High-Fidelity Structural Loads Analysis of the ONERA 7A Rotor

Abstract

The ONERA 7A rotor wind tunnel test data are investigated to assess the accuracy of analytical tools in the calculation of rotor airloads and structural loads. Comprehensive analysis codes, HOST and RCAS, and coupled computational fluid dynamics/comprehensive analysis codes, elsA/HOST and Helios/RCAS, are used to examine the ONERA 7A rotor blade dynamics, trim, airloads, and structural loads, and the calculated results are compared with the measured data for both high-speed and high-thrust conditions. The present elsA and Helios analyses include the test stand modeling. Comprehensive analyses show significant phase differences for the airloads and structural loads. The phase correlation is substantially improved by the coupled analyses for both high-speed and high-thrust conditions. In general, the coupled analyses also improve the half peak-to-peak correlation of structural loads compared to the comprehensive analyses. The majority of the predictions from the coupled analyses in half peak-to-peak blade structural loads are within 20% of the measured data. The present study shows unprecedented correlation of structural loads for the 7A rotor, consistently better than the previous structural loads correlation for the UH-60A rotor using Helios/RCAS analysis.

Modeling Aerodynamics, Including Dynamic Stall, for Comprehensive Analysis of Helicopter Rotors

“…The last configuration was obtained by slowing the rotor speed, from its nominal speed of about 1020 rpm to about 700 rpm. Many attempts to improve the analysis were made based on comprehensive analysis and then on comprehensive analysis coupled with CFD techniques [13][14][15]; only recently [16][17][18] …”

“…The predictions of the structural loads are clearly improved by the aerodynamics modeling, but lack the precision features of coupled analysis based on high-fidelity CFD techniques [18]. One particular remark about the chord bending moment prediction is that the amplitude predicted by the French CA codes (ONERA, Airbus Helicopters) is much higher than in experiments, whereas the American code RCASprovides the correct amplitude [18].…”

“…The predictions of this test flight have been recently improved by coupled analysis of comprehensive analysis with CFD techniques, by teams at the US Army and ONERA [16,18]. However, no computation based on stand-alone comprehensive analysis with reasonable correlation between predictions and experimental results has been published.…”

Uncertainty Quantification of the ONERA 7A Rotor Performance and Spanwise Structural Loads using a Surrogate-Based Approach

“…The ONERA 7A rotor is a four-bladed fully articulated rotor with a radius of 2.1m and solidity, σ, of 0.084. In the analysis, it is studied at high-speed condition (advance ratio: µ = 0.4, lift coefficient / solidity: C L /σ = 0.063), and has been investigated in the literature using various analysis tools and methods [5,13,6,14]. The rotor was trimmed to satisfy the Modane flapping law (lateral flapping: β 1s = 0, longitudinal flapping:…”

Coupling Mid-Fidelity Aerodynamics and Multibody Dynamics for the Aeroelastic Analysis of Rotary-Wing Vehicles

“…Sophisticated numerical tools have been developed to support the analysis of rather different operating flight conditions typical of VTOL vehicles with increasing level of detail. Indeed, a substantial effort was spent in past years to develop sophisticated structural dynamics codes (CSD) that were effectively used for rotorcraft applications (e.g., References [2][3][4]). In detail, structural dynamics of rotary-wing vehicles was typically investigated using the multibody approach [5,6], which takes into account the nonlinear dynamics of the interconnected rigid and flexible bodies representing the aircraft components during transients.…”