Abstract: A method for determining a wall shear stress distribution on a surface of a body around which air flows. The method includes determining a heat flow distribution into the surface of the body around which air flows by infrared thermography, obtaining a surface pressure distribution on the surface optically and determining the wall shear stress distribution on the surface of the body by processing from at least the heat flow distribution and the surface pressure distribution. The instant abstract is neither intended to define the invention disclosed in this specification nor intended to limit the scope of the invention in any way.

Abstract: A method and an apparatus determines at least one parameter of a material flow. The parameter is for example temperature, pressure or velocity of the gas or plasma flow. The material flow is either a gas or a plasma flow. The method and the apparatus are utilizing atomic absorption spectroscopy and feed a Rubidium compound into the gas or plasma flow, in which the Rubidium compound dissociates into Rubidium atoms. The Rubidium atoms are stimulated with a first laser beam and a first transmitted laser intensity is detected. First absorption lines are determined from the first transmitted laser intensity. Rubidium atoms are stimulated with a second laser beam, a second transmitted reference laser intensity is detected and second reference absorption lines are determined from the second transmitted reference laser intensity. Finally, at least one parameter of the gas or plasma flow is determined from the comparison of the first absorption lines and the second reference absorption lines of the Rubidium atoms.