Schlierenvalaistus

Schlierenvalaistus, also known as schlieren photography or schlieren imaging, is an optical technique used to visualize density variations in transparent media. These variations can arise from changes in temperature, pressure, or composition, and they often manifest as subtle refractive index differences that are invisible to the naked eye. The technique works by exploiting these refractive index gradients to deflect light rays.

A basic schlieren setup typically involves a light source, two concave mirrors, and a knife-edge. Light from the source is collimated into a parallel beam by the first mirror, passes through the medium being studied, and is then refocused by the second mirror. If the medium is uniform, the light rays converge perfectly at the focal point of the second mirror. However, if there are density variations, the light rays are deflected. A knife-edge is placed at the focal point to block a portion of the light. When density variations are present, they cause some of the deflected light to either pass the knife-edge or be blocked by it more than it would in a uniform medium. This differential blocking of light creates a visible image of the density gradients.

Schlieren photography has numerous applications in various scientific and engineering fields. It is commonly used to study fluid dynamics, including the flow of air around aerodynamic objects like aircraft wings and projectiles, and the behavior of gases in combustion processes. It's also employed in heat transfer studies to visualize thermal plumes and convection currents, and in materials science to detect internal defects or stress in transparent materials. The technique provides a non-intrusive way to observe phenomena that would otherwise be difficult or impossible to see.