Numerical aerodynamic analysis on a trapezoidal wing with high lift devices: a comparison with experimental data

The aerodynamic analysis on the DLR-F11 high lift configuration model has been performed on the supercomputing grid infrastructure SCoPE of the University of Naples ???Federico II???. The model geometry is representative of a wide-body commercial aircraft, which experimental investigations at high Reynolds number have been performed at the European Transonic Wind-tunnel (ETW) for the 2nd AIAA High Lift Prediction Workshop. The commercial CAE package Star-CCM+ has been used to solve the Reynolds-averaged Navier-Stokes equations. Inviscid, viscous incompressible, and compressible analyses have been performed with mesh refinement. The inviscid calculations have been used to assess how far is the eulerian prediction from experimental data. Viscous and compressible calculations have been realized using the Spalart-Allmaras turbulence model at 0.175 Mach number and 15.1 million Reynolds number. Results show that the simple Spalart-Allmaras turbulence model can predict quite accurately the stall and post-stall behaviour, getting the angle of stall and underestimating the maximum lift coefficient by less than 5%. Comparisons among numerical and experimental pressure coefficients at several sections are also shown. Finally, the stall path is described

An Investigation on Vertical Tailplane Design

The paper presents a deep investigation on the methodologies to design a vertical tailplane. Nowadays the most used methodologies in preliminary design to estimate the contribution of vertical tailplane on aircraft directional stability and control are: the classical method proposed by USAF DATCOM (also presented in several aeronautics textbooks) and the method presented in ESDU reports. Both methodologies derive from NACA world war II reports of the first half of the ’900, based on obsolete geometries, and give quite different results for certain configurations, e. g. in the case of horizontal stabilizer mounted in fuselage. As shown in literature, the main effects on the side force coefficient of the vertical tail are due to the interactions among the aircraft components: the fuselage acts like a cylinder increasing the local sideslip angle, the wing position and aspect ratio have an influence on the airflow near the tail zone and the horizontal tail, depending on position and size, can act as an endplate increasing the side force. In order to better highlight these effects, a different approach using the RANS equations has been adopted. Several CFD calculations have been performed on some test cases (used as experimental database) described in NACA reports and used in the past to obtain the semi‐empirical methodology reported in USAF DATCOM, to verify the compliance of CFD results with available experimental data. The CFD calculations (performed through the use of a parallel supercomputing platform) have shown a good agreement between numerical and experimental data. Subsequently the abovementioned effects have been deeply investigated on a new set of propeller transport aircraft configurations. The different configurations that have been prepared differs for wing aspect ratio, wing‐fuselage relative position (high‐wing/low‐wing), vertical tailplane aspect ratio (vertical tail span versus fuselage radius) and horizontal tailplane position respect to the vertical tailplane (in particular investigation the effect of fin‐mounted T configuration, typical of regional turboprop transport aircraft). For all configurations the computational mesh has been carefully analyzed and prepared. All the CFD analyses will be useful to obtain new curves to predict the above-mentioned effects and to have a more accurate estimation of vertical tailplane contribution to aircraft directional stability and control

Development of new preliminary design methodologies for regional turboprop aircraft by CFD analyses

Since 2011 the aerodynamic research group of the Dept. of Industrial Engineering of the University of Naples "Federico II" makes use of the University's computing grid infrastructure SCoPE to perform parallel computing simulations with the commercial CAE package Star-CCM+. This infrastructure allows Navier-Stokes calculations on complete aircraft configurations in a relative short amount of time. Therefore, the software and the above mentioned infrastructure allow the parametric analysis of several configurations that are extremely useful to the correct estimation of aerodynamic interference among aircraft components and to highlight some useful trends that could indicate how a specific aerodynamic characteristic (i.e. the drag of a component, the wing downwash or the directional stability contribution of the vertical tail) is linked to aircraft geometrical parameters. Thus, with the choice of a specific set of test-cases it is possible to make a deep investigation on some aerodynamic features and, from the analyses of results, it is possible to extract and develop ad-hoc semi-empirical methodologies that could be used in preliminary design activities. In this paper, two investigations are presented: the aerodynamic interference among aircraft components in sideslip and the aerodynamic characteristics of a fuselage, focusing on typical large turbopropeller aircraft category

