Thrust Production in Highly Flexible Pectoral Fins: A Computational Dissection

2011 ◽  
Vol 45 (4) ◽  
pp. 56-64 ◽  
Author(s):  
Srinivas Ramakrishnan ◽  
Meliha Bozkurttas ◽  
Rajat Mittal ◽  
George V. Lauder
Keyword(s):  
Computational Analysis ◽  
Autonomous Underwater Vehicles ◽  
Underwater Vehicles ◽  
Bluegill Sunfish ◽  
Robust Performance ◽  
Pectoral Fin ◽  
Pectoral Fins ◽  
And Performance ◽  
Thrust Production ◽  
Computational Dissection

AbstractBluegill sunfish pectoral fins represent a remarkable success in evolutionary terms as a means of propulsion in challenging environments. Attempts to mimic their design in the context of autonomous underwater vehicles have overwhelmingly relied on the analysis of steady swimming. Experimental observations of maneuvers reveal that the kinematics of fin and wake dynamics exhibit characteristics that are distinctly different from steady swimming. We present a computational analysis that compares, qualitatively and quantitatively, the wake hydrodynamics and performance of the bluegill sunfish pectoral fin for two modes of swimming: steady swimming and a yaw turn maneuver. It is in this context that we comment on the role that flexibility plays in the success of the pectoral fin as a versatile propulsor. Specifically, we assess the performance of the fin by conducting a “virtual dissection” where only a portion of fin is retained. Approximately 90% of peak thrust for steady swimming is recovered using only the dorsal half. This figure drops to 70% for the yaw turn maneuver. Our findings suggest that designs based on fin analysis that account for various locomotion modes can lead to more robust performance than those based solely on steady swimming.

Understanding the Hydrodynamics of Swimming: From Fish Fins to Flexible Propulsors for Autonomous Underwater Vehicles

2008 ◽  
Vol 58 ◽  
pp. 193-202 ◽  
Author(s):  
Meliha Bozkurttas ◽  
James Tangorra ◽  
George Lauder ◽  
Rajat Mittal
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Mechanical Design ◽  
Research Effort ◽  
Autonomous Underwater Vehicles ◽  
Lepomis Macrochirus ◽  
Direct Result ◽  
Bluegill Sunfish ◽  
Pectoral Fin ◽  
Pectoral Fins ◽  
Vectored Thrust

The research effort described here is concerned with developing a maneuvering propulsor for an autonomous underwater vehicle (AUV’s) based on the mechanical design and performance of sunfish pectoral fin. Bluegill sunfish (Lepomis macrochirus) are highly maneuverable bony fishes that have been the subject of a number of experimental analyses of locomotor function [5, 6]. Although swimming generally involves the coordinated movement of many fin surfaces, the sunfish is capable of propulsion and maneuvering using almost exclusively the pectoral fins. They use pectoral fins exclusively for propulsion at speeds of less than 1.1 body length per second (BL/s). The curve in Fig. 1 depicts two peaks of body acceleration of bluegill sunfish during steady forward swimming. These abilities are the direct result of their pectoral fins being highly deformable control surfaces that can create vectored thrust. The motivation here is that by understanding these complex, highly controlled movements and by borrowing appropriately from pectoral fin design, a bio-robotic propulsor can be designed to provide vectored thrust and high levels of control to AUVs. This paper will focus on analyses of bluegill sunfish’s pectoral fin hydrodynamics which were carried out to guide the design of a flexible propulsor for AUV’s

Motion Analysis of a Manta Robot for Underwater Exploration by Propulsive Experiments and the Design of Central Pattern Generator

2014 ◽  
Vol 8 (2) ◽  
pp. 231-237 ◽  
Author(s):  
Masaaki Ikeda ◽  
◽  
Shigeki Hikasa ◽  
Keigo Watanabe ◽  
Isaku Nagai
Keyword(s):  
Autonomous Underwater Vehicles ◽  
Central Pattern Generators ◽  
Underwater Vehicles ◽  
Loud Noise ◽  
Motion Generation ◽  
Pectoral Fins ◽  
Underwater Propulsion ◽  
Pattern Generators ◽  
Underwater Exploration ◽  
Manta Ray

Although, Autonomous Underwater Vehicles (AUVs) used for investigating underwater ecology have attracted the attention of underwater researchers, conventional AUVs moved underwater by screw propellers generate loud noise thatmay disturb the underwater environments and inhabitants to be observed. This paper discusses the development of an AUV that mimics the manta ray. Central Pattern Generators (CPGs) are also proposed to generate the motion of pectoral fins for Manta robot. The practicality of the robot is checked in underwater propulsion experiments, and the effectiveness of the proposed motion generation method is demonstrated in numerical simulations.

