FLOW VISUALIZATION OF INTERACTIONS BETWEEN PARTICLE WAKES AND JET VORTICES
The interactions between vortices of a round free shear jet and particle’s wakes are visualized by means of smoke-gas flow visualization technology. Particles in different diameters are fixed at different positions along the jet axial central line. The typical flow structural compositions of the gas jet at the different flow developing stages are presented. Particle wakes occur obviously for the larger particle when the particle Reynolds number is larger than 100, and they change the overall flow structural pattern. More ejections in the vortex rings are accused in the radial direction at the initial flow status. The large-scale structures are broken up because of the presence of the wakes behind large particles. The local turbulence anisotropy is then attenuated in the downstream. Small particles without wakes do not change the flow structure pattern. The results are valuable to develop accurate turbulence modulation models including wake effects.
Flow visualization and laser measurement on particle modulation to gas-phase turbulence
Particle modulation to turbulence is investigated experimentally by means of PDPA, PIV and flow visualization for a gas-particle two-phase jet flow. Large particles can enhance the small-scale vortex, so that gas-phase turbulence intensity is increased, while small particles may delay the rolling up of the gas vortex, so that gas-phase turbulence intensity is attenuated. The critical particle size range for such different effects is between 150 σm and 200 σm, corresponding to the Stokes number is between 88 and 157 under the present flow conditions. The PIV results show small particles can retain the gas-phase vortex structure, while large particles can break large vortex structure. The particle Stokes number is not the only judgment standard whether particles enhance or attenuate gas-phase turbulence. The CTI (Change of Turbulence Intensity) number can mark off particle modulation on turbulence in two-phase flow, but more studies are needed.
Botulinum toxin in the management of chronic migraine: clinical evidence and experience
Chronic migraine (CM) is a severely disabling neurological condition characterized by episodes of pulsating unilateral or bilateral headache. The United States Food and Drug Administration (FDA) approved onabotulinumtoxinA (Botox®) for the prophylactic treatment of CM in 2010. It has been shown that onabotulinumtoxinA is effective in the reduction of headache frequency and severity in patients with CM. Treatment is well tolerated by the patients. This review reports on the history of botulinum neurotoxin (BoNT) in CM and presents the current clinical evidence for the use of onabotulinumtoxinA in the treatment of CM.