System Dynamics Simulation

1
System Dynamics Simulation

• Slobodan P. Simonovic

2
Introduction

• Water resources systems are too complex to be
  understood by intuition, compromise and
  superficial debate
• pollution
• energy shortages
• engineering unemployment
• No one person can be an expert in every field

3
Introduction

• So what are we to do?
• Mind are own business and ignore everything else?
• No way everything else invades our lives ( job
  loss .... )
• Anticipate
• Our choice or anothers depends on what is
  happening in the rest of our society.
• We do need to understand the world around us, but
  we cant possibly become experts in every
  subject.

4
Introduction

• Is there a way out of this trap ?
• Yes, and its called systems thinking.
• Still a new subject ( strange for people trained
  in the traditional way )
• most of what has been written about it has been
  very technical, and difficult.

5
Introduction

• I expect
• That you will learn to learn new subjects easier
  and apply basic principles/rules of how systems
  work to social, political, economic, ecological,
  and physical systems.
• You will learn how to make complex problems
  easier to understand, (solving problems that
  cross the boundaries between different
  disciplines ).
• You will get some suggestions about effective
  strategies for influencing the world around you,
  ( identification of high leverage points ).
• You will get some help in developing a
  comprehensive world view of your own.

6
What is a system approach?

• Science approach to learning take apart and find
  out what it is made of (division of science into
  specialties).
• to extreme known as reductionism.
• something is nothing but the sum of its parts.
• Example a comfy house is the same as a pile of
  building material.
• The main difference is organization (patterns)

7
What is a system approach?

• In 1920 research of patterns began (general
  systems theory).
• startling discovery no matter how different the
  ingredients of different systems looked, they
  were all put together according to the same
  general principles of organization.
• great impact development of computers (practical
  application of systems analysis - essential for
  the management of all business and institutions).
• two most important conditions
• systems theory provides a way of tackling big,
  messy, real-world problems.
• systems theory provides a way for average people
  to get a good, clear picture of how their
  environment works

8
System

• A system is a collection of parts which interact
  with each other to function as a whole
• Example cooling system in a car radiator, fan,
  water pump, thermostat, hoses and clamps.

9
System

• Systems can be part of a larger system
  (subsystems)
• particle
• atom
• molecule
• brain cell
• brain
• nervous system
• individual
• local community
• state
• nation
• world civilization
• world ecosystem
• planet earth
• solar system
• galaxy
• universe

10
System

• Why not just have larger and larger atoms instead
  of building molecules up?
• answer is stability
• maximum size of animals (whale - food)
• social organizations (5 can work as a team, 5000
  hardly)

11
System Dynamics

• System Dynamics
• A rigorous method of system description, which
  facilitates feedback analysis via a simulation
  model of the effects of alternative system
  structure and control policies on system behavior
• Management science MIT (Forester)

12
System Dynamics

• System Dynamics simulation approach relies on
  understanding complex inter-relationships
  existing between different elements within a
  system.
• This is achieved by developing a model that can
  simulate and quantify the behavior of the system.
  
• Simulation of the model over time is considered
  essential to understand the dynamics of the
  system.

13
System Dynamics

• Steps
• Understanding of the system and its boundaries
• Identification of the key variables
• Representation of the physical processes or
  variables through mathematical relationships
• Mapping the structure of the model and
• Simulating the model for understanding its
  behavior.

14
System Dynamics

• Well suited for representing mental models that
  have been developed using systems thinking
  paradigm.
• Build around a progression of structures.

15
System Dynamics

• A system is defined as a collection of elements
  which continually interact over time to form a
  unified whole.
• The underlying pattern of interactions between
  the elements of a system is called the structure
  of the system.
• The term dynamics refers to change over time.

16
System Dynamics Definitions

• A dynamic system is thus a system in which the
  variables interact to stimulate changes over
  time.
• System Dynamics is a methodology used to
  understand how systems change over time.
• The way in which the elements or variables
  composing a system vary over time is referred to
  as the behavior of the system.

17
System Dynamics Definitions

• A systems structure determines the systems
  behavior.
• System Dynamics links the behavior of a system to
  its underlying structure.
• System Dynamics can be used to analyze how the
  structure of a system can lead to the behavior
  which the system exhibits.