An algorithm for fully resolved simulation of self-propulsion through fluid and an analysis of the hydrodynamics of ribbon-fin propulsion

The study of aquatic locomotion can help us understand the relationship between an organism's hydrodynamics, its motor control, and its morphology. It can also provide fundamental knowledge for applications such as the design of underwater vehicles. To study aquatic locomotion, in this thesis work we present a computational method to fully resolved simulation of self-propulsion. We then go on to apply this algorithm to the hydrodynamics of ribbon fin propulsion. This type of propulsion is used by gymnotiform fish, such as the weakly electric black ghost knifefish (Apteronotus albifrons), a biological model to study sensory processing in vertebrates.;The computational method for the problem of self-propulsion presented here is an iterative algorithm which we call the Fully Implicit Iterative Self-Propulsion Algorithm (FIISPA). The computational method solves for the swimming velocities of the organism with prescribed deformation kinematics. A solution for the surrounding flow field is also obtained. This approach uses a new constraint-based formulation of the problem of self-propulsion developed by Shirgaonkar et al. [1]. The key idea for the constraint-based formulation is to assume that the entire fluid-body domain is a fluid. Then we imposed the constraint that the deformation rate tensor associated with the rigid motion component of the swimming body is equal to zero.;We validate the computational method by simulating self-propulsion of bacterial flag-ella, toroidal swimmers, jellyfish (Aurelia aurita ), and larval zebrafish (Danio rerio). Comparison of the computational results with theoretical or experimental results for the test cases is found to be very good.;We also present a computational and experimental study of the hydrodynamics of ribbon-fin propulsion. The weakly electric knifefish, A. albifrons, can perform impressive maneuvers such as backward swimming, rapid switch of swimming direction and vertical swimming using an elongated anal ribbon fin. Using computational fluid dynamics and digital particle velocimetry, we examine the hydrodynamics of a non-translating ribbon fin in stationary water. We also examine experimentally and computationally how A. albifrons can swim vertically using ribbon fin propulsion. The underlying mechanism and hydrodynamics of this maneuver is presented.