The dynamic behavior of a cavitation bubble near an asymmetric hydrofoil is investigated experimentally through high-speed photography and theoretically using a Kelvin impulse model.The typical deformations arising du...The dynamic behavior of a cavitation bubble near an asymmetric hydrofoil is investigated experimentally through high-speed photography and theoretically using a Kelvin impulse model.The typical deformations arising during bubble collapse near the hydrofoil are analyzed qualitatively.The effects of the bubble position and the hydrofoil’s eccentricity angle are analyzed quantitatively.The spatial distribution of the Kelvin impulse near the hydrofoil are explored.Different morphological evolutions of a bubble near an asymmetric hydrofoil are revealed,with B-shaped,heart-shaped,and arc-shaped collapses.The velocity of the bubble interface close to the hydrofoil is significantly affected by the bubble-hydrofoil distance and the hydrofoil’s eccentricity angle,increasing as both the distance and the eccentricity angle grow.It is found that the Kelvin impulse sensitivity varies at different positions with respect to the asymmetric hydrofoil,being higher at the head and tail,and lower in the middle.展开更多
In this paper,the dynamic behaviors of the cavitation bubble near a fixed spherical particle during the second oscillation period are analyzed based on the high-speed photographic system.The deformation and motion of ...In this paper,the dynamic behaviors of the cavitation bubble near a fixed spherical particle during the second oscillation period are analyzed based on the high-speed photographic system.The deformation and motion of the bubble during the second period are investigated by changing the distance between the particle and the bubble and the maximum radius of the bubble.Meanwhile,the variation of the equivalent radius and the centroid motions are analyzed,and the dynamic behaviors of the bubble are categorized according to the bubble morphological characteristics during the second period.Through this research,it is found that(1)The dynamic behaviors of the bubble during the second oscillation period could be divided into three typical cases:For case 1,a bulge would exist on the bubble interface away from the particle,and for case 2,a bulge would appear on the bubble interface and evolve towards the particle,while for case 3,the bubble would be divided into two parts.(2)The larger the dimensionless distance between the particle and the bubble,the smaller the maximum bubble equivalent radius in the second period,and the shorter the second oscillation period.(3)When the bubble is close to the particle,a counter-jet appears at the bubble interface away from the particle during the rebound stage.展开更多
Vortex dynamics and wall shear stress induced by cavitation bubble oscillations under the influence of particles are numerically investigated with the aid of a compressible two-phase flow solver in OpenFOAM.The genera...Vortex dynamics and wall shear stress induced by cavitation bubble oscillations under the influence of particles are numerically investigated with the aid of a compressible two-phase flow solver in OpenFOAM.The generation,evolution,and disappearance of vortexes for three jet behaviors are discussed in detail.The variations of wall shear stress induced by the jets and the vortexes during the bubble oscillations are analyzed.Numerical results reveal that vortex dynamics is related to bubble evolution and jet behavior.After the jet pierces the bubble,an annular vortex with the bubble as the vortex core is generated by the bubble collapse.For the bubble that collapses near the wall,it generates multiple small vortexes near the wall and causes discontinuities in the wall shear stress.For the bubble that collapses away from the wall,it does not generate vortexes near the wall,and its oscillations cause the wall shear stress to vary periodically with different periods.In addition,the wall shear stress at the axis of symmetry increases abruptly when the jet hits the wall.展开更多
This paper investigates the bubble collapse characteristics near dual cylinders within confined spaces.Firstly,the impacts on the bubble morphology,with respect to the bubble positions and the cylinder spacings,are ex...This paper investigates the bubble collapse characteristics near dual cylinders within confined spaces.Firstly,the impacts on the bubble morphology,with respect to the bubble positions and the cylinder spacings,are explored using high-speed photography experiments.Subsequently,based on the circle theorem,the liquid velocity field is qualitatively analyzed and compared with the experimental bubble interface motion.Finally,employing the Kelvin impulse theory,an analysis of the variation in Kelvin impulse at various cylinder spacings is conducted,which shows good consistency with the bubble centroid movement.The main conclusions are summarized as follows:(1)High-velocity regions are observed on both sides of the bubble.Low-velocity regions are observed between the bubble and cylinders.As the cylinder spacing and the bubble abscissa increase,the liquid velocity in the high-velocity regions decreases,and the low-velocity regions expands.(2)The characteristics of the bubble cross-sectional roundness,interface displacement,and cross-sectional area are significantly affected by the cylinder spacing and the bubble abscissa.(3)As the bubble abscissa increases,the Kelvin impulse intensity initially rises rapidly and subsequently declines gradually to a fixed value.As the cylinder spacings increases,the Kelvin impulse intensity decreases.展开更多
基金supported by the National Natural Science Foundation of China(Project No.51976056).
