New implementation of stability-based transition model by means of transport equations

International audienceA new natural laminar-turbulent transition model compatible with Computation Fluid Dynamics is presented. This model accounts for longitudinal transition mechanisms (i.e. Tollmien-Schlichting induced transition) thanks to systematic stability computation on similar boundary profiles from Mach zero to four both on adiabatic and isothermal wall. The model embeds as well the so-called “C1-criterion” for transverse transition mechanisms (i.e. cross-flow wavesinduced transition). The transition model is written under transport equations formalism and has been implemented in the solver elsA (ONERA-Airbus-Safran property). Comparisons are performed on two-dimensional and three-dimensional configurations against transition database approach

Turbulence-airfoil interaction noise reduction using wavy leading edge: an experimental and numerical study

International audiencePassive treatments aiming at reducing turbofan broadband noise have been recently studied in the framework of European Project FLOCON. A concept based on a sinusoidal variation of the leading edge of a single airfoil expected to decrease interaction noise has been investigated by ONERA. Turbulence-airfoil interaction mechanism is achieved using a turbulence grid located upstream of a NACA airfoil tested in ISVR anechoic open wind tunnel. High noise reductions are obtained (3-4 dB) for all studied flow speeds. Experimental work is supplemented by numerical simulations using RANS/LES and CAA Euler-based approaches to predict the acoustic response of the wing. Isentropic turbulence is synthetically injected by means of a suited inflow boundary condition. Unsteady simulations are restricted to the baseline case (without treatment) and the present paper focuses on direct Euler methodology which provides reliable power spectrum density comparing to experiment. Effect of leading edge serrations on aerodynamics and noise is emphasized using Amiet thin airfoil theory, RANS solutions and available measurements

Turbulence-airfoil interaction noise reduction using wavy leading edge: an experimental and numerical study

International audiencePassive treatments aiming at reducing turbofan broadband noise have been recently studied in the framework of European Project FLOCON. A concept based on a sinusoidal variation of the leading edge of a single airfoil aiming at reducing interaction noise has been investigated by ONERA. Turbulence-airfoil interaction mechanism is achieved using a turbulence grid located upstream of a NACA airfoil tested in ISVR anechoic open wind tunnel. High noise reductions are obtained (3-4 dB) for all studied flow speeds. Moreover, aerodynamic performances are shown to be slightly increased by the treatment that tends to reduce the drag without modify the mean loading. Experimental work is supplemented by numerical simulations using Large Eddy Simulations (LES) and direct Euler approaches to predict the acoustic response of the wing. LES is chained to a FWH (Ffowcs-Williams and Hawkings) integral to assess the radiated field. Isentropic turbulence is synthetically injected by means of a suited inflow boundary condition. Present computations are focused on the reference case (without treatment). Numerical predictions are compared to the experiment, and to analytical solutions issued from Amiet theory

Stability-Based Transition Model Using Transport Equations

A laminar–turbulent transition model is presented. The model accounts for longitudinal transition mechanisms (i.e., Tollmien–Schlichting-induced transition) and was calibrated using stability computations on similar boundary-layer profiles at Mach number ranging from zero to four on both adiabatic and isothermal walls. The model embeds the so-called C1 criterion for transverse transition mechanisms (i.e., crossflow-wave-induced transition). Finally, the model accounts for separation-induced transition by means of the Gleyzes criterion. The transition model is written under a transport equation formalism. Validations are performed on three-dimensional configurations, and comparisons against results from a transition database method for natural transition, exact linear stability computations, and experimental data are shown

Modélisation de paroi pour la simulation des grandes échelles avec une approche numérique d’ordre élevé

Cette étude porte sur le couplage d’un modèle de paroi avec une approche numérique d’ordre élevé pour la réalisation de calculs aéroacoustiques d’écoulements pariétaux à hauts nombres de Reynolds par la Simulation des Grandes Echelles (SGE). La modélisation de paroi est basée sur l’utilisation de lois analytiques et est combinée à des schémas numériques implicites d’ordre élevé développés en Volumes Finis (VF). Les performances de ce couplage sont évaluées en réalisant la simulation d’un écoulement de canal plan bi-périodique turbulent à un nombre de Reynolds Re = 2000, puis la SGE d’un jet subsonique isotherme à un nombre de Reynolds ReD = 5,7 x 10(5)

A flux reconstruction technique for non-conforming grid interfaces in aeroacoustic simulations

International audienc

A flux reconstruction technique for non-conforming grid interfaces in aeroacoustic simulations

International audienc

Turbulence-airfoil interaction noise reduction using wavy leading edge: an experimental and numerical study

International audiencePassive treatments aiming at reducing turbofan broadband noise have been recently studied in the framework of European Project FLOCON. A concept based on a sinusoidal variation of the leading edge of a single airfoil expected to decrease interaction noise has been investigated by ONERA. Turbulence-airfoil interaction mechanism is achieved using a turbulence grid located upstream of a NACA airfoil tested in ISVR anechoic open wind tunnel. High noise reductions are obtained (3-4 dB) for all studied flow speeds. Experimental work is supplemented by numerical simulations using RANS/LES and CAA Euler-based approaches to predict the acoustic response of the wing. Isentropic turbulence is synthetically injected by means of a suited inflow boundary condition. Unsteady simulations are restricted to the baseline case (without treatment) and the present paper focuses on direct Euler methodology which provides reliable power spectrum density comparing to experiment. Effect of leading edge serrations on aerodynamics and noise is emphasized using Amiet thin airfoil theory, RANS solutions and available measurements

Analysis of bypass transition process using large eddy simulations

International audienceThis paper describes the setup of a wall-resolved large eddy simulation (LES) of bypass transition on a realistic flat plate and the results obtained. This simulation is the first to compute a bypass transition flow on a flat plate from the receptivity stage to the laminar-turbulent transition onset. The key mechanisms of bypass transition are highlighted by the simulation: the shear-sheltering, the birth of Klebanoff-modes, their amplification, and destabilization