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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., Cataloged from student-submitted PDF version of thesis., Includes bibliographical references (pages 143-151)., Fish present a natural source of inspiration for the design of high-performance under-water robots. Conventionally, fish-like robotic systems consist of a chain of rigid links connected by a series of rigid actuators. Devices of this nature have demonstrated impressive speeds and maneuverability, but from a practical perspective, their mechanical complexity can make them expensive to build and prone to failure. One possible solution is to replace the mechanical body of the swimmer with a passive elastic element. In this scenario, the robot uses a single actuator, housed within a rigid forebody, to generate a fish-like propagating wave along a flexible trailing tail. A number of groups have explored this approach, but so far, these devices have demonstrated relatively limited performance. Here, we study the kinematics and dynamics of elastic swimmers and apply the results of this process to guide the design and testing of a high-performance passive robotic swimmer. We begin the investigation with a first-principles approach. We use analytical models of fish hydrodynamics to characterize the kinematics of efficient propulsion in swimming animals. Armed with the insight developed through this process, we construct a numerical model of a passive elastic swimming sheet. Through the application of optimization methods, we demonstrate that the sheet can achieve 70-80% of the efficiency of an equivalent swimmer with actuators along its entire body. Based on this, we design, build, and test a passive elastic swimming robot which uses a novel inertia-based actuation system. Experiments with the robot show that it can achieve a top speed of 1m/s (3.17 body lengths/s) and a peak turning rate of 515 deg/s, among the highest reported to date, while swimming at efficiencies comparable to those of fully actuated systems., by Alexander Joshua Wiens., Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., Cataloged from student-submitted PDF version of thesis., Includes bibliographical references (pages 129-134)., This thesis investigates the mechanics of swellable elastomeric seals for the purpose of hydraulic fracturing in oil and gas applications. The first component of the thesis is the development of a laboratory-scale apparatus for the visualization of swellable seals in situ up to the point of leakage. Experiments using this apparatus show that leakage is a result of large, nonuniform deformation that stretches the seal material tangential to the sealing surfaces and leads to a corresponding loss of traction normal to the sealing surfaces due to Poisson contraction. This phenomenon was investigated in two analogous seal systems - an O-ring and a rectangular swellable elastomer used to seal a rectangular channel. Both analog systems exhibit leakage due to the same mechanism. Corresponding finite element simulations predict a fluid leakage path that agrees qualitatively with experiments. The second part of this thesis consists of an experimental investigation of the eect of geometry and metal support rings on the performance of swellable seal systems. Although this work is highly applied, it reveals two interesting results. The first is that mechanical supports, in the form of rigid metal support rings, provide most of the support for the applied differential pressure. Secondly, in some seals, changing the length of the rubber part of the seal does not significantly affect the maximum differential pressure that the seal can support. Motivated by the experiments showing no dependence of critical leakage pressure on seal length, we conduct an analytic investigation of the combined effects of compressibility and aspect ratio on the performance of the seal system. We nd an approximate, linear elastic Saint-Venant type solution that agrees well with nonlinear (finite deformation neo-Hookean) finite element simulations, indicating nonlinear effects are unimportant in the bulk of the seal, and only important at the high-pressure and low-pressure ends. Using finite element simul, by Benjamin C. Druecke., Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015., Cataloged from PDF version of thesis., Includes bibliographical references (pages 45-46)., According to the Munch mechanism, vascular plants rely on osmotic pressure gradients to export sugars from regions of synthesis (mature leaves) to sugar sinks (roots, fruits). A crucial step in this process is the loading of sugars from photosynthetic cells to the export conduit (the phloem). In this thesis, we developed a synthetic microfluidic osmotic pump mimicking the mechanism of passive phloem loading, where sugars are transported by diffusion from a sugar reservoir to the phloem. This design allows the development of steady flow over several hours. We show that in our system, phloem concentration is set by a relative balance between loading by diffusion from the source and export by convection through the phloem, via a single nondimensional system-scale Peclet number that we call the flushing number. For large flushing numbers, export is limited by diffusion