Longitudinal stability and motion of trimaran wing in ground effect model during take-off

Abstract

Wing in Ground Effect is a relatively new concept in transportation technology. It is more efficient than conventional aircraft and quicker compared to conventional marine vehicles. However WIG is still not widely use as a public transportation. One of the criteria to be fulfilled is stability. Longitudinal stability of WIG craft is still of concern to the designer and the solutions are being investigated. Instability of a small WIG craft occurs when aerodynamic-hydrodynamic phase changes into pure aerodynamic phase during the take-off. In this research, investigations were conducted to determine the longitudinal static and dynamic stability effect of Trimaran WIG craft during takeoff and to verify the factors affecting its stability. Two parameters considered are aerodynamic and hydrodynamic characteristics. The investigation resorts to vortex lattice method and examines the effects of flat ground and end plate on the performance of aerodynamic characteristic of the WIG craft. Planing hull has been chosen for the hull shape of the WIG craft due to higher speed takeoff. The hydrodynamics of prismatic planing surfaces, presented by Savitsky, is used to calculate the hydrodynamic characteristic. Numerical result is compared to the experimental results and against published data. The Static Stability Margin (SSM) for longitudinal static stability of Trimaran WIG model has been investigated and using the classical aircraft motion modification and calculating the aerodynamic, hydrostatic and hydrodynamic forces, the complete equation of motion that uses a small perturbation assumption for WIG during takeoff has been derived and solved. Finally, dynamic stability for Trimaran WIG during take-off has been investigated and analyzed using Routh-Hurwitz Stability Criterion and Control Anticipation Parameter (CAP).