Assessment of gamma−theta transitional model for laminar-turbulent transition prediction in supercritical airfoils

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.A numerical study on the capability of the γ−θ turbulence model for predicting the laminar/turbulent transition in the boundary layer developing around a supercritical airfoil (NLR 7301) is described. The range in the Mach number explored is [0.3, 0.825], thus covering a fully transonic flow regime. For this purpose, a CFD solver (ANSYS CFX©) is used on a hybrid structured-triangular grid, where an accurate mesh setup of the wall boundary layer was performed in order to ensure (i) a value of y+ less than 6 everywhere and (ii) a number of boundary layer rows within the physical boundary layer no less than 4. Results obtained are compared to the experimental data described in the open literature and discussed in detail. Despite the various sources of uncertainty affecting the experimental data, the results regarding the transition location revealed a very good model predictive capacity for low-to-medium Mach numbers (Mach<0.6), while exhibiting a less satisfactory ability in the transonic regime (Mach>0.6). In this case, prediction of transition location on both sides of the airfoil is still accurate even if the correlation on the pressure distributions gets poorer.mp201

Conceptual-level evaluation of a variable stiffness skin for a morphing wing leading edge

A morphing leading edge produces a continuous aerodynamic surface that has no gaps between the moving and fixed parts. The continuous seamless shape has the potential to reduce drag, compared to conventional devices, such as slats that produce a discrete aerofoil shape change. However, the morphing leading edge has to achieve the required target shape by deforming from the baseline shape under the aerodynamic loads. In this paper, a conceptual-level method is proposed to evaluate the morphing leading edge structure. The feasibility of the skin design is validated by checking the failure index of the composite when the morphing leading edge undergoes the shape change. The stiffness of the morphing leading edge skin is spatially varied using variable lamina angles, and comparisons to the skin with constant stiffness are made to highlight its potential to reduce the actuation forces. The structural analysis is performed using a two-level structural optimisation scheme. The first level optimisation is applied to find the optimised structural proper- ties of the leading edge skin and the associated actuation forces. The structural properties of the skin are given as a stiffness distribution, which is controlled by a B spline interpolation function. In the second level, the design solution of the skin is investigated. The skin is assumed to be made of variable stiffness composite. The stack sequence of the composite is optimised element-by-element to match the target stiffness. A failure criterion is employed to obtain the failure index when the leading edge is actuated from the baseline shape to the target shape. Test cases are given to demonstrate that the optimisation scheme is able to provide the stiffness distribution of the leading edge skin and the actuation forces can be reduced by using a spatially variable stiffness skin

Comparison of Constrained Parameterisation Strategies for Aerodynamic Optimisation of Morphing Leading Edge Airfoil

In the context of ambitious targets for reducing environmental impact in the aviation sector, dictated by international institutions, morphing aircraft are expected to have potential for achieving the required efficiency increases. However, there are still open issues related to the design and implementation of deformable structures. In this paper, we compare three constrained parameterisation strategies for the aerodynamic design of a morphing leading edge, representing a potential substitute for traditional high-lift systems. In order to facilitate the structural design and promote the feasibility of solutions, we solve a multi-objective optimisation problem, including constraints on axial and bending strain introduced by morphing. A parameterisation method, inherently producing constant arc length curves, is employed in three variants, representing different morphing strategies which provide an increasing level of deformability, by allowing the lower edge of the flexible skin to slide and the gap formed with the fixed spar to be closed by a hatch. The results for the optimisation of a baseline airfoil show that the geometric constraints are effectively handled in the optimisation and the solutions are smooth, with a continuous variation along the Pareto frontier. The larger shape modification allowed by more flexible parameterisation variants enables an increase of the maximum lift coefficient up to 8.35%, and efficiency at 70% of stall incidence up to 4.26%

Hoverspill: a new amphibious vehicle for responding in difficult-to-access sites

Oil spill experience often shows that response activities are hampered due to the absence of operative autonomous support capable of reaching particular sites or operate in safe and efficient conditions in areas such as saltmarshes, mudflats, river banks, cliff bottoms… This is the purpose of the so-called FP7 Hoverspill project (www.hoverspill.eu), a 3-year European project that recently reached completion: to design and build a small-size amphibious vehicle designed to ensure rapid oil spill response. The result is an air-cushion vehicle (ACV), known as Hoverspill, based on the innovative MACP (Multipurpose Air Cushion Platform) developed by Hovertech and SOA. It is a completely amphibious vehicle capable of working on land and on water, usable as a pontoon in floating conditions. Its compactness makes it easy to transport by road. The project also included the design and building of a highly effective integrated O/W Turbylec separator developed by YLEC. Spill response equipment will be loaded on-board based on a modular concept enabling the vehicle to carry out specific tasks with just the required equipmen

Development of a contactless measurement system for real time monitoring of a proprotors flapping angle – Part two

To ensure the flight safety of a tilt-rotor aircraft, it is important to monitor the flapping motion of the proprotor in real time. Therefore, as part of the Clean Sky 2 Joint Undertaking funded project "FLAPsense" (No. 785571), a sensor system is being developed that can perform this measurement task in a non-contact and real-time manner. The system, which is integrated into the proprotor assembly and rotates with the rotor hub, is based on a high-precision optical sensor method that provides the avionics system with the actual flapping motion of the rotor disc. As a continuation of the "part one paper" from ETTC '21, the "part two paper" will provide a reminder of the details of the measurement task and present the latest achievements in terms of the FLAPsense sensor unit development. Finally, it gives an outlook on the next steps to bring the FLAPsense sensor system into flight

Design Exploration for an Axisymmetric Rear BLI Propulsor

none3noIn the context of aircraft propulsion using Boundary Layer Ingestion (BLI), the possibility to determine a fast and consistent numerical model for the exploration of the design space can lead to a deep insight on the influence of geometrical and functional design variables on the performance of a propulsor. The present work deals with a parametric CFD analysis of a 2D axisymmetric BLI propulsor, aimed at determining the most promising regions of the design space to be considered for further optimization studies.restrictedBattiston A.; Ponza R.; Benini E.Battiston, A.; Ponza, R.; Benini, E