from the source, and flow rates scale weakly with transport resistance. For low flushing numbers, export is limited by convection through the phloem and phloem concentration is close to that of the source, leading to efficient export of water and sugars. In plants, passive phloem loading is used predominantly by trees. We show that the hydrostatic pressures developed in our synthetic system can reach up to ten bars and are thus compatible with the pressures expected to drive long-distance transport in large trees. Moreover, we show that the regime of efficient export in passive loaders is more accessible to plants with large transport resistances, providing a rational for the use of the passive loading mechanism by most tree species., by Jean Comtet., S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014., Cataloged from PDF version of thesis., Includes bibliographical references (page 30)., Immunology researchers require a new type of fish tank that provides a linear thermal gradient for experimental zebrafish in order to improve the accuracy and validity of their research. Zebrafish require the ability to select their surrounding water temperature in order to react to a simulated viral infection with an optimized immune response. Although countless immunology studies have been performed with zebrafish to date, their validity came into question in early 2013 when it was demonstrated by MacKenzie et. at that the immune response in fish is critically coupled with a form of environmental temperature selection known as behavioral fever. Current research tanks feature a uniform temperature throughout, preventing the fish from being able to "choose" their surrounding water temperature in response to a simulated viral infection. "Fish that are not offered a choice of temperatures and that therefore cannot express behavioral fever show decreased survival under viral challenge." (MacKenzie, et al., 2013) In this study, a conceptual thermal-fluid system was designed, built, and tested for its ability to establish a stable, linear thermal gradient in a standardsize 10L laboratory tank. The thermal profile of the volume of water contained within the experimental tank was determined from temperature measurements taken at incremental depths. The apparatus was found to produce a suitably linear temperature gradient over a base-to-surface temperature difference of 19.6°0C; far greater than the temperature difference of 8°C necessary for unrestricted behavioral fever to be expressed in experimental zebrafish. As such, it was determined that the approach taken is suitable for future use in the development of aquaria for immunology research and water tanks for other applications., by Romi Sinclair Kadri., S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013., Cataloged from PDF version of thesis., Includes bibliographical references (p. 73-75)., Interactions between capillary and elastic effects are relevant to a variety of applications, from micro- and nano-scale manufacturing to biological systems. In this thesis, we investigate capillary flows in extremely flexible, millimeter-scale cylindrical elastic tubes. We demonstrate that surface tension can cause sufficiently flexible tubes to collapse and coalesce spontaneously through non-axisymmetric buckling, and develop criteria for the initial deformation and complete collapse of a circular tube under capillary pressure. Experimental results are presented for capillary rise and evaporation of a liquid in a flexible tube. Several regimes are seen for the equilibrium state of a flexible tube under capillary pressure, and deformations of the tube walls are measured in different regimes and compared with a shell theory model. Good agreement is found between experiments and theory overall. Analysis and experimental results show that despite the complex and non-axisymmetric deformed shapes of cylindrical structures, the elastocapillary length used in previous literature for flat plates and sheets can also apply for flexible tubes, if the tube radius is used as the characteristic length scale., by Theresa B. Hoberg., S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013., Cataloged from PDF version of thesis. Page 168 blank., Includes bibliographical references (p. 155-167)., The motion of biological systems in fluids is inherently complex, even for the simplest organisms. In this thesis, we develop methods of analyzing locomotion of both mechanical and biological systems with the aim of rationalizing biology and informing robotic design. We begin by building on existing visualization framework by studying an idealized swimmer: Purcell's three-link swimmer, at low Reynolds number. This framework allows us to illustrate the complete dynamics of the system, design gaits for motion planning and identify optimal gaits in terms of efficiency and speed. We extend the three-link swimmer case to include effects such as the interaction between the links. By studying several systems, we broaden the applicability of our framework. These systems include a two-link swimmer at low Reynolds number with offset centers of buoyancy and mass and a swimmer with a continuously deformable shape, the serpenoid swimmer. Drawing on the principles behind the serpenoid swimmer, we develop