Flow Control in Wings and Discovery of Novel Approaches via Deep Reinforcement Learning

In this review we summarize existing trends of flow control used to improve the aerodynamic efficiency of wings. We first discuss active methods to control turbulence, starting with flat-plate geometries and building towards the more complicated flow around wings. Then, we discuss active approaches to control separation, a crucial aspect towards achieving high aerodynamic efficiency. Furthermore, we highlight methods relying on turbulence simulation, and discuss various levels of modelling. Finally, we thoroughly revise data-driven methods, their application to flow control, and focus on deep reinforcement learning (DRL). We conclude that this methodology has the potential to discover novel control strategies in complex turbulent flows of aerodynamic relevance.

Aerodynamic Optimization of the Sizing and Blade Designs of Hovering Corotating Coaxial Rotors

Corotating coaxial rotors are seeing renewed interest in distributed electric propulsion systems and electric vertical take-off and landing (eVTOL) aircraft. The recent literature reports many interesting investigations, using prescribed rotor blades, into the flow phenomena as well as aerodynamic and aeroacoustic benefits of corotating rotors. However, the subject of the design of blade geometries, optimized to a design goal, for corotating rotors is currently lacking in the literature. This paper is written from such a design perspective, by extending a previous generalized approach to the aerodynamic optimization of counterrotating rotors to corotating rotors. The previous requirement for upper and lower counterrotating rotor torques to be equal can now be lifted in the case of corotating rotors, enabling improved versatility in the optimization of corotating blade designs. The optimization is demonstrated on an application example to address the conflicting conditions that index angles (high) for aeroacoustic benefits of reduced noise are at odds with those (low) for aerodynamic efficiency. The approach demonstrated in this paper is to set the index angle for reduced noise and then recover back the aerodynamic efficiency by using the newly developed aerodynamic optimization technique.

Computational investigation of the aerodynamic performance of reversible airfoils for a bidirectional tidal turbine

A reversible airfoil is an airfoil that has equal performance when the flow is reversed. Such airfoils are relevant for many different applications, including use in ventilation fans, helicopter rotors, wind turbines and tidal turbines. Compared to traditional airfoils, reversible airfoils have different performance characteristics and have been less explored in the scientific literature. This work investigates the aerodynamic performance of some selected reversible airfoils using computational fluid dynamics. The selected airfoils are based on existing NACA 6 profiles and a profile using B-spline parameterization. The results show reduced performance for the reversible airfoils compared to a unidirectional airfoil. Of the investigated airfoils, the B-spline airfoil has the highest performance, with a maximum aerodynamic efficiency which is 87 % of the unidirectional design.

Twist Morphing: A Simulation Approach to Compare Twist Morphed Wing and Flap Configuration

The aim of the work is to explore and justify an innovative concept in the niche of aerospace industry called as Wing Morphing. To narrow down the study, specifically twist morphing is taken into consideration. Wings with twist and their flap counterparts are compared in similar conditions and their aerodynamic efficiency is observed. The project implementation is done with XFLR5, a VLM solver software. The results show that this concept brings about an improvement in the aerodynamic efficiency without adding much to the drag penalty. Keywords: Wing Morphing, Twist Morphing, Cl (coefficient of lift), Cd (Coefficient of drag), Alpha (angle of attack)

Computational numerical analysis of drag force on a standard AeroDesign wing in accordance with winglet application

This work goal is to achieve a better flight performance and to support the loading of the highest payload possible. The aerodynamics sector works to improve the aircraft aerodynamic efficiency; therefore, the aerodynamicist looks for the best solution to contribute to the aircraft efficiency by reducing drag forces. The induced drag comes from the lift force, it is related to the escape vortices which occur at the wing tips and it is the most relevant drag component. The use of structural components, as winglets, helps to reduce these vortices and the total aircraft drag. In the context of the SAE Brazil AeroDesign competition, the use of these components can support the project requirements due to the regulatory restrictions. The methodology employed was a simulation using the ANSYS CFX® software for wings modeled with different winglet configurations and the same boundary conditions to verify the best application for the studied wing. The winglet dihedral angle was set at 45°, the strings were maintained and the winglet height was used as a parameter. In the simulations, the wing attack angle was varied to obtain the variation of the drag force. With the obtained results, it was possible to verify that the wings lift forces with h=10% of the half-span winglet have lower values of drag force and present higher values of lift force, for all the analyzed angles, with a variation of up to 6 N of lift force, regarding to the wing without winglet. It is concluded the possibility to observe an improvement in the performance of the wing with the application of the winglet, in the above-mentioned context, and the compensation of a higher efficiency can help competition teams to carry more load on the aircraft due to the lift increase, and to assist the aircraft takeoff and landing handling.

Flight efficiency is a key to diverse wing morphologies in small insects

Insect wings are hybrid structures that are typically composed of veins and solid membranes. In some of the smallest flying insects, however, the wing membrane is replaced by hair-like bristles attached to a solid root. Bristles and membranous wing surfaces coexist in small but not in large insect species. There is no satisfying explanation for this finding as aerodynamic force production is always smaller in bristled than solid wings. This computational study suggests that the diversity of wing structure in small insects results from aerodynamic efficiency rather than from the requirements to produce elevated forces for flight. The tested wings vary from fully membranous to sparsely bristled and were flapped around a wing root with lift- and drag-based wing kinematic patterns and at different Reynolds numbers ( Re ). The results show that the decrease in aerodynamic efficiency with decreasing surface solidity is significantly smaller at Re = 4 than Re = 57. A replacement of wing membrane by bristles thus causes less change in energetic costs for flight in small compared to large insects. As a consequence, small insects may fly with bristled and solid wing surfaces at similar efficacy, while larger insects must use membranous wings for an efficient production of flight forces. The above findings are significant for the biological fitness and dispersal of insects that fly at elevated energy expenditures.

Regularities in aerodynamic efficiency control for gas cooler fans

Research relevance. The paper establishes the regularities in the impact the geometry and structural elements of a fan system piping have on the fan system’s aerodynamic efficiency in a wide range of the specific speed variation. Objectives and methods of research. A mathematical model has been obtained for the dependence of fan system’s geometry and kinematic parameters and the aerodynamic efficiency on the specific speed. Results. It has been proved that in order to reach higher aerodynamic efficiency of fan systems, in view of the increasing specific speed of fan systems, the aerodynamic quality of the impeller blade profiles should be increased and the aerodynamic resistance of the piping elements should be reduced. It has been shown that it is possible to create a gas cooler fan system with at least 400 specific speed and at least 0.85 efficiency if the impeller profiles aerodynamic quality is more than 25, and piping drag coefficient doesn’t exceed 0.2.

Aerodynamic Investigation of Double Surface Airfoil

Aircraft industry has been deeply concerned about reduction of drag by reducing flow separation and improving the aerodynamic efficiency of flight vehicles, particularly in commercial and military market by adopting various methods. Reduction of flow separation is a concept by which we can increase aerodynamic efficiency. The purpose of the project is to perform an experimental investigation on aerodynamic performance of NACA 0012 airfoil model with and without splits. It is evident from this research work that the airfoil model with split possesses greater aerodynamic performance by producing lesser overall drag. This is due to the delay in flow separation from the surface.