Jason Etele

Modeling of Urban Wind Field Effects on Unmanned Rotorcraft Flight

Surveillance applications of unmanned aerial vehicles within urban areas is made difficult by turbulent winds generated by buildings. A methodology is proposed by which urban wind data is evaluated, selected, and applied during flight simulation. The urban environment is represented by a combination of discrete single buildings and canyons each easily amenable to computational fluid dynamics. These simulations are used to generate a database of building wakes for various wind conditions and building configurations typical to the North American urban environment. A selection algorithm is used that determines if the current aircraft position is influenced by the building wake and, if so, calculates the resulting effect on the aircraft. Results are presented for a Yamaha R-50 R/C helicopter in both forward and vertical flight. Variations in aircraft attitude by as much as 10 are observed when considering building wake effects generated by a 8 kt wind. It is also demonstrated that this approach is able to identify locations within a given wake at which aircraft flight is most affected.

Modeling of the Urban Gust Environment with Application to Autonomous Flight

Desirable surveillance applications of unmanned aerial vehicles (UAV) around urban areas provides motivation for the investigation of turbulent wind generated by buildings which can potentially cause instability in aircraft flight. It has been shown that the urban canyons an d single buildings which form the basic components of the urban geometry have classifiable flows with signi ficant degrees of circulation and shear, a potential danger to light aircraft. A first generation methodology is p roposed by which wind data important to flight planning in an urban environment is selected, accessed and applied. It is assumed the urban environment can be represented as a combination of discrete single buildings and canyons each easily amenable to computational fluid dynamics (CFD). A set of single buildings an d canyons typical to the North American urban environment is selected to provide a set of wind data. A selection algorithm is proposed which will determine if the flow at a location in a given urban environment fits a member of the wind data set. Results from simulations for the Aerosonde UAV in a simple urban environment are presented and analyzed.

Simulation Tool for Testing and Validating UAV Autopilots in Wind Gust Environments

Small unmanned aerial vehicles operating in urban settings are prone to wind gust conditions. The development of effective flight control strategies are required to successfully deal with wind gust effects. A simulation environment was previously established to allow for testing potential techniques under realistic wind gust conditions. In order to experimentally validate the predictions of this simulation tool a quadrotor UAV testbed has been developed. Its validation of the simulation tool is presented in this paper. An average of absolute difference is evaluated to quantify the accuracy and predictive capability of the simulation tool. Overall, the experimental flights remained within the flight envelope predicted by the simulation tool.

Urban Wake-Field Generation Using Large-Eddy Simulation for Application to Quadrotor Flight

A method is presented for using large-eddy simulation to generate urban wake fields for use in studying the effects on the autonomous flight performance of a small quadrotor. The flowfield is solved around a single square building using OpenFOAM and stored in a database accessed by a MATLAB/Simulink flight simulator. Four flight missions are evaluated to compare the difference in performance between wake fields generated by Reynolds-averaged Navier–Stokes and large-eddy simulation solutions. The results of the holding position in a constant freestream wind show both methods produce similar results and can hold position in all three directions within approximately ±1.5 body lengths. When the quadrotor is in or on the boundary of the building wake, the maximum deviation volumes, as calculated when using a Reynolds-averaged Navier–Stokes or large-eddy simulation air wake, can differ by two orders of magnitude. Additionally, the large-eddy simulation air wakes can cause skewed deviations by as much as five to...

Control Volume Approach to Quasi-1D Flow Control within Electromagnetic Fields

A quasi one dimensional, control volume based methodology is presented which can solve for the exit o w conditions and the shock structure of a gas plasma o wing through a converging or diverging duct with straight walls and through which both a current and a magnetic eld are applied normal to each other and the o w direction (Faraday device). The method works for both accelerating and decelerating Lorentz forces and can be used to separate the effects of changing either the current density or the magnetic ux density on the overall plasma behavior. For the case of supersonic o ws with shocks, the method can also be used to determine the shock intersection angle and the intersection location in the streamwise direction. Comparison of these shock properties shows that the method falls within 18% of experimental values obtained by other researchers.