Fr.: limite, bord
Something that indicates a border or limit; the border or limit so indicated.
From Fr., from O.Fr. bodne, from M.L. bodina, butina "boundary, boundary marker."
Karân, karâné, kenâr from Mid.Pers. karânag, Av. karana- "boundary."
butârhâ-ye karân, ~ karâni
Fr.: conditions à la limite
1) Math: Restriction on the limits of applicability of an equation.
In a differential equation, conditions that allow to fix the constant
of integration and reach a unique solution. The number of boundary conditions
necessary to determine a solution matches the order of the equation.
Fr.: effet de bords
An effect that forbids or invalidate locally the use of an idealized model of a system in which one or several of its dimensions are supposed to be infinite.
Fr.: couche limite
A layer of fluid that is formed wherever a fluid flows past a solid surface and the effects of → viscosity are important. The boundary level forms because as the fluid moves past the object, the molecules which are in direct contact with the surface stick to the surface. The molecules just above the surface are slowed down in their collisions with the molecules sticking to the surface. These molecules in turn slow down the flow just above them, but less effectively. This creates a thin layer of fluid near the surface in which the velocity changes from zero at the surface to the free stream value away from the surface. The boundary layer may be either → laminar or → turbulent in character, depending on the value of the → Reynolds number. The concept of boundary level was first put forward by Ludwig Prandlt (1875-1953) in 1904.
laminar boundary layer
lâye-ye karâni-ye varaqe-yi
Fr.: Couche limite laminaire
In a fluid flow, layer next to a fixed boundary. The fluid velocity is zero at the boundary but the molecular viscous stress is large because the velocity gradient normal to the wall is large. → turbulent boundary layer.
no boundary hypothesis
engâre-ye giti bi karân-e âqâzin
Fr.: l'hypothèse de l'Univers sans limite initiale
The proposal whereby the → Universe would not have begun with a → singularity. Instead, the → Big Bang would be an ordinary point of → space-time. The proposal, advanced by James Hartle and Stephen Hawking (1983) results from an attempt to combine aspects of → general relativity and → quantum mechanics. Based on an imaginary time assumption, it predicts a closed Universe that would start at a single point, that can be compared to the North Pole of the Earth on a two-dimensional space. Before the → Planck era there was space, but the real time began with the Big Bang event. → Hartle-Hawking initial state.
turbulent boundary layer
lâye-ye karâni-ye âš:ubnâk
Fr.: couche limite turbulente
The layer in which the Reynolds stresses are much larger than the viscous stresses. When the → Reynolds number is sufficiently high, there is a turbulent layer adjacent to the → laminar boundary layer.