Gregory Delattre

Aero-mechanical optimization of a contra-rotating open rotor and assessment of its aerodynamic and acoustic characteristics:

Within the frame of the ongoing 7th Framework European Project DREAM, this article presents a synthesis of Cenaero, DLR, and Oneras joint effort to demonstrate the aerodynamic and acoustic optimization potential of a contra-rotating open rotor. Within WP 3.2 led by Snecma, the objective was to maximize the propellers efficiency at top-of-climb conditions and to minimize the noise emission at take-off focusing on interaction noise while fulfilling the thrust and torque split specifications at both operating points. These objectives were successfully met by the development and exploitation of efficient multi-objective three-dimensional Reynolds-averaged Navier–Stokes (RANS)-based surrogate-assisted optimization strategies. In order to assess the aerodynamic and acoustic characteristics of both baseline and optimized geometries, coupled unsteady RANS (URANS) simulation and farfield prediction based on an integral Ffowcs Williams–Hawkings approach were then carried out. The results demonstrate that although the acoustic criterion driving the optimization process did not lead to an improvement of the noise characteristics over the whole directivity range, it may be regarded as a cost-effective way to incorporate noise-related aspects into the design intent.

Influence of Torque Ratio on Counter-Rotating Open-Rotor Interaction Noise

This paper investigates the influence of the torque ratio, at constant total thrust, on the interaction noise of a generic counter-rotating open rotor in pusher configuration. It is shown that torque ratio has a small influence on the open-rotor aerodynamic performance but a strong impact on interaction noise at takeoff condition. The noise source mechanisms are investigated in detail and linked with the characteristics of the front rotor blade-tip vortices. Tip vortex characteristics are detailed and compared with analytical vortex models. It is verified that torque ratio variation has no strong impact on the open-rotor aerodynamic performance at cruise condition.

Investigation of Counter Rotating Open Rotor Orthogonal Blade/Vortex Interaction Noise

This paper investigates the influence of vortex models on the noise radiated by the orthogonal interaction of a rotating blade with a prescribed vortex. The blade motion, the vortex maximum velocity and core radius are set to produce an interaction representative of the ones occurring on a counter-rotating open-rotor at takeoff condition where interaction noise is prominent. Different compressible vortex models are considered. Links are made between radiated noise and the vortex velocity profiles. It is shown that velocity decay in the free-vortex region has a strong impact on the noise radiated at low frequencies while the inner structure of the vortex influences the acoustic spectra content at high frequencies.

Computational Fluid Dynamics as a Support to Counter-Rotating Open-Rotor Wind-Tunnel Test Analysis

The rising price of oil since the early 21st century produced a regain of interest in the counter-rotating open rotor, seen as an economic propulsive device for future transport aircraft. Although simple methods are used for design and optimization, the need for advanced methods to assess aerodynamic and acoustic performance of a counter-rotating open rotor within a complex configuration and to support wind-tunnel tests analysis is rising. In this paper, a methodology for complex counter-rotating open-rotor installations is set up to compute an actual test-rig geometry using high performance computing capabilities of ONERA computational-fluid-dynamics software elsA. Comparing the numerical results with the wind-tunnel test data enables to assess both the computational-fluid-dynamics code accuracy and the representativity of the wind-tunnel test, which relies on a somewhat intrusive test rig through a better understanding of the flowfield around the test rig.

Aeroacoustic Computation of a Contra Rotating Open Rotor Model with Test Rig Installation Effects

Aerodynamic and acoustic measurements of a scale model Contra Rotating Open Rotor (CROR) have been performed by TsAGI within the DREAM European Project. This paper presents the aerodynamic and aeroacoustic computations performed by ONERA to account for test rig installation effects on both aerodynamics and aeroacoustics. These numerical results are compared to experimental measurements for both validation and understanding of the installation impact of the test rig on noise emission.

Influence of Blade Deformations on Open-Rotor Low-Speed and High-Speed Aerodynamics and Aeroacoustics

This paper investigates by means of computational fluid dynamics (CFD) and acoustic analogy the influence of blade deformations on open-rotor aerodynamics and aeroacoustics for three key operating points: cruise, takeoff, and approach conditions. For each operating point, simulation results obtained with unrunning blade shapes and running blade shapes are compared with wind tunnel test measurements. Experiments show that blade deformations affect mostly the front rotor, with twist deviations at tip varying within a range of ±2  deg and of opposite sign between cruise and takeoff conditions. Although blade deformations are low for the rear rotor, aerodynamic performance exhibits significant variations due to the modifications of the front rotor wash. Numerical results show that accounting for blade deformations increases or decreases the thrust or power depending on the operating point and leads to a much better prediction of the open-rotor aerodynamic performance. The same comments apply for the noise pre...