Helicopter Main Rotor aerodynamic simulation with CFD

Abstract

The Bell 212 helicopter is one of the major general purposes utility rotorcraft currently in use in SLAF which is containing NACA 0012 aerofoil in the two blades of main rotor. The primary objective of this research project is to evaluate the aerodynamics behavior of the Bell 212 main rotor in hovering, forward and vertical flight by conducting Computational Fluid Dynamics (CFD) analysis and make comparison with the theoretical solutions in both Blade Element and Momentum theories. The CFD simulations have been done in subsonic flight regimes only. As a means of validating the results, the CFD analysis has been done with turbulence model. CFD analysis of a rotating blade was achieved by using the rotating mesh. A 1:1 SOLID WORKS solid model (14.201m) of Bell 212 main rotor was used to generate computational mesh and subsequent CFD simulations were performed mainly with ANSYS Fluent. A surface and volume mesh continuum was generated that contained approximately seven million polyhedral cells, where the Finite Volume Method (FVM) was chosen as a discretization technique. During the post processing phase of the CFD results, the aerodynamic characteristics of the Bell 212 main rotor have been predicted in terms of main rotor speed of 800rpm for hovering forward and vertical flight with angles of attack of the blades to 2?. In CFD simulation process, results were recorded such as rotor RPM, Tip velocity, Mass flow rate, Heat flux, Temperature changes and total and static pressure variation over and around the main rotor. Throughout those values comparisons have made with theoretical aerodynamic results under Blade Element theorem and Momentum Theorem. An implicit unsteady flow solver, with an ideal gas and a SST (Mentar) K-Epsilon turbulence model were used. Hover, vertical and forward cases were examined. Several aerodynamic forces such as Coefficient of Drag, Coefficient of Lift and Coefficient of Momentum were estimated during the Fluent analyzing process in CFD. The flow physics revealed with CFD analysis are well aligned with selected main rotor practical theories in both Blade Element and Momentum theories in hover, vertical and forward flight maneuvers. The forecasted values of aerodynamic parameters for Bell 212 main rotors are little bit different than expected. It has been found this particular fact is directly related to computational limitations associated with CFD. The final outcomes of this research will provide a better guide in future CFD analysis on the helicopter main rotor analysis since it is more valuable as a rotating meshed CFD research.