An Airfoil Shape Optimization Technique coupling PARSEC Parameterization and Evolutionary Algorithm

In this work an innovative optimization process for airfoil geometry design is introduced. This procedure is based on the coupling of a PARSEC parameterization for airfoil shape and a genetic algorithms (GA) optimization method to find Nash equilibria (NE). While the PARSEC airfoil parameterization method has the capability to faithfully describe an airfoil geometry using typical engineering parameters, on the other hand the Nash game theoretical approach allows each player to decide, with a more physical correspondence between geometric parameters and objective function, in which direction the airfoil shape should be modified. As a matter of fact the optimization under NE solutions would be more attractive to use when a well posed distinction between players variables exists

Commuter aircraft aerodynamic design: wind-tunnel tests and CFD analysis

The paper presents wind-tunnel tests and CFD numerical aerodynamic analysis of Tecnam P2012 Traveller aircraft. An extensive wind tunnel tests campaign of several different modular aircraft configurations analyzed has been performed on a scaled model in order to experimentally estimate both longitudinal and lateral-directional stability, control derivatives, and to improve the aircraft aerodynamic performances. Simultaneously numerical investigations through a CFD software has been performed, both at wind-tunnel tests Reynolds number (Re=0.6millions) and at free flight Reynolds number of the full scale aircraft (Re=4 or 9 millions). Finally results are compared showing a good agreement in the lift and pitching moment coefficient both with and without control surfaces or flap deflections, and an underestimation of drag coefficient in the CFD numerical analysis. Horizontal tail positions are also tested in wind-tunnel and compared to CFD analysis highlighting how an accurate design leads to improvement both in stability and control. Results will be very useful in the final design of the aircraft and to perform dynamic simulations

Assessing the Integration of Electrified On-Board Systems in an MDAO framework for a small transport aircraft

The integration of on-board systems design within the aircraft design process is often considered only in the late part of the initial design. This is acceptable for civil aircraft using standard technology systems. However, facing with MEA and AEA concepts and different possible architectures, the systems design and the assessment of their effects on the overall aircraft should be moved up in the usual design process. This paper deals with evaluation of the effect of different on-board systems architecture, with a different electrification level, on the overall aircraft design. These effects have been evaluated using three different MDA workflows developed within the AGILE4.0 European research project. The workflows are defined with an increasing number of disciplines to show how the effect of a proper selection of a systems architecture is differently caught by each one. In this way it is possible to define which disciplines should be included for the systems architecture assessment. The results show a save of 1% of MTOM for the AEA applied to a small turboprop aircraft when only the OBS mass is assessed. Increasing workflow complexity, adding performance and engine design the save increase to 1.2%. Finally, the save increases to 1.3% when the effect on engine SFC is also considered

Advanced turboprop multidisciplinary design and optimization within agile project

The present paper deals with the design, analysis and optimization of a 90 passengers turboprop aircraft with a design range of 1200 nautical miles and a cruise Mach number equal to 0.56. The prescribed aircraft is one of the use cases of the AGILE European project, aiming to provide a 3rd generation of multidisciplinary design and optimization chain, following the collaborative and remote aircraft design paradigm, through an heterogenous team of experts. The multidisciplinary aircraft design analysis is set-up involving tools provided by AGILE partners distributed worldwide and run locally from partners side. A complete design of experiment, focused on wing planform variables, is performed to build response surfaces suitable for optimization purposes. The goal of the optimization is the direct operating cost, subject to wing design variables and top-level aircraft requirements

Retrofitting Cost Modeling in Aircraft Design

Aircraft retrofitting is a challenging task involving multiple scenarios and stakeholders. Providing a strategy to retrofit an existing platform needs detailed knowledge of multiple aspects, ranging from aircraft performance and emissions, development and conversion costs to the projected operating costs. This paper proposes a methodology to account for retrofitting costs at an industrial level, explaining the activities related to such a process. Costs are mainly derived from three contributions: development costs, conversion costs and equipment acquisition costs. Different retrofitting packages, such as engine conversion and onboard systems electrification, are applied in the retrofitting of an existing 90 PAX regional turbofan aircraft, highlighting the impact on both aircraft performance and industrial costs. Multiple variables and scenarios are considered regarding trade-offs and decision-making, including the number of aircraft to be retrofitted, the heritage of an aircraft and its utilization, the fuel price and the airport charges. The results show that a reduction of 15% in fuel demand and emissions are achievable, considering a fleet of 500 platforms, through a conspicuous investment of around EUR 20 million per aircraft (50% of the estimated price). Furthermore, depending on the scenarios driven by the regulatory authorities, governments or airlines, this paper provides a useful methodology to evaluate the feasibility of retrofitting activities

CFD sensitivity analysis on bumped airfoil characteristics for inflatable winglet

