Ventilated cavitation has been successfully employed as ship drag reduction technology and potentially can mitigate flowinduced vibration. The obtained successes were based on solutions of design problems considered i...Ventilated cavitation has been successfully employed as ship drag reduction technology and potentially can mitigate flowinduced vibration. The obtained successes were based on solutions of design problems considered in the framework of ideal fluid theory with their following validation by towing tank tests. However, various aspects of the interaction of ventilated cavities with the viscous flows around the ship hulls remain unclear, whereas there is usually no possibility to simultaneously keep the full-scale Froude number and cavitation number in the test facilities. So, the further progress of the application of ventilated cavitation substantially depends on the ability of computational tools to predict this interaction. This paper briefly describes the state-of-the-art computation of ventilated cavitation and points out the most challenging unsolved problems that appeared in the model tests (prediction of air demand by cavities, ventilation effect on ship drag, on hydrofoil lift, and on the propagation of shock waves in cavities).展开更多
Bottom ventilated cavitation is the successfully proven ship drag reduction technology,but the impact of sea waves on ships with bottom cavities is the substantial concern for a broad technology implementation.The inf...Bottom ventilated cavitation is the successfully proven ship drag reduction technology,but the impact of sea waves on ships with bottom cavities is the substantial concern for a broad technology implementation.The influence of waves on vertical force experienced by such ships is analyzed in this paper using a perturbation technique.The unperturbed cavity shape at given Froude number and cavity length was found from a nonlinear steady ideal fluid problem.The ship response to an impact of a wave of the given length and amplitude is considered as the one-frequency perturbation.This perturbation was found by combined consideration of compressible flow in the cavity and incompressible flow in the surrounding water.Computational examples relate to an earlier tested model with the bottom cavity restricted by skegs.The vertical forces on the model with bottom cavities and in cavitation-free conditions were compared in head and following seas.It was found that within the major part of the consider range of wavelengths the cavity acts as a shock absorber significantly reducing the vertical force pulsation and ship acceleration in waves.展开更多
文摘Ventilated cavitation has been successfully employed as ship drag reduction technology and potentially can mitigate flowinduced vibration. The obtained successes were based on solutions of design problems considered in the framework of ideal fluid theory with their following validation by towing tank tests. However, various aspects of the interaction of ventilated cavities with the viscous flows around the ship hulls remain unclear, whereas there is usually no possibility to simultaneously keep the full-scale Froude number and cavitation number in the test facilities. So, the further progress of the application of ventilated cavitation substantially depends on the ability of computational tools to predict this interaction. This paper briefly describes the state-of-the-art computation of ventilated cavitation and points out the most challenging unsolved problems that appeared in the model tests (prediction of air demand by cavities, ventilation effect on ship drag, on hydrofoil lift, and on the propagation of shock waves in cavities).
文摘Bottom ventilated cavitation is the successfully proven ship drag reduction technology,but the impact of sea waves on ships with bottom cavities is the substantial concern for a broad technology implementation.The influence of waves on vertical force experienced by such ships is analyzed in this paper using a perturbation technique.The unperturbed cavity shape at given Froude number and cavity length was found from a nonlinear steady ideal fluid problem.The ship response to an impact of a wave of the given length and amplitude is considered as the one-frequency perturbation.This perturbation was found by combined consideration of compressible flow in the cavity and incompressible flow in the surrounding water.Computational examples relate to an earlier tested model with the bottom cavity restricted by skegs.The vertical forces on the model with bottom cavities and in cavitation-free conditions were compared in head and following seas.It was found that within the major part of the consider range of wavelengths the cavity acts as a shock absorber significantly reducing the vertical force pulsation and ship acceleration in waves.
