Search Results

Abstract The airline industry faces a crisis in the future as consumer demand is increasing, but the environmental effects and depleting resources of kerosene mean that growth is unsustainable. Hydrogen is touted as the leading candidate to replace kerosene, but it needs significant technological and economical endeavors. In such a scenario, cryogenic liquid hydrogen (LH2) is predicted to be the most feasible method of using hydrogen. The major challenge of LH2 as an aircraft fuel is that it requires approximately four times the storage volume of kerosene—due to its lower density. Thus the design of cryogenic storage tanks to handle larger quantities of fuel is becoming increasingly important. But the increase in drag associated with larger storage tanks causes an increase in fuel consumption. Hence, this paper aims to evaluate the aerodynamic performance of different storage configurations and aid in the selection of an economic and efficient storage system.

Abstract Turboprop aircraft have the capability of reversing thrust to provide extra stopping power during landing. Reverse thrust helps save the wear and tear on the brakes and reduces the landing distance under various conditions. The article explains a methodology to predict the disking drag (reverse thrust) from the Computational Fluid Dynamics (CFD) technique using Blade Element Momentum (BEM) theory and estimation of the same from high-speed taxiing trial (HSTT) and ground roll data for a turboprop aircraft using system identification techniques. One-dimensional kinematic equation was used for modeling the aircraft dynamics, and the error between measured and estimated responses was optimized using the Output Error Optimization Method (OEOM). The estimated propeller drag was matched with CFD predictions to arrive at a relation between the propeller blade pitch angle and throttle position.

Abstract From the fact that a propulsor consumes less power for a given thrust if the inlet air is slower, simulations are conducted for a propulsor imposed behind an airfoil as ideal boundary layer ingestion (BLI) propulsor to stand on the benefits of this configuration from the point of view of power and efficiency and to get a closer look on the mutual interaction between them. This interaction is quantified by the impact on three main sets of parameters, namely, power consumption, boundary layer properties, and airfoil performance. The position and size of the propulsor have great influence on the flow around the airfoil. Parametric studies are carried out to understand their influence. BLI propulsor directly affects the power saving and all of the pressure-dependent parameters, including lift and drag. For the present case, power saving reached 14.4% compared to the propeller working in freestream.

Abstract This study consists of a novel approach based on Classical Mechanics to explain the aerodynamic forces on a body in motion relating to a fluid. This new approach does not require the presence of viscosity to generate the forces and is compatible with the Kutta condition. The physical reasoning of the approach is outlined with the introduction of the aerodynamic suction effect of the body. Next, the mathematical expressions and a code that models the physical phenomena are developed. These are applied for the case of a sphere immersed in a moving fluid and then an airfoil. An initial validation of this new approach is performed by a comparison of the theoretical results and the available results of the National Advisory Committee for Aeronautics (NACA) airfoils. This new mathematical approach is especially valid for high Reynolds numbers where viscosity can be neglected.

Abstract High-altitude long-endurance (HALE) unmanned aerial vehicles (UAVs) are used for high flight altitudes, which enable low drag and fast flight with minimal fuel consumption. Two-stage turbocharging is necessary to sustain sea-level power at high flight altitudes. In this study, the limitations of two-stage turbocharging at high flight altitudes typical for HALE UAVs are analyzed for the first time. The obtained results show that the minimum available engine power increases as the altitude rises. This will limit the ability of the aircraft to descend rapidly. Furthermore, at high altitudes, if a lower operating point is required for a fast descent, further recovery to full power for climbing or cruising could be unavailable. In the latter cases, a lower altitude must be reached before full power would be available again. A basic algorithm for the assessment and analysis of the limitations of UAV engines with two-stage turbochargers operating at high altitudes is suggested.

