Simulation and Modeling: An Introduction to Building and Using Models and Simulations, Exams of Turbomachinery

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Introduction To Introduction To

Simulation and Simulation and

Modeling Modeling

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Goals Of This Course

Introduce Modeling

Introduce Simulation

Develop an Appreciation for the Need for

Simulation

Develop Facility in Simulation Model

Building

Types of Models:

Physical (Scale models, prototype plants,…) Mathematical (Analytical queueing models, linear programs, simulation)

What is Simulation?

 A Simulation of a system is the operation of a

model, which is a representation of that system.

 The model is amenable to manipulation which

would be impossible, too expensive, or too

impractical to perform on the system which it

portrays.

 The operation of the model can be studied, and,

from this, properties concerning the behavior of

the actual system can be inferred.

Applications:(continued)

Designing and operating transportation

facilities such as freeways, airports,

subways, or ports

Evaluating designs for service organizations

such as hospitals, post offices, or fast-food

restaurants

Analyzing financial or economic systems

Steps In Simulation and

Model Building

1. Define an achievable goal

2. Put together a complete mix of skills on the

team

3. Involve the end-user

4. Choose the appropriate simulation tools

5. Model the appropriate level(s) of detail

6. Start early to collect the necessary input

data

Define An Achievable Goal

“To model the…” is NOT a goal! “To model the…in order to select/determine feasibility/…is a goal. Goal selection is not cast in concrete Goals change with increasing insight

Put together a complete

mix of skills on the team

We Need:

-Knowledge of the system under investigation

-System analyst skills (model formulation)

-Model building skills (model Programming)

-Data collection skills

-Statistical skills (input data representation)

INVOLVE THE END USER

-Modeling is a selling job!

-Does anyone believe the results?

-Will anyone put the results into action?

-The End-user (your customer) can (and must)

do all of the above BUT, first he must be

convinced!

-He must believe it is HIS Model!

Choose The Appropriate

Simulation Tools

Assuming Simulation is the appropriate

means, three alternatives exist:

1. Build Model in a General Purpose

Language

2. Build Model in a General Simulation

Language

3. Use a Special Purpose Simulation

Package

GEN. PURPOSE LANGUAGES

USED FOR SIMULATION

FORTRAN

• (^) Probably more models than any other language.

PASCAL

• (^) Not as universal as FORTRAN

MODULA

• (^) Many improvements over PASCAL

ADA

• (^) Department of Defense attempt at standardization

C, C++

• (^) Object-oriented programming language

MODELING W/ GENERAL

SIMULATION LANGUAGES

 Advantages:

• (^) Standardized features often needed in modeling
• (^) Shorter development cycle for each model
• (^) Much assistance in model verification
• (^) Very readable code

 Disadvantages:

• (^) Higher software cost (up-front)
• (^) Additional training required
• (^) Limited portability

GEN. PURPOSE SIMULATION

LANGUAGES (continued)

 MODSIM III

• (^) Modern Object-Oriented Language
• (^) Modularity Compiled Programs
• (^) Based on Modula2 (but compiles into C)
• (^) World-view: Processes

 SIMULA

• (^) ALGOL-based Problem Description Language
• (^) Compiled Programs
• (^) World-view: Processes

GEN. PURPOSE SIMULATION

LANGUAGES (continued)

 SLAM

• (^) Block-structured Language
• (^) Interpretive Execution
• (^) FORTRAN-based (and extended)
• (^) World-view: Network / event / continuous

 CSIM

• (^) process-oriented language
• (^) C-based (C++ based)
• (^) World-view: Processes