Computations of Flapping Flow Propulsion for UUV Design

Abstract

Three-dimensional unsteady computations of the flow past a flapping and deforming fin are performed. The computed unsteady lift and thrust force time histories are validated with experimental data and are in good agreement. Several fin parametric studies are performed for a notional Unmanned Underwater Vehicle (UUV). The parametric studies investigated the force production of the fin as a function of varying the flexibility, the bulk amplitude of fin rotation, the vehicle speed and the fin stroke bias angle. The results of these simulations are used to evaluate the hydrodynamic performance of the vehicle and to support controller development.Computations are also performed to map out the hydrodynamic characteristics of a new test vehicle, designed and built at NRL to demonstrate the hovering and low-speed maneuvering performance of a set of actively controlled curvature fins.

Robotic Pectoral Fin Thrust Vectoring Using Weighted Gait Combinations

“…Unlike in Equation 3, the total weight does not need to add up to 100%. By reducing or increasing the total weight percentage by using scale factors, the total output thrust will also be reduced or increased respectively [11,15]. For supporting evidence, CFD calculated thrust surfaces corresponding to weight amplification are shown in Fig.…”

“…Experimentally, gaits were validated in our test tank in static water -in absence of an applied external flow. As the fin was designed and the gaits were selected for performance in external flow on an UUV, we studied and validated each gait under various realistic flow conditions using CFD coupled with vehicle-level controls simulations [11,15]. Assuming a sensing capability to determine flow was added directly onto or near the pectoral fin [26,27], it would be possible to expand WGC to incorporate additional preprogrammed optimal gaits for any typical external flow.…”

“…Since the importance of each major flapping fin parameter is now relatively well-understood, forward thrust can be determined given any set of fin parameters both computationally [1,2,[5][6][7][8][9][10][11] and experimentally [1,12]. However, no previously published work offered a technique that could take full advantage of these parameters to controllably vector fin thrust at any desired vector -the key focus of this work.…”

Fuzzy logic PID based control design and performance for a pectoral fin propelled unmanned underwater vehicle

“…Initial computational studies to optimize the performance of the NRL fin [3,8] provided a basis for determining which fin parameters to analyze as potential control variables. These controllable fin parameters include bulk fin stroke amplitude (Φ), fin mean stroke position (Φ mean ), deflection of each of the four actuated fin ribs (Γ 1-4 ), and flapping frequency.…”

Research on Under-actuated Flexible Pectoral Fin of Labriform Fish

“…Fig.1 is the skeleton structure of pectoral fin of labriform fish. J.Palmisano et al [10,11] built the bionic fin ray according to the structural and physical properties of fin rays and installed the fin rays on the fin base(viz. scapula, coracoid, radial bones, cartilage pad and so on) in line.…”