Abstract A novel use of state estimation methods as initial input for a landing response analysis is proposed in this work. Six degrees of freedom (DOF) non-linear landing response model is conceived by considering longitudinal dynamics of aircraft as a rigid body with heave-and-pitch motions coupled onto a bicycle landing gear † arrangement. The DOF for each landing gear consist of vertical and longitudinal motions of un-sprung mass, considering strut bending flexibility. The measurement data for state estimation is obtained for three landing cases using non-linear flight mechanics model interfaced with pilot-in-loop simulation. State estimation methods such as Upper Diagonal Adaptive Extended Kalman Filter (UD-AEKF) with fuzzy-based adaptive tuning and Un-scented Kalman Filter (UKF) were adapted for landing maneuver problem. On the basis of estimation error metrics, aircraft state from UKF is considered during onset of touchdown.

Abstract This article aims to analyze the effect of vortex generators (VGs) placed on symmetrical and cambered aerofoil. Simulation and experimental works were carried out using NACA 6321 and NACA 0021 aerofoils at different angles of attack (AOA) and aerodynamic performance obtained at a velocity of 15 m/s and 140625 Reynolds number (Re). In this study, aerofoils with the same thickness and a novel design of minute VGs were introduced and placed at a location of 0.5C (50% of chord). The VGs improved the stall AOA by 4° and 2° in simulation and experimental methods, respectively, with no drag increment compared to the baseline aerofoil. These VGs controlled the boundary layer over an aerofoil with enhancement in aerodynamic efficiency of subsonic aircrafts.

Abstract A flight envelope for aircraft performance in the vertical plane illustrates the performance limitations on the aircraft, usually indicating the minimum and maximum airspeeds at a given altitude, the airspeeds for maximum rate of climb and maximum angle of climb at a given altitude, and the maximum altitude or absolute ceiling of the aircraft. This study outlines the procedure for constructing a vertical-plane flight performance aircraft for an aircraft with a fixed-pitch propeller, which involves additional complexities due to the variable propeller efficiency. The propeller performance, engine power, and drag polar models are described, as is the computational procedure. Envelopes for the flight performance in the vertical plane are presented for a particular remotely-piloted aircraft at different take-off weights.

Abstract An investigation was carried out to evaluate the potential aerodynamic benefit of spanwise jet injection from the wingtips. Aircraft currently use conventional solid winglets that add extra structural weight. However, results reveal that fluidic on-demand winglets effectively reduce drag for low-speed flight regimes without the addition of any extra weight. These utilize the spanwise airflow from the wingtips using hydraulic actuators to create jets that negate tip vortices. This research aims to investigate the fluidic winglet jet characteristics on the aerodynamic performance of the wing. Results indicate that the spanwise blowing shifts the core of the wingtip vortices upward and outward from the wing surface. In a particular range of jet velocity ratio, the magnitude of vorticity near the wingtips tends to reduce, resulting in a reduction of induced drag.

Abstract Part I introduced the aerodynamic equation of state. This Part II introduces the aerodynamic equation of state for lift and induced drag of flapping wings and applies it to a hovering and forward-flying bumblebee and a mosquito. Two- and three-dimensional graphical representations of the state space are introduced and explored for engineered subsonic flyers, biological fliers, and sports balls.

Abstract In subsonic aircraft design, the aerodynamic performance of aircraft is compared meaningfully at a system level by evaluating their range and endurance, but cannot do so at an aerodynamic level when using lift and drag coefficients, CL and CD , as these often result in misleading results for different wing reference areas. This Part I of the article (i) illustrates these shortcomings, (ii) introduces a dimensionless number quantifying the induced drag of aircraft, and (iii) proposes an aerodynamic equation of state for lift, drag, and induced drag and applies it to evaluate the aerodynamics of the canard aircraft, the dual rotors of the hovering Ingenuity Mars helicopter, and the composite lifting system (wing plus cylinders in Magnus effect) of a YOV-10 Bronco. Part II of this article applies this aerodynamic equation of state to the flapping flight of hovering and forward-flying insects.