Simulation

A simulation is an imitative representation of a process or system. It can represent something real or something imagined. Scientists and engineers often use simulations to study complex systems. This is helpful when the real system is too dangerous to touch. It is also useful if the system is too expensive or not yet built. Sometimes, a real system is simply impossible to access. By using a simulation, we can explore different conditions and see the results.

To understand how this works, we must distinguish between a model and a simulation. A model represents the key characteristics or behaviors of a system. A simulation represents how that model evolves over time. You can think of the model as a blueprint and the simulation as the building process. Simulation is essentially experimentation using a model. Often, computers execute these simulations to handle complex calculations. This allows researchers to virtually investigate how a system behaves under different variables.

There are several distinct ways to classify simulations based on their mechanics. Continuous simulation uses numerical integration of differential equations to follow time smoothly. In contrast, discrete-event simulation studies systems that only change at specific moments. For example, an epidemic simulation might only change when someone gets sick or recovers. Hybrid simulations combine these two methods to reduce mathematical errors. There is also stochastic simulation, which uses random variations and Monte Carlo techniques. This means running the same test multiple times will produce different results within a specific range. Deterministic simulations are the opposite, as they use fixed algorithms to produce identical results every time.

Simulations can also be categorized by how they are built and run. Physical simulation involves using real objects that are smaller or cheaper than the original. Interactive simulation, or human-in-the-loop simulation, includes a person in the process.

Pilots use flight simulators to practice, and sailors use ship bridge simulators to learn.

In terms of computing, a stand-alone simulation runs on one workstation. Distributed Interactive Simulation uses more than one computer to share resources. Parallel simulation speeds up the work by distributing the workload over multiple processors. Finally, interoperable simulation allows different models to work together over a network.

Historically, different fields developed their own types of simulations independently. This changed during the 20th century due to new scientific ideas. The study of systems theory and cybernetics helped unify these different approaches. As computers became more common across all fields, the view of simulation became more systematic. Today, we can even access modeling and simulation as a service over the web. This makes these powerful tools available through cloud computing. This evolution has turned simulation from a niche tool into a global scientific standard.

When evaluating a simulation, experts look at its fidelity. Fidelity describes how accurately a simulation imitates its real-life counterpart. It is usually classified into three levels: low, medium, and high. Low fidelity is the minimum required to provide inputs and outputs. Medium fidelity responds to stimuli but has limited accuracy. High fidelity is nearly indistinguishable from the real system.

High fidelity is essential for tasks like failure analysis. This helps engineers identify why equipment fails in a safe, virtual environment.

Simulation connects to many different scientific and technical disciplines. In computer science, an emulator is a type of simulator. It allows a computer to run programs designed for a different or obsolete machine. This is helpful for testing new hardware before it is even built. In biochemistry, projects like Folding@home use computer simulations to study complex molecules. In economics, simulations help researchers understand human and social systems. Whether it is studying airflow over an engine or predicting the spread of a disease, simulation provides a window into the workings of our world.