Vijayakumar Rajagopalan

An early estimation of the ship–helicopter dynamic interface flow environment is one of the most challenging and precarious tasks in any naval organization across the globe. The First-Of-Class Flying Trials (FOCFT) is one of the most common methods to evaluate the complexities associated with the ship–helicopter dynamic interface. These trials are very expensive and highly demanding, with added limitation that these can be conducted only after post-construction of the ship and restricting the scope of any further design modifications. This study presents an investigation to gain understanding of the aerodynamic impact of helicopter on shipboard flight deck flow physics under a ship–helicopter dynamic interface flow environment. The prime goal of this work is to investigate the influence of helicopter downwash aerodynamics over the ship flight deck using the simplified dynamic interface (SDI) model. A parametric analysis has been conducted for three identified rotor configurations at different crossflow conditions. The paper reports the influence of rotor ground effect over the flight deck region in terms of the downwash airflow characteristics, variation of rotor plane velocity gradients and the airwake existing over the flight deck region. Finally, an attempt has been made to grade the effect of ground on a ship–helicopter dynamic interface for safeguarding the helicopter operations.

The combined operation of a ship and a helicopter is ubiquitous in every naval organization. The operation of a ship in combination with the landing and take-off operations of a helicopter results in a very complex flow phenomenon. This is due to the presence of ship airwakes, strong velocity gradients and widely varying turbulence length scales. An accurate assessment of the resultant flow phenomena is an outstanding challenge for naval architects as well as researchers. A conceptual method to gain insight into the combined ship-helo flow phenomena over a helodeck is presented. The prime objective of this work is to develop an economical design tool employing both experimental as well as computational techniques to simulate the ship-helicopter coupled environment regime at early design stages reasonably well so as to ease the burden of expensive and risky sea trials. For this purpose, a simplified dynamic interface (SDI) model is proposed to investigate the coupled effects of ship airwake and helicopter rotor downwash. The paper reports a parametric analysis to study the coupled ship-helo airwake behaviour and its impact on helicopter fuselage over the ship helodeck for different ship speed regimes by the proposed SDI model. Further, an attempt has been made to set up preliminary design criteria to grade the ship-helicopter interface for ensuring minimum standards of safe helo operations. Finally, we discuss the impact of the coupled flow dynamics in terms of induced fuselage drag, cross-flow characteristics, rotor plane wake and velocity gradients existing over the helodeck region and evaluate the proposed design criteria.