Decambering

Abstract: A vortex-lattice numerical scheme that uses a novel decambering technique to predict post-stall aerodynamic characteristics is used to study the aerodynamics of tandem Cessna 172 aircrafts flying in echelon formation. Results like CL − α from the current method are compared with experiment. Additional results like section Cl distributions over wing spans, CM − α and CLW − αtw (i.e. CL of the leading aircraft for different angles of attack of the trailing aircraft) and analysis for (-)ve y-offset, which are available only from the current numerical method are reported that supplement the experimental results. Detailed post-stall numerical analysis and the effect of chord-wise, span-wise and vertical offsets on the aerodynamics of the formation are also reported.

Abstract: The nonlinear aerodynamic characteristic of a wing is investigated using the frequency-domain panel method. To calculate the nonlinear aerodynamic characteristics of a three-dimensional wing, the iterative decambering approach is introduced into the frequency-domain panel method. The decambering approach uses the known nonlinear aerodynamic characteristic of airfoil and calculates two-variable decambering function to take into consideration the boundary-layer separation effects for the each section of the wing. The multidimensional Newton iteration is used to account for the coupling between the different sections of wing. The nonlinear aerodynamic analyses for a rectangular wing, a tapered wing, and a wing with the control surface are performed. Present results are given with experiments and other numerical results. Computed results are in good agreement with other data. This method can be used for any wing having different nonlinear aerodynamic characteristics of airfoil. The present method will contribute to the analysis of aircraft in the conceptual design because the present method can predict the nonlinear aerodynamic characteristics of a wing with a few computing resources and significant time. Copyright © 2007 John Wiley & Sons, Ltd.

Abstract: A complete tool chain is developed for generating extended and enhanced flight models for low speed flights for applications of upset recovery research. Starting from geometry based automatic generation of the baseline model, additional algorithms are introduced to supplement the model for simulation of aircraft dynamics near stall and post-stall regions using decambering corrections, dynamic stall calculation and spin dynamics modelings. Together with additional functions for 3D lift corrections, drag estimations and weight distributions, significant enhancement has been made to the model generation capability of the vortex lattice method program. The generated Fokker 100 aircraft model is validated with direct comparisons to wind-tunnel measurements, manufacturer’s reports, academic publications as well as the flight data recordings of different accidents involving aircraft upsets.

Abstract: An airfoil for a micro air vehicle that includes components enabling the airfoil to adjust the angle of attack (AOA) of the airfoil in response to wind gusts, thereby enabling the airfoil to provide smooth flight. The airfoil may include a first compliant region positioned between an inboard section and a first outboard section and may include a second compliant region between a second outboard section and the inboard section. The compliant regions enable the first and second outboard sections to bend about a leading edge section and move relative to an inboard section. This action creates smoother flight due to numerous aerodynamic advantages such as a change in the angle of attack and improved wind gust rejection due to adaptive washout as a result of the airfoil flexing, twisting and decambering.