Introduction to the Flow Model  

Many biological and environmental systems involve the flow of fluid from one receptacle to another. A reservoir is filled by rainfall or the opening of a dam, and it is emptied by a spillway into a river. A patient in a hospital is hooked up to an IV which needs to be set to an appropriate drip rate. An antibiotic taken three times a day is designed to release a certain amount of medication into the bloodstream over an 8 hour period. Each of these systems may be modeled by a burette with variable inflow and outflow settings. MVHS offers two activities for the investigation of fluid flowing from one place to another.

In the first activity, the students build a computer model in a systems programming language. By allowing students to practice making and testing hypotheses about liquid flowing through a simple burette, it provides an excellent introduction to the scientific method. The collection and analysis of real-time data provides students with the opportunity to use their graphing and algebra skills in a real problem-solving situation. Sample data may be found in this article.

The second activity is a web-based simulation derived from the systems model. Here the burette apparatus is set up to allow for a constant rate of water to flow into the burette. This would be similar to the constant drip rate for an IV or a steady rainfall adding water to a pond at a constant rate. However, the outflow rate for the burette is not constant. The outflow rate is related to the height of water still in the burette. The more water left in the burette, the faster the water flows out. By manipulating the inflow and outflow rates, the student is able to investigate when a state of equilibrium is reached.

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