Session: 01-06-01 CFD Modeling Practice & Verification

Paper Number: 101602

101602 - Creating a Realistic Piloted Simulation of Helicopter Recovery to an Offshore Platform 

Operators of offshore platforms routinely employ helicopters to provide essential services such as the transport of crew and freight, equipment inspection, and in emergencies, evacuation and search and rescue missions. However, when the helicopter arrives at the offshore platform, the pilot is often faced with a difficult and dangerous landing, mainly due to strong winds. If the helicopter is unable conduct missions due to poor flying conditions, the operation of the offshore platform may be affected, leading to significant commercial penalties.

The unsteady air flow generated by the wind moving over and around the platform structure creates a highly turbulent air flow known as the ‘airwake’. The airwake turbulence is regarded by pilots to be the principal safety hazard and source of the highest pilot workload during helicopter operations to offshore platforms. Prior to helicopter operations to new or modified offshore platforms, analysis of the air flow over the helideck is performed. Wind tunnel testing or Computational Fluid Dynamics (CFD) is typically used to establish the wind environment in which helicopters will be expected to operate; however, regulatory bodies do not stipulate the type of CFD turbulence modelling required and, therefore, analysis is often limited to low-cost time-averaged solutions.

The proposed paper will describe how a full-motion flight simulator has been used to perform a series of real-time piloted deck landings for a specific wind direction at different wind speeds. A crucial component of the simulation is a realistic unsteady airwake, which has been computed using time-accurate CFD. An unsteady full-scale airwake has been generated for a realistic generic offshore platform, and to create a challenging flying environment for the pilot, a wind direction was chosen such that the helideck was positioned in the lee of the main derrick.

A CAD model of a generic semi-submersible offshore platform was used to create a suitable mesh for an unsteady CFD analysis of the platform’s airwake with an approximate cell count of 50 million. Delayed Detached Eddy Simulation with a k-w Shear Stress Transport turbulence model was used to compute the air flow over the platform and required a time of about 7 days on a High-Performance Computer. A steady Atmospheric Boundary Layer was used to represent the air flow approaching the platform over an oceanic sea-surface. The unstructured mesh generated for CFD analysis included a number of regions of smaller cells in areas of specific interest, such as over the helideck, to ensure that the turbulence was accurately resolved for analysis and for piloted flight simulation. The CFD solution generated a thirty second airwake which was integrated with a helicopter flight dynamics model representative of an SH60B Seahawk and, together with a visual model of the offshore platform, was incorporated into the full-motion HELIFLIGHT-R research simulator.

During the simulation trials, the pilot was asked to perform several mission tasks, including recovery to the helideck at different wind speeds, and asked to provide workload ratings using the Bedford Workload rating scale. The proposed paper will describe the setup and results of the CFD solution, while the effect of platform-generated turbulence on the helicopter will be assessed through the results of the simulated trial where pilot workload and control inputs will be presented.

Presenting Author: Neale A. Watson University of Liverpool

Presenting Author Biography: Neale Watson is a newly appointed lecturer in Aerospace Engineering at the University of Liverpool. After graduating in Aerospace Engineering from Queen’s University Belfast, Neale completed his PhD at the University of Liverpool in 2021. The major theme of his research is the investigation of aircraft operating in challenging environments through the validation and application of CFD-generated airwakes and their integration with flight simulation. He has also contributed to a number of industrial projects related to ship airwake generation and validation such as the Queen Elizabeth Class Aircraft Carriers, UK Type 26 Frigates, Australian Type 26 “Hunter” and the UK 23 frigate.

Authors:

Neale A. Watson University of Liverpool
Mark Prior M Prior Consulting Ltd
Ieuan Owen University of Liverpool
Mark D. White University of Liverpool