Mechanical Engineering
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Item BIO-INSPIRED PUMPING MECHANISMS IN AN INTERMEDIATE REYNOLDS NUMBER(2018) Saffaraval, Farhad; Kiger, Kenneth; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Pumps are important to applications across a wide range of scales. Most of traditional applications occur within a range where inertia is the dominating factor influencing the pump performance, and hence many practical designs are based on mechanisms that rely on this assumption. As one moves towards smaller devices, however, the increasing effect of viscosity renders these traditional mechanisms ineffective. The current work looks towards a bio-inspired system consisting of an array of oscillating plates to contend with this challenge. The plates are placed within a channel, and the pumping performance generated is examined for a small range of Reynolds numbers intermediate between inertial and viscous regimes (0.1 < Re < 10). The goal of this work is to observe the effect of how different plate kinematics can be utilized to break the symmetry the system to produce a net pumped flow. Rigid and flexible plates are studied, using both sinusoidal and triangle wave actuation kinematics. The tests are first conducted with a single appendage, and then repeated with an array of 5 closely spaced plates to observe the effect of their interaction on the overall performance. The results of the single plate tests indicate that increased asymmetry introduced in the triangle wave actuation results in increased pumping performance as well as energy consumption. Tests were conducted at two Reynolds number conditions, Re = 0.6 and 6. The pumping performance was found to be an order of magnitude higher for the Re = 6 case. In the case of flexible plates, the results show that a mass specific pumping efficiency was higher for the flexible case with a higher frequency at the same Reynolds numbers. For the plate array, the results indicate five flexible plates with 〖∆θ〗_i=-90 will generate more than 4 times the flow rate in comparison to the single flexible plate. Asymmetric triangle actuation in conjunction with symplectic metachronal motion (〖∆θ〗_i=30) exhibits pumping performance more than 10 times of using a single rigid plate. Total work is noticeably higher for multiple plate system and will result in a reduced overall pumping efficiency in comparison to the single appendage.Item FLY-EAR INSPIRED MINIATURE SENSOR SYSTEM FOR TWO-DIMENSIONAL SOUND SOURCE LOCALIZATION(2011) Lisiewski, Andrew Paul; Yu, Miao; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A micro-scale sound localization sensor is developed and studied in this thesis to address the fundamental challenge of miniaturizing sound localization systems. When miniaturizing a microphone array, there is a critical size limitation at which the array will be unable to localize the sound source in a discernible manner. However, a solution to this dilemma came about when studying the hearing mechanisms of a particular fly, known as Ormia ochracea. Background research into the hearing mechanisms of the fly found that it can accurately locate a sound source even though its eardrums are separated by a distance of only 500 μm. The fly's exceptional directional hearing capability has been linked to a distinct mechanical coupling between its two eardrums, which helps amplify minute directional cues. Inspired by the remarkable hearing capabilities of the fly's micro-scale ear, researchers have sought to develop micro-scale sensors to mimic the fly's ear. One limitation of simply imitating the fly's ear is that the fly is only capable of localizing a sound source in one dimension. In this thesis work, the knowledge gained from understanding the fly ear mechanism is applied to achieve the goal of developing a micro-scale sound localization sensor capable of sound source localization in two dimensions. In this thesis, for the first time, micro-scale fly-ear inspired sensor devices employing three or four coupled membranes have been designed. Reduced-order models have been developed to achieve a fundamental understanding of the performance of each sensor design. Furthermore, a micro-scale sensor device incorporating three mechanically coupled membranes arranged in an equilateral triangular configuration has been successfully developed. Experimental study of the sensor device incorporated with a low coherence fiber optic interferometric detection system has suggested that the micro-scale fly-ear inspired sensor can achieve a much improved performance in terms of phase differences and directional sensitivities when compared to a similar sized microphone array constructed with separate microphones. In addition, localization techniques have been developed to best use the fly-ear inspired sound localization sensors. Future work is suggested to incorporate this sensor system with a fully autonomous robot to improve robot homing and navigation.