This report describes the computational fluid dynamics (CFD) modelling that was carried out on the Bell-47 helicopter. The hover flight condition was simulated to estimate the drag produced by the original cabin and to evaluate the effects of implementing a new low drag cabin. This was motivated by the possibility of achieving a performance gain by redesigning the cabin. The topic was supported by HeliMods, a company based at Caloundra Airport (Southeast Queensland). To begin the analysis, an approximation of the wake produced by the hovering rotor had to be made. This was done by using blade element momentum theory. A MATLAB program was written to perform these calculations. The representation of the flow field could then be used for the CFD calculations.
The CDF package used for the project was Fluent. Fluent allows simulation of a wide range of fluid flow problems. To model the helicopter in a hover, the rotor wake approximation was implemented into Fluent. This required the selection and testing of the simulation boundary conditions.
Modelling of the original cabin shape was performed in Solid Edge. This is a software package that allows 3-D geometries to be created. New cabin geometries were also created in Solid Edge. The main requirement set by HeliMods was that a new cabin shape should have room for two pilots. It was also desired that the helicopter was able to be flown from both seating positions. The current Bell-47 cabin seats three people side by side, surrounded by a large bubble canopy. With the design requirements in mind it was decided that the new cabin would seat the pilots in tandem formation, allowing for a much narrower cabin design.
After having implemented the wake approximation into Fluent, CFD analysis of the new and original cabin geometries could be performed. From the simulation results it was concluded that a new two seater cabin could be implemented, for approximately the same drag penalty as the original cabin. This is a positive result since the new cabin with its narrow shape would be expected to perform much better in forward flight than the original cabin.