Papers by Keyword: Strip Theory

Abstract: In flying animal world, there are different flapping motions to produce lift and thrust depending on their species and size. Recent development in Unmanned Aerial Vehicle had tried to mimic flying animal. Rather than having two separate systems in providing lift and thrust, the wing upstroke and downstroke movement combined with wing twisting produce the necessary lift and thrust. Insects and some small birds have even the ability to fly hover.The present study is focused on the modeling of wing flapping motion. Instead of only accommodating flapping motion in a vertical plane and spanwise pitching motion, the model permits to include wing lead-lag motion in the horizontal plane. This more degree of freedom permit to model more complex wing flapping motion.

Abstract: Aircrafts with high aspect ratio wings are most eligible candidates for high altitude and long endurance flights. Such wings show a non-linear deformation behavior because of structural geometric non-linearity. In the present study both linear and non-linear static aeroelastic behaviors of a high aspect ratio rectangular flat plate wing are analyzed using a simplified approach. The main emphasis lies in the tremendous change of lift distribution on the flexible high aspect ratio wing when large deflections are incorporated in the static aeroelastic analysis. The computational static aeroelastic simulations are performed in the finite element method based commercial software ANSYS-14. The aerodynamic load is calculated using the strip theory. Since the aero-load changes with the twisting deformation hence a user defined script is written using ANSYS parametric design language (APDL). The computationally achieved divergence velocity results are compared with the analytical results. The results of parametric study at different flight load conditions and angles of attack have highlighted the role of geometric nonlinearities in both bending and twisting deformations. The impact of follower pressure forces on the aeroelastic response is also investigated.

Abstract: Based on the research of wave loads calculation methods for the submarine and ship, compared the date of wave loads obtained by strip theory with that obtained by linear-simplified calculation method, we proved the engineering feasibility of linear-simplified calculation method of wave loads on underwater vehicles cabin when sailing on the water surface and near the water surface, the linear-simplified calculation method shorten the calculation cycle and guarantee the engineering accuracy.

Abstract: This paper presents a methodology to design the optimum proprotor for tilt-body micro-air-vehicles (TB-MAV) with efficient global propulsion system and long flight endurance in both cruise and hover modes. The TB-MAV developed at ISAE, which is called MAVion, was used as a baseline in the design process. To acquire maximum performance of TB-MAV’s global propulsion system, an efficient optimization process of the proprotor propulsion system was carried out. The optimization process consists of two-step inverse design methods. The first step determines the optimal operating conditions in terms of power and rotational speed of proprotor and the second step designs the optimal blade geometry in terms of twist angle distribution. The optimal blade twist distribution along the blade was computed using the Glauert’s strip theory for minimum energy loss condition. Meanwhile, the optimal operating conditions were determined by the motor outputs corresponding to high motor efficiency. A comparison of performance in terms of total efficiency and flight endurance between the optimized flexible proprotor, the optimized rigid proprotor, optimized propeller and optimized rotor is presented.

Abstract: By comparing the advantages and disadvantages of several different aerodynamic theories for propellers, the strip theory is applied to predict the performance of propeller at the primary design station of propellers, and the Multiple Rotating Reference Frames (MRRF) method based on solving the N-S equations is applied to evaluate the aerodynamic performance of propeller. The validation of the MRRF method is against the experimental data of a propeller. The comparison of calculated result with the experimental data shows that, the MRRF method used in this paper is reliable to predict the aerodynamic performance of propellers. The cruise altitude of Solar Airplanes is usually very high, so the Reynolds numbers of the propeller sections are very low. The key factor of the aerodynamic design of the propeller is that how to keep the propeller at high cruise efficiency by the output power restriction of the electromotor. The analysis of the designed propeller shows that the cruise efficiency of the designed propeller is no lower than 70%, and the power required at the best cruise efficiency condition is match for the rated output power of the electromotor.

Abstract: Based on a laminated composite structure, vibration and nonlinear stall aeroelastic stability of rotor blades modeled as anisotropic thin-walled closed-section beams are systematically addressed. The analysis is applied to a laminated construction of the circumferentially asymmetric stiffness (CAS) that produces bending-bending-twist coupling. The vibration characteristics of composite beam are determined by the Galerkin Method. The unsteady aerodynamic loads and centrifugal force are integrated with the nolinear aerodynamic model to deal with aeroelastic stability analysis. The influence of some related factors, pretwisted angle, ply-angle rotational speed, and wind speed, is investigated. The paper gives methods of eigenvalue analysis and aeroelastic response, which can determine the stability of the blade forced by the nolinear aerodynamics.