The new aerospace technological milestone is aimed to reducing direct operating costs and pol- lution. In order to obtain pollution reductions via high aerodynamic efficiency, a performance anal- ysis for bumped airfoil based winglet has been pro- posed. Most conventional aircrafts are equipped with fixed winglets to decrease the induced drag; thus, saving more fuel. New projects point to- wards advanced smart materials and telescopic wing tip devices to obtain an adaptive morphing shape that gives, through performance improve- ment, a fuel consumption reduction resulting in less pollutants. The focus of this paper is to evalu- ate the aerodynamic performance, in terms of lift, drag and moment coefficient for a bumped airfoil in climb/descent flight condition at 5000 meters altitude. The performance analysis has been con- ducted via a numerical investigation of the effects of bumps number, height and width for inflatable winglet airfoil, a system that would guarantee a more comfortable arrangement of extraction sys- tem and just minor surplus of weight compared to classical winglet solutions, with all the subsequent advantages

Preliminary investigation on the water retention behaviour of cement bentonite mixtures

Cement bentonite mixtures are often used to build slurry walls for the containment of both aqueous and non aqueous pollutants, due to their quite low hydraulic conductivity and relatively high ductility and strength. Although their hydro-mechanical behaviour in saturated conditions has been studied in the past, a part of the slurry wall is expected to rest above the groundwater level. The hydraulic characterization in unsaturated conditions is then particularly relevant to evaluate the performance of the barrier, especially when it is aimed at containing non aqueous pollutant liquids which are lighter than water (LNAPL). These non wetting fluids rest above the water table and their penetration is possible just if the barrier is unsaturated. This paper presents some preliminary results of a laboratory characterization of the water retention behaviour of three different cement bentonite mixtures. The mixtures, prepared at cement - bentonite mass ratios ranging from 4:1 to 6:1, were immersed in water and cured for 28 days. Their water retention behaviour was then determined along drying and wetting paths through different techniques, namely axis translation, filter paper and vapour equilibrium. In the high suction range, the water content - suction relationship was found to be independent of cement-bentonite ratio. In the low suction range, the water content at a given suction was found to decrease for increasing cement bentonite ratios

Monitoring drying and wetting of a cement bentonite mixture with Electrical Resistivity Tomography

Cement bentonite slurry cutoff walls are used to encapsulate pollutants within contaminated areas, so avoiding their spreading in the environment. In both temperate and arid climates, at shallow depths, slurry walls are exposed to interaction with the atmosphere and thus to relative humidity values which might induce desaturation and significant shrinkage. This note presents the main results of a study aimed at investigating the impact of drying processes on the integrity and the hydraulic performance of cement bentonite slurry walls. Cement bentonite samples were cured under water for different times (1 months, 2 months and 4 months) and then dried naturally by exposing them to the laboratory environment (T = 21 °C, relative humidity approximately 38%). Once dried, the bottom of the samples was placed in contact with a thin layer of water to induce wetting. The distribution of the electrical conductivity within these samples was evaluated through Electrical Resistivity Tomography measurements, and electrical conductivity maps were converted then into maps of water contents on basis of a phenomenological relationship. The reconstructed water contents compared very well to the measured ones. Drying induced a limited cracking of the samples, which might affect to some extent the hydraulic performance of the barriers

Structural validation of a realistic wing structure: the RIBES test article

Several experimental test cases are available in literature to study and validate fluid structure interaction methods. They, however, focus the attention mainly on replicating typical cruising aerodynamic conditions forcing the adoption of fully steel made models able to operate with the high loads generated in high speed facilities. This translates in a complete loss of similitude with typical realistic aeronautical wing structures configurations. To reverse this trend, and to better study the aerolastic mechanism from a structural point of view, an aeroelastic measurement campaign was carried within the EU RIBES project. A half wing model for wind tunnel tests was designed and manufactured replicating a typical metallic wing box structure, producing a database of loads, pressure, stress and deformation measurements. In this paper the design, manufacturing and validation activities performed within the RIBES project are described, with a focus on the structural behavior of the test article. All experimental data and numerical models are made freely available to the scientific community

AIRCRAFT DIRECTIONAL STABILITY AND CONTROL: NEW IMPROVED APPROACH IN TAIL DESIGN

This work deals with a review and proposed improvements of vertical tail classical design methods dealing with aircraft directional stability and control. The research presented is based on many numerical and experimental results obtained by the authors (DAF research group, www.daf.unina.it) through both CFD calculations and wind-tunnel tests carried out on an aircraft modular configuration. A new improved methodology to predict the directional stability and control characteristics of an aircraft and a reliable sizing procedure for the vertical tail is proposed. The methodology obtained and all results are particularly relevant for the regional turboprop category, but they can also be applied to other transport aircraft configurations. A wind tunnel investigation involving more than 150 configurations has also been involved in order to validate the numerical approach for which about 200 configurations were involved. The analyses covered both the linear and the non-linear range of the aerodynamic coefficients