Volumetric flow
Introduction
In fluid dynamics, flow is the amount of fluid that circulates through a section of the pipeline (pipe, pipe, oil pipeline, river, canal, ...) per unit of time. It is normally identified with the volumetric flow or volume that passes through a given area in the unit of time. Less frequently, it is identified with the mass flow or mass that passes through an area in the unit of time. It is represented with (from Italian, quantità [1]).
mathematical definition
In the event that the flow is normal to the surface or section considered, of area A, the relationship exists between the flow rate and the average velocity of the fluid:
where.
In the case that the fluid velocity forms an angle θ with the perpendicular to the section of area A crossed by the fluid with uniform velocity v, then the flow is calculated as:.
In the particular case that the flow is perpendicular to area A (therefore θ = 0 and ) then the flow is:
If the fluid velocity is not uniform or if the area is not flat, the flow must be calculated by means of an integral:.
where dS is the surface vector, which is defined as.
where n is the unit vector normal to the surface and dS a differential element of area.
In physics and engineering, flow rate is the amount of fluid that circulates per unit of time in a certain system or element. It is expressed in the unit of volume divided by the unit of time (e.g., m³/s).
In the case of river or stream basins, flow rates are generally expressed in cubic meters per second or thousands of cubic meters per second. They are variables in time and space and this evolution can be represented with so-called hydrographs.
Flow in agricultural and hydraulic engineering
Contenido
El caudal de un río es fundamental en el dimensionamiento de presas "Presa (hidráulica)"), embalses y obras de control de avenidas. Dependiendo del tipo de obra, se emplean los caudales medios diarios, con un determinado tiempo de recurrencia o tiempo de retorno, o los caudales máximos instantáneos. La forma de obtención de uno y otro es diferente y, mientras para los primeros se puede tomar como base los valores registrados en una estación de medición, durante un número considerable de años, para los segundos, es decir para los máximos instantáneos, muy frecuentemente se deben calcular a través de modelos matemáticos.