Meshing Efficiently

by Nate on November 19, 2008

GeoStudio 2007 tries to let you focus on the definition of the geometry, boundary conditions and material properties, without being distracted by the mesh. If you want, you can define your model, solve it, and view the results without once looking at the mesh.

But the reality is if you’re doing a finite-element analysis, the mesh can’t be ignored forever.

Start Simple

We always encourage you to start your model simply, and add complexity.  The same can be said for meshing.  Start with the default mesh, look at your results, and then decide if you need to use a finer mesh in certain areas (or everywhere).

Set the Global Element Size

If you want a finer mesh, the place to start is to use Draw Mesh Properties to change the “Approx. Global Element Size”.  This will change the entire mesh.

You’re setting the preferred length of each element edge.  So a smaller number will make for a finer mesh, and a larger number gives a coarser mesh.

Remember this size is “approximate”.  The mesher will do the best it can to stay close to the size you specified, but it won’t be exact.

Constrain the Mesh

Often you’ll find there are certain areas of your geometry that have more “activity”.  These areas may benefit by having a finer mesh.  You’ll get more exacting results at the expense of a longer solve time.

To get a finer (or coarser) mesh in specific areas, you select a region, line or point in that area, and change the Element Edge Length for the object you selected.  (You can also multi-select to adjust several objects simultaneously.) 

This is called “constraining the mesh”, because you’re giving the mesher specific instructions about this part of the mesh.

When adding a constraint, you are again specifying the preferred (or approximate) length of every element edge in this area.  But there are several ways to specify it:

  1. Using a ratio of the global length.
  2. Specifying the approximate length.
  3. Specifying the exact number of divisions (this option is only avialable on lines).

Normally #1 is the better approach, just defining it as a ratio, like “0.5″ to make the mesh in this area half the size as the rest of the mesh.  That way you can later adjust the Global Element Size to make the entire mesh finer, and this area becomes finer yet.

Here’s an Example

Draw a simple geometry.  Choose Draw Mesh Properties to look at the mesh.

Make a finer mesh everywhere by adjusting the global element size.

Make the left side finer still, using a ratio.

Make the entire mesh finer by adjusting the global element size again.  Notice that elements along the left side are still half the size of the rest of the mesh.

Conclusions

Meshing is half science and half black art.  Making a finer mesh does NOT always give you a better result.  Discussing the ins and outs of how to mesh properly is beyond the scope of this article.  Read the engineering books that came with your software for a better treatment of this subject.

But adjusting and fine-tuning the mesh in GeoStudio 2007–or ignoring it completely–is easier than it has been in any previous version.

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Copying and Pasting Regions

by Nate on November 10, 2008

While you can’t copy regions from one .gsz file to another, you can do better than just re-creating them all by hand.

To start out, run two copies of GeoStudio side-by-side, one with the source file and one with the destination file.

Copy the Points

Choose the KeyIn Points command in both GeoStudio windows.

  1. In the source file, select every point in the list;
  2. copy them to the clipboard.
  3. In the destination file, paste the points into the list.

When pasting the points, you may get this error:

You can safely hit OK and forget about it. The problem is just that when you copied the points to the clipboard, you included the last one in the list, which is just a placeholder and has “—” as the X and Y values. When you try to paste those values GeoStudio complains that they aren’t numbers. You can avoid the error in the future by selecting all but the last point.

Both files now have the same points. All that’s left is to hook them up together into regions.

Copy the Regions

Unfortunately you can’t copy and paste the entire list of regions like we did with points. Instead you have to do them one region at a time.

For each region in the source list:

  1. Select the region;
  2. Select and Copy the “Region Points” text;
  3. In the destination, click the Add button;
  4. Paste the points into the Region Points control.

For simple regions you may find it easier to just redraw them. At least all the points exist already at the same coordinates. But for complex region this tip will save you some time and avoid errors.

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Ordering Analyses

by Nate on October 27, 2008

Here is a quick tip to put you on friendly terms with KeyIn Analyses:

When you create analyses in KeyIn Analyses, they are always listed in alphabetical order. If you really want them to be displayed in a different order, just put a number at the beginning of each analysis name, and they’ll get sorted by that number.

