The purpose is here to briefly present some of the techniques I am used to work with since they can be useful for a wide range of applications.
FOCUS ON VISUALIZATION TECHNIQUES ...
Planar Laser Induced Fluorescence (PLIF)
Left: Set-up with a cell containing DI water and a fluorescent dye. Middle: Excitation of a the dye with a vertical planar laser beam (Nd:Yag, 2x200 mJ, 532 nm) flashing from the right-side to the left of the picture. Right: Visualization of the fluorescence phenomenon in the cell after excitation. Extracted from Jimenez (2013), Ph.D thesis.
PLIF is a technique based on the addition of a fluorescent dye in a liquid phase whose fluorescence is sensitive to some specific parameters such as the temperature, pH, presence of oxygen molecules, etc. The dye first needs to be excited with an adequate source, usually a laser light, and will then reemit light for returning to its fundamental state. This techniques allows both parameter visualization and quantification but is obviously limited to transparent medium to allow the laser to excite the dye and the camera to record the fluorescence intensity.
- Want to learn more? Refer to Jimenez et al. (2014) for instance.
Colorimetry for oxygen transfer visualization
To avoid the use of expensive equipment such as lasers, the visualization of oxygen in liquid can also be performed by colorimetry. In this case, specific chemical products such as the resazurin are added to the liquid to be studied in such a way that the liquid becomes pink in the presence of oxygen. Its presence can thus easily be identified.
- Want to learn more? Refer to Dietrich et al. (2013) for instance.
Particle Image Velocimetry (PIV) for liquid velocity measurements
The principle of the PIV technique is somehow close to the one of the PLIF. Reflective or fluorescent particles are incorporated in the liquid phase and excited with a laser light. By reflection or fluorescence, these particles can easily be detected and are supposed (regarding their density) to follow the fluid motion. By recording the position of these particles with a know time interval and using dedicated software, their velocity and thus this of the fluid can be estimated.
Kalliroscope is a liquid additive which contains microscopic reflective flakes that orient themselves with flow. The flakes are strongly reflective in some areas and nearly transparent in others which allow a direct visualization of the hydrodynamics behavior with a really simple implementation.