The unsteady organization and the evolution of thecoherent structures within the immediate wake of the sharpsymmetric trailing-edge of a NACA0012 airfoil is investigatedusing two-component (2C) and tomographic particle imagevelocimetry (Tomo-PIV). The inspection of the Tomo-PIVresults showed new vortical structures, introduced here ascounter-hairpin vortices, evolve in the wake region to directthe turbulent mechanism towards recovery of the wake deficit.These vortical structures are topologically similar to thehairpins of a turbulent boundary layer as they appear to be Ushapedbut with inverted orientation. The spanwise portion ofa counter-hairpin vortex is in the vicinity of the wakecenterline and the legs are inclined at an approximately 60degree to the wake axis in the downstream direction. Theypartially wrap around the high speed streaks and frequentlysweep the high-speed flow towards the wake centerline. Apattern recognition algorithm is applied to establishcharacterization based on an ensemble averaged counterhairpinvortex. The formation mechanism of the counterhairpinvortices is attributed to the shear layer produced alongthe wake centerline by the neighboring of a low and a highspeed streak which promotes formation of spanwise vorticesthat form the vortex by connection to quasistreamwisevortices.
左卡尼汀和其2个中间体杂质均为带正电荷化合物,因此我们首先选择使用CAPCELL PAK SCX色谱柱对其进行保留,并使用PDA检测器检测。由左卡尼汀杂质结构式可知,两杂质紫外吸收非常弱,因此我们使用质谱对左卡尼汀及其两杂质进行检测,并使用CAPCELL PAK CR 1:4色谱柱对其进行了保留和分离。使用CAPCELL PAK CR 1:4柱进行LC-MS分析,左卡尼汀、杂质1、杂质2间得到了较好分离结果。 在进行LC-MS分析时,由于带正电荷化合物的静电吸引作用,我们发现左卡尼丁及杂质2均有一定程度的残留。因此建议客户在分析前对进样浓度进行考察,杂质浓度建议设置为定量限浓度,左卡尼汀浓度设置为杂质浓度100倍,以避免残留的发生。