the kinematic decomposition, a method using a singular value decomposition (SVD) that describes the motion of complex systems in a low order manner. We show that with only two degrees of freedom, one can adequately describe an animal's motion. We apply this method to species in both high and low Reynolds number environments to elucidate different phenomena, including chemotaxing and species comparison in spermatozoa, gait changes in eels (steady versus accelerating), kinematic responses to viscosity and viscoelasticity in C. elegans (nematodes), and the Kirmin gait in trout. Combined with our visualization framework, we successfully illustrate the generalized utility of the kinematic decomposition method to explore and understand fundamental kinematics of a wide range of both natural and man-made systems., by Lisa Janelle Burton., Ph.D.

We consider a small droplet of water sitting on top of a heated superhydrophobic surface. A toroidal convection pattern develops in which fluid is observed to rise along the surface of the spherical droplet and to accelerate downwards in the interior towards the liquid/solid contact point. The internal dynamics arise due to the presence of a vertical temperature gradient; this leads to a gradient in surface tension which in turn drives fluid away from the contact point along the interface. We develop a solution to this thermocapillary-driven Marangoni flow analytically in terms of streamfunctions. Quantitative comparisons between analytical and experimental results, as well as effective heat transfer coefficients, are presented., National Science Foundation (U.S.) (CTS-045609), National Science Foundation (U.S.) (CCF-0323672)

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012., Cataloged from PDF version of thesis., Includes bibliographical references (p. 35)., The ability of surfactants to lower surface tension makes them a key element in many products in a variety of industries. Trisiloxane surfactants have shown extraordinary wetting on hydrophobic surfaces, and are known as "superspreaders". Studies in the past have had inconsistent results characterizing the spreading of these surfactants. In this study, the radius and contact angle during spreading of different concentrations of trisiloxane ethoxylate are measured in a humidity-controlled box. Consistent with other studies, concentrations above the critical aggregation concentration spread more, resulting in lower contact angles and larger radii. The spreading behavior for radius and contact angle can be modeled using an exponential fit. Using the exponential models, a relationship between spreading velocity and contact angle can be found. For concentrations above the critical aggregation concentration, a linear relationship between contact angle and spreading velocity was found., by Sean K. Vaskov., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012., Cataloged from PDF version of thesis., Includes bibliographical references (p. 43)., This thesis reviews the design of a fluidized bed test setup for testing digging kinematics of RoboClam, a burrowing device based on Atlantic Razor Clams. This test bed allows for in-lab testing in an environment covered by water, eliminating the need to test in the mud flats where razor clams live. Between each RoboClam test, water is pumped through a distributor plate, which suspends and fluidizes the glass bead media, leading to redistribution of the substrate and unpacking. The new fluidized bed system has two key improvements over the current system. It improves the redistribution that is needed between each test to reset the substrate. Before each test it also unpacks the beads, which prevents packing over time created by the current vibration redistribution system that causes changes to the soil mechanics. This system will enable continued testing of the current RoboClam device and facilitate the development of the next generation burrowing device., by Daniel Scott Dorsch., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012., Cataloged from PDF version of thesis., Includes bibliographical references (p. 18)., In many locations, soil is held in place by the roots of plants. When these plants are removed or die, the soil loses its cohesive strength and erodes away. We seek to create artificial soil stabilizers that use the same physical principles as the plant roots. To investigate how flexible materials can stabilize soil, we use photoelastic particles to analyze the forces within a system when a flexible intruder is introduced to the system. We report on the increase in system forces as an effect of the flexible intruder and compare it to experiments with plant roots. Since soil is a granular material, using this method to increase the forces within patches of soil may help prevent erosion or landslides., by Katharine Luginbuhl., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., Cataloged from student-submitted PDF version of thesis., Includes bibliographical references., MIT has a vibrant culture of innovation and a rich history of entrepreneurship. Over the years, many organizations, programs, centers, courses, and competitions have been created to kindle, foster, and celebrate the entrepreneurial spirit on-campus. Together, these form the MIT