.edu
Research Project:
My research and teaching interests are in computational solid and structural mechanics and in the development of engineering practices in antiquity. Ongoing research projects open to qualified undergraduates are in the structural analysis of monumental concrete domes and vaults from Roman Imperial architecture (1st to 4th century A.D.)
Specific objectives for summer 2012: to determine the structural response and the process of structural damage for the Great Hall of Trajan’s Markets in Rome subjected to a typical earthquake. Engineering undergraduates participating in this project are trained in the application of 3D finite element stress analysis, a fundamental modeling technique widely used for research and product development in many areas of modern engineering. They also participate in the development of augmented reality visualization procedures for the display of finite element results on complex 3D models.
The investigation is based on systematic 3D computational modeling and stress analysis of the structural skeleton of each monument and involves creating detailed solid modeling reconstructions on which static and dynamic finite element analysis is performed to simulate gravitational and earthquake loading conditions. This summer the project may involve the laboratory testing of actual structural models. This research is highly interdisciplinary: my students and I work with colleagues in archaeology, architecture and optical engineering, and with curators of monuments in Rome.
