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In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol Q (sometimes ˙). It contrasts with mass flow rate, which is the other main type of fluid flow rate.
The solution of the equations is a flow velocity. It is a vector field—to every point in a fluid, at any moment in a time interval, it gives a vector whose direction and magnitude are those of the velocity of the fluid at that point in space and at that moment in time. It is usually studied in three spatial dimensions and one time dimension ...
If correctly selected, it reaches terminal velocity, which can be measured by the time it takes to pass two marks on the tube. Electronic sensing can be used for opaque fluids. Knowing the terminal velocity, the size and density of the sphere, and the density of the liquid, Stokes' law can be used to calculate the viscosity of the fluid. A ...
On the other hand, in the Lagrangian specification, individual fluid parcels are followed through time. The fluid parcels are labelled by some (time-independent) vector field x 0. (Often, x 0 is chosen to be the position of the center of mass of the parcels at some initial time t 0. It is chosen in this particular manner to account for the ...
Flux F through a surface, dS is the differential vector area element, n is the unit normal to the surface. Left: No flux passes in the surface, the maximum amount flows normal to the surface.
The three terms are used to define the state of a closed system of an incompressible, constant-density fluid. When the dynamic pressure is divided by the product of fluid density and acceleration due to gravity, g, the result is called velocity head, which is used in head equations like the one used for pressure head and hydraulic head.
The velocity of the surface can by related to the outflow velocity by the continuity equation =, where is the orifice's cross section and is the (cylindrical) vessel's cross section. Renaming v 2 {\displaystyle v_{2}} to v A {\displaystyle v_{A}} (A like Aperture) gives:
In steady flow (when the velocity vector-field does not change with time), the streamlines, pathlines, and streaklines coincide. This is because when a particle on a streamline reaches a point, a 0 {\displaystyle a_{0}} , further on that streamline the equations governing the flow will send it in a certain direction x → {\displaystyle {\vec ...