Dynamic Response Of Rising And Falling Balloon Wind Sensors With Application To Estimates Of Wind Loads On Launch Vehicles

The responses of balloon and falling sphere wind sensors in turbulent flows are analyzed using Fourier transform techniques. The linearized equations of motion of a sensor that is subject to drag and gravitational body forces are developed by perturbing a sensor about an equilibrium uniform motion with turbulent or random wind fluctuations. The wind environment and sensor velocities are decomposed with stochastic Fourier-Stieltjes integrals, and the linearized equations of motion are used to derive the response functions and phase angles of the sensor motions. The results of the analysis are used to analyze the response properties of the Jimsphere balloon wind sensor and the effects that balloon motions would have on turbulence spectra if they were calculated with ballon and falling sphere wind data. The Kolmogorov inertial subrange and the Lumley subrange for nearly inertial isotropic turbulence in stably stratified fluids are used as specific examples in the calculations.