The Synthetic Jet(S J)control on the propulsion behavior of a foil in plunge-pitch motion is examined in this work by numerical simulations.An elliptic foil with ratio of 8 performs the plunge and pitch motions synchr...The Synthetic Jet(S J)control on the propulsion behavior of a foil in plunge-pitch motion is examined in this work by numerical simulations.An elliptic foil with ratio of 8 performs the plunge and pitch motions synchronously.A pair of SJs with the same frequency and strength is integrated into the upper and lower surfaces of the foil.As a result,the local flow field around the foil could be obviously modified by the SJs.At the Reynolds number of 200,the effects of the inclined angle between the jet direction and the chord line,the phase angle between the SJs and the flapping motion as well as the location of SJ on the propulsion performance are systematically investigated.Compared with the pure plunging and pitching foil,it is indicated that the enhancement of mean thrust and propulsive efficiency can be obtained by the SJs with suitable working parameters.Based on the numerical analysis,it is found that the jet flow on the foil surfaces,which changes the local pressure distribution to increase the pressure difference between upper and lower surfaces,can benefit the propulsion behavior of the flapping foil.展开更多
High-precision numerical methods are utilized to study the shock waves interacting with an elliptical heavy bubble.The influence of different bubble gases(SF6 and R22)and shock intensities(Ma=1.21 and Ma=2.1)is analyz...High-precision numerical methods are utilized to study the shock waves interacting with an elliptical heavy bubble.The influence of different bubble gases(SF6 and R22)and shock intensities(Ma=1.21 and Ma=2.1)is analyzed qualitatively and quantitatively.The results show that the focusing position is farther from the right bubble interface in the SF6 bubble(case 1)than in the R22 bubble(case 2)when Ma=1.21;thus,case 2 exhibits an outward jet structure,while case 1 does not.When Ma=2.1(case 3),the shock wave propagates faster,and the shock focusing is nearer to the right bubble interface.Finally,outward jet structures form on the bubble interfaces.The maximum values of density and pressure of shock focusing are different in the three cases,which imply that different gas densities and shock intensities significantly affect the shock-bubble interaction.The effective bubble volume and gases mixing degree are both smaller in case 2 than in case 1,but the trends over time are essentially the same.The increased shock intensity in case 3 leads to a smaller effective bubble volume than in case 1,but a much greater gases mixing degree.In all three cases,the compression term plays a more important role in the vorticity development than the other terms.展开更多
基金The authors acknowledge the support of the National Natural Science Foundation of China(Grant No.11622219)the Natural Science Foundation of Jiangsu Province(Grant No.BK20191271)This work is also supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘The Synthetic Jet(S J)control on the propulsion behavior of a foil in plunge-pitch motion is examined in this work by numerical simulations.An elliptic foil with ratio of 8 performs the plunge and pitch motions synchronously.A pair of SJs with the same frequency and strength is integrated into the upper and lower surfaces of the foil.As a result,the local flow field around the foil could be obviously modified by the SJs.At the Reynolds number of 200,the effects of the inclined angle between the jet direction and the chord line,the phase angle between the SJs and the flapping motion as well as the location of SJ on the propulsion performance are systematically investigated.Compared with the pure plunging and pitching foil,it is indicated that the enhancement of mean thrust and propulsive efficiency can be obtained by the SJs with suitable working parameters.Based on the numerical analysis,it is found that the jet flow on the foil surfaces,which changes the local pressure distribution to increase the pressure difference between upper and lower surfaces,can benefit the propulsion behavior of the flapping foil.
基金supported by the National Natural Science Foundation of China(Grant No.11872193)the Youth Talent Cultivation Plan of Jiangsu University.
文摘High-precision numerical methods are utilized to study the shock waves interacting with an elliptical heavy bubble.The influence of different bubble gases(SF6 and R22)and shock intensities(Ma=1.21 and Ma=2.1)is analyzed qualitatively and quantitatively.The results show that the focusing position is farther from the right bubble interface in the SF6 bubble(case 1)than in the R22 bubble(case 2)when Ma=1.21;thus,case 2 exhibits an outward jet structure,while case 1 does not.When Ma=2.1(case 3),the shock wave propagates faster,and the shock focusing is nearer to the right bubble interface.Finally,outward jet structures form on the bubble interfaces.The maximum values of density and pressure of shock focusing are different in the three cases,which imply that different gas densities and shock intensities significantly affect the shock-bubble interaction.The effective bubble volume and gases mixing degree are both smaller in case 2 than in case 1,but the trends over time are essentially the same.The increased shock intensity in case 3 leads to a smaller effective bubble volume than in case 1,but a much greater gases mixing degree.In all three cases,the compression term plays a more important role in the vorticity development than the other terms.
