Static roughness element effects on protuberance full-span wing at micro aerial vehicle application

Abstract

Although the tubercle wings provide good maneuverability at post-stall conditions, the aerodynamic performance at pre-stall angles is threatened by forming a laminar separation bubble at the trough section of the tubercle wing; consequently, the flight endurance and range are reduced. In the present study, the idea of passive flow control is introduced by using the distribution of static roughness elements on a full-span wing with a sinusoidal leading edge. Initially, the effect of roughness element length, height, and its location are studied at a pre-stall angle (16-degree). Their effect on the laminar separation bubble and vortex shedding formed behind the wing are also investigated. The Reynolds number is assumed to be equal to [Formula: see text] which is in the range of critical Reynolds number and matches to the micro aerial vehicles application. An improved hybrid model, improved delay detached eddy simulation IDDES, has been used to model the flow turbulence structure. In the extended transition region at low Reynolds numbers, the roughness bypassed the instability. Consequently, roughening the surface of the aerofoil increased the boundary layer’s flow momentum, making it more resistible to adverse pressure gradients. By suppressing the bubble, the static roughness element led to pre-stall flow control, which saw an increase in lift coefficient, [Formula: see text], and a decrease in drag coefficient, [Formula: see text]. The results have been demonstrated that the aerodynamic performance, [Formula: see text], has been improved approximately 22.7%, 38%, and 45% for [Formula: see text], and [Formula: see text], respectively. The optimal arrangement of static roughness elements could decline the size of the vortices and strengthen the cores associated with them. This claim can be interpreted with the vortex shedding frequency.

Investigating Mechanical Response and Structural Integrity of Tubercle Leading Edge under Static Loads

“…The experimental investigation performed by N. Karthikeyan et al [25,26] examined the impact of wavy leading edges, revealing tubercles' effectiveness in maintaining attached flow and reducing recirculating zones, although their influence on separation point variability and wake width post-stall requires further exploration. However, Jabbari et al [27], by employing static roughness elements, significantly improved the performance of these unconventional wing configurations. The aerodynamic performance of varying leading-edge tubercle configurations was numerically [28,29] and experimentally [30] evaluated, indicating that a larger tubercle amplitude leads to gentler stall, while a smaller tubercle wavelength improves maximum lift.…”

Combined passive and active flow control for fixed-wing micro air vehicles

“…Therefore, manipulation of the shear layer reattachment as well as of the turbulence upstream separation helps to avoid the formation of LSBs. 31 This is achieved via passive methods 32,33 by selecting a specific airfoil shape or by installing mechanical turbulators upstream of the laminar separation point; or via active methods 34 using pneumatic turbulators, acoustic excitation, and plasma actuators. It is recognized that PFC operates well at the design point but cannot manage the flow as effectively at off-design conditions.…”

Scavenging energy from aeroelastic vibrations for hybrid stall control in a fixed-wing micro aerial vehicle

“…In this flow regime, the prevalent aerodynamic deadlock concerns the ability to generate a sufficiently high lift-to-drag ratio, given the tendency of laminar boundary layers to separate at relatively low incidence angles (Jabbari et al, 2021a), and the occurrence of early aerodynamic stall (Mueller and DeLaurier, 2003). Consequently, these undesirable phenomena raise the need for passive or active flow control, and it is perhaps not surprising that researchers have sought inspiration from nature and biomimetics (Jabbari et al, 2021b).…”