Physics-Based Hydraulic Damper Model for Rotor Structural Loads

Abstract

A physics-based, fully nonlinear hydraulic damper model was developed within the framework of the Rotorcraft Comprehensive Analysis System in order to facilitate integrated damper and rotorcraft analysis and design. The hydraulic damper governing equations of motion were formulated using flow continuity equations for each hydraulic device within the damper. The developed damper model was compared with bench test data of a hydraulic damper under harmonic oscillation. It was also evaluated as an integrated rotor-damper solution against test data from the NASA–Army UH-60A Airloads Program. For these evaluations, the accuracy of blade load predictions using the newly developed damper model was compared against conventional linear and nonlinear (table lookup) damper models. From these comparisons, the physics-based damper model is able to capture the hysteresis loops of the isolated damper under harmonic oscillation and provide physical insight by modeling the damper’s component parts. When integrated into Rotorcraft Comprehensive Analysis System, the physics-based model was found to be consistent with the legacy nonlinear model for calculating blade loads for the high-speed and high-thrust conditions evaluated.