SUMMARY. By means of the principles and assumptions used to calculate the profile drag of aerofoils a method is developed for calculating the total and skin friction drags of bodies of revolution at zero incidence. The method is applied to three bodies of different fineness ratio for three Reynolds numbers and three transition points. From the results curves are drawn showing the variation of t...

A new adaptive controller based on a neural network was constructed and applied to turbulent channel flow for drag reduction. A simple control network, which employs blowing and suction at the wall based only on the wall-shear stresses in the spanwise direction, was shown to reduce the skin friction by as much as 20% in direct numerical simulations of a low-Reynolds number turbulent channel flo...

The γ-Reθ-model, a two equation, correlation-based transition model using local variables, has been employed to predict the extension of the laminar regions on a stiff geometry of the common dolphin (delphinus delphis) moving in the Reynolds regime of 5.5 ·10 to 10. Mesh independence was gained for a domain resolution of approximately 30 million cells in an unstructured polyhedral mesh with a p...

It has been known for over six decades that the dissolution of minute amounts of high molecular weight polymers in wall-bounded turbulent flows results in a dramatic reduction in turbulent skin friction by up to 70%. First principles simulations of turbulent flow of model polymer solutions can predict the drag reduction (DR) phenomenon. However, the essential dynamical interactions between the ...

Riblets are micro-grooves capable of decreasing skin-friction drag, but recent work suggests that additional benefits possible for other components aerodynamic drag. The effect riblets on a fixed-wing, low-speed Unmanned Aerial Vehicle (UAV) the total drag assessed here first time by means RANS simulations. Since microscopic scale precludes their direct representation in geometric model UAV, we...

Conventional aircraft use discrete flight control surfaces to maneuver during flight. The gaps and discontinuities of these generate drag, which degrades aerodynamic power efficiencies. Morphing technology aims replace conventional wings with advanced that can change their shape the minimum possible induced drag. This paper presents MataMorph-3, a fully morphing unmanned aerial vehicle (UAV) ca...

Designing transonic laminar swept wing at high Reynolds numbers is challenging due to the premature flow transition from prominent crossflow instabilities (CFIs). Hence, natural (NLF) wings are limited lower sweep angles. In this study, hybrid control (HLFC) used extend limit design low-drag infinite wing. A multi-objective genetic algorithm with competing drag components as objectives NLF and ...

The permeability of frog skin under the influence of urea hyperosmolarity has been studied. Flux ratio asymmetry has been demonstrated again for tracer mannitol. The inhibitors DNP, CN(-), and ouabain have been used to eliminate active sodium transport and it was found that urea hyperosmolarity produces asymmetrical mannitol fluxes on frog skins having no short-circuit current. These findings s...

To reduce the drag of a cylinder, numerical simulations and experiments for both smooth cylinder circular with dimpled surface are carried out in this paper. The simulation focuses on variation pressure coefficient, skin friction vortex shedding strength surface. It is found that structure can effectively within specific range Reynolds number, maximum reduction rate reaches up to 19%. Another c...

Abstract The paper presents the derivation of a new equivalent skin friction coefficient for estimating parasitic drag short-to-medium range fixed-wing unmanned aircraft. is derived from an aerodynamic analysis ten different aircraft used surveillance, reconnaissance, and search rescue missions. simulated using validated unsteady Reynolds-averaged Navier Stokes approach. UAV’s significantly inf...