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3D vs Quasi 3D

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  • ashley.phillips75
    Can anyone explain to me the difference between a 3D modflow model and a quasi-3D modflow model? Thanks, Ashley
    Message 1 of 4 , Mar 5, 2009
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      Can anyone explain to me the difference between a 3D modflow model and a quasi-3D modflow model?

      Thanks,
      Ashley
    • Richard B. Winston
      In a quasi-3D model, the confining units are not represented by model layers. Instead, the vertical conductance between the aquifers is set to a low value to
      Message 2 of 4 , Mar 5, 2009
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        In a quasi-3D model, the confining units are not represented by model
        layers. Instead, the vertical conductance between the aquifers is set
        to a low value to simulate the resistance to flow due to the confining
        units.

        ashley.phillips75 wrote:
        >
        > Can anyone explain to me the difference between a 3D modflow model and
        > a quasi-3D modflow model?
        >
        > Thanks,
        > Ashley
        >
        >
      • Kick Hemker
        Quasi-2D models and quasi-3D models are properly defined to classify analytical solutions for groundwater flow in layered aquifer systems. Modflow borrowed the
        Message 3 of 4 , Mar 6, 2009
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          Quasi-2D models and quasi-3D models are properly defined to classify
          analytical solutions for groundwater flow in layered aquifer systems.
          Modflow borrowed the term 'quasi-3D model', but it is used somewhat
          differently.

          And somewhat confusing, in my view. Let me give an example:
          When you make a fully 3-dimensional numerical model, for example when you
          simulate the flow to a partially penetrating well in an aquifer that is
          represented by many model layers, then Modflow terminology tells that this
          is a quasi-3D model when the confining layer is represented by a low
          conductance. So a model can be fully 3D, and a quasi-3D Modflow model at
          the same time.

          Kick Hemker


          Richard B. Winston wrote:
          >In a quasi-3D model, the confining units are not represented by model
          >layers. Instead, the vertical conductance between the aquifers is set
          >to a low value to simulate the resistance to flow due to the confining
          >units.
          >
          >ashley.phillips75 wrote:
          >>
          >> Can anyone explain to me the difference between a 3D modflow model and
          >> a quasi-3D modflow model?
          ==========================
          C.J. (Kick) Hemker
          Elandsgracht 83
          1016 TR Amsterdam
          The Netherlands
          tel: +31 20 6228 711
          fax: +31 20 6234 628
          mail: hemker@...
          http://www.microfem.com
          ==========================
        • Schreiber, Robert
          Ashley: Quasi-3D usually means that the model represents leaky, confining layers with purely vertical (1D) flow connections between the aquifer layers
          Message 4 of 4 , Mar 6, 2009
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            Ashley:

            Quasi-3D usually means that the model represents leaky, confining layers
            with purely vertical (1D) flow connections between the aquifer layers
            surrounding each confining unit. The equations govening the simulated
            flow rely upon specfication or computation of "leakance" (equal to
            vertical hydraulic conductivity of the confining unit divided by the
            vertical thickness of the unit), area-of-flow (i.e., the plan-view area
            of the grid cell), and the difference in head vertically between the
            aquifer units above and below the confining unit.

            Fully-3D means that each confining layer is represented in exactly the
            same way as each aquifer layer. The porous media being simulated are
            continuously discretized and represented by the standard governing
            equations, written in 3D form.

            Hope this helps.

            Bob Schreiber

            Robert P. Schreiber, P.E., BCEE, D.WRE
            VP & Groundwater Subdiscipline Leader

            CDM
            One Cambridge Place
            50 Hampshire Street
            Cambridge, MA 02139 USA
            email:schreiberrp@...
            Phone and Fax: (617) 452-6251
            Cell: (617) 512-6819
            Alternate email: schreiberrp@...

            ________________________________

            From: gwmodel@yahoogroups.com [mailto:gwmodel@yahoogroups.com] On Behalf
            Of ashley.phillips75
            Sent: Thursday, March 05, 2009 1:39 PM
            To: gwmodel@yahoogroups.com
            Subject: [gwmodel] 3D vs Quasi 3D



            Can anyone explain to me the difference between a 3D modflow model and a
            quasi-3D modflow model?

            Thanks,
            Ashley
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