Take this case, for example. We develop three analyses as an experiment, with increasing complexity:

  • Dry Frictional Material with No Cohesion
  • Wet Frictional Material with No Cohesion
  • Wet Frictional Material with Cohesion

But GeoStudio displays them in alphabetical order, resulting in this:

To get the analyses displayed in a more logical order, simply rename them, like this:

P.S. Our own examples online do this all the time, but are not really good examples to follow IMO. Our engineers tend to go crazy and use numbering even when it isn’t necessary.

In my experience, most of the time the default alphabetical and parent/child ordering is fine.

While there’s nothing wrong with something like the following example, the numbering is unnecessary, because the parent-analysis / child-analysis structure will keep the analyses in sequential order anyway:

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Long Analysis Names

by Nate on October 20, 2008

Mike recently emailed me from Australia trying to understand why a long analysis name would cause a “Path too long” error when running Verify.

Background - Path Length

Windows imposes a maximum number of characters allowed for any path, including the drive letter, the directories, and the file name. In XP I believe the limit is 260 characters.

In this example (and in Mike’s case) his file name was within the 260 character limit that Windows imposes on paths.

The problem is a bit hidden, and has to do with how GeoStudio handles .gsz files.

A Gsz is a Zip File

I’ve mentioned before that a .gsz file is really just a Zip file that can be opened with WinZip or any other Zip reader.

When GeoStudio opens a .gsz file, it unzips any internal files it needs into your TEMP directory. In Windows 2000, Windows 98, and older versions, the TEMP directory is normally C:\TEMP. But in XP (and Vista) each user on a computer gets their own TEMP directory for privacy reasons, so the path is something like:

C:\Documents and Settings\YourUsername\Local Settings\Temp\

That’s a pretty long path to start out with. Maybe you can see where this is headed.

After that TEMP path, GeoStudio adds a unique folder name that is derived from the name of the .gsz, so now we’re up to something like:

C:\Documents and Settings\YourUsername\Local Settings\Temp\gs_Your Gsz File Name_89284fa64a8df8a7cf04a40a75c2b96c\

That’s the root folder the .gsz gets unzipped into. Nasty. But that’s not all, oh no, that is not all!

Inside that folder you get another folder named after each analysis. Now we’re at:

C:\Documents and Settings\YourUsername\Local Settings\Temp\gs_Your Gsz File Name_89284fa64a8df8a7cf04a40a75c2b96c\Your Descriptive Analysis Name\

Inside that analysis folder you get one folder for each time step:

C:\Documents and Settings\YourUsername\Local Settings\Temp\gs_Your Gsz File Name_89284fa64a8df8a7cf04a40a75c2b96c\Your Descriptive Analysis Name\001\

And for the coup de grâce, in SLOPE/W we then fnish the path off with the name of the analysis again (in the flow products we use shorter names like “nodes.csv”):

C:\Documents and Settings\YourUsername\Local Settings\Temp\gs_Your Gsz File Name_89284fa64a8df8a7cf04a40a75c2b96c\Your Descriptive Analysis Name\001\Your Descriptive Analysis Name.frc01

You can see that even if you keep your filename and analysis names below the 260 character limit, you may still end up going over the limit inadvertantly. With SLOPE/W especially, keeping your analysis names shorter makes a big difference since they are used twice.

Verify

The good news is that in the latest versions, Verify catches the problem. In earlier versions it wasn’t so friendly. I don’t remember if it would crash, give strange results, or if the solver would just give an unhelpful error message.

If you get the “Path too long” error in Verify, just shorten your analysis name and/or the name of your .gsz file.

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When to Use GeoStudio Betas

by Nate on October 14, 2008

Wow, I have not been very good at updating this blog this fall!  Work has been very busy here lately and I just haven’t been able to find the time to write.

Betas

Two weeks ago I talked about how we let people know about updates to GeoStudio being released, and why there’s usually a delay between a release and when GeoStudio’s Start Page tells you about it.  I ended the article by mentioning that we now post betas weeks or even months before a release.

You can always find the latest beta on the Beta Downloads page.

