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Title:Modeling and validation of a subscale aerobatic aircraft configuration in spin
Author(s):Ragheb, Adam M
Director of Research:Selig, Michael S.
Doctoral Committee Chair(s):Selig, Michael S.
Doctoral Committee Member(s):Elliott, Gregory S.; Ansell, Phillip J.; Chamorro, Leonardo P.
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Aircraft spin
Extended envelope
Aviation safety
Modeling & simulation
High alpha
Post-stall aerodynamics
Six-degree-of-freedom (6DOF)
Flight simulation
Unmanned aerial vehicle (UAV)
Flight testing
Wind tunnel testing
Spinning wings
Rotary aerodynamics
Abstract:An approach for modeling the stall/spin regime of single engine aircraft is presented. A three-pronged approach is taken that involves the following components: flight testing, the development of a new analytical model for calculating the forces on a stalled spinning wing, and validation of that model through wind tunnel tests. Significantly, these results are combined to form a new code, SpinSim, which assists with the six-degree-of-freedom (6DOF) simulation of the aerodynamics and flight dynamics of an aircraft. This code places particular emphasis on the simulation of the stall/spin regime. The flight-testing phase of this research was conducted using a radio-controlled unmanned aerial vehicle (UAV) that was flown into a wide variety of different stall/spin configurations. This UAV was equipped with onboard instrumentation and fitted with a data acquisition system specifically configured for this spin research. A large number of spins were flown, and the data were used in the development of the analytical model and 6DOF simulations. Four proposed ventral fin configurations were implemented, and their beneficial effects on the spin and recovery characteristics were demonstrated and explained. The SpinSim analytical model considers the normal force on a stalled spinning wing as a function of the aircraft pitch, the spin parameter, and the wing aspect ratio. The proposed first-principles-based approach allows for a standard flight model to be corrected for the three-dimensional flow effects and structures inherent in the spin regime. This approach demonstrates a significant improvement to the current state of the art. Notably, this model is based on the following: (1) the centrifugal pumping of the fluid in the elliptical trapped wing wake and (2) its eventual ejection at the wing tip. Also, wind tunnel tests were conducted to validate the analytical model, which revealed that the aspect ratio causes an increased effect on the wing normal force as the pitch angle is decreased. It is also concluded that the normal force coefficient is proportional to the spin parameter squared and that no Reynolds number effects exist within the range of Reynolds numbers tested. At values of the spin parameter in excess of unity, a maximum wing normal force coefficient limit appears to exist. This normal force coefficient limit increases in value for higher aspect ratio wings. The 6DOF simulations maintain a low computational cost in order to serve as a useful design tool for stall/spin studies. Such simulations incorporate the results of the flight and wind tunnel tests as well as the new analytical model. Simulations of the UAV in stall/spin situations showed strong agreement with the flight test data, especially in regard to the angular rates, spin radii, and aerodynamic angles. By using the proposed analytical model, SpinSim extends the range of the modelable parameter space that would otherwise require hazardous piloted testing or expensive dynamically-scaled model testing. Also, SpinSim functions as a tool to aid in the design-for-spin of airplanes and successfully captures the first-order effects attributable to the yawing motion of a stalled spinning wing.
Issue Date:2016-11-23
Rights Information:Copyright 2016 by Adam M. Ragheb
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12

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