Table of Contents
Journal of Fluids
Volume 2016 (2016), Article ID 3587974, 15 pages
http://dx.doi.org/10.1155/2016/3587974
Research Article

A Volumetric Approach to Wake Reduction: Design, Optimization, and Experimental Verification

1Duke University, P.O. Box 90300, Hudson Hall, Durham, NC 27705, USA
2Duke University, P.O. Box 90291, Hudson Hall, Durham, NC 27708, USA
3Office of Naval Research, Naval Undersea Warfare Center, Newport, RI 02841, USA

Received 22 October 2015; Revised 23 February 2016; Accepted 20 March 2016

Academic Editor: Jose M. Montanero

Copyright © 2016 Dean R. Culver et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Wake reduction is a crucial link in the chain leading to undetectable watercraft. Here, we explore a volumetric approach to controlling the wake in a stationary flow past cylindrical and spherical objects. In this approach, these objects are coupled with rigid, fluid-permeable structures prescribed by a macroscopic design approach where all solid boundaries are parameterized and modeled explicitly. Local, gradient-based optimization is employed which permits topological changes in the manifold describing the composite solid component(s) while still allowing the use of adjoint optimization methods. This formalism works below small Reynolds number (Re) turbulent flow (–10,000) when simulated using small Reynolds-averaged Navier-Stokes (RANS) models. The output of this topology optimization yields geometries that can be fabricated immediately using fused deposition modeling (FDM). Our prototypes have been verified in an experimental water tunnel facility, where the use of Particle Image Velocimetry (PIV) described the velocity profile. Comparisons with our computational models show excellent agreement for the spherical shapes and reasonable match for cylindrical shapes, with well-understood sources of error. Two important figures of merit are considered: domain-wide wake (DWW) and maximum local wake (MLW), metrics of the flow field disturbance whose definitions are described.