WE found, on experimental grounds in Article I, that the field of air‐flow past a short body of low resistance shape, such as an aerofoil, comprises two dissimilar parts: (a) a thin boundary layer enveloping the body and dominated by viscous effects, and (b) a motion outside the boundary layer in which viscosity is much less important. It will be remembered that in the external motion occur the large pressure changes, which, transmitted through the boundary layer, account for nearly all the lift and for part of the drag. These pressures we observed to be calculable from the velocities without appreciable error by Bernoulli's equation. In the present Article we confine attention to this external flow, assuming it to be steady, incompressible, and inviscid. Its dependence upon (a), already discussed to some extent, we ignore; the boundary layer is conceived to be everywhere very thin, so that the only role it plays is to allow of relative velocity at the surface of the body. The assumptions made, excepting that of incompressibility, will appear drastic, and it will not be surprising if some of our deductions prove discordant with experimental fact. Nevertheless, they lead to a theory which finds many applications and uses in real fluid motion, and, in particular, gives an intimate view of aerofoil flow that is very close to the truth. It is convenient to develop our reasoning in analytical terms and for simplicity to restrict the flow to two dimensions (Article 1, §5). But the engineer will find special scope in this part of aerodynamics for graphical methods in the solution of particular problems.

Aerodynamics for Engineers

Flight Vehicle System Identification: A Time-Domain MethodologyJategaonkarR. V., Progress in Aeronautics and Astronautics, 2nd ed., AIAA, Reston, VA, 2015, 648 pp., $119.95.

The process of aerodynamic shape optimisation requires the development of intelligent models to address the stipulated design goals. The Direct Numeric Optimisation (DNO) approach is examined in this paper, which analyses the feasibility of a shape, in iteration until convergence based on defined objectives and constraints. The method is computationally intensive hence the components of the DNO architecture are defined, validated and modified to generate an efficient search optimisation model. Efficiency is enhanced by mapping the solution space for High-Altitude Long Endurance (HALE) airfoil design problem, through an inverse mapping of PARSEC airfoil shape variables over a series of benchmark profiles. Solution regions with aerodynamically infeasible shapes are identified and eliminated from the search process, to reduce computational time. A single-point airfoil optimisation with Gradient-Based method, over the defined search space is examined. Variations in base airfoils confirmed the solution space is highly multimodal and gradient methods merely locate the local optima. A Particle Swarm Optimisation (PSO) algorithm incorporating a double-mutation operator to mitigate sub-optimal solutions, for highly multimodal solution topologies was defined and validated. The swarm algorithm for airfoil shape optimisation confirmed the limited search flexibility of gradient methods, by establishing a global solution with a 16% reduction in drag. The swarm algorithm is computationally intense for shape optimisation. An Artificial Neural Network (ANN) is developed and validated with a relationship between the mapped PARSEC solution space and the aerodynamic coefficients of lift and drag established. A network sensitivity study indicated a double-layered network with 30 neurons for lift and 20 for drag is required to establish the aerodynamic coefficients with acceptable accuracy. The surrogate model is used for airfoil shape optimisation by replacing the flow solver from the DNO loop. Time savings are established with the aerodynamic performance of the output solution in line with the results of the direct PSO-Flow-Solver combination. Neural network simulations for fitness function approximation are prone to errors. Hence, future research will focus on developing a hybrid search methodology by integrating the flow solver and ANN in the DNO approach.

Airfoil Optimisation by Swarm Algorithm with Mutation and Artificial Neural Networks

Introduction of full flight dynamic stability constraints in aircraft multidisciplinary optimization

Purpose – The present study aimed to demonstrate different computational models, data and stability results obtained in a wide number of projects of various aircrafts such as unmanned aerial vehicles (UAVs), general aviation and big passenger flying airliners in blended wing body (BWB) configurations. Many details of modeling and computing are shown for unconventional configurations, namely, for a BWB aircraft and for tailless UAVs. Design/methodology/approach – Mathematical models for analysis of static and dynamic stability were built and investigated based on equations of motion in the linearized form using the so-called state variable model for a steady-state disturbed, generally asymmetric, flight. Findings – Flight dynamics models and associated computational procedures appeared to be useful, both in a preliminary design phase and during the final assessment of the configuration at flight tests. It was also found that the difference between thresholds for static and dynamic stability conditions was ...

