Abstract
The sharp 90°corner of bow found on American Tarawa class general amphibious assault ship LHA-1 will produce large separated region in the airwake over the ship, and the turbulence in the separation region seriously affects the operation safety of the helicopter. In order to reduce the separation in bow region of the LHA-1, and optimize the helicopter operating environment, the numerical simulation method is used to study the influence of the bow flap on the airwake of LHA-1. The study results show that: the ANSYS k-ε two equation model based on the hybrid grid can be used to predict the steady-state characteristics of the ship airwake; the bow flap can improve the flow field downwind of the flap installation position, and the impact range can cover two spots; in headwind, the optimal installation angle of the bow flap is 15°~25°. The research results of this paper can provide modification and improvement reference for the amphibious assault ship in-service and under construction, so as to achieve the purpose of optimizing the ship airwake, thereby improving the safety of helicopter landing process and extending the service life.
Highlights
The amphibious assault ship that is the helicopter carrier, is available for launch and recovery operations of the helicopter formation, while the launch and recovery of helicopters on ships, especially the recovery, has become a worldwide technical issue
The airwake contains relatively small length scales which will pass through the rotor, being felt as vibrations, and larger length scales that will affect the performance of the rotor as well as the handling characteristics of the helicopter[1]
Different from the rear flight deck ship with the hangar, the amphibious assault ship has several landing spots on the straight flight deck, and the related research show that the flow separation of the bow edge will seriously affect the safety of the helicopter operating at the front spots of LHA-1
Summary
The amphibious assault ship that is the helicopter carrier, is available for launch and recovery operations of the helicopter formation, while the launch and recovery of helicopters on ships, especially the recovery, has become a worldwide technical issue. Does the pilot have to track a target moving with multiple degrees of freedom, but one must land the helicopter in the highly unsteady airwake of the various pieces comprising the ship superstructure. Different from the rear flight deck ship with the hangar, the amphibious assault ship has several landing spots on the straight flight deck, and the related research show that the flow separation of the bow edge will seriously affect the safety of the helicopter operating at the front spots of LHA-1. In order to reduce the separation zone of the sharp 90-degree corner found on LHA-1, Czerwiec and Polsky[7] investigated the effect of adding a 22.5° downward-deflected flap to the bow. This paper will continue research the relationship between flap mounting angle and the airwake characteristics in different wind angles
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