1,721,106 research outputs found
Effect of Spectroscopic and Radiative Transport Models on the Computation of Thermal Radiation in High Temperature Gases.
No full textAnalysis of plasma formation during hypersonic flight in the earth atmosphere
Get PDFIn this study we investigate the formation of plasma in hypersonic flight and its impact on radio communications and radar tracking. The transfer of kinetic energy from the vehicle to the surrounding gas in the hypersonic regime leads to the formation of plasma, which can cause interference with electromagnetic waves. By conducting a numerical simulation campaign using Computational Fluid Dynamics (CFD), we are determining the critical Mach number and altitude conditions that lead to plasma formation. The plasma generated at the nose of the vehicle and its subsequent convection along the body and in the wake are the main subjects of our investigation. The simulations include physical models that account for chemical, vibrational and electronelectron energy non-equilibria, using a two-temperature approach. The results indicate the Mach numbers and altitudes at which plasma formation can significantly affect the propagation of electromagnetic waves
Large Eddy simulations and Reynolds-averaged Navier-Stokes simulations of separation-induced transition using an unstructured finite volume solver
Get PDFThe study aims to assess the capability of different methodologies in capturing the separation-induced transition phenomenon. This transition mechanism occurs when the flow separates from the airfoil surface, and transitions from a laminar to a turbulent state due to the amplification of the Kelvin-Helmholtz instability developed in the separated shear layer. The simulations employ high-order numerical methods for solving the Navier-Stokes equations, while the transition modeling for RANS is based on the γ-Re_θ transition model. LES enables prediction of the onset and location of transition and provides turbulent flow statistics
Aerodynamic optimization and analysis of quadrotor blades operating in the Martian atmosphere
No full textThe design of unmanned aerial systems (UAS) for flight in the Martian atmosphere is a relevant and current topic. The successful flight of the Ingenuity helicopter recently proved its applicability. We present a numerical approach to the aerodynamic optimization of blades for rotors working in flow regimes with Reynolds numbers smaller than 15,000. Due to the atmospheric gas density and viscosity on Mars and the required rotation speed and rotor diameter, rotary-wing works mainly in the so-called ultra-low Reynolds number regime (103<104), where the flow is likely laminar. The tip region is in the lower range of the very-low Reynolds number regime (104<105), where separation-induced laminar-turbulent transition may occur. Such conditions characterize rotor blades of UAS operating in the Martian atmosphere or at very high altitudes (30 km) in the Earth's atmosphere. The blade design procedure consists of a two-step optimization process. The process starts with an initial two-dimensional airfoil design analysis followed by three-dimensional Blade Element Momentum (BEM) simulations to achieve the chord and twist radial distributions necessary to define the blade geometry. Then, a procedure to perform three-dimensional adjoint-based CFD simulations enhances the performance. The aerodynamic characteristics of optimal blades are evaluated with Navier-Stokes (N-S) and Large Eddy Simulations (LES), demonstrating the negligible effect of turbulence in blade performance for these Reynolds numbers when the boundary layer is attached. The implemented BEM method and high-fidelity CFD simulations show a good agreement
Investigation of high speed flows over a flat plate
No full textSupersonic viscous flows over a flat plate a r einvestigated using anumericaltechnique that solves theparabolizedform o fthe Navier-Stokes equations. Results are computed fordifferentfree-streamconditions and used to evidence the most imporantfeaturesthat characterizesuchflows, with particular attention to viscous interaction phenomena. In addition, comparisonsare carried out both withcomputations performed by other authors and with boundary layer results
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