Experimental and numerical studies of boat waterjets with increased seakeeping performance

Abstract

Object and purpose of research. The object of the research is a fundamentally new waterjet, intended for installation on ships of increased seakeeping performance with discrete-variable bottom deadrise. The purpose of the research is to develop and test three waterjet designs that can be installed on vessels with large deadrise, operating in severe weather conditions.
 Materials and methods. Experimental data of waterjet tests as a part of self-propelled models obtained in deep-water and cavitation test tanks of KSRC. Numerical simulation of the flow in water conduits of full-scale vessel taking into account the waterjet performance.
 Main results. As a result of the performed experimental and computational studies, the characteristics of three waterjet designs with partial-pressure water inlets were obtained: two waterjets with isolated single-elbow water ducts and inlets on the bottom section with medium deadrise, "II"design; two waterjets with combined water duct and inlets on the bottom section with maximum deadrise and double jet, “X” design; single waterjet with bifurcating two-elbow water duct and a pair of water inlets on the bottom section with maximum deadrise, “Y” design.
 Conclusion. The studies have shown that all the developed innovative waterjet designs are practically equal to conventional ones (or even better than them), and air suction creates a smooth, rather than a sharp force decrease on the impeller. The preference is given to a high-pressure water inlet with a bifurcated water inlet and a combined water conduit, because in intense waves, even if one of the inlets is aerated, the vessel will not abruptly lose speed or run off the course.

Influence of the Inclined Pipe Section on the Performance of a Waterjet Propulsion Device

“…By analytically studying parameters, such as flow velocity and pressure, Kang et al [14] determined that device performance was superior and thrust was larger when the angles of incidence and emergence of conduit were 30°; however, they disregarded the influence of change in rotational speed on device performance. Rodionov et al [15] designed three inlet passage models with bias voltage through numerical simulation, effectively improving the stability of ship propulsion under intense sea waves. However, they did not consider the performance of the propulsion device under parametric changes, such as navigational speed.…”