Modeling and Simulation in Engineering

1. Modeling and Simulationin Engineering Chris Paredis G.W. Woodruff School of Mechanical Engineering Georgia Institute of Technology

2. Lecture Overview • Objective: • Define what a model is • Illustrate why models are important in engineering • Topics: • What is a model? • What are some properties of models? • How does one create a new model? • How are models used in engineering?

3. What is a Model? • Examples of Models… • What do these examples have in common?

4. Noise, Vibration, and Harshness Thermal Crash Testing Examples of Models in Vehicle Design Computational Fluid Dynamics Stress Analysis

5. All models are 'wrong'. Some are useful. Attributed to George Box What is a Model? • Definition (based on Marvin Minsky's definition) : • A model (M) for a system (S) and an experiment (E) is anything to which E can be applied in order to answer questions about S • A model is an abstraction of reality Who has created a new model today?

6. How Do We Create Models? • Gather data about real system • Postulate hypotheses about the relationships in the data • Formalize these hypotheses in models • Validate models by performing simulations • If necessary, modify the hypotheses and models until valid (Adapted from F. Cellier)

7. Models can never be proven correct – only falsified. (Adapted from Karl Popper) A Quick Aside:When is a Model Valid? Is this model valid? f(x) x

8. Unanticipated Phenomena May Invalidate Model Tacoma Narrows Bridge, Nov 7, 1940.

9. Simulator Simulator Simulator Simulator System Model System Model System Model System Model Why are Models Important in Engineering? Initial Guess Satisficing Solution Decision Solver Predict theOutcome of Engineering Design Decisions DesignAlternative Evaluation ofDesign Alternative

10. When are Models Most Useful? • When the system is not available • When the physical experiments cannot be performed • When the cost of experimentation is too high • When the time scale of the system is not compatible with those of the experimenter • Under controlled circumstance (e.g. no disturbances)

11. Noise, Vibration, and Harshness Thermal Crash Testing Examples of Models in Engineering Computational Fluid Dynamics Stress Analysis

12. Manufacturing Simulation • DFM – DFA – DFX • Take life cycle cost into account at the design stage

13. Training Simulators • Use the previously developed simulation models for training • Train operators before prototypes are built • Test whether user interface is user-friendly

14. Immersive Environments • Allow user to interact with models through • 3-dimensional vision • Touch (tactile interface) • Complete virtual prototype

15. Crash Testing If a picture is worth 1000 words,how about a simulation? Summary • We all create and use models all the time • Models should be validated • In engineering, models are used for predicting the outcome of decisions, but also for training or documentation. • In this class you will use models to solve engineering problems