Integration of Hydraulic Lag-Damper Models with Helicopter Rotor Simulations

This paper describes the design and integration of a generic hydraulic lag-damper model into an industrial helicopter rotor simulation code. The paper explains the details of an implementation of a computational platform integrating the rotor simulation code with a damper model. A parametric physical damper model is developed here in order to allow physically consistent improvements to helicopter performance studies. Further, this model enables investigating novel uses of lag dampers, such as for vibration reduction. The physical consistency of this work is demonstrated in two case studies. In the first instance, the damper laboratory experimental data are used for a correlation and validation study illustrating the capability of the modeling methodology to generate the model with refined response predictions. The second case study considers a physics-based lag-damper model with an active flow restrictor based on a modified version of the validated passive damper model. This realistic model is shown to be able to induce physically consistent changes in the nonrotating rotor-hub responses. A parametric study with harmonic three-per-revolution flow-restrictor activity suggests that significant load changes are possible in the nonrotating in-plane hub forces and moment. The study also shows possible tradeoffs such as high damper peak forces corresponding to the reduced in-plane forces. Therefore, the presence of these tradeoffs will require the use of constrained optimization formulation to address more complex problem configurations.