The separating/reattaching flow over an axisymmetric backward-facing step is analyzed experimentally by means of particle image velocimetry （PIV）, The main purpose of the measurements is the investigation of the mea...The separating/reattaching flow over an axisymmetric backward-facing step is analyzed experimentally by means of particle image velocimetry （PIV）, The main purpose of the measurements is the investigation of the mean flow field as well as of the Reynolds stress distributions at a Mach number of 0,7 and at a Reynolds number of 3,3 x 10s based on the step height, Due to the strong progress of optical flow measurements in the last years it was possible to resolve all flow scales down to 180 μm （≈1% of the step height） with high precision, Thanks to the high spatial resolution it was found for the first time that the Reynolds stress distribution features a local minimum between the first part of the shear layer and a region inside the recirculation region, This implies a more complex wake dynamics than assumed before,展开更多
Pressure-sensitive paint(PSP) technique was employed to experimentally investigate the aerodynamic force effect of vacuum plume in this study. The characterization and comparison for two types of PSP were firstly cond...Pressure-sensitive paint(PSP) technique was employed to experimentally investigate the aerodynamic force effect of vacuum plume in this study. The characterization and comparison for two types of PSP were firstly conducted in an air pressure range from0.05 to 5000 Pa. The PSPs were prepared using PtTFPP as the active dye and different binders, i.e., polymer-ceramic(PC) and poly(1-trimethylsilyl-1-propyne) [poly(TMSP)]. The static calibrations showed that PtTFPP/poly(TMSP) had a higher pressure sensitivity and a lower temperature dependency compared to PtTFPP/PC in this pressure range. The pressure distributions of a single and two interacting plumes impinging onto a flat plate model were measured using PSP technique. The experimental data were compared to numerical solutions that combined both the computed fluid dynamics(CFD) and direct simulation Monte Carlo(DSMC) methods. Remarkable agreements were achieved, demonstrating the feasibility and accuracy of the numerical approach.Finally, the aerodynamic force effect of interacting plumes at different separation distances was investigated numerically.展开更多
Our objective is to analyze the atomization processes of a pneumatic atomizer by measuring the size and velocity distributions of droplets in a liquid paint spray. The droplet size and velocity distributions have been...Our objective is to analyze the atomization processes of a pneumatic atomizer by measuring the size and velocity distributions of droplets in a liquid paint spray. The droplet size and velocity distributions have been determined at different axial positions in the spray; a mathematical description of how these quan- tities vary throughout the spray is then proposed. Additionally, the relative number density of droplets and the relative local mass flux are estimated.展开更多
基金supported by the German Research Foundation DFG in the framework of the TRR40
文摘The separating/reattaching flow over an axisymmetric backward-facing step is analyzed experimentally by means of particle image velocimetry （PIV）, The main purpose of the measurements is the investigation of the mean flow field as well as of the Reynolds stress distributions at a Mach number of 0,7 and at a Reynolds number of 3,3 x 10s based on the step height, Due to the strong progress of optical flow measurements in the last years it was possible to resolve all flow scales down to 180 μm （≈1% of the step height） with high precision, Thanks to the high spatial resolution it was found for the first time that the Reynolds stress distribution features a local minimum between the first part of the shear layer and a region inside the recirculation region, This implies a more complex wake dynamics than assumed before,
文摘Pressure-sensitive paint(PSP) technique was employed to experimentally investigate the aerodynamic force effect of vacuum plume in this study. The characterization and comparison for two types of PSP were firstly conducted in an air pressure range from0.05 to 5000 Pa. The PSPs were prepared using PtTFPP as the active dye and different binders, i.e., polymer-ceramic(PC) and poly(1-trimethylsilyl-1-propyne) [poly(TMSP)]. The static calibrations showed that PtTFPP/poly(TMSP) had a higher pressure sensitivity and a lower temperature dependency compared to PtTFPP/PC in this pressure range. The pressure distributions of a single and two interacting plumes impinging onto a flat plate model were measured using PSP technique. The experimental data were compared to numerical solutions that combined both the computed fluid dynamics(CFD) and direct simulation Monte Carlo(DSMC) methods. Remarkable agreements were achieved, demonstrating the feasibility and accuracy of the numerical approach.Finally, the aerodynamic force effect of interacting plumes at different separation distances was investigated numerically.
文摘Our objective is to analyze the atomization processes of a pneumatic atomizer by measuring the size and velocity distributions of droplets in a liquid paint spray. The droplet size and velocity distributions have been determined at different axial positions in the spray; a mathematical description of how these quan- tities vary throughout the spray is then proposed. Additionally, the relative number density of droplets and the relative local mass flux are estimated.
