CFD based multi-point multi objective optimization method is performed to search optimum tail boom strake geometry in order to improve helicopter hover and sideward flight (10kts, 20kts, 30kts and 40kts) performance at hot and high atmospheric conditions. Upper and lower strake geometries are parametrized by using NX CAD tool and effect of the designed strake geometries are analyzed at specified flight conditions by using computation fluid dynamic (CFD) methods. Star CCM+ is used as mesher and solver. Downwash of the main and tail rotor is modelled by using built-in virtual disk model in Star CCM+. Optimization is performed by using multi-point multi objective optimization tool HEEDS and multi-objective SHERPA optimization algorithm is preferred for optimization. Accumulated pedal improvement and total power reduction are specified as objectives. At the end of the optimization workflow, improvements of the best strakes on pedal input and power required at hover are investigated. Furthermore, sensitivity of the design parameters, population of the design space and flow field around tail boom are examined in detail.
A methodology to implement agility as a tradeoff parameter into multi-disciplinary optimization of a helicopter rotor is proposed. Being a qualitative evaluation measure and having no clear definition, agility is tried to be quantified through utilization of "ease", "speed" and "precision" metrics. The developed methodology utilizes a non-linear model predictive control approach to generate trajectory and control input history specifically to track the agile maneuver of interest. Deviation from reference path, state and input history and quickness are managed to determine integrated agility score. Then effect of rotor primary design parameters on agility characteristics is studied. A sensitivity analysis is performed to identify driving parameters and agility simulations are performed for four different maneuvers that are commonly used in nap-of-earth flights/missions. Slalom course, acceleration & deceleration, hurdle-hop and teardrop turn maneuvers analogous with ADS 33 Mission Task Elements are selected as the agile maneuvers to be considered and response surface analyses are performed to study the tradeoff between primary design parameters.
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