This work investigates the active control of a fully developed turbulent boundary layer by a submerged synthetic jet actuator.The impacts of the control are explored by measuring the streamwise velocities using partic...This work investigates the active control of a fully developed turbulent boundary layer by a submerged synthetic jet actuator.The impacts of the control are explored by measuring the streamwise velocities using particle image velocimetry,and reduction of the skin-friction drag is observed in a certain range downstream of the orifice.The coherent structure is defined and extracted using a spatial two-point correlation function,and it is found that the synthetic jet can efficiently reduce the streamwise scale of the coherent structure.Proper orthogonal decomposition analysis reveals that large-scale turbulent kinetic energy is significantly attenuated with the introduction of a synthetic jet.The conditional averaging results show that the induction effect of the prograde vortex on the low-speed fluid in a large-scale fluctuation velocity field is deadened,thereby suppressing the bursting process near the wall.展开更多
The turbulent boundary layer(TBL)is actively controlled by the synthetic jet generated from a circular hole.According to the datasets of velocity fields acquired by a time-resolved particle image velocimetry(TR-PIV)sy...The turbulent boundary layer(TBL)is actively controlled by the synthetic jet generated from a circular hole.According to the datasets of velocity fields acquired by a time-resolved particle image velocimetry(TR-PIV)system,the average drag reduction rate of 6.2%in the downstream direction of the hole is obtained with control.The results of phase averaging show that the synthetic jet generates one vortex pair each period and the consequent vortex evolves into hairpin vortex in the environment with free-stream,while the reverse vortex decays rapidly.From the statistical average,it can be found that a low-speed streak is generated downstream.Induced by the two vortex legs,the fluid under them converges to the middle.The drag reduction effect produced by the synthetic jet is local,and it reaches a maximum value at x^(+)=400,where the drag reduction rate reaches about 12.2%.After the extraction of coherent structure from the spatial two-point correlation analysis,it can be seen that the synthetic jet suppresses the streamwise scale and wall–normal scale of the large scale coherent structure,and slightly weakens the spanwise motion to achieve the effect of drag reduction.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11732010,11972251,11872272,11902218,and 11802195)the National Key Research and Development Program of China,on‘Green Buildings and Building Industrialization’(Grant No.2018YFC0705300)。
文摘This work investigates the active control of a fully developed turbulent boundary layer by a submerged synthetic jet actuator.The impacts of the control are explored by measuring the streamwise velocities using particle image velocimetry,and reduction of the skin-friction drag is observed in a certain range downstream of the orifice.The coherent structure is defined and extracted using a spatial two-point correlation function,and it is found that the synthetic jet can efficiently reduce the streamwise scale of the coherent structure.Proper orthogonal decomposition analysis reveals that large-scale turbulent kinetic energy is significantly attenuated with the introduction of a synthetic jet.The conditional averaging results show that the induction effect of the prograde vortex on the low-speed fluid in a large-scale fluctuation velocity field is deadened,thereby suppressing the bursting process near the wall.
基金the National Natural Science Foundation of China(Grant Nos.11732010,11972251,11872272,11902218,and 12172242)the National Key Research and Development Program of the Ministry of Science and Technology,China(Grant No.2018YFC0705300)。
文摘The turbulent boundary layer(TBL)is actively controlled by the synthetic jet generated from a circular hole.According to the datasets of velocity fields acquired by a time-resolved particle image velocimetry(TR-PIV)system,the average drag reduction rate of 6.2%in the downstream direction of the hole is obtained with control.The results of phase averaging show that the synthetic jet generates one vortex pair each period and the consequent vortex evolves into hairpin vortex in the environment with free-stream,while the reverse vortex decays rapidly.From the statistical average,it can be found that a low-speed streak is generated downstream.Induced by the two vortex legs,the fluid under them converges to the middle.The drag reduction effect produced by the synthetic jet is local,and it reaches a maximum value at x^(+)=400,where the drag reduction rate reaches about 12.2%.After the extraction of coherent structure from the spatial two-point correlation analysis,it can be seen that the synthetic jet suppresses the streamwise scale and wall–normal scale of the large scale coherent structure,and slightly weakens the spanwise motion to achieve the effect of drag reduction.
