Presentation Title

Nonlinear Aeroelastic Analysis

Faculty Mentor

Michael Butros, Kurt Kloesel

Start Date

18-11-2017 10:00 AM

End Date

18-11-2017 10:15 AM

Location

9-285

Session

Physical Sciences 2

Type of Presentation

Oral Talk

Subject Area

physical_mathematical_sciences

Abstract

The accurate prediction of aeroelastic flutter and related phenomena are of major importance during the design phase of any aircraft. The use of an accurate computational model to predict when flutter occurs can save many hours of wind tunnel testing, confirm the structural integrity of the airframe, and ensure safety for the pilot when operating within the intended flight envelope. Additionally, an accurate computational model can aid in back-checking the fidelity of wind tunnel test data. Linear aeroelasticity has been the predominant method for modeling and predicting flutter and other aeroelastic phenomena for decades. However it can be potentially insufficient in certain cases, for example, when an aircraft has a highly flexible structure. Nonlinear methods are needed to account for the structural nonlinearities associated with deformation possible with highly flexible wings. Similarly, aerodynamic nonlinearities can pose problems even in more rigid aircraft structures. This project aims to utilize MATLAB to evaluate nonlinear flutter prediction methods, namely bifurcations and potentially Limit Cycle Oscillations (LCO), to analyze the aeroelastic behavior of simple wings with structural nonlinearities.

Summary of research results to be presented

Numerical models for solving the nonlinear aeroelastic equations of motion were successfully constructed using MATLAB for flat-plate wing sections with 1, 2, and 3 degrees of freedom. Bifurcation diagrams were utilized to analyze the 1 degree of freedom, pitching nonlinear wing; the static divergence airspeed for this case was effectively determined using this method. For the 2 degree of freedom, quasi-steady nonlinear pitch-plunge wing section, phase diagrams and time histories were successfully leveraged in order to discover the presence of limit cycle oscillations above the calculated flutter airspeed. Lastly, for the 3 degree of freedom, quasi-steady nonlinear pitch-plunge-control wing section, time histories for all 3 degrees of freedom were studied in order to find out the airspeeds when limit cycle oscillations presented themselves and were also utilized to display which degrees of freedom were strongly coupled, and those which were loosely coupled.

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Nov 18th, 10:00 AM Nov 18th, 10:15 AM

Nonlinear Aeroelastic Analysis

9-285

The accurate prediction of aeroelastic flutter and related phenomena are of major importance during the design phase of any aircraft. The use of an accurate computational model to predict when flutter occurs can save many hours of wind tunnel testing, confirm the structural integrity of the airframe, and ensure safety for the pilot when operating within the intended flight envelope. Additionally, an accurate computational model can aid in back-checking the fidelity of wind tunnel test data. Linear aeroelasticity has been the predominant method for modeling and predicting flutter and other aeroelastic phenomena for decades. However it can be potentially insufficient in certain cases, for example, when an aircraft has a highly flexible structure. Nonlinear methods are needed to account for the structural nonlinearities associated with deformation possible with highly flexible wings. Similarly, aerodynamic nonlinearities can pose problems even in more rigid aircraft structures. This project aims to utilize MATLAB to evaluate nonlinear flutter prediction methods, namely bifurcations and potentially Limit Cycle Oscillations (LCO), to analyze the aeroelastic behavior of simple wings with structural nonlinearities.