Estimation of IFOV of Rosette Scan System

The methods of estimating the minimum allowed value of IFOV (instantaneous field of view) of the detector in a rosette scan system are investigated. The common method for the estimation of IFOV is described. A new method which uses the maximum distance between two neighboring petals as the estimated value of IFOV is developed and a comparison between the common method and the new method is given. It is concluded that the minimum allowed value of IFOV of rosette scanning is over estimated by the common method while this value can be calculated accurately with the new method.

Experimental Investigation of Effects of Suction-Side Squealer Tip Geometry on the Flow Field in a Large-scale Axial Compressor using SPIV

It is well known that the non-uniform tip geometry is a promising passive flow control technique in turbomachinery.However,detailed investigation of its effects on the unsteady flow field of turbomachinery is rare in the existiug hteratures.This paper presents an experimental investigation of effects of suction side squealer tip configuration on both the steady and unsteady flow field of an isolated compressor rotor.The flow field at 10%chord downstream from the trailing edge was measured using a mini five-hole probe.Meanwhile,the unsteady flow field inside the passage was investigated using stereo particle image velocimetry(SPIV).The steady results show that the SSQ tip configuration exerts positive effect on the static pressure rise performance of this compressor,and the radial equilibrium at the rotor outlet is obviously rearranged.The SSQ tip configuration would create a stronger tip leakage vortex at the formation phase,and it experiences a faster dissipation process around the rear chord.Also,the splitting process of the tip leakage vortex is severer,which is the main cause of the relatively higher probability of the presence of the streamwise reverse flow.The quantitatively analysis of the tip leakage vortex indicates that the velocity loss inside the blockage region is direct response of the evolutionary procedure of the tip leakage vortex.It keeps increasing until the end of the splitting process.Although the blockage coefficient grows sustainably,the velocity loss will reduce once the turbulent mixing procedure is dominant.

Quantitative analysis of coherent structures affecting instantaneous fluctuation of point-source plumes based on PIV-POD method

For an enclosed space like an industrial plant where devices and equipment generate a large amount of heat,the fluctuation characteristics of thermal plume become more crucial.This paper aims to study the unique air distribution of the point-source plume by shutting down all valves in a thermostatic chamber.250 consecutive instantaneous flow fields(in each zone)were measured by a two-dimensional particle image velocimetry(PIV)system at a sampling frequency of 3 Hz to quantify the air distribution of the plume.Based on the experimental data,the indoor instantaneous velocity and vorticity fields were analyzed,and the transient velocity fluctuation characteristics of typical points were discussed.The fluctuation periods of the plume at different heights were ini-tially estimated.Through the proper orthogonal decomposition(POD)analysis,the dominant coherent structures in complex instantaneous flow fields were excavated,and the turbulent kinetic energy of coherent structures was calculated.In addition,POD analysis provided a new method for validating and improving transient numerical simulation models.