Search

In this work, wake-tail plane interactions are investigated for a tandem wing configuration in buffet conditions using hybrid RANS/LES simulations with the Automated Zonal Detached Eddy Simulation (AZDES) method. The analyzed configuration consists of two untapered and unswept wing segments, representative of a wing-tail plane configuration. The shock oscillation on the front wing segment and the development of its turbulent wake are characterized, including a spectral analysis of the pressure and velocity fluctuations in the wake and a modal analysis of the flow field applying Proper Orthogonal Decomposition (POD). The impact of the wake on the aerodynamics and loads of the rear wing segment is then studied, with a spectral analysis of its lift and surface pressure oscillations. Finally, the influence of the position and the incidence angle of the rear wing segment are investigated. For the considered flow conditions, 2D buffet is present on the front wing segment. During the downstream movement of the shock, the amount of separation reaches its minimum and small vortices are present in the wake. During the upstream movement of the shock, the amount of separation is at its maximum and larger turbulent structures are present together with high fluctuation levels of velocity and pressure. A distinct peak can be associated with the meandering motion of wake vortices, identified by means of a modal analysis of the flow field using Proper Orthogonal Decomposition. The impingement of the wake causes a strong variation of the loading of the rear wing segment. A comparably low-frequent oscillation of the lift coefficient, attributed to the change of intensity of the downwash caused by the front segment, can be distinguished from fluctuations of high frequency that are caused by the impingement of the turbulent structures in the wake., Comment: Updated arXiv version to version published in CEAS Aeronautical Journal

Generating turbulent inflow data is a challenging task in zonal Large Eddy Simulation (zLES) and often relies on predefined DNS data to generate synthetic turbulence with the correct statistics. The more accurate, but more involved alternative is to use instantaneous data from a precursor simulation. Using instantaneous data as an inflow condition allows to conduct high fidelity simulations of subdomains of e.g. an aircraft including all non-stationary or rare events. In this paper we introduce a tool-chain that is capable of interchanging highly resolved spatial and temporal data between flow solvers with different discretization schemes. To accomplish this, we use interpolation algorithms suitable for scattered data in order to interpolate spatially. In time we use one-dimensional interpolation schemes for each degree of freedom. The results show that we can get stable simulations that map all flow features from the source data into a new target domain. Thus, the coupling is capable of mapping arbitrary data distributions and formats into a new domain while also recovering and conserving turbulent structures and scales. The necessary time and space resolution requirements can be defined knowing the resolution requirements of the used numerical scheme in the target domain.

This work provides an overview of aerodynamic data acquired in the European Transonic Windtunnel using an XRF-1 transport aircraft configuration both at cruise conditions and at the edges of the flight envelope. The goals and design of the wind tunnel test was described, highlighting the use of the cryogenic wind tunnel's capability to isolate the effects of Mach and Reynolds numbers and the dynamic pressure. The resulting dataset includes an aerodynamic baseline characterization of the full span model with vertical and horizontal tailplanes and without engine nacelles. The effects of different inflow conditions were studied using data from continuous polars, evaluating the changes in aeroelastic deformation which are proportional to $q/E$ and the influence of $M$ and $Re$ on the shock position. Off-design data was analyzed at the lowest and highest measured Mach numbers of 0.84 and 0.90, respectively. Wing lower surface flow and underside shock motion was analyzed at negative angles of attack using $c_p$ distribution and unsteady pressure transducer fluctuation data, identifying significant upstream displacement of the shock close to the leading edge. Wing upper side flow and the shock motion near buffet onset and beyond was analyzed using unsteady pressure data from point transducers and unsteady pressure sensitive paint (PSP) measurements. Buffet occurs at lower angles of attack at high Mach number, and without clearly defined lift break. Spectral contents at the acquired data points in the buffet range suggest broadband fluctuations at Strouhal numbers between 0.2 and 0.6, which is consistent with recent literature. The spanwise shock propagation velocities were determined independently via analysis of unsteady PSP and pressure transducers to be in the range between $u_s / u_{\infty} = 0.24$ and $0.32$.