Simulation is the imitation of the operation of a real-world process or system.[1] The act of simulating something first requires that a model be developed; this model represents the key characteristics, behaviors and functions of the selected physical or abstract system or process. The model represents the system itself, whereas the simulation represents the operation of the system over time.

Simulation is used in many contexts, such as simulation of technology for performance optimization, safety engineering, testing, training, education, and video games. Often, computer experiments are used to study simulation models. Simulation is also used with scientific modelling of natural systems or human systems to gain insight into their functioning,[2] as in economics. Simulation can be used to show the eventual real effects of alternative conditions and courses of action. Simulation is also used when the real system cannot be engaged, because it may not be accessible, or it may be dangerous or unacceptable to engage, or it is being designed but not yet built, or it may simply not exist.[3]

Key issues in simulation include acquisition of valid source information about the relevant selection of key characteristics and behaviours, the use of simplifying approximations and assumptions within the simulation, and fidelity and validity of the simulation outcomes. Procedures and protocols for model verification and validation are an ongoing field of academic study, refinement, research and development in simulations technology or practice, particularly in the field of computer simulation.

Classification and terminology

Human-in-the-loop simulation of outer space
Visualization of a direct numerical simulation model.

Historically, simulations used in different fields developed largely independently, but 20th century studies of systems theory and cybernetics combined with spreading use of computers across all those fields have led to some unification and a more systematic view of the concept.

Physical simulation refers to simulation in which physical objects are substituted for the real thing (some circles[4] use the term for computer simulations modelling selected laws of physics, but this article does not). These physical objects are often chosen because they are smaller or cheaper than the actual object or system.

Interactive simulation is a special kind of physical simulation, often referred to as a human in the loop simulation, in which physical simulations include human operators, such as in a flight simulator or a driving simulator.

Continuous simulation is a simulation where time evolves continuously based on numerical integration of Differential Equations.[5]

Discrete Event Simulation is a simulation where time evolves along events that represent critical moments, while the values of the variables are not relevant between two of them or result trivial to be computed in case of necessity[6]

Stochastic Simulation is a simulation where some variable or process is regulated by stochastic factors and estimated based on Monte Carlo techniques using pseudo-random numbers, so replicated runs from same boundary conditions are expected to produce different results within a specific confidence band [5]

Deterministic Simulation is a simulation where the variable are regulated by deterministic algorithms, so replicated runs from same boundary conditions produce always identical results.

Hybrid Simulation (sometime Combined Simulation) corresponds to a mix between Continuous and Discrete Event Simulation and results in integrating numerically the differential equations between two sequential events to reduce number of discontinuities [7]

Stand Alone Simulation is a Simulation running on a single workstation by itself.

Distributed Simulation is operating over distributed computers in order to guarantee access from/to different resources (e.g. multi users operating different systems, or distributed data sets); a classical example is Distributed Interactive Simulation (DIS) [8]

Parallel Simulation is executed over multiple processor usually to distribute the computational workload as it is happening in High Performance Computing [9]

Interoperable Simulation where multiple models, simulators (often defined as Federates) interoperate locally on distributed over a network; a classical example is High Level Architecture.[10][11]

Modeling & Simulation as a Service where Simulation is accessed as a Service over the web.[12]

Modeling, interoperable Simulation and Serious Games where Serious Games Approaches (e.g. Game Engines and Engagement Methods) are integrated with Interoperable Simulation.[13]

Simulation Fidelity is used to describe the accuracy of a simulation and how closely it imitates the real-life counterpart. Fidelity is broadly classified as 1 of 3 categories: low, medium, and high. Specific descriptions of fidelity levels are subject to interpretation but the following generalization can be made:

  • Low – the minimum simulation required for a system to respond to accept inputs and provide outputs
  • Medium – responds automatically to stimuli, with limited accuracy
  • High – nearly indistinguishable or as close as possible to the real system

Human in the loop simulations can include a computer simulation as a so-called synthetic environment.[14]

Simulation in failure analysis refers to simulation in which we create environment/conditions to identify the cause of equipment failure. This was the best and fastest method to identify the failure cause.

Other Languages
Alemannisch: Simulation
العربية: محاكاة
български: Симулация
català: Simulador
čeština: Simulace
dansk: Simulation
Deutsch: Simulation
español: Simulación
Esperanto: Simulado
euskara: Simulazio
Gaeilge: Ionsamhlóir
galego: Simulación
한국어: 시뮬레이션
हिन्दी: सिमुलेशन
Bahasa Indonesia: Simulasi
italiano: Simulazione
עברית: סימולציה
қазақша: Симулятор
latviešu: Simulācija
lietuvių: Imitacija
magyar: Szimuláció
Bahasa Melayu: Simulasi
Nederlands: Simulatie
norsk: Simulering
norsk nynorsk: Simulering
polski: Symulacja
português: Simulação
русский: Симулятор
sicilianu: Simulazzioni
Simple English: Simulation
Basa Sunda: Simulasi
suomi: Simulointi
svenska: Simulering
తెలుగు: అనుకరణ
Türkçe: Simülasyon
українська: Симуляція
Winaray: Simulasyon
中文: 仿真