Betas have turned out to be a great way to get small changes out quickly.  Normally when we become aware of an important bug, we can fix it the same day or at least within the week.  But we don’t want to post a new release every week–you’d probably be annoyed having to download a 70 MB file that often!

Instead we post a new beta, and email the person who reported the bug.  Anyone else over the next weeks who reports the same bug can be pointed to the beta as well and be quickly up and running again.

It is beta software though!

A word of caution:  a beta has not been fully tested, and could contain new bugs worse than what we fixed.

As a result, we don’t recommend everyone run the beta.  But if you encounter a bug with no easy workaround that has been fixed in the beta, using the beta can be better than waiting for the next release.

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Automatic Updates

by Nate on September 30, 2008

With version 7.13 just released last week, I’d like to describe how the automatic update notification works.

The Simple Story

The theory is simple.  Every time you run GeoStudio, it checks our web site to see if there’s a newer release.  If it finds one, it displays a message on the Start Page.

If you have version 7.10 or higher you get a message like this:

If you have an older version you get something like this instead:

In either case, simply click the link and you’ll get taken to a page where you can download the new version. Download it, run it, and it updates your current installation to the latest.

Exceptions to the Rule

7.13 was released last Wednesday.  But some of you are likely thinking, “hey, I ran GeoStudio last Friday and it didn’t say anything about a new version!”

In fact the very astute among you may even have noticed that you’ve been running version 7.11 for the last four months without getting any update notification, even though version 7.12 has been available on our web site since July.

What’s going on here?!

What’s going on is that we intentionally delay alerting people through the Start Page.  And in a few exceptional cases we may choose never to publish the alert at all.

The Overseas Bug

We almost always wait about a week from when a new version is released before publishing the notification that GeoStudio displays.  I think that practice dates back to version 6.18–did any of you experience 6.18?

We do some pretty rigorous testing in-house before every release, but we had some very embarassing days in March 2006 when we released version 6.18: we introduced a bug in 6.18 that only happened to people in Europe.  It passed all our tests, but within hours after we released it (and in those days we published the update notice immediately) our phone started ringing off the hook from irate Europeans.  And rightly so!  GeoStudio would corrupt any data file saved on a system where the comma was used as the decimal character.  Once you saved, you could never open the file again.

We found and fixed the problem quickly and posted a new update (and we could manually fix any corrupted files customers emailed us), but those were not happy days in our office.

Real-Life Testing

We do two things differently now:

  1. We post betas before publishing a new release.  A handful of people from all over the world use the betas on real-life problems, so there’s more chance to find unusual bugs that our normal testing doesn’t reveal.
  2. We trickle out new releases.  We don’t want everyone to download a new release the moment it’s out.  We let a few people download it, a few others get it on CD, and if we don’t hear any negative feedback within the first few days, then we’ll let the rest of our users know.

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Banff Workshop

by Nate on September 25, 2008

We just wrapped up our Banff workshop, with about the best weather imaginable for a mountain autumn. Chilly mornings but gorgeous sun and highs in the 20s (Celsius) all week.  

It was great to see some of you there.  Believe it or not, I always learn a tonne from talking with you and watching how you work.  I walk away from workshops feeling invigorated and excited about the potential the future holds.

There are often some embarrassing moments.  Like when View Slice Information crashed within the first hour or two of the workshop, on the presenter’s computer as well as many of the attendees’.  We’ve been fighting that crash for months and thought we had it licked, but apparently not.  

There’s a happy ending to that story, however.  As a result of watching it happen to a whole roomful of people, by the end of the next day I was able to find the bad line of code and finally fix it.  I think for real this time!  The next release (7.13–which we just released yesterday) includes this fix as well as a host of other improvements.

This was our first time to offer an optional fourth day.  The dynamics of that last day were much different than the first three.  The smaller group and more casual sessions allowed us to have more informal discussions and get to know each others’ backgrounds a bit more.

I’m definitely looking forward to next year’s workshop.

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Blogiversary

by Nate on September 19, 2008

Grokking GeoStudio was launched a year ago today.  I’d like to take a few moments to reminisce about the past year, and think ahead toward the coming one.

