A mathematical model for simulating combustion and detonation of a fuel–air mixture in the gas cavity above the free water surface is developed. The model is based on solving the conservation equations of mass, momentum, and energy for a two-phase reacting gas–water medium with the phases treated as interacting interpenetrating continua having their own values of velocity, temperature, and turbulence characteristics. The model is validated by laboratory experiments. The test rig included a transparent cylindrical tube with one closed-end, a pool with an optically transparent window, as well as power, ignition, control, and measurement systems. The tube was vertically immersed with its open end in water and filled with a gaseous explosive mixture. In the experiments, a stoichiometric propane–air mixture was ignited and burned in the semi-closed 60 mL cylindrical volume above the free surface of water. The model is shown to predict satisfactorily the lift force acting on the tube, the time history of pressure in the volume, and the dynamics of the flame and gas–water interface motion during combustion in the volume. The model is intended to be applied for the design of boats with propulsion solely by combustion/detonation of fuel–air mixture in cavities constructed into a bottom surface of the boat. This propulsion system replaces conventional propellers, thereby reducing hydrodynamic resistance.

For reducing the hydrodynamic drag of a boat, a gas cavity can be made under the boat bottom, which will partially isolate the bot- tom from direct contact with water and provide ¤gas lubrication¥ by forced supply of atmospheric air or exhaust gases from a boat motor.

To reduce the hydrodynamic drag force to the movement of the boat, an artificial gas cavity is organized under its bottom. Such a cavity partially insulates the bottom from direct contact with water and provides “gas lubrication” by means of forced supply of atmospheric air or exhaust gases from the main propulsion system. A proper longitudinal and transverse shaping of the gas cavity can significantly (by 20%-30%) reduce the hydrodynamic drag of the boat at low (less than 3%) consumption of the propulsion system power for gas supply.

Проведены экспериментальные исследования процессов пульсирующего горения пропано-воздушной смеси в модельной днищевой каверне судна (без обводов судна), погруженной в бассейн с покоящейся водой. В экспериментах регистрировались расходы воздуха и горючего, распространение пламени, а также выталкивающая и толкающая силы, действующие на модельную каверну. Результаты экспериментов сравниваются с результатами трехмерных расчетов, основанных на физико-математической модели горения подготовленной горючей смеси в полузамкнутом объеме над свободной поверхностью воды, разработанной ранее: по форме и положению фронта пламени и границы раздела сред«газ-вода» в разные моменты времени и по динамике изменения сил, действующих на днище и на редан каверны. Получено удовлетворительное качественное и количественное согласие результатов расчетов и измерений.