THE TRACKED WING IN GROUND-EFFECT (TWIG)

The Tracked Wing In Group-Effect (TWIG) is a track-guided aerodynamically levitated vehicle for high speed intercity transportation. This study develops and applies methodologies for the aerodynamic, dynamic, and economic analysis and evaluation of TWIGs. The study starts by outlining some objectives of TWIG design and presenting some alternative TWIG design concepts. Preliminary designs of two roadable TWIGs are made. These comprise a five seat 'TWIGcar' and a forty passenger 'TWIGbus'. An extensive series of aerodynamic theories are developed for the flow between the guideway and the lower surface of a fairly arbitrary TWIG configuration. These treat the lower surface flow as either 2-D or 1-D incompressible potential flow, with account taken of 'winglet gap leakage flow' around the vehicle sides. Steady and unsteady perturbation solutions are developed. Extensions are made to TWIGs with underbody keels. The aerodynamic theories collectively permit the prediction of frequency dependent longitudinal and lateral aerodynamic generalized stability derivatives, as well as trim and drag characteristics of TWIGs. Wind-tunnel and moving model experimental studies have been successfully conducted to corroborate the aerodynamic theories. A TWIG dynamic analysis methodology is developed, for a TWIG with four degrees of freedom each in decoupled longitudinal and lateral dynamic modes. A formulation of TWIG dynamic response to random guideway inputs is presented, with implications towards ride quality, vehicle-guideway contact frequency, and derailment probability. A TWIG stability analysis is also presented. The aerodynamic and dynamic theories are applied to the TWIGcar and TWIGbus preliminary designs, and results discussed. The TWIGs have L/D (TURNEQ) 15, and are expected to have satisfactory dynamic performance if equipped with winglet automatic control. Various comparisons are made between TWIGs and other existing vehicles. Preliminary cost, demand, and mode split calculations show that the TWIGcar and TWIGbus can capture model shares of about 7.5% each in a Northeast Corridor transportation system, competing against the car, bus, train, and plane. Finally, a summary, conclusions, and recommendations are presented.