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1. Dynamic aeroelastic instabilities of fixed-wing aircraft in transonic and supersonic flows using a fully-coupled model

   https://doi.org/10.2514/6.2023-1041  

   Ilie, Marcel; Havenar, John (January 2023, AIAA SCITECH 2023 Forum)

   Published by the American Institute of Aeronautics and Astronautics, Inc. (Ed.)

   The aeroelastic phenomena of ONERA M6 wing in transonic and supersonic flight regimes is computationally studied using a fully-coupled aeroelastic approach. The present research concerns the development of a computationally efficient and accurate method for the aeroelastic studies of fixed wing in transonic and supersonic flows. Therefore, we propose a fully-coupled, time-marching aeroelastic approach utilizing an URANS model. The computational studies are carried out to assess the effect of the freestream Mach number and angle of attack on the structural dynamics and stresses developed in the ONERA M6 wing. The studies are carried out for a range of Mach numbers, M∞ = 0. 8 – 1. 4, and angles of attack, α = {2°, 4°, 6°}. The analysis reveals that the aeroelastic deformation of the wing and induced stress in the wing structure increase with the freestream Mach number. 

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2. Mach number effect on the aeroelastic phenomenon of fixed wing aircraft

   M. Ilie and J. Havenar (January 2022, AIAA SciTech Conference)

   AIAA SciTech (Ed.)

   The aeroelastic phenomenon plays a critical role in the aerodynamic performance and stability of fixed wing aircrafts. Aeroelastic phenomena may cause flow separation and large deformations of the wing, and implicitly high stresses into the structure. The computational study of aeroelasticity, in high-speed fixed wing, requires fully-coupled aeroelastic algorithms. Therefore, in the present research we propose a CFD based approach using the large-eddy simulation approach along with a finite-element method for the computations of the structural deformations. The analysis is performed for subsonic and transonic flows with Mach number . The analysis reveals that the elastic deformations of the wing and stresses in the wing increase with the Mach number. 

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3. Reynolds number dependency in supersonic spatially-developing turbulent boundary layers

   https://doi.org/10.2514/6.2020-0574  

   Araya, Guillermo; Lagares, Christian; Jansen, Kenneth E. (January 2020, 2020 AIAA SciTech Forum (AIAA 3247313) 6 - 10 January, Orlando, FL, 2020.)

   Direct Numerical Simulation (DNS) of compressible spatially-developing turbulent boundary layers (SDTBL) is performed at a Mach number of 2.5 and low/high Reynolds numbers over isothermal Zero-Pressure Gradient (ZPG) flat plates. Turbulent inflow information is generated via a dynamic rescaling-recycling approach (J. Fluid Mech., 670, pp. 581-605, 2011), which avoids the use of empirical correlations in the computation of inlet turbulent scales. The range of the low Reynolds number case is approximately 400-800, based on the momentum thickness, freestream velocity and wall viscosity. DNS at higher Reynolds numbers (~3,000, about four-fold larger) is also carried out with the purpose of analyzing the effect of Reynolds number on the transport phenomena in the supersonic regime. Additionally, low/high order flow statistics are compared with DNS of an incompressible isothermal ZPG boundary layer at similar low Reynolds numbers and the temperature regarded as a passive scalar. Peaks of turbulence intensities move closer to the wall as the Reynolds number increases in the supersonic flat plate. Furthermore, Reynolds shear stresses depict a much larger "plateau" (constant shear layer) at the highest Reynolds number considered in present study. 

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4. Implicit Subgrid-Scale Modeling of a Mach 2.5 Spatially Developing Turbulent Boundary Layer

   https://doi.org/10.3390/e24040555  

   Araya, Guillermo; Lagares, Christian (April 2022, Entropy)

   We employ numerically implicit subgrid-scale modeling provided by the well-known streamlined upwind/Petrov–Galerkin stabilization for the finite element discretization of advection–diffusion problems in a Large Eddy Simulation (LES) approach. Whereas its original purpose was to provide sufficient algorithmic dissipation for a stable and convergent numerical method, more recently, it has been utilized as a subgrid-scale (SGS) model to account for the effect of small scales, unresolvable by the discretization. The freestream Mach number is 2.5, and direct comparison with a DNS database from our research group, as well as with experiments from the literature of adiabatic supersonic spatially turbulent boundary layers, is performed. Turbulent inflow conditions are generated via our dynamic rescaling–recycling approach, recently extended to high-speed flows. Focus is given to the assessment of the resolved Reynolds stresses. In addition, flow visualization is performed to obtain a much better insight into the physics of the flow. A weak compressibility effect is observed on thermal turbulent structures based on two-point correlations (IC vs. supersonic). The Reynolds analogy (u′ vs. t′) approximately holds for the supersonic regime, but to a lesser extent than previously observed in incompressible (IC) turbulent boundary layers, where temperature was assumed as a passive scalar. A much longer power law behavior of the mean streamwise velocity is computed in the outer region when compared to the log law at Mach 2.5. Implicit LES has shown very good performance in Mach 2.5 adiabatic flat plates in terms of the mean flow (i.e., Cf and UVD+). iLES significantly overpredicts the peak values of u′, and consequently Reynolds shear stress peaks, in the buffer layer. However, excellent agreement between the turbulence intensities and Reynolds shear stresses is accomplished in the outer region by the present iLES with respect to the external DNS database at similar Reynolds numbers. 

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5. Modal Analysis on MVG Controlled Supersonic Flow at Different Mach Numbers

   https://doi.org/10.3390/pr10081456  

   Yang, Yong; Yan, Yonghua; Chen, Caixia; Wu, Qingquan; Kwembe, Tor A.; Wu, Ryan (August 2022, Processes)

   Modal analysis on micro-vortex generator (MVG)-controlled supersonic flow at different Mach numbers is performed in this paper. The purpose of this investigation is to clarify the different properties of streamwise and ring-like vortical modes, and the effects of different Mach numbers on these modes, to further understand the vortical structures as they travel from MVG down to the shock wave/boundary-layer interaction (SWBLI) region. To this end, a high order and high resolution large eddy simulation (LES) was carried out, which identified the vortical structures behind the MVG and in the shock wave/boundary-layer interaction (SWBLI) region in the supersonic ramp flow with flow speeds of three different Mach numbers 1.5, 2.0, and 2.5. The proper orthogonal decomposition (POD) then was adopted to investigate the modes of the fluctuation flow field. It emerged that the streamwise and ring-like vortical modes were disparate in energy distribution, structural order, frequency and amplitude. Furthermore, it showed that as the Mach number increased, the energy of the streamwise modes increased while the opposite was true for ring-like modes; and the streamwise modal structures were altered more significantly than the ring-like modes, and the frequency of each mode scarcely varied. It was also found that the streamwise vortices absorbed energy from the ring-like vortices while they traveled from the MVG down to the SWBLI region, but the dominant frequency of each mode rarely changed during this process. 

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