Last Year

This whole blogging thing was an experiment from the beginning.  I had a couple of goals:

  1. Provide help for GeoStudio users to learn how to use the software, with a different focus than the manuals and online help.
  2. Get a better feel personally for how our software is being used “in the real world” through feedback from readers.
  3. Be a friendly personal face to GEO-SLOPE.

I tried to blog weekly, and although I wasn’t that regular, I did (coincidentally?!) end up writing 52 posts over the year!

Did I meet my goals?

  1. Much of what I wrote about is not discussed in the online help or the engineering books, or is mentioned but is hard to find.  With the recent changes to the blog categories and layout, I hope that those 52 gems will be easier for newcomers to find, so the blog can be used as a bit of a reference tool.
  2. I receive several emails or comments a month, and from those I do get a small feel for how the software is being used.  A big thank you to everyone who felt the freedom to write!  This is an area I’d like to improve on next year–I would love to see more feedback, especially comments left on the blog, and even to have readers responding to other reader’s comments.
  3. I’ll leave #3 to you to decide!

Some interesting statistics (at least to me!):

  • 52 posts;
  • 12 comments from readers, and a similar number of emails (all of which I respond to);
  • Around 48 regular readers, and growing slowy, 37 of whom subscribe by email, the rest using RSS readers;  The biggest jumps in subscribers come when the blog gets mentioned in a Direct Contact newsletter, especially when it’s the main article.
  • The web site has been visited from 90 countries, but only gets about ten visits a day.

The most popular articles were:

  1. Global vs Analysis Objects
  2. Prettying Up Graphs

Next Year

Before starting to blog I wrote up a list of topics I wanted to write on, just to make sure there was enough to keep me going.  I’m mostly through that list now, but from the comments, from tech support we do, and from discussions at the Banff Workshop that just finished, I feel I have plenty more to keep this blog going another year.

To spice things up a bit, though, I’d like to have more guest bloggers this year.  It would be nice to hear some tricks from people who use the software regularly.  Do any of you have something you’d be willing to share on this blog?  Email me privately (hekman at geo-slope dot com) to discuss.

I’d also like to stretch my limits a bit and write about a few more engineering-related topics, like the Multi-Stage Rapid Drawdown article.  Those are harder for me to write, I normally have to sit down for a lesson with one of our engineers, but they are useful things for me to know and they are obviously topics you are wanting addressed.  If you have topic suggestions, please let me know by leaving a comment.

But mostly I intend this year to focus where my strengths lie, which is the user interface.  I’m going to take a look at DXF issues, dig deeper into functions and graphs, take a stab at plug-ins, and as much as possible help you to get past the software and focus on your modeling.

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New Look to the Blog

by Nate on September 12, 2008

In an attempt to make this blog be more useful, I’ve updated the layout, hoping to make it easier to find what you need.

One change in particular I’d like to point out:

  • The Categories have been rearranged, around commands, objects or concepts in the software.  That should help you if you don’t follow the blog regularly, or you only ran across it recently.  If you’re struggling to understand functions you can click on the Functions category and immediately see everything I’ve written about functions.

Summer is definitely over here in Calgary, with temperatures dipping and leaves changing colour.  When our workshop is over next week I will be getting back into serious blogging mode again and try to bring you a new tip every week.

As always, if you have comments, suggestions or questions, please leave a comment or email me.

Nate

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summer holidays

by Nate on August 26, 2008

Gentle Readers,

I hope your summers have been going well (or your winter–do I have any readers from the southern hemisphere?).  This summer we’ve enjoyed beautiful weather here in Calgary, which has allowed me to rack up 800 km on my bike commuting to work.  Woohoo!

I’m going to take a short blogging break.  Grokking GeoStudio will be on holidays for the next couple of weeks, but I’ll be back in time to celebrate Grokking’s first anniversary, September 19th!

Will any of you be attending our annual workshop in Banff this year?  September 15-18.  Look me up, I’d love to chat with you face to face.  If you haven’t signed up yet you’ll have to wait for next year–the workshop is full and the waiting list already a mile long.

Enjoy the rest of your summer, and look for me again in September.

Nate

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