@phdthesis {engelmann2000a, title = {3D-Flow Measurement by Stereo Imaging}, year = {2000}, publisher = {IWR, Fakult{\"a}t f{\"u}r Physik und Astronomie, Univ.\ Heidelberg}, abstract = {A new method to record three-dimensional liquid flow fields by using {\textquoteleft}Particle Tracking Velocimetry{\textquoteright} is presented. It is based on a two-dimensional Particle Tracking Velocimetry method. It was extended to the third space dimension in order to include the complete physical space. This procedure allows to determine the Lagrange-flow field and to calculate from it the Euler-velocity flow field obtained from many other flow measuring techniques. A calibration method was developed for the wind-wave-flume which allows a high resolution in space. The stereo camera setup and the experimental setup were optimized for the liquid flow measurements. For the first time a liquid prism and a Scheimpflug-camera geometry was used. Numerical calculations using the finite element method demonstrate the complexity of the problem of dealing with free surfaces with wind-induced shear forces as a boundary condition. They show clearly that experimental studies are indispensable for describing phenomena such as {\textquoteleft}bursts{\textquoteright} (descending of liquid elements from close to the surface into deeper layers). Flow measurements were performed in a newly constructed wind-wave-flume (AEOLOTRON) and in a smaller predecessor by using the newly developed imaging methods. In this way the flow fields of wind driven water waves could be characterized by the velocity field and the {\textquoteleft}turbulence{\textquoteright} conditions.}, url = {http://www.ub.uni-heidelberg.de/archiv/1070}, author = {D. Engelmann} }