Volumetric particle image velocimetry(PIV)is a laser technique measuring three-component velocity field in a volume.Common volumetric PIV techniques are defocusing PIV,multi-view PIV and holographic PIV.Tomographic PI...Volumetric particle image velocimetry(PIV)is a laser technique measuring three-component velocity field in a volume.Common volumetric PIV techniques are defocusing PIV,multi-view PIV and holographic PIV.Tomographic PIV is an advanced approach of multi-view PIV,which significantly improves the spatial resolution of the measurement by using the multiplicative algebraic reconstruction technique(MART)to reconstruct the particle field.Due to the rapid progress being made in volumetric PIV measurements,this article focuses on introducing the principles of different volumetric PIV methods from aspects of particle reconstruction and velocity reconstruction.Advantages and limitations on applications are elaborated.Issues specific to volumetric PIV regarding illumination,digital imaging,depth of focus,ghost particle and spatial resolution are discussed.展开更多
This article carries out synthetic measurements and analysis of the characteristics of the asymmetric surface dielectric barrier discharge plasma aerodynamic actuation. The rotational and vibrational temperatures of a...This article carries out synthetic measurements and analysis of the characteristics of the asymmetric surface dielectric barrier discharge plasma aerodynamic actuation. The rotational and vibrational temperatures of an N2 （ C3 Ⅱu ） molecule are measured in terms of the optical emission spectra from the N2 second positive system. A simplified collision-radiation model for N2 （C）and N2 ＋ （B）is established on the basis of the ratio of emission intensity at 391.4 nm to that at 380.5 nm and the ratio of emission intensity at 371. 1 nm to that at 380.5 nm for calculating temporal and spatial averaged electron temperatures and densities. Under one atmosphere pressure, the electron temperature and density are on the order of 1.6 eV and 10H cm-3 respectively. The body force induced by the plasma aerodynamic actuation is on the order of tens of mN while the induced flow velocity is around 1.3 m/s. Starting vortex is firstly induced by the actuation ; then it develops into a near-wall jet, about 70 mm downstream of the actuator. Unsteady plasma aerodynamic actuation might stimulate more vortexes in the flow field. The induced flow direction by nanosecond discharge plasma aerodynamic actuation is not parallel, but vertical to the dielectric layer surface.展开更多
基金supported by the National Natural Science Foundation of China(11102013 and 11327202)the"Weishi"Foundation of Beijing University of Aeronautics and Astronautics(YWF-12-RHRS-008)
文摘Volumetric particle image velocimetry(PIV)is a laser technique measuring three-component velocity field in a volume.Common volumetric PIV techniques are defocusing PIV,multi-view PIV and holographic PIV.Tomographic PIV is an advanced approach of multi-view PIV,which significantly improves the spatial resolution of the measurement by using the multiplicative algebraic reconstruction technique(MART)to reconstruct the particle field.Due to the rapid progress being made in volumetric PIV measurements,this article focuses on introducing the principles of different volumetric PIV methods from aspects of particle reconstruction and velocity reconstruction.Advantages and limitations on applications are elaborated.Issues specific to volumetric PIV regarding illumination,digital imaging,depth of focus,ghost particle and spatial resolution are discussed.
基金National Natural Science Foundation of China(50906100)China Postdoctoral Science Foundation(20090450373)
文摘This article carries out synthetic measurements and analysis of the characteristics of the asymmetric surface dielectric barrier discharge plasma aerodynamic actuation. The rotational and vibrational temperatures of an N2 （ C3 Ⅱu ） molecule are measured in terms of the optical emission spectra from the N2 second positive system. A simplified collision-radiation model for N2 （C）and N2 ＋ （B）is established on the basis of the ratio of emission intensity at 391.4 nm to that at 380.5 nm and the ratio of emission intensity at 371. 1 nm to that at 380.5 nm for calculating temporal and spatial averaged electron temperatures and densities. Under one atmosphere pressure, the electron temperature and density are on the order of 1.6 eV and 10H cm-3 respectively. The body force induced by the plasma aerodynamic actuation is on the order of tens of mN while the induced flow velocity is around 1.3 m/s. Starting vortex is firstly induced by the actuation ; then it develops into a near-wall jet, about 70 mm downstream of the actuator. Unsteady plasma aerodynamic actuation might stimulate more vortexes in the flow field. The induced flow direction by nanosecond discharge plasma aerodynamic actuation is not parallel, but vertical to the dielectric layer surface.