entrepreneurial ecosystem. Despite the wealth of these resources, more than half of graduating seniors say that they are not prepared to start a company. This thesis seeks to understand this phenomenon by investigating the undergraduate student body's awareness of various parts of the entrepreneurial ecosystem through a survey questionnaire. Lack of visibility of these resources is hypothesized and then proven. It was found that students who are not interested in entrepreneurship have not heard about any resource other than the $100K Competition. It was also found that the majority of students who are interested did not know about many of the resources that their peers have found the most helpful. Based on survey data, three groups (the Martin Trust Center for MIT Entrepreneurship, Founder's Journey, and the MIT $100K Competition) were chosen for an in-depth study because they have done an exceptional job raising awareness for themselves, allowing them to provide tremendous value for their students. Longer interviews were conducted with a representative from each of these groups. Shorter interviews, often by email, were also conducted with 25+ students to learn about what resources were most valuable to them and how they found them. It was found that these programs reached out to the student body in two major ways: emails to large mailing lists and word of mouth. Using emails sent to the majority of the student body, the$100K was able to gain tremendous visibility to undergraduate students, unrivaled by any other groups. On the other hand, the Trust Center does not use mass emails, relying instead on word-of-mouth recommendations from the students who are already familiar with the Center. Thi, by Kuan Cheng., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012., Cataloged from PDF version of thesis., Includes bibliographical references (p. 27)., This thesis describes and analyses sedimentation experiments of a bead in various concentrations of aqueous PEG. These experiments are intended to be first order approximations of free-swimming organisms sedimenting in viscoelastic fluids and serve as a precursor to further experiments involving free-swimming organisms swimming in viscoelastic fluids. The post-processed data from these experiments are presented as colour maps in graphs of Reynolds number versus Deborah number, revealing that the velocity and vorticities are more sensitive to changes in Reynolds number than in Deborah number. However, for the range of viscoelastic fluids experimented with, no quantitative trends were apparent. As such, further experiments will need to be conducted to gain information about the velocity and viscosity maps from a wider range of viscoelastic fluids. Further improvements to the current setup are also suggested and outlined where possible., by Latifah binti Hamzah., S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011., Cataloged from PDF version of thesis., Includes bibliographical references (p. 67-69)., Multi-scale surface interaction methods have been studied to achieve optimal locomotion over surface features of differing length scales. It has been shown that anisotropy is a convenient way of transferring an undirected force to a preferred direction or movement. In this thesis, the fundamentals of friction were studied to achieve a better understanding of how to design multi-scaled robotic feet that use anisotropy for terrestrial locomotion. Static and kinetic friction coefficients were found for novel test geometries under varying load conditions. The test geometries were manufactured with materials of variable durometer and were tested using unconventional rheometry methodology. Test results were then compared to standard friction laws. As predicted, the effects of contact area were shown to have an effect on the friction forces experienced by the softer materials. The contact area effects were then modeled as Hertzian contacts for a given material. Verification of the area dependencies for the materials with adhesive effects was performed for the samples used in the friction tests. The samples were subjected to varying compressive force and images of the corresponding contact areas were obtained using an inverted microscope. The microscope images were then processed using MATLAB's image processing toolbox to find the actual contact area for the samples. The contact area results were shown to be in accordance with Herztian contact principles. The effects of varying surface roughness were also studied for a given anisotropic arrangement of bristles. The array of bristles was used to provide propulsion to a controllable robot called BristleBot. The untethered nature of the robot allowed for unhindered velocity and force measurements that were used to analyze the effects of surface roughness. The force input for the robot was provided by two vibration motors that created an excitation which was then translated to horizontal movement by the anisotropic formation of, by Jeffrey W. Morin., S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011., Cataloged from PDF version of thesis., Includes bibliographical references (p. 91-97)., The aim of the research presented in this thesis is to generate compact, lightweight, low-energy, reversible, and dynamic burrowing