Flipper

About: Flipper is a research topic. Over the lifetime, 201 publications have been published within this topic receiving 3517 citations.

Leading-edge tubercles delay stall on humpback whale (Megaptera novaeangliae) flippers

Abstract: The humpback whale (Megaptera novaeangliae) is exceptional among the baleen whales in its ability to undertake acrobatic underwater maneuvers to catch prey. In order to execute these banking and turning maneuvers, humpback whales utilize extremely mobile flippers. The humpback whale flipper is unique because of the presence of large protuberances or tubercles located on the leading edge which gives this surface a scalloped appearance. We show, through wind tunnel measurements, that the addition of leading-edge tubercles to a scale model of an idealized humpback whale flipper delays the stall angle by approximately 40%, while increasing lift and decreasing drag.

Hydrodynamic design of the humpback whale flipper.

Abstract: The humpback whale (Megaptera novaeangliae) is reported to use its elongate pectoral flippers during swimming maneuvers. The morphology of the flipper from a 9.02-m whale was evaluated with regard to this hydrodynamic function. The flipper had a wing-like, high aspect ratio planform. Rounded tubercles were regularly interspersed along the flipper's leading edge. The flipper was cut into 71 2.5-cm cross-sections and photographed. Except for sections near the distal tip, flipper sections were symmetrical with no camber. Flipper sections had a blunt, rounded leading edge and a highly tapered trailing edge. Placement of the maximum thickness placement for each cross-section varied from 49% of chord at the tip to 19% at mid-span. Section thickness ratio averaged 0.23 with a range of 0.20-0.28. The humpback whale flipper had a cross-sectional design typical of manufactured aerodynamic foils for lift generation. The morphology and placement of leading edge tubercles suggest that they function as enhanced lift devices to control flow over the flipper and maintain lift at high angles of attack. The morphology of the humpback whale flipper suggests that it is adapted for high maneuverability associated with the whale's unique feeding behavior.

Hydrodynamic flow control in marine mammals

Abstract: The ability to control the flow of water around the body dictates the performance of marine mammals in the aquatic environment. Morphological specializations of marine mammals afford mechanisms for passive flow control. Aside from the design of the body, which minimizes drag, the morphology of the appendages provides hydrodynamic advantages with respect to drag, lift, thrust, and stall. The flukes of cetaceans and sirenians and flippers of pinnipeds possess geometries with flexibility, which enhance thrust production for high efficiency swimming. The pectoral flippers provide hydrodynamic lift for maneuvering. The design of the flippers is constrained by performance associated with stall. Delay of stall can be accomplished passively by modification of the flipper leading edge. Such a design is exhibited by the leading edge tubercles on the flippers of humpback whales (Megaptera novaeangliae). These novel morphological structures induce a spanwise flow field of separated vortices alternating with regions of accelerated flow. The coupled flow regions maintain areas of attached flow and delay stall to high angles of attack. The delay of stall permits enhanced turning performance with respect to both agility and maneuverability. The morphological features of marine mammals for flow control can be utilized in the biomimetic design of engineered structures for increased power production and increased efficiency.

Numerical Study of stall delay on humpback whale flippers

Abstract: this range of Re numbers is necessary. Recently was reported 2 that the humpback whale flipper is optimized to prevent stall and to improve aerodynamic performance. These features allow these animals to be extremely mobile with great turning ability which is necessary to catch prey. This observation together with the fact that the Reynolds number for the humpback whale falls in the aforementioned low Re range propelled the experimental study the humpback whale flipper. The flippers for this species display a very characteristic scalloped leading edge, whereas the flippers of other species less maneuverable are much smoother. 3 The experiments compared a flipper with tubercles with a smooth flipper. The researchers reported an improvement in the aerodynamic performance as well an increase in the angle of attack at which the flipper stalls. However no flow visualization was performed, therefore the reasons why the scalloped flipper performs better were not uncovered. In this work we performed the numerical simulation of the setup used for the experimental study. The unsteady turbulent flow field for the scalloped flipper and for the smooth flipper was accurately determined which produced detailed information necessary to fully understand the mechanism behind the reported improvement. Our goal with this work is to increase the knowledge about these lower Re number flows which will be useful for the design of more ecient UAV’s wings.

Morphological specializations of baleen whales associated with hydrodynamic performance and ecological niche.

Abstract: Feeding behavior, prey type, and habitat appear to be associated with the morphological design of body, fluke, and flippers in baleen whales. Morphometric data from whaling records and recent stranding events were compiled, and morphometric parameters describing the body length, and fluke and flipper dimensions for an ''average'' blue whale Balaenoptera musculus, humpback whale Megaptera novaeangliae, gray whale Eschrichtius robustus, and right whale Eubalaena glacialis were determined. Body mass, body volume, body surface area, and fluke and flipper surface areas were estimated. The resultant morphological configurations lent themselves to the following classifications based on hydrodynamic principles: fast cruiser, slow cruiser, fast maneuverer, and slow maneuverer. Blue whales have highly stream- lined bodies with small, high aspect ratio flippers and flukes for fast efficient cruising in the open ocean. On the other hand, the rotund right whale has large, high aspect ratio flukes for efficient slow speed cruising that is optimal for their continuous filter feeding technique. Humpbacks have large, high aspect ratio flippers and a large, low aspect ratio tail for quick acceleration and high-speed maneuvering which would help them catch their elusive prey, while gray whales have large, low as- pect ratio flippers and flukes for enhanced low-speed maneuvering in complex coastal water habitats. J. Morphol.