KINEMATICS OF PECTORAL FIN LOCOMOTION IN THE BLUEGILL SUNFISH LEPOMIS MACROCHIRUS

1994 ◽  
Vol 189 (1) ◽  
pp. 133-161 ◽  
Author(s):  
A Gibb ◽  
B Jayne ◽  
G Lauder
Keyword(s):  
Swimming Speed ◽  
Beat Frequency ◽  
Lepomis Macrochirus ◽  
Force Balance ◽  
Total Force ◽  
Bluegill Sunfish ◽  
Pectoral Fin ◽  
Lateral Projection ◽  
Pectoral Fins ◽  
Distal Edge

The pectoral fins of ray-finned fishes are flexible and capable of complex movements, and yet little is known about the pattern of fin deformation during locomotion. For the most part, pectoral fins have been modeled as rigid plates. In order to examine the movements of different portions of pectoral fins, we quantified the kinematics of pectoral fin locomotion in the bluegill sunfish Lepomis macrochirus using several points on the distal fin edge and examined the effects of swimming speed on fin movements. We simultaneously videotaped the ventral and lateral views of pectoral fins of four fish swimming in a flow tank at five speeds ranging from 0.3 to 1.1 total lengths s-1. Four markers, placed on the distal edge of the fin, facilitated field-by-field analysis of kinematics. We used analyses of variance to test for significant variation with speed and among the different marker positions. Fin beat frequency increased significantly from 1.2 to 2.1 Hz as swimming speed increased from 0.3 to 1.0 total lengths s-1. Maximal velocities of movement for the tip of the fin during abduction and adduction generally increased significantly with increased swimming speed. The ratio of maximal speed of fin retraction to swimming speed declined steadily from 2.75 to 1.00 as swimming speed increased. Rather than the entire distal edge of the fin always moving synchronously, markers had phase lags as large as 32 with respect to the dorsal edge of the fin. The more ventral and proximal portions of the fin edge usually had smaller amplitudes of movement than did the more dorsal and distal locations. With increased swimming speed, the amplitudes of the lateral and longitudinal fin movements generally decreased. We used two distal markers and one basal reference point to determine the orientation of various planar fin elements. During early adduction and most of abduction, these planar fin elements usually had positive angles of attack. Because of fin rotation, angles of attack calculated from three-dimensional data differed considerably from those estimated from a simple lateral projection. As swimming speed increased, the angles of attack of the planar fin elements with respect to the overall direction of swimming approached zero. The oscillatory movements of the pectoral fins of bluegill suggest that both lift- and drag-based propulsive mechanisms are used to generate forward thrust. In addition, the reduced frequency parameter calculated for the pectoral fin of Lepomis (sigma=0.85) and the Reynolds number of 5x10(3) indicate that acceleration reaction forces may contribute significantly to thrust production and to the total force balance on the fin.

NOAA’s National Undersea Research Program

2000 ◽  
Vol 34 (4) ◽  
pp. 61-68 ◽  
Author(s):  
Andrew N. Shepard
Keyword(s):  
Research Program ◽  
Environmental Changes ◽  
Autonomous Underwater Vehicles ◽  
Underwater Vehicles ◽  
Federal Program ◽  
Ocean Science ◽  
Oceanographic Research ◽  
And Performance ◽  
Scientific Diving

The National Oceanic and Atmospheric Ad/ministration (NOAA) works to understand ocean and Great Lakes’ environments and their resources, and develop the capability to predict environmental changes. This mission requires a comprehensive oceanographic research program, including the use of undersea technologies. The in situ undersea approach to ocean science allows acquisition of otherwise unobtainable observations, samples, and experimentation. NOAA’s National Undersea Research Program (NURP) places scientists underwater, directly through the use of submersibles, underwater laboratories, and wet diving, or indirectly using remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), and ocean observatories. Scientific diving is an integral part of NURP’s research efforts. The program seeks to safely maximize the capabilities of the nation’s scientific diving community through direct assistance from program experts, and development of new and improved technologies. NURP is also the only federal program with the legislative mandate to improve the safety and performance of divers.