systems for use in subsea applications such as anchoring, oil recovery, underwater cable installation, mine detonation, and sensor placement. As many organisms have evolved to embed themselves within undersea substrates, unsurprisingly, nature has provided a viable basis for a novel, efficient burrowing technology. This work centers around understanding the burrowing mechanisms of Ensis directus, the Atlantic razor clam, which was discovered to burrow by using motions of its valves to locally fluidize the surrounding substrate. Moving through fluidized, rather than static, soil reduces drag forces to a level within the animal's strength capabilities and results in burrowing energy that scales linearly with depth, rather than depth squared. As Ensis contracts its valves, the resulting stress imbalance within the soil creates a failure surface around the clam, within which particles can freely move and fluidize, and outside of which the soil remains static. Theoretical derivations and experimental results demonstrate that the location of the failure surface can be predicted using only two parameters commonly measured in geotechnical surveys: coefficient of lateral earth pressure and friction angle. To explore the feasibility of transferring localized fluidization burrowing into engineering applications, RoboClam, a robot that burrows using the same mechanisms as Ensis, was designed, constructed, and tested. Experimental data show the machine is able to match the animal's linear burrowing energy versus depth relationship and achieve localized fluidization in both granular and cohesive substrates., by Amos Greene Winter, V., Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010., Cataloged from PDF version of thesis., Includes bibliographical references (p. 20)., Data was gathered and analyzed through a survey of the Mechanical Engineering Course 2 and Course 2-A Alumni to analyze the impact of their choice of major on their current career path and to investigate the career paths of mechanical engineering majors. Data was gathered on their jobs taken, confidence level compared to their peers, preparation and importance abilities, experiences, and reflections. Over 350 graduates completed the survey and several differences were found. Course 2-A students had more transfers from other majors, engaged in a wider variety of career options, and found their elective classes more useful. Course 2 students reported to have a greater importance for technical skills and a higher confidence level with respect to their peers in their profession. There was little difference in most abilities, and what was missing in their MIT experience. Overall, Course 2 and 2-A reported being better prepared for technical subjects and less prepared for communication-related subjects than was required in their job. Moreover, all respondents mentioned missing the same courses in their curriculum that was needed for their job. Finally, Course 2 and 2-A respondents held widely divergent impressions of the other's program. Empirical data suggests that each major possesses qualities to satisfy the specific course's individual needs. This resulted in the conclusion that the Mechanical Engineering Department was on the right path by supporting the Course 2-A major and by recognizing and catering to two separate populations, one with an interest in depth and one with an interest in breadth., by Neha Batra., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009., Cataloged from PDF version of thesis., Includes bibliographical references (p. 38)., This paper presents the detailed design process for a compliant underwater angle sensor to be used in analyzing the precise burrowing motions of razor clams in order to aid in the development of intelligent anchoring devices. The angle sensor was developed using a set of specific functional requirements, theoretical kinematic and structural models, and an iterative prototyping process. The resulting sensor is a device that can measure the angle between the two halves of a clam's shell versus time using a thermal-centric strain gauge configuration. The device is saltwater compatible, does not hinder the motions of the clam and only increases the axial drag on the clam by 2.3 to 5.5%. Data can now be collected using this sensor that will be important to creating a strategy for the coordination of the movements of a robotic anchor that would improve upon existing anchoring technologies for marine applications ranging from small boats, to Autonomous Underwater Vehicles (AUVs), to spy equipment., by Caitrin Elizabeth Jones., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009., Cataloged from PDF version of thesis., Includes bibliographical references (p. 30)., In the realm of systems with Reynolds numbers less than 1, swimming is a difficult task. Viscous forces from the fluid dominate inertial forces. In order to propel itself, a mechanism must be designed to overcome the viscous forces from the fluid and satisfy the non-reciprocal, cyclic motion requirements of the Scallop Theorem. Furthermore, a swimmer must employ one of the three mechanisms stated by Purcell to be capable of swimming at low Reynolds number, a three link swimmer, a corkscrew, or a flexible tail. Three devices utilizing the