This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found th...This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found that the average velocity and influence range of the synthetic jet actuator increase with the increasing of driving frequency and driving amplitude.LSB occurs at Re=1.0×10^(5),and ruptures atα=6°.But with intermittent disturbance control,the stall angle of attack(AoA)increases while significantly reducing drag.Research shows that although certain disturbance cannot fully recover from LSB stall,decreasing driving amplitude partially restores wing aerodynamic performance,more effectively than increasing driving amplitude.展开更多
This paper is concerned with the generation of waves due to initial disturbances at the upper surface of a two-layer fluid, as the upper layer is covered by an inertial surface and the lower layer extends infinitely d...This paper is concerned with the generation of waves due to initial disturbances at the upper surface of a two-layer fluid, as the upper layer is covered by an inertial surface and the lower layer extends infinitely downwards. The inertial surface is composed of thin but uniform distribution of non-interacting material. In the mathematical analysis, the Fourier and Laplace transform techniques have been utilized to obtain the depressions of the inertial surface and the interface in the form of infinite integrals. For initial disturbances concentrated at a point, the inertial surface depression and the interface depression are evaluated asymptotically for large time and distance by using the method of stationary phase. They are also depicted graphically for two types of initial disturbances and appropriate conclusions are made.展开更多
In this artilce a new optical trap 2D array by the acoustic modulation is proposed. Based on the ＂called＂ acoustic-elasticity of the fluid embedding trapped microparticle, the expression describing the refractive in...In this artilce a new optical trap 2D array by the acoustic modulation is proposed. Based on the ＂called＂ acoustic-elasticity of the fluid embedding trapped microparticle, the expression describing the refractive index induced by cross-interference of two perpendicular ultrasonic waves is approximately derived. By simulation, the 2D array of the Graded-refractive index lenses appeared in the fluid layer with certain strain-acoustic constant and thickness. The trapping capability of the plane-wave laser beam propagating through those lenses is shown out, and the appearance of the optical trap 2D array has been affirmed.展开更多
The effect of magnetohydrodynamic(MHD)plasma actuators on the control of hypersonic shock wave/turbulent boundary layer interactions is investigated here using Reynolds-averaged Navier-Stokes calculations with low mag...The effect of magnetohydrodynamic(MHD)plasma actuators on the control of hypersonic shock wave/turbulent boundary layer interactions is investigated here using Reynolds-averaged Navier-Stokes calculations with low magnetic Reynolds number approximation.A Mach 5 oblique shock/turbulent boundary layer interaction was adopted as the basic configuration in this numerical study in order to assess the effects of flow control using different combinations of magnetic field and plasma.Results show that just the thermal effect of plasma under experimental actuator parameters has no significant impact on the flow field and can therefore be neglected.On the basis of the relative position of control area and separation point,MHD control can be divided into four types and so effects and mechanisms might be different.Amongst these,D-type control leads to the largest reduction in separation length using magnetically-accelerated plasma inside an isobaric dead-air region.A novel parameter for predicting the shock wave/turbulent boundary layer interaction control based on Lorentz force acceleration is then proposed and the controllability of MHD plasma actuators under different MHD interaction parameters is studied.The results of this study will be insightful for the further design of MHD control in hypersonic vehicle inlets.展开更多
The mechanism for transporting liquid from the bottom of the pipe to the top still to be established in the prediction of the film thickness distribution in horizontal annular two-phase flow. To resolve this issue, us...The mechanism for transporting liquid from the bottom of the pipe to the top still to be established in the prediction of the film thickness distribution in horizontal annular two-phase flow. To resolve this issue, using five parallel-wire conductance probes, time records of local liquid film thickness at five circumferential positions were collected. The characteristics of circumferential liquid film thickness profiles and its variation with gas and liquid velocities were obtained. The basic features of probability distribution function, probability density function, auto-correlation, cross-correlation and power spectrum density function of the disturbance waves in angular flow were studied respectively. The characteristics of circumferential profiles of disturbance waves and its variation with gas and liquid velocities were presented.展开更多
The transition criterion in the improved eN method is that transition would occur whenever the velocity amplitude of disturbance reaches 1%-2% of the free stream velocity,while in the conventional eN method,the N fact...The transition criterion in the improved eN method is that transition would occur whenever the velocity amplitude of disturbance reaches 1%-2% of the free stream velocity,while in the conventional eN method,the N factor is an empirical factor.In this paper the reliability of this key assumption in the improved eN method is checked by results of transition prediction by using the Parabolized Stability Equations(PSE).Transition locations of an incompressible boundary layer and a hypersonic boundary layer at Mach number 6 on a flat plate are predicted by both the improved eN method and the PSE method.Results from both methods agree fairly well with each other,implying that the transition criterion proposed in the improved eN method is reliable.展开更多
文摘This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found that the average velocity and influence range of the synthetic jet actuator increase with the increasing of driving frequency and driving amplitude.LSB occurs at Re=1.0×10^(5),and ruptures atα=6°.But with intermittent disturbance control,the stall angle of attack(AoA)increases while significantly reducing drag.Research shows that although certain disturbance cannot fully recover from LSB stall,decreasing driving amplitude partially restores wing aerodynamic performance,more effectively than increasing driving amplitude.
