WIND CHARACTERIZATION AROUND OFFSHORE PLATFORM FOR REAL-TIME HELICOPTER SIMULATOR

摘要

In the last years, flight safety has constantly improved. But accidents still occur, and ground proximity operations (e.g. take-off and landing, search and rescue, et al.) are among the most dangerous flight phases. With the development of offshore deep water fields, helicopter transportation and consequently helicopter deck becomes very important. To ensure helicopter safe operations, aerodynamic hazards around an offshore platform need to be identified and simulated during flight training simulations. OpenFoam CFD features provides the full capability to evaluate air-to-ground interactions for the different boundary conditions (wind speed, wind direction), but also include onerous computational time not compatible with real-time simulation and requires handling with a huge quantity of data. To overcome the long-time calculation time, it has been decided to run the incompressible static RANS computation stand-alone and to create a database to store the wind velocities in grid points. To overcome the bulk of data to handle it has been decided to select a restricted area around the offshore platform of about 1km with a mesh refinement of about 5m and another one of about 150m with a mesh refinement of 1m, where velocity gradients are the highest. During real-time-simulation, it is extracted from the database only a set of CFD data using a query based on oil rig shape, wind direction, wind speed and relative helicopter position. To further reduce the computational cost only CFD results around helicopter are extracted and a new query will be performed every time that helicopter moves away of a predefined distance from current position. Wind velocities extracted have been evaluated in about 100 control points on helicopter, placed on the main rotor, tail rotor, fin, tabs and fuselage using a linear interpolation weighted on the distance of the 8 grid points nearest to each one. Unsteady effects are reproduced by passing band-limited white noise through appropriate forming filters, based on statistical indicators obtained by CFD computations. More than 1000 CFD computation on different oil rigs and ships were performed covering different sets of boundary conditions. A successfully integration within Full Flight Simulator real-time software was confirmed by very positive pilots' evaluation during all ground proximity maneuvers.