flexible-tail paradigm of swimming were tested using silicon oil to simulate a Reynolds number of approximately 0.6. Design parameters were uncovered which determine the successfulness of the swimmer and can be used for creating future successful flexible-tail swimmers., by Sarah Elizabeth Cole., S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010., Cataloged from PDF version of thesis., Includes bibliographical references (p. 105-[111])., Locomotion of biological systems have fascinated physicists and engineers alike for centuries. In particular, we are interested in the motion of self-propelling bodies near an air-water interface in the low Reynolds number limit. To investigate this problem, we take two very different approaches. We first consider the locomotion of a specific organism, namely, a water snail, that exhibits a striking ability to "crawl" beneath the free surface. By modeling the foot of the snail as undergoing a simple sinusoidal motion, we apply lubrication approximations for small deformations to rationalize this peculiar mode of transport and its dependency on surface tension. Inspired by this study, the second part of my thesis focuses on the general two-dimensional model of an organism that utilizes a free surface to propel itself. Based on conformal mapping techniques, we are able to derive exact solutions describing the highly nonlinear coupling between the motion of the swimmer and the free surface deformations, without putting any limits on the deformation size. These closed-form solutions are then applied to optimization questions. In the high Reynolds number limit, swimming near the free surface is known to increase drag on the swimmer due to the cost associated with creating surface waves. However, we find that, for a low Reynolds number swimmer that utilizes the free surface to move, a different power law relation between the distance from the interface and the swimming efficiency exists, implying that the presence of the free surface can be beneficial in certain parameter regimes., by Sungyon Lee., Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010., Cataloged from PDF version of thesis., Includes bibliographical references (p. 38)., In 2004, The National Academy of Engineers (NAE) released a report calling for changes to be made to the current engineering education system in response to the growing need for engineering graduates who would be able to understand engineering problems in a larger context. The present study hopes to gain a better understanding of the growth of flexible engineering education by determining differences in student characteristics and their effect on a student's choice of academic program, identifying the perceptions of the MIT community of flexible and traditional engineering programs and how these perceptions changed over time, and establishing whether or not a correlation exists between students' perceived self-efficacy in engineering and professional abilities and his or her career plans. An online survey was developed and administered to the Course 2 and Course 2-A student body. Significant differences in motivation, opinion of Course 2 and Course 2-A, as well as perceived self-efficacy were found between Course 2 and Course 2-A students., by Shanette A. Go., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008., Includes bibliographical references (leaf 17)., Current wheelchair designs in developing countries create many difficulties for their users. In Kenya, wheelchair users are often unable to use public transportation, and thus are isolated and usually without work. This thesis outlines a feasible design for a retrofittable motorized module for a hand-powered tricycle produced and widely distributed throughout Kenya. There are many mobility aids that are similar to the Kenyan handcycle, which can also adapt the module design. By using this innovative module, users will be able to increase their range of travel and access areas where human-powered transport is not sufficient. This simple addition will improve the quality of life for the physically disabled user. This work will be presented to a wheelchair workshop summer 2008 in hopes to convert it into a feasible design for production. Increased reliable mobility will allow the disabled community in Kenya to apply for jobs, and even be afforded opportunities in micro-business for the first time. The design of the powertrain consists of a common motorized bicycle 2 hp engine and a two-stage gear reduction. The control system uses an analogous setup to that of a motorcycle. This control system is integrated into the layout of the chair. Three operation modes are possible with this design: hand-powered only, engine-powered only, or hand-powered with motor-assist., by Nathan Philip Wang., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007., Includes bibliographical references (p. 27)., Deployable Structures had not been designed for use in the oil field industry, and additionally have not been designed as devices to perform mechanical work. By analyzing deployable structures a detailed understanding of the mechanism kinematics has been developed. Further, we have analyzed new design concepts of deployable structures that include void filling alterations and snap fit