Flight dynamics models used in different national and international projects

This paper describes a design process of HALE PW-114 sensor-craft, developed for high altitude (20 km) long endurance (40 h) surveillance missions. Designed as a blended wing (BW) configuration, to be made of metal and composite materials. Wing control surfaces provide longitudinal balance. Fin in the rear fuselage section together with wingtips provide directional stability. Airplane is equipped with retractable landing gear with controlled front leg that allows operations from conventional airfields. According to the initial requirements it is twin engine configuration, typical payload consists of electro-optical/infra-red FLIR, big SAR (synthetic aperture radar) and SATCOM antenna required for the longest range. Tailless architecture was based on both Horten and Northrop design experience. Global Hawk was considered as a reference point – it was assumed that BW design has to possess efficiency, relative payload and other characteristics at least the same or even better than that of Global Hawk. FLIR, SAR and SATCOM containers were optimised for best visibility. All payload systems are put into separate modular containers of easy access and quickly to exchange, so this architecture can be consider as a „modular”. An optimisation process started immediately when the so-called “zero configuration”, called PW-111 was ready. It was designed in the canard configuration. A canard was abandoned in HALE PW-113. Instead, new, larger outer wing was designed with smaller taper ratio. New configuration analysis revealed satisfactory longitudinal stability. Calculations suggested better lateral qualities for negative dihedral. These modifications, leading to aerodynamic improvement, gave HALE PW-114 as a result. The design process was an interdisciplinary approach, and included a selection of thick laminar wing section, aerodynamic optimisation of swept wing, stability analysis, weight balance, structural and flutter analysis, many on-board redundant systems, reliability and maintability analysis, safety improvement, cost and performance optimisation. Presented paper focuses mainly on aerodynamics, wing design, longitudinal control and safety issues. This activity is supported by European Union within V FR, in the area Aeronautics and Space.

/pdf/high-altitude-long-endurance-unmanned-aerial-vehicle-of-a-1cw9b07y4h.pdf

High altitude long endurance unmanned aerial vehicle of a new generation - a design challenge for a low cost, reliable and high performance aircraft

The paper presents a concept of tandem-wing configuration aircraft that was a Warsaw University of Technology proposal for the personal air transport system. The project was developed at Warsaw University of Technology, within the PPLANE project (FP7 – Personal Plane: Assessment and Validation of Pioneering Concepts for Personal Air Transport Systems). First, analysis of the general concept, advantages and disadvantages of tandem-wing configuration, and possible application as a personal air transport system vehicle are presented. Next, aerodynamic design is analyzed and dynamic stability is tested. All numerical analyses were made by use of the well-tested professional software for aerodynamic (MGAERO) and stability (SDSA) analyses.

Aerodynamic and stability analysis of personal vehicle in tandem-wing configuration:

The article includes study on the influence of a LEX (leading-edge extension) and wing tip plates on aerodynamic characteristics of the Rocket Plane in tailless configuration for manned suborbital flights. The research was conducted only for the low speed regime in the wind tunnel at the Warsaw University of Technology. Tests were carried out for a few configurations of the Rocket Plane. Moreover, two shapes of LEX were investigated. Analysis of results was focused on the aerodynamic synergism effect only. The influence of LEX and the wing tip plates of the Rocket Plane on the aerodynamic coefficients was identified.

LEX and wing tip plates’ interaction on the Rocket Plane in tailless configuration

This paper presents results of an initial investigation on the Modular Aeroplane System, consisting of the flying wing carrier and cranked delta wing carried aeroplane. The system takes off in “conventional” configuration with the wing of the carried aeroplane working as a horizontal stabilizer of the system. At the certain altitude carried aeroplane is detached and both vehicles continue their missions separately. Each of them maintain flying wing configuration after split. The paper includes results of aerodynamic investigation related to the whole system, the carrier and the highly maneuverable airplane as an isolate components. Moreover analysis of stability for all vehicles configurations are presented. Furthermore paper contains initial performance calculations and discussion on possible applications of Modular Aeroplane System.

Modular aeroplane system: A concept and initial investigation

This paper presents the results of a numerical study of the aerodynamic shape of the Rocket Plane LEX. The Rocket Plane is a main part of the Modular Airplane System – MAS; a special vehicle devote...

Aerodynamic optimisation of the rocket plane in subsonic and supersonic flight conditions

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