NetLogo User Community Models
by George W. Dombi (Submitted: 07/02/2007)
WHAT IS IT?
This model is like one in a series of GasLab models.It uses the same basic rules for simulating the behavior of gases. Each model integrates different features in order to highlight different aspects of gas behavior.
The basic principle of the models is that gas particles are assumed to have two elementary actions: they move and they collide - either with other particles or with any other objects such as walls.
This model is illustrates gas distillation, separating gases of different masses it also shows the relationship between temperature and pressure in a fixed volume gas container.
HOW IT WORKS
The particles are modeled as hard balls with no internal energy except that which is due to their motion. Collisions between particles are elastic. On the hot-side, molecules are heated and boil up into the condenser-side when they cool.
1. A particle moves in a straight line without changing its speed, unless it collides with another particle or bounces off the wall.
As the walls of the box are heated, the sides of the walls will change color from a deep red (cool) to a bright red, to pink to a pale pink white (hot). The walls contain a constant heat value throughout the simulation. If ONE-SIDE? is set to ON, only the left wall will be heated, while the other three walls remain yellow.
The exact way particles gain energy from the walls of the box is as follows:
This model also uses Gravity as a way to bring the gas molecules to the bottom of the
HOW TO USE IT
THINGS TO NOTICE
How does adding heat to the box walls affect the pressure?
How does adding heat to the wall affect the particle behavior?
How does the particle behavior or system response change with only one wall heated instead of all walls heated?
Does the system reach an equilibrium temperature faster when the wall is heated or cooled the same amount in comparison to the temperature of the particles?
How does gravity affect the rate of boiling?
THINGS TO TRY
Try to get the inside temperature to reach the outside temperature. Is this possible?
Try to increase the wall hits per particle.
EXTENDING THE MODEL
Give the wall a mass and see how that affects the behavior of the model.
Close off the right side of the box. Create two valves on either side to the wall that allow the user to "spurt" particles into the chambers to see how number of particles affects pressure.
Vary the width and length of the box, does this effect how fast the particle temperature changes?
Notice how the collisions are detected by the turtles and how the code guarantees the same two particles do not collide twice. What happens if we let the patches detect them?
Problems with this model: The gas does not return to the initial volume. The future goal of this work is to model a liquid being distilled. This has an additional challenge that water has internal cohesion between molecules which a gas does not.
CREDITS AND REFERENCES
This model was based on the NetLogo GasLab Heat Box model originally written by Wilensky, U. (2003). http://ccl.northwestern.edu/netlogo/models/GasLabHeatBox. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
Current version composed by George W. Dombi, 7/1/2007 with some coding help from James Steiner.
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