Reduction of aerodynamic drag is central to the ACARE 2020 goal of reducing fuel consumption in air transportation. For rotorcraft, the majority of the drag occurs due to extensive flow separation around the fuselage and rotor hub. Such highly unsteady flows present significant challenges for computational fluid dynamics (CFD) techniques in terms of solution fidelity and computational expense.
However, a new family of hybrid RANS/LES techniques addresses this conflict by mixing pure modelling (RANS) and partial resolution (LES) of the turbulent motion to provide an optimal trade-off between solution fidelity and computational cost. Of these, the well-established detached-eddy simulation (DES) method has been selected for the HELIDES simulations due to its high maturity and inherent suitability. Through participation in numerous EU projects (e.g. FLOMANIA, DESider, ATAAC), the consortium has developed a very high level of expertise with the development and application of these methods, including to helicopter fuselage simulation. The HELIDES consortium has furthermore played a central role in the implementation and validation of cutting-edge DES methods in an efficient, incompressible, unstructured CFD solver that can capture complex geometries with rotating components. Furthermore, novel analysis techniques for the quantification of the random error in statistical quantities provides a pragmatic means to manage the significant problem of finite simulated time samples.
With these well-suited tools and expertise, together with access to very large computing resources, the HELIDES consortium considers itself ideally equipped to perform the demanding high-fidelity simulations specified by the Call.
Reduction of aerodynamic drag (and hence fuel consumption) of rotorcraft is a key goal to improving the sustainability of this means of transport. Helicopter drag in fast forward flight is dominated by the phenomenon of flow separation from the rear fuselage and rotor hub, which also gives rise to unsteady aerodynamics loads on the helicopter tail. Drag reduction may be achieved by various means, such as geometry optimisation or flow control devices. The cost-effective design of such measures requires predictive tools to enable their assessment in the preliminary design stage.
Advances in computer capacity have led to an increasingly important role being played by Computational Fluid Dynamics (CFD) in aerodynamic design across the ground and air transport sectors. The principle limiting factor in CFD arises from the phenomenon of turbulence, which introduces a fundamental cost-accuracy trade-off. The methodology applied in HELIDES, namely Detached-Eddy Simulation (DES), is a prominent member of a new family of turbulence modelling strategies aimed at offering a step forward in accuracy by exploiting near-future computational resources.