Unsteady Low-Speed Windtunnel Test of a Straked Delta Wing, Oscillating in Pitch. Part 5. Power Spectral Density Plots of the Overall Loads for Harmonic Oscillation and the Response of Overall Loads to (1-COS) Inputs

摘要

Results of a wind tunnel test of an oscillating straked wing. The report provides unsteady airloads and pressure distributions for a range of incidences (-8 to 50 deg.) and amplitudes (1 to 16 deg.). The wind speed was 80 meters/second, which provided reduced frequencies up to 0.50 based on root chord. The zeroth and first harmonic as well as the continuous time history of the pressure and overall loads were measured. Flow visualization was performed for flow of 30 meters/second using a pulsating laser light sheet. The power spectral densities for various conditions present the relative frequency content of selected overall loads at continuous oscillating model conditions ranging from nearly linear (first harmonic dominant) to highly nonlinear (many higher harmonics) characteristics. A survey of the selected runs and their test conditions is given including the components of the balance and the corresponding plotnumbers of the spectra presented. The time history plots are given of incidence and all air loads for (1-cos) pitch pulses that simulate transient aircraft maneuvers. Included are half pulse data which represent a pitch-up and hold at a higher angle of attack as well as a pitch-down and hold at a lower angle of attack. To give an idea of the reproducibility plots for all three runs of the balance components vs. incidence for two test conditions are also enclosed at the end. Keywords: Unsteady flow; Vortex flow; Wind tunnel test. (JHD)