Investigation on effects of time-frequency characteristics of ship airwake on helicopter flight characteristics

舰艉流时/频特征对直升机飞行特性影响研究

China Helicopter Research and Development Institute, Jingdezhen 333001, China

Received: 16 January 2021

Abstract

A conventional helicopter flight dynamics model, which can be coupled with ship airwake date, is developed in this study. In the method, the ship airwake data is obtained by the high-accuracy DES model, and a strategy which can transmit CFD data to the flight dynamics model is established based on the "one-way" coupling idea. Then, the SFS2 ship model and UH-60A helicopter are chosen as a combination to investigate the influences of the spatial and temporal characteristics of ship airwake from the aspects of control margins and unsteady level. The time-averaged simulation results show that for the counterclockwise-rotor helicopter, although pilot could have more collective pitch margin under crosswind condition compared to the headwind condition, he might possess much less pedal margin due to the sidewash in the airflow. The unsteady results indicate that the unsteady loading level of the helicopter would increase significantly under the crosswind condition compared to the headwind condition due to the increase of turbulent density in the airwake. Furthermore, for the conventional helicopter, the disturbances on the forces and moments which along the rotor hub (i.e., thrust and yaw moment) are the critical factors that increasing the pilot workload during the landing procedure.

摘要

发展了一套能够耦合非定常舰船流场的直升机飞行动力学模型。采用DES方法以获得高精度非定常舰船流场，并基于"单向耦合"思想构建了CFD向飞行力学模型的数据传递策略。以SFS2舰船模型和UH-60A直升机组合为研究对象，从直升机操纵余量和非定常载荷水平两方面分析了着舰过程中舰艉流场对常规单旋翼直升机的扰动特征。时均研究结果显示：对于右旋旋翼直升机，在右侧风情形下飞行员能够具有更多的总距操纵余量，但由于尾桨受侧洗流的影响，脚蹬余量相较于0°风向角情形会大幅降低。非定常水平结果表明：侧风情形下舰艉流场湍流脉动强度增大，使得飞行员的工作载荷要显著高于0°风向角情形；常规单旋翼直升机在其旋翼轴方向的气动力和力矩（即拉力和偏航力矩）的非定常波动是导致着舰过程中飞行员工作载荷增大的主要因素。