2014 Preview – 1D analyses

by Nate Hekman on July 4, 2013

Let’s take a look at one of the new features of the GeoStudio 2014 Preview: performing a true 1D analysis.

In the past you could imitate a 1D analysis by simply defining a single column of regions and making sure to apply boundary conditions that only vary vertically (for a horizontal column). In fact we demonstrate that technique in an example file.

A 1D analysis in the 2014 Preview is truly a single dimension, which has a few important implications.

Dimensionality is Per-Analysis

It’s important to understand that the “dimensionality” is a per-analysis setting, set in KeyIn Analyses: in the same .gsz file, one analysis can be 1D while another is 2D. Furthermore, geometry (regions, lines and points) is always shared by all analyses in a .gsz file. It follows then that the geometry in a 1D analysis is a subset of that in a 2D analysis.

For example, run the 2014 Preview and open Convective Surface on Semi Infinite Domain. Go into KeyIn Analyses and select the first analysis, “small time steps”. Notice it is set to “2D”; note the boundary condition on the ground surface, and the material colour over the entire region.

2d-analysis

Now move down to the second analysis, “using a 1D analysis”. The Analysis Dimension settings changes to 1D, the boundary condition is now applied to the point at the ground surface, the line has a material colour, and the region is greyed out.

1d-analysis

The important point is that a 1D analysis is a simplification of a 2D analysis, just as a 2D analysis is a simplification of reality.

Good modeling practice is to start simple and add complexity as you gain understanding. In many cases that may mean starting with a 1D analysis and progressing to 2D only when (or if) you need to.

Materials and Boundary Conditions

As we noticed, in a 1D analysis, materials are applied to lines instead of regions. That’s reflected in the Draw Materials command:

1d-draw-materials

Boundary conditions work similarly: they can be applied only to lines or points, not to regions in a 1D analysis.

Unit flux (“q”) boundary conditions are worth highlighting: most unit flux boundary conditions have a new optional “surface perimeter” field. If you leave that option off, then they will function as they always have in GeoStudio 2012 and older. In a 2D analysis, a “q” BC can be applied to a line or a region; in a 1D analysis, it can be applied to a point or a line. I’ll try to expand on that in a future blog post about the “surface perimeter”.

Results

The best way to look at results of a 1D analysis is using Draw Graph to look at results over time or along a line:

1d-draw-graph

or use View Result Information to see results at a specific node:

1d-view-result-information

Caveats

Some things to keep in mind when working with 1D analyses:

  • At the project level (in Set Units and Scale), the “View” must be set to “2-Dimensional” if you want to do a 1D analysis. Although that sounds counter-intuitive at first, bear in mind the “View” is setting the dimensionality of the entire project’s geometry. It doesn’t make sense to have a “1-dimensional axisymmetric” analysis.
  • Only TEMP/W does 1D analysis for now. Other products will follow in future previews, but for now you can’t do SEEP/W – TEMP/W convective 1D, for example, though I believe a 1D TEMP/W analysis should be able to get its initial conditions from a 2D VADOSE/W analysis if you really wanted to, or vice versa.
  • In this early Preview we have not yet implemented Draw Vectors, Draw Contours, or selecting gauss regions in View Result Information for 1D analyses, but those should be coming later.

 Your Voice

Remember the point of this Preview is to let you try it out and to hear your feedback. You can comment on this blog, or email support [at] geo-slope [dot] com. We are actively working on these features, so your ideas will be discussed right away and will influence the next release.

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