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@PHDTHESIS{Englert:32565,
      author       = {Englert, Andreas},
      title        = {{M}easurement, {E}stimation and {M}odelling of
                      {G}roundwater {F}low {V}elocity at {K}rauthausen {T}est
                      {S}ite},
      volume       = {4084},
      issn         = {0944-2952},
      school       = {Techn. Hochsch. Aachen},
      type         = {Dr. (FH)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-32565, Juel-4084},
      series       = {Berichte des Forschungszentrums Jülich},
      pages        = {XVIII, 89 p.},
      year         = {2003},
      note         = {Record converted from VDB: 12.11.2012; Aachen, Techn.
                      Hochsch., Diss., 2003},
      abstract     = {To enable precise understanding and prediction of transport
                      in porous media, physical, chemical and biological processes
                      and the interaction between these processes have to be
                      considered. This is an interdisciplinary problem. In the
                      scope of this work the focus is on the physically mmpelling
                      force of the transport, the groundwater flow velocity. A
                      groundwater flow velocimeter (Fig. 1), using the point
                      dilution technique, has been developed to measure in situ
                      the groundwater flow velocity. The resolution of the
                      groundwater flow velocimeter in the vertical direction is 25
                      cm. The in situ dilution measurement of the tracer uranin is
                      carried out by laser-induced fluorimetry. The calibration of
                      the groundwater flow velocimeter and subsequent field
                      experiments at Krauthausen test site showed that the
                      groundwater flow velocity inside a borehole can be measured
                      with sufficient accuracy. The accuracy in deriving the Darcy
                      velocity from the measurements inside a borehole is strongly
                      dependent on the accuracy in determining the
                      $\alpha$-factor, which corrects for the convergence of
                      streamlines towards the borehole. The estimation of the
                      $\alpha$-factor is difficult due to a general lack of
                      knowledge of the state of the well. Measurements with the
                      groundwater velocimeter showed that, the local Darcy
                      velocity is strongly space and time dependent. For the
                      strongly anisotropic structure of the hydraulic conductivity
                      at the Krauthausen test site, statistics for a three
                      dimensional heterogeneous flow velocity field have been
                      estimated using stochastic theories and Monte Carlo analysis
                      which is based on numerical calculations. It is shown that
                      correlograms in the mean flow direction, estimated by 1st
                      order approximation, are in agreement with the results from
                      the Monte Carlo analysis. The variances for the Darcy
                      velocity components, estimated by 1st order approximation,
                      are clearly below the results of the Monte Carlo estimation.
                      Estimation of the variance, based on 2nd order
                      approximation, showed accordance only for the longitudinal
                      component of the Darcy velocity, whereas the vertical
                      transversal component is below and the horizontal
                      transversal component is above the results from Monte Carlo
                      analysis. The estimated mean Darcy velocity is similar for
                      1st and 2nd order approximation as well as for the Monte
                      Carlo analysis. Estimation of the Darcy velocity statistics,
                      both from numerical modelling and from stochastic theories,
                      show smaller mean by factor 2, smaller variances by factor 4
                      and longer correlation length in the horizontal direction by
                      factor 7 than the directly measured Darcy velocity using the
                      groundwater flow velocimeter. The high discrepancies in
                      mean, variance and horizontal autocorrelation length are due
                      to the limited knowledge of the $\alpha$-factor and the time
                      variability of the Darcy velocities. A comparison shows that
                      the relative standard deviation is similar for modelling,
                      2nd order approximation and direct measurements with the
                      groundwater flow velocimeter.},
      cin          = {ICG-IV},
      cid          = {I:(DE-Juel1)VDB50},
      pnm          = {Chemie und Dynamik der Geo-Biosphäre},
      pid          = {G:(DE-Juel1)FUEK257},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/32565},
}