NATO Generic Destroyer Moving-Ship Airwake Validation and Rotor-Ship Dynamic Interface Computations using Immersed Boundary Lattice-Boltzmann Method

Abstract

During rotorcraft ship-deck landing operations, complex interactional aerodynamic phenomena occur between the rotor and ship airwakes, and these phenomena are not fully understood. Many traditional ship - rotorcraft interactional simulation approaches use a one-way coupling, where the ship airwake is superimposed on the rotor, modifying its inflow. However, because the rotor wake does not alter the ship airwake in such a simulation, one-way coupling may not capture all relevant phenomena, especially when ship motion is accounted for; two-way fully-coupled simulations may be needed. In this study, the NATO Generic Destroyer, a shared, representative ship geometry created for collaborative studies, was investigated numerically, and the ship airwake results validated by wind tunnel measurements using discrete velocity probes on the landing deck. Lattice-Boltzmann Method (LBM) simulations of the standalone ship airwake and one- and two-way coupled ship-rotorcraft interactional simulations were conducted using a Graphics Processing Unit (GPU) accelerated solver. The ship surface was represented using a novel Grad immersed boundary approach. Using this boundary condition, effects of ship motion were included in the simulations. Ship airwake results showed good agreement with the experiment and excellent computational performance; simulations took less than four hours to run on a single GPU node. Through ship-rotorcraft interactional simulations, it was determined that one-way and two-way coupling strategies resulted in different frequency profiles of unsteady induced inflow velocity variations, with considerable differences in the closed-loop pilot response range.