The SHRL have been awarded a £1.3m EPSRC research grant to study the deformation of microscopic fuel droplets.
We are seeking to recruit two EPSRC Research Fellows.
We are currently offering a fully funded PhD studentship on laser diagnostics for sprays.
Contact: Dr Guillaume de Sercey
Schlieren is a simple, inexpensive and somewhat spectacular optical technique for visualising density gradients in fluids. it has popularly been used for studying shockwaves in air, for example generated by bullets or planes. However, it can also be used to visualise evaporation, fluids mixing, and flame.
Schlieren is based on the principle that changes in refractive index of a medium will modify the path of light as it traverses it (as can be witnessed by the shimmering effect just above a road on a hot day). A light source is used to illuminate uniformly the test area and the image is visualised on a screen or recorded on a camera. A knife edge is then placed in between the test area and its image so that it blocks half of the image. If there was no changes in density gradients then the knife edge would only result in a dimmer image. However, changes in density gradient in the test area bend the light and bent rays that would otherwise be obstructed by the knife edge are now visible and reciprocaly some of the rays that would otherwise be visible are now obstructed. This results in sharp contrast in the image.
In practice, a Z-type system is often used. the test area is placed between two spherical mirros and a point light source is placed next to the test area at the focal point of one of the mirror so that a light rays passing through the test area are parallels. The knife edge is placed on the other side of the test area, at the focal point of the second mirror. Finally the imaging system is placed behind the knife edge. This can either be a screen with a focussing length, or for recording, a camera with its aperture fully open.