A high-order shock-fitting method is developed within the discontinuous flux reconstruction framework to compute shock waves accurately. The method is realized using a dynamic mesh solution approach and a robust shock detection algorithm. A strategy analogous to the method of characteristics is employed to determine the velocity of the identified shock front. The shock velocity is, then, used to move the mesh in a physically consistent manner. A one-sided operator is used to compute the common flux at the shock front, automatically satisfying the Rankine-Hugoniot condition. To accommodate the motion of the shock front, a computationally efficient mesh deformation algorithm is introduced, including a methodology that enables the shock nodes to move along the domain boundaries. In the present study, linear (Q1) and quadratic (Q2) triangular meshes are used, the latter allowing curved shocks to be represented by piecewise quadratic curves, thus achieving high-order accuracy. Several benchmark problems are used to evaluate the method’s performance and accuracy for steady applications, leading to excellent agreement with analytical solutions or data available in the literature.
Transitional Reynolds-averaged Navier–Stokes (RANS) models have become relevant in the computational fluid dynamics (CFD) community as a practical approach to predict the transition to turbulence over the surface of aerospace configurations. These models capture the transition caused by the amplification of Tollmien-Schlichting waves, the bypass transition, and the stationary crossflow vortices. A fundamental aspect of transitional RANS models that still deserve continued attention is their numerical behavior. The source terms that are part of their formulation are commonly based on highly nonlinear functions, rendering more challenges in their convergence when compared to the underlying fully turbulent RANS models. The present work investigates the effects of smoothing these highly nonlinear, discontinuous functions that are embedded in the source terms of the Langtry-Menter transition model and its companion turbulence closure. There is particular interests in identifying improvements in the lift and drag coefficient convergence behavior. We consider the flat plate, the NACA 0012 and NLF(1)-0416 airfoils, and the 6:1 prolate spheroid configuration as test cases for transition caused by the amplification of Tollmien-Schlichting (TS) waves. We also consider flow conditions for which transition over the inclined 6:1 prolate spheroid is triggered by the amplification of stationary crossflow vortices. Our results show that the smooth functions lead to a faster convergence of the aerodynamic coefficients, which represents a reduced computational cost when compared to the original model.
This article presents a flight-test campaign conducted to investigate abnormal vibration-related events observed in AS365-K2 helicopters equipped with upgraded engines. The aircraft was instrumented with acceleration sensors at multiple fuselage locations (near doors, floor, main rotor, and center of gravity), inside the radome (surrounding the weather-avoidance radar system), and on the empennage (covering the horizontal stabilizer and the lateral fin). The helicopter was flown under several operating conditions, both with and without an externally mounted armament, ranging from hover to approximately 130 kt within the normal operational envelope. The vibration measurements obtained during real helicopter flight operations are rarely available in the open literature, particularly for military platforms. In this context, the main contribution of this work is twofold: (i) we provide a detailed description of the instrumentation layout and flight-test procedures applied to an operational AS365-K2 aircraft, and (ii) we make publicly available a curated dataset of the acquired time-domain acceleration measurements to support future research in aeroelastic modeling, vibration assessment, structural dynamics, and related analysis. Inspection of the collected data reveals that the vibration response of the aircraft changes significantly under certain operating conditions, with some airframe locations exhibiting non-monotonic trends that are not directly correlated with increasing flight speed. These findings, together with the released dataset, support specialized investigations into phenomena such as buffeting-like vibrations on the empennage, recurrent malfunctioning of electronic devices, and the emergence of atypical fuselage cracks.
This paper investigates the dynamical behavior of a system of ordinary differential equations (ODEs) governed by a matrix that represents the division in the algebra of the Alpha group. As the system evolves, the matrix induces topological transitions in geometric spaces, controlled by a rotational parameter. Numerical simulations are performed using a fourth-order Runge-Kutta method implemented in Python. The re- sults reveal the emergence of topological nodes, the existence of critical points at which the rotation between dividing planes transitions from 0 to π/2 radians. Near zero radians, the system exhibits a Euclidean geomet- ric structure, while rotations close to π/2 define an Alpha Group space. At these nodes, the matrix-driven ODE system undergoes qualitative dy- namic changes, reflecting distinct topological behaviors. The Alpha Group matrix is interpreted as a generator of symmetry transformations, poten- tially analogous to gauge fields under local or global symmetries. This work provides a computational framework for exploring dynamic topolo- gies, attractors at infinity, and internal coherence in hyper-complex vector spaces.
The specific surface area of a filler influences its dispersion and interaction with the rubber and consequently the properties of thermal insulation in aerospace components. However, its determination generally requires complex instrumental methods. Therefore, the development of simpler methodologies with equivalent or higher precision remains of scientific interest. This study investigates the application of Fourier transform infrared spectroscopy using near-infrared (NIR) reflectance and the more conventional diffuse reflectance for silica analysis, a filler widely used in polymeric formulations. The analyzed samples presented surface area values between 170 and 800 m2·g-1. Results showed a methodological error within the instrumental limit (2%), lower than that reported for conventional methods (4-7%). The NIR reflectance methodology based on the relative band (A5260/A4540) provided the most accurate results and can be considered a practical alternative to conventional gas adsorption techniques, enabling shorter analysis times, a feature that is particularly relevant for aerospace processes subject to demanding project schedules.