Hybrid Underwater Glider for Underwater Docking: Modeling and Performance Evaluation

2014 ◽  
Vol 48 (6) ◽  
pp. 112-124 ◽  
Author(s):  
Shilin Peng ◽  
Canjun Yang ◽  
Shuangshuang Fan ◽  
Shaoyong Zhang ◽  
Pinfu Wang ◽  
...  
Keyword(s):  
Dynamic Model ◽  
Autonomous Underwater Vehicles ◽  
Experimental Tests ◽  
Underwater Vehicles ◽  
Open Loop ◽  
Hydrodynamic Coefficients ◽  
Underwater Glider ◽  
Underwater Docking ◽  
Motion Performance ◽  
And Performance

AbstractThe development of a novel type of hybrid underwater glider that combines the advantages of buoyancy-driven gliders and propeller-driven autonomous underwater vehicles has recently received considerable interest. However, few studies have considered a hybrid glider with docking capability, which would expand the glider's applications. This study presents a hybrid glider with a rotatable thruster for realizing underwater docking. A tailored dynamic model of the hybrid glider is derived, and the motion performance is evaluated by simulations and experimental tests. A comparison between the experiments and simulations shows that results are in agreement, thus indicating the feasibility of the dynamic model and the accuracy of the hydrodynamic coefficients. In addition, the hybrid glider open-loop docking tests validate the feasibility of the mechanical docking system. Moreover, the experimental tests also validate the glider's different functions and indicate that the hybrid glider with rotatable thruster has high maneuverability even at low speeds. Thus, this type of hybrid glider can be used for underwater docking.

A hydrodynamic analysis of fish swimming speed: wake structure and locomotor force in slow and fast labriform swimmers

2000 ◽  
Vol 203 (16) ◽  
pp. 2379-2393 ◽  
Author(s):  
E.G. Drucker ◽  
G.V. Lauder
Keyword(s):  
Vortex Ring ◽  
Swimming Speed ◽  
Lepomis Macrochirus ◽  
Vortex Rings ◽  
Bluegill Sunfish ◽  
Pectoral Fin ◽  
Pectoral Fins ◽  
Lateral Forces ◽  
Low Speeds ◽  
All Speeds

Past study of interspecific variation in the swimming speed of fishes has focused on internal physiological mechanisms that may limit the ability of locomotor muscle to generate power. In this paper, we approach the question of why some fishes are able to swim faster than others from a hydrodynamic perspective, using the technique of digital particle image velocimetry which allows measurement of fluid velocity and estimation of wake momentum and mechanical forces for locomotion. We investigate the structure and strength of the wake in three dimensions to determine how hydrodynamic force varies in two species that differ markedly in maximum swimming speed. Black surfperch (Embiotoca jacksoni) and bluegill sunfish (Lepomis macrochirus) swim at low speeds using their pectoral fins exclusively, and at higher speeds switch to combined pectoral and caudal fin locomotion. E. jacksoni can swim twice as fast as similarly sized L. macrochirus using the pectoral fins alone. The pectoral fin wake of black surfperch at all speeds consists of two distinct vortex rings linked ventrally. As speed increases from 1.0 to 3.0 L s(−)(1), where L is total body length, the vortex ring formed on the fin downstroke reorients to direct force increasingly downstream, parallel to the direction of locomotion. The ratio of laterally to downstream-directed force declines from 0.93 to 0.07 as speed increases. In contrast, the sunfish pectoral fin generates a single vortex ring per fin beat at low swimming speeds and a pair of linked vortex rings (with one ring only partially complete and attached to the body) at maximal labriform speeds. Across a biologically relevant range of swimming speeds, bluegill sunfish generate relatively large lateral forces with the paired fins: the ratio of lateral to downstream force remains at or above 1.0 at all speeds. By increasing wake momentum and by orienting this momentum in a direction more favorable for thrust than for lateral force, black surfperch are able to swim at twice the speed of bluegill sunfish using the pectoral fins. In sunfish, without a reorientation of shed vortices, increases in power output of pectoral fin muscle would have little effect on maximum locomotor speed. We present two hypotheses relating locomotor stability, maneuverability and the structure of the vortex wake. First, at low speeds, the large lateral forces exhibited by both species may be necessary for stability. Second, we propose a potential hydrodynamic trade-off between speed and maneuverability that arises as a geometric consequence of the orientation of vortex rings shed by the pectoral fins. Bluegill sunfish may be more maneuverable because of their ability to generate large mediolateral force asymmetries between the left- and right-side fins.

