Toward design and fabrication of wind-driven vehicles: Procedure to optimize the threshold of driving forces

AbstractWind energy has been continuously considered as a green, available, and economical alternative source of energy. For centuries, the transformed wind energy to drag-force has been used for transportation in watercrafts. With improvement of aerodynamics, the airfoil was invented to create and use a higher magnitude aerodynamic force, lift-force, in order to elevate airplanes. Later, the lift-force was horizontally applied as the thrust force in land/water wind-crafts. Whereas in airplanes horizontal airfoils (wing) create a vertical lift-force, installed vertical airfoils (wing-sail) produce a horizontal lift-force in wind-crafts. Therefore, this force can be used as thrust (driving) force in lift-based ice, water, and land vehicles. If the prevailing wind is constantly available, the vehicle speed can even exceed the wind velocity. Due to the complex kinematics of such vehicles, however, it should be noted that there would be always an optimum for the thrust force in order to control and navigate the vehicle to the destination point, and to avoid the severe undesired side-forces. This optimum is calculated in wind-craft trajectory software (WTS) which requires many inputs, including variable and constant parameters. Variable parameters consist of wind direction and magnitude in addition to vehicle’s position, velocities, and accelerations. On the other hand, design characteristics of the wind-driven vehicle are known as constant parameters. The land-yacht body’s drag is an unknown constant parameter which alters according to the relative wind. This implies that several wind tunnel experiment in different wind directions and speeds are required in order to obtain the drag coefficients.Therefore in order to bypass the wind tunnel measurements, this study aims to propose a fast and economical procedure to find the aforementioned drag coefficient by integration of a measurement and by a simulation approach. The obtained data can be later used in the optimization and control module of the WTS. The performance of this procedure has been investigated using a case study. For this purpose, a 1:4 prototype three-wheel land-yacht is first designed and fabricated. The land-yacht comprises of three major parts; horizontal airfoil (axle), vertical airfoil, and body. The dimensions of these elements are obtained after development of a code based on kinematics of the land-yacht. The axle is designed to increase the stability of the land-yacht, whereas the shape of the body is intended to produce a low drag coefficient in various directions. Furthermore, a set of experiments has been conducted to measure the body drag of the land-yacht in a direction parallel to the relative wind. This experiment is later used to develop and validate a computational fluid dynamics (CFD) model in order to estimate the drag of the land-yacht body in its various directions against the relative wind. The results show the adequate efficacy of this procedure to provide the required data for the optimization and control module of the WTS