This Procurement Decision Tool is designed to help Supply Chain professionals simulate the impact of common procurement variables on service, cost and working capital:

This model fills a bathtub, while outflow occurs at a flow determined by the volume of water (or pressure at outlet) of the bathtub. It could just as well be a dam or lake that is modeled.

The following example provides students with step by step ​guidance on drawing a simple systems model.

A new double-lane roundabout has some issues with an offramp being very close to the exits from one side of the roundabout.
There have been some safety concerns so I thought I'd look at the system to determine what the problems might be, if any, and to see if there are some viable solutions if some issues are brought to light.

This stock-flow simulation model is to show Covid-19 virus spread rate, sources of spreading and safety measures followed by all the countries affected around the world.