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Welcome to this month's newsletter! In this issue you'll find:

• An article by Andrew Rooney on Tanks and Pipes
• Details on free downloads added to the website this month
• Some Hints and Tips on using SIMUL8
• Share your modeling success at this year's Winter Simulation Conference
  

Tanks and Pipes by Andrew Rooney

This Newsletter is the first in a series of 3, covering some new features of Tanks and Pipes. This Newsletter covers the basics of the new features and the next 2 will move on to cover their control through Visual Logic

SIMUL8's Tanks and Pipes are a neat and powerful tool. They are a powerful and flexible solution to the simulation of most types of fluid or fluid-like processes and have been used to simulate scenarios ranging from candy production to oil exploration.

Most modeling with Tanks and Pipes involves Stocks and Flows - where a volume flows into a tank and if the outflow rate is less than the inflow then a volume builds up in the tank. This is easy in SIMUL8 as you can simply set the Tank capacities and Pipe flow rates and let SIMUL8 handle everything else.

Real world modeling can get a lot more complex than this as you can have variable feed rates from the fluid source, pipes can block at random, pipes can be subdivided into sections with pumping nodes connecting the sections, and full or partial blockages due to pumping failures.

Tanks and Pipe basics.

OK, so how do Tanks and Pipes work? SIMUL8 pushes fluid along pipes at the maximum flow rate allowed by the pipes. When the fluid reaches a junction point, when a Tank has 2 or more pipes leading from it, then SIMUL8 pushes the fluid along the pipe that was connected first - just like the Priority Routing Out rule in a work center, and pushes any excess fluid along the remaining pipes. If the capacity all of the pipes is not enough to cope with the volume then the volume in the tank will build up.

Download An Example

Any imbalance between the Inflow and Outflow from a Tank will result in a build up of fluid in the Tank. But what if there is no capacity in the tank or the junction point is not a tank but a valve, manifold or some other device, and you are only using the Tank so that you can split up the flow? You could set the capacity of the Tank to a very small value, but this is not the best way as it can slow down the run speed - and anyway it simply looks wrong.

SIMUL8's developers have developed a feature called Auto Adjust Inflow Rate. This feature stops a Tank building up any stock and instead passes the effect of a blockage back through the tank and automatically adjusts the effective flow into the Tank to be the same as the flow out. What this means is that you can connect together a network of Tanks and pipes to simulate a pipe network with splits and joins. There will be no fluid build up in an Auto Adjust Inflow Rate tank, so it acts just like a "node" or connecting point.

So how do I know how much is actually going through the pipe?

What this means is that the Flow Rate through a Pipe can be constrained by something going on downstream. So the pipe has 2 properties to describe the volume of fluid at any time - the Flow Rate, which is the maximum volume of fluid that could pass through the pipe in any time period and the Constrained Rate which is the actual volume passing through the Pipe. You can read the Constrained Rate through Visual Logic or monitor it by using the Watch Window.

Download An Example

If you have any questions on this topic please email support@SIMUL8.com, we're here to help!

Free Downloads

Our website is always being updated with new support resources. Here are details on some of the downloads that were added this month.

New Learning Zone Model
Schedule of Product Types. Use Batch by Type to setup a Work Center to process different product types depending on the time of day.
Download the Example

Hints and Tips

Find a Screen Location
If you're using Display+ it can take a lot of trial and error to find the exact location on screen where you want to place your image. QuickView (F11) tells you the location of an object on screen, so drop or move an object to where you want the image to be placed and check QuickView for the coordinates.

Passive Routing In
If you have a Work Center directly feeding another Work Center then you'll probably want to set the Routing In of the second Work Center to Passive. Otherwise if your second Work Center is ready to accept work it will pull the Work Item from the feeding Work Center regardless of whether the feeding Work Center has finished processing the Work Item.

Share your Modeling Success at this Year's Winter Simulation Conference

This year the Winter Simulation Conference will have a new Simulation Case Study Track. It's a presentation only track (no Proceedings papers) whose focus is on simulation applications. If you have developed a successful solution to process improvement using simulation and would like to share your experience with the simulation community visit the Winter Simulation Conference website. You must submit your story by October 11, 2004.

If you have any questions generated from, or comments about this newsletter then email Newsletter@SIMUL8.com