Reduced-order models are usually thought of as computationally inexpensive mathematical representations that offer the potential for near real-time analysis. Although most reduced-order models can operate in near real-time, their construction can be computationally expensive, as it requires accumulating a large number of system responses to input excitations. Furthermore, reduced-order models usually lack robustness with respect to parameter changes and therefore must often be rebuilt for each parameter variation. Together, these two issues underline the need for a fast and robust method for adapting precomputed reduced-order models to new sets of physical or modeling parameters. To this effect, this paper presents an interpolation method based on the Grassmann manifold and its tangent space at a point that is applicable to structural, aerodynamic, aeroelastic, and many other reduced-order models based on projection schemes. This method is illustrated here with the adaptation of computational-fluid-dynamics-based aeroelastic reduced-order models of complete fighter configurations to new values of the freestream Mach number. Good correlations with results obtained from direct reduced-order model reconstruction, high-fidelity nonlinear and linear simulations are reported, thereby highlighting the potential of the proposed reduced-order model adaptation method for near real-time aeroelastic predictions using precomputed reduced-order model databases.

Interpolation Method for Adapting Reduced-Order Models and Application to Aeroelasticity

Effects of ice accretions on aircraft aerodynamics

Iced-airfoil aerodynamics

Reduced-order fluid/structure modeling of a complete aircraft configuration

Aircraft icing: an ongoing threat to aviation safety

Measurements of specific heat, thermal conductivity and thermal diffusivity of Utah tar sands

A wind-tunnel test was conducted to determine the performance degradation of a scaled two-dimensional NAC A 23012 airfoil (outboard wing section of the Wyoming King Air 200T) resulting from various liquid hydrometeor sizes. The hydrometeor sizes consisted of cloud, drizzle, and rain drops. The NASA Lewis Research Center's LEWICE 1.6 computer code was used to predict the ice shapes based on natural distributions obtained by the Wyoming King Air. The tests were conducted for angles of attack between —2 and +18 deg. Test results showed a moderate reduction in CLmax for the cloud, drizzle, and rain drop ice shapes; however, the rain drop (or freezing rain) ice shape delayed flow separation when compared to the cloud and drizzle shapes, resulting in a higher angle of attack at stall. Profile drag increased by 5 35% for the cloud drop ice shape, 48-56% for the drizzle ice shape, and 10-42% for the rain ice shape. After a simulated de-icing boot activation, test results showed a 50% reduction in CLmax for the residual drizzle ice shape and 34% reduction for the residual rain ice shape. Profile drag increased by up to 790% for the residual drizzle ice shape and up to 590% for the residual rain ice shape. The residual cloud ice was assumed to be cleared by the de-icing boot activation. These results do not support the current aircraft community belief that freezing rain causes the most severe icing conditions. On the contrary, aircraft encounters with supercooled drizzle, or freezing drizzle, may result in the most severe icing.

Airfoil performance degradation by supercooled cloud, drizzle, and rain drop icing

Viscous characteristics of a Utah tar sand bitumen

Initial Studies of Low-Order Turbulence Modeling of the Wind Turbine In-Flow Environment

Two-dimensional NACA 23012 airfoil performance degradation by super cooled cloud, drizzle, and rain drop icing

William R. Lindberg

Papers

Measurements of specific heat, thermal conductivity and thermal diffusivity of Utah tar sands

Airfoil performance degradation by supercooled cloud, drizzle, and rain drop icing

Viscous characteristics of a Utah tar sand bitumen

Initial Studies of Low-Order Turbulence Modeling of the Wind Turbine In-Flow Environment

Two-dimensional NACA 23012 airfoil performance degradation by super cooled cloud, drizzle, and rain drop icing