Study on jet characteristics of the cone-straight nozzle under high confining pressures

High-pressure water jet technology is a clean and efficient technology that is widely employed in deep-water geological exploration, deep-water environmental management, and deep well drilling. Nevertheless, the impact mechanism of high confining pressures (high hydrostatic pressures) on jet characteristics remains unclear in deep water and deep well applications, limiting the application of water jet technology in deep water and wells. This paper investigates the water jet characteristics of a cone-straight nozzle through a combination of theoretical analysis, numerical simulation, and laboratory experiments. It analyzes the variations in the potential core length, nozzle pressure drops, and jet dynamic pressure distribution under different confining pressures. The result indicates that within a low confining pressure range, the cavitation is prone to occur at the nozzle's inflection point, with the most significant cavitation under normal pressure. Under the influence of cavitation, the confining pressure affects the jet flow field distribution, jet structure, and nozzle pressure drop with constant flow rate conditions. As the confining pressure increases, the jet dynamic pressure distribution changes, the potential core length initially decreases, subsequently increases, and then stabilizes, and the nozzle pressure drop initially decreases and then remains constant. The impact of confining pressures on jet characteristics is enhanced with the increase in flow rate. This study provides theoretical guidance for enhancing the application of water jet technology under high confining pressures.