Multichannel Magnetometric System for Increasing the Search Capabilities of Autonomous Uninhabited Underwater Vehicles

2021 ◽  
Vol 7 (7) ◽  
pp. 51-60
Author(s):  
Nikolay A. SOKOLOV ◽  
◽  
Andrey V. RYCHKOV ◽  
Grigori N. SHCHERBAKOV ◽  
Igor A. EFREMOV ◽  
...  
Keyword(s):  
Autonomous Underwater Vehicles ◽  
Magnetic Anomalies ◽  
Underwater Vehicles ◽  
Water Area ◽  
Object Type ◽  
Preliminary Assessment ◽  
Spatially Distributed ◽  
Area Survey ◽  
Survey Results ◽  
And Performance

The advantages of using autonomous underwater vehicles in searching for ferromagnetic objects based on recording of spatially distributed magnetic anomalies are considered. The development lines of multichannel magnetometric search tools are shown. The potential capabilities of multichannel magnetometric systems for identifying search objects are revealed. Processing the survey results and drawing up a map of magnetic anomalies will make it possible to identify structures the geomagnetic properties of which differ essentially from the natural magnetic background. The use of such technique opens the possibility to achieve a significantly fuller information content and better reliability of the water area survey results and reveal visually undistinguished objects that have their own magnetic field. Based on the electromagnetic field and magnetostatics theory, a method for calculating the parameters and performance efficiency of the multichannel magnetometric system for autonomous underwater vehicles has been developed. The method is designed to evaluate the parameters of and capabilities for detecting ferromagnetic objects and to make a preliminary assessment of the search efficiency. The results obtained from computer simulation of the multichannel magnetometric system signals have confirmed the possibility of drawing up a map of magnetic anomalies to assess the occurrence depth and location of the search object in the ground. The shape of the search object magnetograms depends not only on the object type, but also on its orientation relative to the surface. By applying this dependence, it is possible to recognize search objects, determine their orientation and occurrence depth.

A Relationship Between Sweep Angle of Flapping Pectoral Fins and Thrust Generation

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Soheil Arastehfar ◽  
Chee-Meng Chew ◽  
Athena Jalalian ◽  
Gunawan Gunawan ◽  
Khoon Seng Yeo
Keyword(s):  
Reynolds Number ◽  
Autonomous Underwater Vehicles ◽  
Water Channel ◽  
Underwater Vehicles ◽  
Flapping Wings ◽  
Decision Making Process ◽  
Sweep Angle ◽  
Pectoral Fins ◽  
Thrust Generation ◽  
Geometrical Factors

Propulsive capability of manta rays' flapping pectoral fins has inspired many to incorporate these fins as propulsive mechanisms for autonomous underwater vehicles. In particular, geometrical factors such as sweep angle have been postulated as being influential to these fins' propulsive capability, specifically their thrust generation. Although effects of sweep angle on static/flapping wings of aircrafts/drones have been widely studied, little has been done for underwater conditions. Furthermore, the findings from air studies may not be relatable to the underwater studies on pectoral fins because of the different Reynolds number (compared to the flapping wings) and force generation mechanism (compared to the static wings). This paper aims to establish a relationship between the sweep angle and thrust generation. An experiment was conducted to measure the thrust generated by 40 fins in a water channel under freestream and still water conditions for chord Reynolds number between 2.2 × 104 and 8.2 × 104. The fins were of five different sweep angles (0 deg, 10 deg, 20 deg, 30 deg, and 40 deg) that were incorporated into eight base designs of different flexibility characteristics. The results showed that the sweep angle (within the range considered) may have no significant influence on these fins' thrust generation, implying no significant effects on thrust under uniform flow condition and on the maximum possible thrust under still water. Overall, it can be concluded that sweep angle may not be a determinant of thrust generation for flapping pectoral fins. This knowledge can ease the decision-making process of design of robots propeled by these fins.

Sign in / Sign up

Export Citation Format

Share Document