Basic Model Behavior with Stella. Learning Objectives: Start learning: 1) how to use Stell a II software; 2) some basics of model construction; and fundamentals of Stocks and Flows. Open Stella II software and get into the odel !i ndow "see left tab). #uild each simple model described in this document "drag and drop icons and connect them together appropriatel$) and run each f or 2% da$s "&un menu select &un Specs to change the length of the run). 'he model is simulating the content "in acre(feet) of waterin a lake. 'he fl ows are in acre(ft per da$ . Set up a graph of and either inflow "or outflow) for each simulation. *o this b$ clicking and dragging the graph pad icon to an empt$ location on the model window. +e,t double click on the graph pad and s elect items for graphing. 'his - ou'u be ideo is a /uick guide to getting started. http:00www.$outube.com0watch-c$345t#67
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Learning Objectives: Start learning: 1) how to use Stella II software; 2) some basicsof model construction; and fundamentals of Stocks and Flows.
Open Stella II software and get into the odel !indow "see left tab).
#uild each simple model described in this document "drag and drop icons and connectthem together appropriatel$) and run each for 2% da$s "&un menu select &un Specs tochange the length of the run). 'he model is simulating the content "in acre(feet) of water
in a lake. 'he flows are in acre(ft per da$. Set up a graph of and either inflow "oroutflow) for each simulation. *o this b$ clicking and dragging the graph pad icon to anempt$ location on the model window. +e,t double click on the graph pad and selectitems for graphing.
'his -ou'ube ideo is a /uick guide to getting started. http:00www.$outube.com0watch-c$345t#67
&esae this document and modif$ it b$ including $our answers to all /uestions and pasting in graphs where appropriate. Submit this document when $ou are finished.
Linear Growth/decrease
Stella odel 1 'ank flow Stella odel 2 'ank flowC
inflow
"t) "t ( dt) 8 "inflow) 9 dtI+I' %
I+F3O!S:inflow
C
inflow
"t) "t ( dt) 8 "inflow) 9 dtI+I' %
I+F3O!S:inflow "note : the inflow was changedfrom uniflow to biflow. 'o do this doubleclick on the inflow when $ou are in themodel screen. )
Stella odel 'ank flow Stella odel < 'ank flowC
outflow
"t) "t ( dt) 8 "( outflow) 9 dtI+I' %
O='F3O!S:outflow
C
inflow"t) "t ( dt) 8 "inflow) 9 dtI+I' %
I+F3O!S:inflow - "note : the inflow waschanged from uniflow to biflow. 'o do thisdouble click on the inflow when $ou are inthe model screen. )
Question1: >ow does the behaior of model 2 compare to that of model 1
?ns1:
Insert a graph here of s time and inflow s time "both on same a,es) for model 2.@lease see the -ou'ube ideo regarding pasting from Stella into !ord. It discusses howto aoid huge electronic file si4es. http:00www.$outube.com0watch2c%,<#-dhfs
Question : >ow does the behaior of model compare to that of model <?ns2:
Question !: *ouble click on the icon for and check or uncheck the non(negatiecheck(bo,. &e(run the model for 2% da$s. ompare the output of model < when thenon(negatie check(bo, is checked to the output when the non(negatie check(bo, is +otchecked. !hat does the non(negatie check bo, do?ns:
@aste graphs of checked and unchecked below. &esi4e so the$ sit side b$ side.
hange the units of time to $ears. 'hereAs nothing reall$ that $ou hae to do e,ceptchange $our mental focus and double click on the graph to change the labelcorresponding to units.
hange the units of time to minutes. 'hereAs nothing reall$ that $ou hae to do e,ceptchange $our mental focus and double click on the graph to change the labelcorresponding to units. below stands for tank content.
'he reason for adding the initial content as a separate conerter here is that this can then be linked to a slider input in the interface window. 'his allows the model user to easil$change the input of a model.
#uild odel 5 and set up a graph of s time in the interface window. !hen setting upthe graph check the comparatie graph check bo,. ?dd slider inputs for both initialcontent and hole parameter.
ake < runs of the model and present a graph showing all of these runs.&un 1: Initial content 1%% ; hole parameter1%&un 2: Initial content 2%% ; hole parameter1%&un : Initial content 1%% ; hole parameter2%&un <: Initial content 2%% ; hole parameter2%
Euestion : as the hole parameter increases the tank becomes "more or less leak$) ?ns:
Insert a graph of s. time here for $our four 2% minute simulations.
hange the units of time to $ears. 'hereAs nothing reall$ that $ou hae to do e,ceptchange $our mental focus and double click on the graph to change the labelcorresponding to units. 'he stock population is the number of organisms of ah$pothetical population.