@incollection {beushausen2009,
	title = {2D-measurement technique for simultaneous quantitative determination of mixing ratio and velocity field in microfluidic applications},
	volume = {106},
	year = {2009},
	pages = {155--164},
	publisher = {Springer},
	abstract = {Two-dimensional Molecular-Tagging-Velocimetry (2D-MTV) has been used to investigate velocity fields of liquid flow in a micro mixer. Optical tagging was realized by using caged dye. For the first time patterns were generated by structured laser illumination using optical masks. This allows the generation of nearly any imaginable pattern. The flow induced deformation of the optically written pattern is tracked by imaging of laser induced fluorescence. Quantitative analysis of raw image series is carried out by novel optical flow based techniques. A comparison to the standard technique of uPIV has also been conducted. Additionally Planar Spontaneous Raman Scattering (PSRS) was applied in order to determine concentration fields for mixtures of ethanol and water.},
	doi = {10.1007/978-3-642-01106-1_16},
	author = {Volker Beushausen and Karsten Roetmann and Waldemar Schmunk and Mike Wellhausen and Christoph S. Garbe and Bernd J{\"a}hne},
	editor = {W. Nitsche and C. Dobriloff}
}
@article {scholz2008,
	title = {Double-pulse planar-LIF investigations using fluorescence motion analysis for mixture formation investigation},
	journal = {Exp. Fluids},
	volume = {45},
	number = {4},
	year = {2008},
	pages = {583--593},
	abstract = {A concept for dynamic mixture formation investigations of fuel/air mixtures is presented which can equally be applied to several other laser induced fluorescence (LIF) applications. Double-pulse LIF imaging was used to gain insight into dynamic mixture formation processes. The setup consists of a modified standard PIV setup. The "fuel/air ratio measurement by laser induced fluorescence (FARLIF)" approach is used for a quantification of the LIF images in order to obtain pairs of 2D fuel/air ratio maps. Two different evaluation concepts for LIF double pulse images are discussed. The first is based on the calculation of the temporal derivative field of the fuel/air ratio distribution. The result gives insight into the dynamic mixing process, showing where and how the mixture is changing locally. The second concept uses optical flow methods in order to estimate the motion of fluorescence (i.e., mixture) structures to gain insight into the dynamics, showing the distortion and the motion of the inhomogeneous mixture field. For this "fluorescence motion analysis" (FMA) two different evaluation approaches the "variational gradient based approach" and the "variational cross correlation based approach" are presented. For the validation of both, synthetic LIF image pairs with predefined motion fields were generated. Both methods were applied and the results compared with the known original motion field. This validation shows that FMA yields reliable results even for image pairs with low signal/noise ratio. Here, the "variational gradient based approach" turned out to be the better choice so far. Finally, the experimental combination of double-pulse FARLIF imaging with FMA and simultaneous PIV measurement is demonstrated. The comparison of the FMA motion field and the flow velocity field captured by PIV shows that both results basically reflect complementary information of the flow field. It is shown that the motion field of the fluorescence structures does not (necessarily) need to represent the actual flow velocity and that the flow velocity field alone can not illustrate the structure motion in any case. Therefore, the simultaneous measurement of both gives the deepest insight into the dynamic mixture formation process. The examined concepts and evaluation approaches of this paper can easily be adapted to various other planar LIF methods (with the LIF signal representing, e.g., species concentration, temperature, density etc.) broadening the insight for a wide range of different dynamic processes.},
	doi = {10.1007/s00348-008-0537-x},
	author = {J. Scholz and T. Wiersbinski and Paul Ruhnau and Daniel Kondermann and Christoph S. Garbe and R. Hain and Volker Beushausen}
}
@article {roetmann2007,
	title = {Micro-flow analysis by molecular tagging velocimetry and planar raman-scattering},
	journal = {Exp. Fluids},
	volume = {44},
	year = {2008},
	pages = {419--430},
