Model of Airflow Field on the Deck for Shipborne Helicopter Flight Dynamics Analysis

For the research of helicopter/ship dynamic interface,the method of combining steady flow and stochastic flow is adopted to establish a flow field model applied to the flight dynamics analysis of shipborne helicopter.The steady flow is calculated by computational fluid dynamics(CFD)method,while the stochastic flow is composed of the compensation velocity derived from ship motion and turbulence above the deck.The accuracy of the proposed flow field model is verified by comparing the helicopter response in the proposed flow field with the results calculated by US Army′s Military Specifications(MIL)model which is commonly used in engineering.Meanwhile,it also shows the proposed flow field model is more appliable to flight dynamics analysis of shipborne helicopter.On that the basis,ship deck flow field is simulated at different sea conditions by adjusting the wind speed on the deck,mother ship movement and shipboard turbulence,etc.And helicopter angular rate response is calculated.The results show that the difference of dynamic stability between helicopter′s roll and pitch leads to the facts that the influence of above factors on the helicopter′s roll angular rate response is greater than that of pitch angular rate,that the frequency and amplitude of mother ship roll motion are much greater than those of pitch motion,and that the disturbance caused by roll motion on the air has greater influence on the helicopter response.The shipboard turbulence is the main disturbance factor that influences helicopter flight stability and its intensity determines the amplitudes of angular rate response.

For the research of helicopter/ship dynamic interface, the method of combining steady flow and stochas- tic flow is adopted to establish a flow field model applied to the flight dynamics analysis of shipborne helicopter. The steady flow is calculated by computational fluid dynamics （CFD） method, while the stochastic flow is com- posed of the compensation velocity derived from ship motion and turbulence above the deck. The accuracy of the proposed flow field model is verified by comparing the helicopter response in the proposed flow field with the re- suits calculated by US Army＇s Military Specifications （MIL） model which is commonly used in engineering. Mean- while, it also shows the proposed flow field model is more appliable to flight dynamics analysis of shipborne heli- copter. On that the basis, ship deck flow field is simulated at different sea conditions by adjusting the wind speed on the deck, mother ship movement and shipboard turbulence, etc. And helicopter angular rate response is calcu- lated. The results show that the difference of dynamic stability between helicopter＇s roll and pitch leads to the facts that the influence of above factors on the helicopter＇s roll angular rate response is greater than that of pitch angular rate, that the frequency and amplitude of mother ship roll motion are much greater than those of pitch motion, and that the disturbance caused by roll motion on the air has greater influence on the helicopter response. The ship- board turbulence is the main disturbance factor that influences helicopter flight stability and its intensity determines the amplitudes of angular rate response.