Powered wind tunnel tests setup of the IRON innovative turboprop aircraft

This paper describes the powered wind tunnel tests setup of the innovative configuration of the IRON regional turboprop aircraft. The objective of the tests is the evaluation of propulsive effects on aircraft stability and control characteristics. During the setup process, several aerodynamic issues have been anticipated and here illustrated. A scaled engine deck has been derived from the full-scale data provided by the IRON powerplant consortium partner. From two representative flight conditions, the characteristics of the scaled motor as RPM, torque and power have been calculated, providing a choice for the electric motors to install in the test section. The motors’ operating voltage and current determined the sizing of the power, acquisition and control system. Similarly, the desired propeller coefficients were the target of a propeller design process, which was performed with XROTOR, MATLAB®, XFOIL and validated with RANS analyses. Finally, to directly evaluate the propeller thrust and normal force, motors’ supporting structures with load cells have been conceptually designed

Numerical high lift prediction on the JAXA standard model

A growing interest in the prediction of highlift aerodynamics has grown in recent years,motivated by the AIAA High Lift PredictionWorkshop (HiLiftPW) series, which publicly re-lease standard wing-fuselage geometries with ex-perimental results from wind tunnel tests andpromote dissemination of meshing strategies,physics modelling, and statistical analyses on theresults provided by participants. The object ofthis work is the JAXA standard model proposedin the3rdAIAA HiLiftPW. The authors want topropose best practices for numerical meshing andanalysis with the lowest possible number of cells,giving indications on physics modelling and onthe location of grid refinements for mesh tuning

A comprehensive review of vertical tail design

This work aims to deal with a comprehensive review of design methods for aircraft directional stability and vertical tail sizing. The focus on aircraft directional stability is due to the significant discrepancies that classical semi-empirical methods, as USAF DATCOM and ESDU, provide for some configurations because they are based on NACA wind tunnel (WT) tests about models not representative of an actual transport airplane. Design/methodology/approach: The authors performed viscous numerical simulations to calculate the aerodynamic interference among aircraft parts on hundreds configurations of a generic regional turboprop aircraft, providing useful results that have been collected in a new vertical tail preliminary design method, named VeDSC. Findings: The reviewed methods have been applied on a regional turboprop aircraft. The VeDSC method shows the closest agreement with numerical results. A WT test campaign involving more than 180 configurations has validated the numerical approach. Practical implications: The investigation has covered both the linear and the non-linear range of the aerodynamic coefficients, including the mutual aerodynamic interference between the fuselage and the vertical stabilizer. Also, a preliminary investigation about rudder effectiveness, related to aircraft directional control, is presented. Originality/value: In the final part of the paper, critical issues in vertical tail design are reviewed, highlighting the significance of a good estimation of aircraft directional stability and control derivatives

A comprehensive review of vertical tail design

This work deals with a comprehensive review of vertical tail design methods for aircraft directional stability and vertical tail sizing. The focus on aircraft directional stability is due to the significant discrepancies that classical semi-empirical methods, as USAF DATCOM and ESDU, provide for some configurations, since they are based on NACA wind tunnel tests about models not representative of an actual transport airplane. The authors performed RANS CFD simulations to calculate the aerodynamic interference among aircraft parts for hundreds configurations of a generic regional turboprop aircraft, providing useful results that have been collected in a new vertical tail preliminary design method, named VeDSC. Semi-empirical methods have been put in comparison on a regional turboprop aircraft, where the VeDSC method shows a strong agreement with numerical results. A wind tunnel investigation involving more than 180 configurations has validated the numerical approach. The investigation has covered both the linear and the non-linear range of the aerodynamic coefficients, including the mutual aerodynamic interference between the fuselage and the vertical stabilizer. Also, a preliminary investigation about rudder effectiveness, related to aircraft directional control, is presented. In the final part of the paper, critical issues in vertical tail design are reviewed, highlighting the significance of a good estimation of aircraft directional stability and control derivatives

