Analysis On Flow Characteristic Of Airfoil Limitating The Humpback Whale Fin

The observation shows that mammoth humpback whales are quite flexible in maneuvering prey as compared to other large sea creatures and can even make maneuvers close to juggling.It is concluded that the whale fin with its leading edge protuberances is the main reason that they still have good underwater performance at larger angles of attack.However,in the aviation field,when the angle of attack of the aircraft is too large,sudden stalling is easy to occur with serious consequences.Increasing the aircraft's stall angle of attack has been a challenge that aircraft designers want to overcome.Therefore,through the bionics principle,it is of great practical significance to apply the special leading edge protuberances structure of humpback whale to helicopter blades and other projects in aircraft wings.However,the research of humpback whale fins is still in its infancy,and the law of the influence of the protruding structures on the wing flow characteristics does not reach a unified understanding.It is necessary to further investigate the flow characteristics of the flirting fins of the humpback whales.Based on the NACA0018 standard airfoil,Establishment of standard wing and humpback whale fin wing model with different parameters to to study the influence of leading edge protuberances.Through FLUENT numerical simulation,the standard wing and each bionic wing were calculated and analyzed every 2 degrees in the range of angle of attack from 0 ° to 30 °.The results show that the lift coefficient of the standard wing descends sharply and the stall characteristic got obvious when the attack angle started to be higher than 20 degrees of attack angle.However,the lift coefficient of the bionic wing decreased by different extents corresponding to some specific attack angles,and the decreasing trend was slower.At high attack angles,the lift coefficient of bionic wings was generally higher than that of standard wings,which can improve effectively the stall characteristic of the wing.The results show that the eading edge of the sudden section of the magnitude and numberof humpback Whale fins are the main factors affecting the wing flow characteristics.The greater the amplitude,the smaller the lift coefficient of the wing in a certain amplitude range when the the number of leading edge protuberance was given.When there is the same amplitude of the leading edge protuberance,the more knuckles,the smaller the lift coefficient.The effects of the amplitude of protuberances on the aero dynamic characteristics were stronger than that of the number of protuberances under unit length.According to the distribution law of wing streamline surface,the pressure distribution on the wing surface and the velocity cloud at the specific section of the wing at a specific angle of attack,the existence of the leading edge protuberances can change the distribution of the flow on the wing surface,The surface of the wing still has a large amount of attached flow at an attack angle.The good flow characteristics at the sudden peak are the main reasons why the bionic wing still has a large lift coefficient under high attack angles.According to the special structure of the leading edge protuberances of the humpback whale,the non-sinusoidal leading edge protuberances problem is proposed and the bionic wing models with different leading edge curves are established.The results show that the curve type of the leading edge protuberances is also the main factor influencing the flow characteristics of the bionic wing,in which the standard sinusoidal leading edge wing has the best flow characteristics at each angle of attack.