strengthening. The actuation and mechanical loading of the structures and the input to output force ratio were investigated. This understanding was applied to several actuation methods., by Logan Munro., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007., Includes bibliographical references (leaf 31)., Hovering is normally achieved using a horizontal wing path to create lift; bees, wasps and helicopters use this technique. Dragonflies hover using a unique method, by flapping along an inclined stroke plane. This seems to create a higher efficiency than is possible for normal hovering. The aim of this project is to build a mechanical model to mimic the aerodynamic properties and hovering motion of dragonflies. Through the design and evaluation of this model, we can evaluate the mechanical feasibility of reproducing the wing path using single motor control and establish whether the difference in stroke plane is advantageous for the dragonfly. By adjusting the initial angle of attack of the ornithopter's wings, we can artificially recreate varying stroke planes. A comparison of the resultant lift generated from different stroke planes showed that greater lift forces were generated with non-zero stroke planes as demonstrated in normal hovering., by Theresa Guo., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004., Includes bibliographical references (leaf 51)., In this thesis, I investigate the utility of high speed imaging for gaining scientific insight into the nature of short-duration transient fluid phenomena, specifically applied to the Kaye effect. The Kaye effect, noted by A. Kaye in the March 9, 1963 issue of Nature, is the deflection and rebound of a free-falling non-Newtonian fluid stream incident on a pool of the same fluid. The effect was successfully reproduced using Suave[TM] shampoo, and imaged using the Phantom[TM] High Speed Video system. This task involved developing a knowledge of the photographic process as applied to high speed imaging, and of non-Newtonian fluid mechanics. No precisely reproducible method for producing rebounding streams was found, and behavior contrary to the existing body of observation were noted. In conclusion, areas that merited further investigation and potential variables of interest to future Kaye effect research are discussed., by Benjamin H. Gallup., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005., Includes bibliographical references (leaf 41)., New technologies and techniques have enabled oil companies to access oil deposits by drilling through the ground horizontally. These increased capabilities have improved drilling efficiencies, and have also reduced the effects that drilling has on the local environment. These boreholes can be enormously long, and it is often necessary to send a tethered robot into the hole in order to gather information. If these robots remain stationary for too long, however, their tethering cables can become stuck in the mud cake lining the walls. The recovery or replacement of these robots is time consuming and expensive, so it is desirable to understand how and why the cables sink. In this analysis, the mud cake is modeled as a Newtonian fluid. The surface of the cable is approximated as being either parabolic or circular, and it is shown that the sinking is governed by exactly two dimensionless parameters in both cases. Matlab is used to visualize the evolution of the fluid pressure distribution with time, as well as the time it takes for the cylinder to settle to 20 percent of the mud cake thickness., by Kevin T. Chen., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004., Includes bibliographical references (p. 18-20)., By imitating nature, man finds ways to expand his capacities. To achieve this aim, he often takes natures designs, simplifies them to their most basic principles and then works in a retrograde fashion to add back the complexity originally stripped away to make the first discoveries. This thesis is based on previous work done on modeling snail movement on a macroscopic scale using a motor driven wave propagation machine. This project scaled down the mechanism to a size more commonly found in nature. This downscaling required a new method for producing waves. Peristaltic pumping achieved through the use of soft-lithography and pneumatics was the method chosen. This combination of ideas proved challenging for several reasons. First, the pumping method had previously only been used with one channel per pneumatic input, whereas the snail required each input to feed a multitude of branching channels creating a more complicated fluid dynamics problem. Second, the snail waves were downscaled from a continuous sinusoid to the three phase stepping mechanism of the peristaltic pump. Each three-phase cycle was considered equivalent to one wavelength. Thus, after creating a design that could move, the ratio between the traveling wavelength speed and subsequent net movement were compared to the aforementioned mathematical model. The model's ratio was 0.56 net/wave velocity. The actual ratio was .05 net/wave velocity. The difference by an order of magnitude could be attributed to the discontinuity of the pumping mechanism as opposed to the continuous nature of an actual traveling wave., by Pey-Hua B. Hwang., S.B.