Browsing by Subject "Automobiles -- Aerodynamics -- Computer simulation"
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Item Vehicle response to aerodynamic loads(Texas Tech University, 1988-05) Muyshondt, ArnoldoImproved fuel economy and reduced power requirement have been major goals of modern automobile designers. Improvements in these areas are usually accomplished by reducing the total structural mass and by altering the exterior body shape to reduce the aerodynamic drag. Unfortunately, changes of the exterior shape may have negative effects on the side wind response of the vehicle and can increase the chances of side wind induced accidents. This study presents a literature survey of previous work done in the field of vehicle response to aerodynamic loads, the development of a FORTRAN 77 subroutine that produces the aerodynamic forces and moments acting on an automobile body due to a side wind, and the implementation of this routine to predict the response of a 1983 standard Ford Ranger XL truck to various wind conditions using a dynamic simulation package called ADAMS. The theory uses a quasi-static approach to calculate the aerodynamic forces and moments. The results of this study demonstrate that ADAMS can be used as an effective tool for predicting the response of a vehicle to a side gust. The response of the truck wa^ found to be highly nonlinear. Increasing the gust strength did not only result in magnified responses, but also resulted in changes in the character of the response.Item Vehicle response to wind excitations(Texas Tech University, 1992-12) Daloglu, AlicanVehicle sensivity to transient cross-wind gusts has gained interest in the recent years. A vehicle's response to side-wind excitations can be determined either experimentally using a full-scale vehicle or model or mathematically using a simulation of transient cross-wind gusts and driver-vehicle model. This study presents a computer simulation of a driver-vehicle system's response to cross-wind excitations. The two-dimensional wind fluctuations at two points on a moving vehicle in a turbulent wind field are derived from a Fourier time series representation of the power spectral density function obtained at a coordinate system moving perpendicular to the mean wind speed. The dynamic model of a vehicle is represented with a form of nonlinear time domain equations of motion with four degrees-of-freedom model. The vehicle dynamic model contains a nonlinear tire model and lateral load transfer for tire forces. A modified two-level model is used for the driver to keep the vehicle in a straight line against cross-wind excitations. After evaluation of the result of wind simulation at two points on a moving vehicle, two vehicles, a 1987 Ford Thunderbird and a 1987 Hyundai Excel, are tested with fixed steering and with driver control for different wind and vehicle speeds. The effects of the driver's parameters on a vehicle's response to cross-wind is investigated.