Design, Analysis, and Testing of a Scaled Propeller for an Innovative Regional Turboprop Aircraft

This paper describes the design, numerical analyses, and wind tunnel tests of the scaled model of a propeller serving as a propulsive element for the experimental tests of an advanced regional turboprop aircraft with engines installed on the horizontal tailplane tips. The design has been performed by complying with the thrust similarity from the full-scale aircraft propulsive requirements. Numerical analyses with a high-fidelity aerodynamic solver confirmed that the initial design made with XROTOR would achieve the expected performance. Finally, a strengthened version of the propeller has been manufactured via 3D printing and tested in the wind tunnel. Test data include measurements of thrust as well as propeller normal force at different angles of attack. Good agreement between numerical and experimental results has been observed, enabling the propeller to be used confidently in the aircraft wind tunnel powered test campaign

An improved preliminary design methodology for aircraft directional stability prediction and vertical tailplane sizing

This work deals with the development of a new preliminary design method for aircraft directional stability and vertical tail sizing. It is focused on regional turboprop aircraft because of their economic advantage over regional jets on short routes, for the increasing oil price, and because of the market needs of new airplanes in the next 20 years. The focus on aircraft directional stability is due to the significant discrepancies that classical semi-empirical methods, as USAF DATCOM and ESDU, provide for some configurations, because they are based on NACA wind tunnel tests about models not representative of an actual transport airplane. This work exploits the CFD to calculate the aerodynamic interference among aircraft parts for hundreds configurations of a given layout, providing a useful method in aircraft preliminary design. A wind tunnel investigation involving about 180 configurations has validated the numerical approach. The innovation of the work concerns the numerical and experimental parametric study on the static directional stability of a model representative of the regional turboprop aircraft category and the direct measurement of the vertical stabilizer aerodynamic forces in the wind tunnel, in addition to the force and moments acting on the whole model. In this way, useful data about aerodynamic interference have been extracted from experimental tests, which are in good agreement with the results of numerical simulations

Game theory and evolutionary algorithms applied to MDO in the AGILE European project

In this paper, an optimization technique in aircraft design field, based on game theory and evolutionary algorithms to define the key variables for Multi-Disciplinary aircraft Optimization (MDO) into AGILE (Aircraft 3rd Generation MDO for Innovative Collaboration of Heterogeneous Teams of Experts) European project, is presented. This work represents one of the contributions given by UniNa (University of Naples “Federico II”) research group within the AGILE project, which is coordinated by the DLR and funded by EU through the project HORIZON 2020 that aims to create an evolution of MDO, promoting a novel approach based on collaborative remote design and knowledge dissemination among various teams of experts. Since the aircraft design field is very complex in terms of number of involved variables and the dimension of the space of variation, it is not feasible to perform an optimization process on all the design parameters; this leads to the need to reduce the number of the parameters to the most significant ones. A multi-objective optimization approach allows many different variables, which could be a constraint or an objective function for the specific investigation; thus, setting the constraints and objectives to reach, it is possible to perform an optimization process and control which parameters significantly affect the final result. Within AGILE project, UniNa research group aims to perform wing optimization processes in a preliminary design stage, coupling Nash game theory (N) with typical genetic evolutionary algorithm (GA), reducing computational time and allowing a more realistic association among objective functions and variables, to identify the main ones that significantly affect final result and that consequently must be considered by the partners of the AGILE consortium to perform MDO in the final part of project, applying the proposed optimization technique to novel aircraft configuration