INTERACTIVE MODEL OF SEA WAVES FOR PRE-FLIGHT PREPARATION OF SMALL CLASS 'A' EKRANOPLAN

摘要

In the process of creating a simulator of pre-flight preparation of a small class "A" ekranoplan, the authors have faced a problem of modelling water surface with wind induced waves of up to 30-50 centimetre height. It is also necessary to calculate and correctly display wake trails of other ships involved in a navigation exercise. Besides, it has become necessary to show on-water traces of wind gusts, critical for the craft of this class. Waves of this kind, despite their small height, may have a decisive effect on the flight dynamics of a small ekranoplan, and wakes of some ship types may become an obstacle for a small height flight, their correct setting, modelling and display is necessary for the trainee's formation of correct professional skills. The paper considers the hydrodynamic method of modelling surface gravitational waves as the most important phenomenon in the study of wind-induced waves, swell and wake. Sea waves of various length are looked into separately with regard to the seabed effect on their propagation. The algorithm described here takes into account attenuation of waves, and change of their motion direction in time. The result of this work is an interactive system capable of generating infinite non-recurrent wave sequences. In a simulator, this model is used for real-time calculations of the following phenomena: wind induced waves in the open fragments of a water area; diffraction of waves circumventing obstacles (breakwaters, etc.); refraction of waves in passing from one depth on another; wake waves of displacement ships; small ripples caused by wind gusts or falling of rain drops. Three-dimensional visualization of a water surface sector seen from the pilot's place in the cockpit is provided in accordance with laws of optics, which ensures adequacy of its visual perception. The sufficient screen refresh rate is owing to the high degree of calculation algorithm optimising, and also owing to the use of up-to-date hardware capabilities.