基金Supported by the DST Research Project No.SR/SY/MS:521/08and CSIR,New Delhi
文摘This paper is concerned with the generation of waves due to initial disturbances at the upper surface of a two-layer fluid, as the upper layer is covered by an inertial surface and the lower layer extends infinitely downwards. The inertial surface is composed of thin but uniform distribution of non-interacting material. In the mathematical analysis, the Fourier and Laplace transform techniques have been utilized to obtain the depressions of the inertial surface and the interface in the form of infinite integrals. For initial disturbances concentrated at a point, the inertial surface depression and the interface depression are evaluated asymptotically for large time and distance by using the method of stationary phase. They are also depicted graphically for two types of initial disturbances and appropriate conclusions are made.
文摘In this artilce a new optical trap 2D array by the acoustic modulation is proposed. Based on the ＂called＂ acoustic-elasticity of the fluid embedding trapped microparticle, the expression describing the refractive index induced by cross-interference of two perpendicular ultrasonic waves is approximately derived. By simulation, the 2D array of the Graded-refractive index lenses appeared in the fluid layer with certain strain-acoustic constant and thickness. The trapping capability of the plane-wave laser beam propagating through those lenses is shown out, and the appearance of the optical trap 2D array has been affirmed.
基金Project supported by the National Key R&D Program of China(Nos.2019YFA0405300 and 2019YFA0405203)the Chinese Scholarship Council(CSC)(No.201903170195)。
文摘The effect of magnetohydrodynamic(MHD)plasma actuators on the control of hypersonic shock wave/turbulent boundary layer interactions is investigated here using Reynolds-averaged Navier-Stokes calculations with low magnetic Reynolds number approximation.A Mach 5 oblique shock/turbulent boundary layer interaction was adopted as the basic configuration in this numerical study in order to assess the effects of flow control using different combinations of magnetic field and plasma.Results show that just the thermal effect of plasma under experimental actuator parameters has no significant impact on the flow field and can therefore be neglected.On the basis of the relative position of control area and separation point,MHD control can be divided into four types and so effects and mechanisms might be different.Amongst these,D-type control leads to the largest reduction in separation length using magnetically-accelerated plasma inside an isobaric dead-air region.A novel parameter for predicting the shock wave/turbulent boundary layer interaction control based on Lorentz force acceleration is then proposed and the controllability of MHD plasma actuators under different MHD interaction parameters is studied.The results of this study will be insightful for the further design of MHD control in hypersonic vehicle inlets.
文摘The mechanism for transporting liquid from the bottom of the pipe to the top still to be established in the prediction of the film thickness distribution in horizontal annular two-phase flow. To resolve this issue, using five parallel-wire conductance probes, time records of local liquid film thickness at five circumferential positions were collected. The characteristics of circumferential liquid film thickness profiles and its variation with gas and liquid velocities were obtained. The basic features of probability distribution function, probability density function, auto-correlation, cross-correlation and power spectrum density function of the disturbance waves in angular flow were studied respectively. The characteristics of circumferential profiles of disturbance waves and its variation with gas and liquid velocities were presented.
基金supported by the National Natural Science Foundation of China (Grant No.11002098)the National Basic Research Program of China (Grant No.2009CB724103)the Specialized Research Fund for the Doctoral Program of Higher Education
文摘The transition criterion in the improved eN method is that transition would occur whenever the velocity amplitude of disturbance reaches 1%-2% of the free stream velocity,while in the conventional eN method,the N factor is an empirical factor.In this paper the reliability of this key assumption in the improved eN method is checked by results of transition prediction by using the Parabolized Stability Equations(PSE).Transition locations of an incompressible boundary layer and a hypersonic boundary layer at Mach number 6 on a flat plate are predicted by both the improved eN method and the PSE method.Results from both methods agree fairly well with each other,implying that the transition criterion proposed in the improved eN method is reliable.
