Mr. Keyur Joshi Profile

Keyur Joshi

at Virginia Polytechnic Institute and State Univ

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Proceedings Article | 8 April 2013 Paper

Physical modeling of Mastigias papua feeding structures and simulation of their effect on bell stress and kinematics

Tyler Michael, Alex Villanueva, Keyur Joshi, Shashank Priya

Proceedings Volume 8686, 868608 (2013) https://doi.org/10.1117/12.2009933

KEYWORDS: Kinematics, Protactinium, Silicon, Biomimetics, Computer aided design, Solid modeling, Video, Finite element methods, Neodymium, Oceanography

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This study reports the progress made towards understanding of the low energy propulsion mechanism of medusae (jellyfish) for developing energy efficient unmanned underwater vehicles (UUV). The focus of this investigation is on identifying the techniques required for prolonged sustainability of UUVs. Inspiration is taken from the constant feeding and energy generation achieved by Rhizostomeae. Rhizostomeae, in particular, utilize oral structures comprised of internal channels that capture zooplankton entrained in flow surrounding and in the wake of jellyfish on distal capture surfaces. A passive model was generated for the capture surfaces utilizing the physical dimensions based upon the morphology of Mastigias papua with a bell diameter of 17.2 cm. Geometry and structure of the oral components were derived from literature, live samples, and digitization of video. Based upon this data, a mold was created using silicone and assembled to achieve jellyfish inspired architecture. Geometries used to create the passive model were input into a Finite Element Analysis (FEA) simulation along with the experimental material properties of jellyfish mesoglea to ascertain the affect that the oral structure has on the kinematics and bell stresses. A forcing function was derived to achieve a close approximation of the jellyfish kinematics for the case of a jellyfish bell with oral structure attached. The same forcing function was applied to the singular bell and an increase in the bending was observed. With the escalation in bending came an increased level of principle stress within the bell closer to the margin. From this the stiffness elements that must be compensated with increased actuation force applied to the bell achieving proper swimming kinematics can be identified.

Proceedings Article | 23 March 2011 Paper

Modeling and optimization of IPMC actuator for autonomous jellyfish vehicle (AJV)

Keyur Joshi, Barbar Akle, Donald Leo, Shashank Priya

Proceedings Volume 7975, 79750Q (2011) https://doi.org/10.1117/12.881483

KEYWORDS: Actuators, Electrodes, Polymers, Thermal modeling, Finite element methods, Polymeric actuators, Optimization (mathematics), Liquids, Optical simulations, Metals

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Ionomeric Polymer Metal Composite (IPMC) actuators generate high flexural strains at small voltage amplitudes of 2-5V. IPMCs bend toward the anode when a potential drop is applied across its thickness. The actuation mechanism is due to the motion of ions inside it; which requires a form of hydration to dissociate and mobilize the charges. In our group IPMCs are developed either water based or Ionic Liquid based which is also known as the dry IPMCs. This combination of small voltage requirement with operation in both dry and underwater conditions makes the IPMCs a viable alternative for an Autonomous Jellyfish Vehicle (AJV). In this study, we estimate the mechanical properties of IPMC actuator having curved geometry using FEM model to match the experimental deformation. We combine the results from an electric model to estimate charge accumulated on electrode surface with piezoelectric model to estimate stress due to this charge accumulation. In the last step, the results are integrated with a structural model to simulate the actuator deformation. We have designed an AJV with embedded IPMC actuators using these properties to achieve the curvature of relaxed and contracted Jellyfish (Aurelia Aurita). Bio-mimetic deformation profile was achieved by using structural mechanics of beams with large deformation with only application of +/- 0.8V to optimized beam within 8.1% error norm in relaxed state and 21.3% in contracted state, with only -0.24% to 0.26% maximum flexural strain at maximum curvature point in contracted state.

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