China
Africa
Explore chapters and articles related to this topic
Modeling and Validation Challenges for Complex Systems
Published in Larry B. Rainey, Mo Jamshidi, Engineering Emergence, 2018
The first of the three defining characteristics of complex systems to be examined for its effect on modeling and validation is sensitivity to initial conditions. Here the phrase “initial conditions” refers, of course, to either the starting state of the system (e.g., a rocket motor at ignition), or, if the system has an effectively continuous existence (e.g., the weather), the state of the system at the beginning of the time period being studied or modeled. The state evolution of a complex system can be highly sensitive to its initial conditions, with the result that small differences in initial state can become magnified over time into large differences in future state (Smith, 2007). Figure 9.3 illustrates this with a set of notional system (or simulation) histories; in the figure, the horizontal axis represents time, advancing from left to right, and the vertical axis represents system state, simplified to a single variable. States that are only slightly different at some initial time tstart can evolve away from each other, becoming arbitrarily different at some future time tend.
Simulation Techniques
Published in Harry G. Perros, An Introduction to IoT Analytics, 2021
An initial condition affects the behavior of the system for an initial period of time. Thereafter, the simulation will behave statistically in the same way whatever the initial condition. During this initial period, the simulation is said to be in a transient state. After that period, the simulation is said to be in a steady state.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
The system has sensitive dependence on initial conditions. The model above is a very simplified version of the dynamics related to meteorological phenomena. It is thus no surprise that the weather is unpredictable since even this simple model behaves chaotically.
Operator Action–Induced Two-Phase Flow Condition Resulting in Performance Degradation of Interfacing Passive System
Published in Nuclear Technology, 2021
Static geometry variables can include piping flow paths (e.g., pipe diameters and lengths), flow field altering devices (e.g., elbow, flow orifice, venturi, etc.), heat transfer surface areas [e.g., heat exchanger (HX) design], and elevation change between thermal centers. Boundary conditions include heat source and heat sink pressures and temperatures defining temperature differential ΔT and flow field and heat transfer conditions at heat transfer surfaces (e.g., single-phase liquid, two-phase or single-phase gas flow, turbulent or laminar flow, nucleate or film boiling, etc.). Boundary conditions can vary in time, i.e., BCs are time dependent. Initial conditions define the states of the working fluids and physical structures forming the system geometry at the time of passive system startup or demand. Important ICs can include flow field conditions (e.g., stagnant versus minimum residual flow), presence of air or noncondensable gases in piping, oxidation layer on HX tubes, or plugged HX tubes, etc. Passive system startup performance can be affected by the reactor coolant system (RCS) ICs such as system demands following reactor trip from full power or during low power and shutdown. Other special TH phenomena is a catch-all, including two-phase flow instability, water hammer, thermal stratification in large pools, choked flow, etc.
Undergraduate students' difficulties with boundary conditions for the diffusion equation
Published in International Journal of Mathematical Education in Science and Technology, 2022
Sofie Van den Eynde, Johan Deprez, Martin Goedhart, Mieke De Cock
The initial condition describes the state of the system at the beginning (t = 0). Boundary conditions refer to the conditions physical quantities must satisfy at the boundary of the system. In this study we focus on boundary conditions of the form , which specify the flux, which in this context is the particle flow, through the boundary. More specifically, we consider a closed tube, so no particles can pass the boundary. Mathematically, this is described by the following boundary conditions: and .
Physics-based simulation ontology: an ontology to support modelling and reuse of data for physics-based simulation
Published in Journal of Engineering Design, 2019
Hyunmin Cheong, Adrian Butscher
An initial condition refers to a situation in which some material entity bears some physical property at the onset of a physical behaviour. Similar to a boundary condition, the physical properties vary depending on the types of the physical behaviour involved, and a simplified definition that does not require quantifying over relations can be used. An initial condition is always applied on the entirety of a domain.