Abstract
In search for quantitative, planar, non-intrusive diagnostics of (compressible) flows, René Tolboom contributes three schemes for number density measurements and one velocimetry tool in his Ph.D. thesis. All four laser diagnostic techniques are based on molecular light scattering rather than scattering off artificially seeded particulates. In his thesis, Tolboom shows that Rayleigh scattering is well suited for investigating the density fields of clean flows of uniform chemical composition, which can be studied on snapshot basis. Although the Raman scattering process is less efficient, it enables species-specific density measurements and data acquisition close to flow models, as opposed to Rayleigh scattering. With prevailing techniques, these planar measurements were not yet practicable, or only in very specific (ideal) flows. Tolboom concludes that Raman scattering is very appropriate for obtaining quantitative density fields, and he argues that this technique may be upgraded towards snapshot imaging as well. Finally, the author explored the viability of a new velocimetry tool called 'APART', for measuring single-component planar velocity fields in supersonic flows. He succeeded to obtain data in complex flow geometries (like flow over strong shock waves and wake flow behind a wedge) that are notoriously difficult or even impossible to investigate with particulate seeded techniques. In conclusion, molecular light scattering techniques are very useful for compressible flow research.
