Off Ship Measurement of Ship Air Wakes Using Instrumented Unmanned Aerial Vehicles

摘要

This paper details an innovative method for measuring and investigating off ship air wakes that develop during the operation of naval vessels in common underway wind conditions. Wind currents, both naturally occurring and those resulting from ship motion, can create ship air wakes that make operation of rotary wing aircraft in the vicinity of the ship particularly challenging. Currently extensive underway flight testing is required to determine safe wind over deck launch and recovery envelopes for rotary wing aircraft. This underway flight testing can be difficult to schedule and is very expensive since it involves multiple flights of manned helicopters. Small unmanned TREX 600 radio controlled (RC) helicopters have been equipped with a custom data package that includes an Inertial Measurement Unit (IMU), Global Positioning System (GPS) receiver and transmitter. The instrumented TREX 600 helicopter is flown back and forth through the ship air wake from YP676, which is a dedicated 108 ft long US Naval Academy research vessel, and detects the impact of the associated ship air wake on the 4.3 ft rotor diameter helicopter. IMU and GPS data are transmitted in real time to another data package mounted on the ship. The ship data package also records pilot control inputs to the helicopter. Through the use of a MATLAB script the TREX 600 helicopter position relative to the ship is determined in real time. Received IMU data from the helicopter is also filtered through a trained neural network which removes IMU oscillations due to pilot flight control inputs. Air wake data A_ω is then determined which measures the intensity of the air wake on the TREX 600 helicopter. Comparison of the air wake data A_ω show good correlation to regions of significant air wake intensity predicted by advanced Computational Fluid Dynamics (CFD) simulations.