Scalar Imaging in Mixing Fluids and Thermal Flows
LaVision’s FluidMaster laser imaging systems measure scalar flow properties such as concentration, mixture fraction, fluid composition and temperature in various fluid dynamical applications. For scalar laser imaging in fluids Laser Induced Fluorescence (LIF) is the most versatile and practical measurement technique featuring high signal levels and spectral selectivity.
Beside accurate signal calibration the LIF software package in DaVis supports preprocessing routines accounting for background offset, nonuniform laser sheet profile, laser pulse-to-pulse fluctuations, image vignetting and distortion.
For LIF imaging accurate flow seeding with LIF-active molecular flow tracers is required and essential for successful measurements. LaVision has strong expertise in flow seeding including the appropriate use of each flow marker and in providing the necessary seeding device.
Sample Application: Background Oriented Schlieren: BOS Imaging
For the visualization of gas motion based on local refractive index variations Background Oriented Schlieren (BOS, also known as Synthetic Schlieren) is a simple and cost-effective alternative to laser imaging methods, because it doesn’t need any complex illumination device like a laser needed for laser imaging, and it works without seeding the flow.
BOS is a line-of-sight imaging technique and measures locally the density gradient as an integrated value over the line-of-sight. In practice, only a random dot pattern in the background of the flow is imaged with a high resolution camera before and during the test. By comparing the two pictures (or more precisely correlating the two patterns similar to the image correlation in PIV) the local displacement of the background pattern can be used to provide lateral information on path-integrated refractive index variations.