Hydrodynamic Performance and Shape Considerations of a Compact AUV for Riverine Environments

The riverine environment presents an interesting operational challenge for an autonomous underwater vehicle (AUV). The fluid dynamics involved are complex and in many ways more demanding than the open ocean waters for which most current vehicles have been designed for. These dynamics encompass strong head-on and side currents, shallow waters with bottoms that may be either rocky, hard or soft mud, topological bends or bifurcations that can lead to strong secondary flows, and local dense vegetation or artificial structures that introduce local flow perturbations. As an initial first step to engineering an AUV shape that can perform well in the riverine environment, one needs to better understand the fluid dynamics involved, both from a discrete, as well as, from a compounded point of view. The current paper reports on an ongoing investigation into the flow physics and dynamics involved within the riverine environment, with the interest of generating requirements that can provide guidance into AUV shape design. A cylindrical shape of high length-to-diameter ratio, indicative of most previously developed AUVs, serves as the nominal point of departure for the analysis.