	abstract = {The two dimensional Molecular Tagging Velocimetry (2D-MTV) was used to measure velocity fields of the flow in a micro mixer. Instead of commonly used micro particles an optical tagging of the flow was performed by using a caged dye. The flow induces a deformation of the optically written pattern that can be tracked by laser induced fluorescence. The series of raw images gained this way were analyzed quantitatively with a novel optical flow based technique. Reference measurements have been carried out allowing to draw conclusions about the accuracy of this procedure. A comparison to the standard technique of uPIV was also conducted. Apart from measuring flow velocities in microfluidic mixing processes, the spatial distribution of concentration fields for different species were also measured. To this end, a new technique has been developed that allows spatial measurements from Planar Spontaneous Raman Scattering (PSRS). The Raman stray light of the relevant species was spectrally selected by a narrow bandpass filter and thus detected unaffectedly by the Raman stray light of other species. The successful operation of this measurement procedure in micro flows will be demonstrated exemplary for a mixing process of water and ethanol.},
	doi = {10.1007/s00348-007-0420-1},
	author = {Karsten Roetmann and Waldemar Schmunk and Christoph S. Garbe and Volker Beushausen}
}
@article {garbe2008b,
	title = {An optical flow MTV based technique for measuring microfluidic flow in the presence of diffusion and Taylor dispersion},
	journal = {Exp. Fluids},
	volume = {44},
	year = {2008},
	pages = {439--450},
	abstract = {A novel technique is presented for accurately measuring flow fields in microfluidic flows from molecular tagging velocimetry (MTV). Limited optical access is frequently encountered in microfluidic systems. Therefore, in this contribution we analyze the special case of tagging a line across the thin dimension of a microchannel and subsequent imaging along this line. This represents a set-up that is applicable to a wide range of microfluidic applications. A volume illumination has to be used, resulting in an integration of the visualized dye across the flow profile. This leads to the well-known effect of Taylor dispersion. Our novel technique consists of measuring motion from digital image sequences in a gradient-based approach. A motion model is developed which explicitly deals with brightness changes due to Taylor dispersion and additional molecular diffusion of dyes. The presented approach is specific to the case of a parabolic velocity profile. In the presence of these effects, an accurate computation of motion is only possible by applying this novel motion model. Our technique is tested on simulated sequences corrupted with varying levels of noise and on actual measurements. Measurements were conducted in a microfluidic mixer of precisely known flow properties. In the same mixer, a comparative study of our MTV technique to uPIV was performed. Also, the results were compared to bulk measurements of the fluid flow velocity. The novel algorithm compared favorably and also, measurements were conducted on inhomogeneous flow configurations.},
	doi = {10.1007/s00348-007-0435-7},
	author = {Christoph S. Garbe and Karsten Roetmann and Volker Beushausen and Bernd J{\"a}hne}
}
@conference {scholz2007,
	title = {Double-pulse planar-LIF investigations using fluorescence motion analysis for mixture formation investigation},
	booktitle = {7th International Symposium on Particle Image Velocimetry Rome, 11. - 14.Sept.},
	year = {2007},
	author = {J. Scholz and T. Wiersbinski and Paul Ruhnau and Daniel Kondermann and Christoph S. Garbe and R. Hain and Volker Beushausen}
}
@conference {roetmann2006,
	title = {Analyse Mikrofluidischer Str{\"o}mungen mit Molecular Tagging Velocimetry und Planarer Ramanstreuung},
	booktitle = {Tagungsband Lasermethoden in der Str{\"o}mungsmesstechnik},
	year = {2006},
	author = {Karsten Roetmann and Waldemar Schmunk and Christoph S. Garbe and Volker Beushausen}
}
@conference {roetmann2006a,
	title = {Micro-flow analysis by molecular tagging velocimetry and planar Raman-scattering},
	booktitle = {Proc.\ of 12th International Symposium on Flow Visualization},
	year = {2006},
	author = {Karsten Roetmann and Christoph S. Garbe and Waldemar Schmunk and Volker Beushausen}
}
@conference {roetmann2005,
	title = {2D-Molecular Tagging Velocimetry zur Analyse Mikrofluidischer Str{\"o}mungen},
	booktitle = {Tagungsband Lasermethoden in der Str{\"o}mungsmesstechnik (GALA)},
	year = {2005},
	pages = {26/1--26/10},
	author = {Karsten Roetmann and Christoph S. Garbe and Volker Beushausen}
}