文摘The dynamic behavior of a cavitation bubble near an asymmetric hydrofoil is investigated experimentally through high-speed photography and theoretically using a Kelvin impulse model.The typical deformations arising during bubble collapse near the hydrofoil are analyzed qualitatively.The effects of the bubble position and the hydrofoil’s eccentricity angle are analyzed quantitatively.The spatial distribution of the Kelvin impulse near the hydrofoil are explored.Different morphological evolutions of a bubble near an asymmetric hydrofoil are revealed,with B-shaped,heart-shaped,and arc-shaped collapses.The velocity of the bubble interface close to the hydrofoil is significantly affected by the bubble-hydrofoil distance and the hydrofoil’s eccentricity angle,increasing as both the distance and the eccentricity angle grow.It is found that the Kelvin impulse sensitivity varies at different positions with respect to the asymmetric hydrofoil,being higher at the head and tail,and lower in the middle.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51976056,52076215).
文摘In this paper,the dynamic behaviors of the cavitation bubble near a fixed spherical particle during the second oscillation period are analyzed based on the high-speed photographic system.The deformation and motion of the bubble during the second period are investigated by changing the distance between the particle and the bubble and the maximum radius of the bubble.Meanwhile,the variation of the equivalent radius and the centroid motions are analyzed,and the dynamic behaviors of the bubble are categorized according to the bubble morphological characteristics during the second period.Through this research,it is found that(1)The dynamic behaviors of the bubble during the second oscillation period could be divided into three typical cases:For case 1,a bulge would exist on the bubble interface away from the particle,and for case 2,a bulge would appear on the bubble interface and evolve towards the particle,while for case 3,the bubble would be divided into two parts.(2)The larger the dimensionless distance between the particle and the bubble,the smaller the maximum bubble equivalent radius in the second period,and the shorter the second oscillation period.(3)When the bubble is close to the particle,a counter-jet appears at the bubble interface away from the particle during the rebound stage.
基金Project supported by the National Natural Science Foundation of China(Grant No.51976056)。
文摘Vortex dynamics and wall shear stress induced by cavitation bubble oscillations under the influence of particles are numerically investigated with the aid of a compressible two-phase flow solver in OpenFOAM.The generation,evolution,and disappearance of vortexes for three jet behaviors are discussed in detail.The variations of wall shear stress induced by the jets and the vortexes during the bubble oscillations are analyzed.Numerical results reveal that vortex dynamics is related to bubble evolution and jet behavior.After the jet pierces the bubble,an annular vortex with the bubble as the vortex core is generated by the bubble collapse.For the bubble that collapses near the wall,it generates multiple small vortexes near the wall and causes discontinuities in the wall shear stress.For the bubble that collapses away from the wall,it does not generate vortexes near the wall,and its oscillations cause the wall shear stress to vary periodically with different periods.In addition,the wall shear stress at the axis of symmetry increases abruptly when the jet hits the wall.
基金Project supported by the National Natural Science Foundation of China(Grant No.52076215).
文摘This paper investigates the bubble collapse characteristics near dual cylinders within confined spaces.Firstly,the impacts on the bubble morphology,with respect to the bubble positions and the cylinder spacings,are explored using high-speed photography experiments.Subsequently,based on the circle theorem,the liquid velocity field is qualitatively analyzed and compared with the experimental bubble interface motion.Finally,employing the Kelvin impulse theory,an analysis of the variation in Kelvin impulse at various cylinder spacings is conducted,which shows good consistency with the bubble centroid movement.The main conclusions are summarized as follows:(1)High-velocity regions are observed on both sides of the bubble.Low-velocity regions are observed between the bubble and cylinders.As the cylinder spacing and the bubble abscissa increase,the liquid velocity in the high-velocity regions decreases,and the low-velocity regions expands.(2)The characteristics of the bubble cross-sectional roundness,interface displacement,and cross-sectional area are significantly affected by the cylinder spacing and the bubble abscissa.(3)As the bubble abscissa increases,the Kelvin impulse intensity initially rises rapidly and subsequently declines gradually to a fixed value.As the cylinder spacings increases,the Kelvin impulse intensity decreases.
