COMPARATIVE ANALYSIS OF BLADE ELEMENT MOMENTUM THEORY AND COMPUTATIONAL FLUID DYNAMICS SIMULATION RESULTS AGAINST EXPERIMENTAL DATA FOR ROTOR PERFORMANCE

• Main Author: Irwanto, Alvin
• Format: Final Project
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/72821
• Institution: Institut Teknologi Bandung

A helicopter is a type of aircraft that uses rotors to lift off the ground and stay in the air. In contrast with fixed-wing airplanes, helicopters can take off and land vertically, hover in place. They are capable of flying forwards, backwards, and sideways, making them highly maneuverable. This maneuverability makes helicopters and helicopter-based Unmanned Aerial Vehicles (UAV) suitable for use in areas with challenging terrain. The performance of a helicopter is largely determined by the performance of its rotor. The accuracy of prediction of the rotor performance becomes an important issue in designing helicopters. This thesis focuses on studying two commonly used methods for predicting rotor hover performance: Blade Element Momentum Theory (BEMT) and steady-state Computational Fluid Dynamics (CFD). The results obtained from BEMT and CFD are then compared to experimental data to validate their accuracy. Additionally, the thesis studies the effects of twist variations on the rotor performance. The experimental data and rotor parameters used in this study were obtained from a previous investigation of a 4-bladed rectangular rotor with a diameter of 1.65 meters and three different airfoils. The BEMT method is used by discretizing the rotor into small elements and summing up the aerodynamic forces acting on each element. CFD is also used in this thesis, using the Multiple Reference Frame (MRF) method in a steady state. Rotor blade geometry is modeled using computer-aided design (CAD) software, and the ANSYS CFX module in the ANSYS Workbench application was used for the solver. Results obtained from the study show that BEMT can predict rotor Figure of Merit with an error of less than 5% compared to the experimental data. The difference of power consumption in BEMT analysis is largely due to underpredicted profile drag which is caused by estimations of airfoil drag coefficient. On the other hand, MRF CFD significantly overpredicts power consumption, thus lowering the Figure of Merit. Profile and induced power equally contribute to power overprediction in CFD results. Both methods can capture trends in rotor performance from effects of twist changes. The peak FM is achieved at twist of 20 and 22 degrees for BEMT and CFD, respectively. For initial design and analysis, it is recommended to use BEMT, while CFD can be used to visualize and analyze flow fields in greater detail.