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Drop (unit) The drop is an approximated unit of measure of volume, the amount dispensed as one drop from a dropper or drip chamber. It is often used in giving quantities of liquid drugs to patients, and occasionally in cooking and in organic synthesis. The abbreviations gt or gtt come from the Latin noun gutta ("drop").
In the integral form, the total pressure drop = is in units (), and is the length of the sample in units (), the Darcy's volumetric flow rate , or discharge, is also defined in units (/) and the cross-sectional area in units (). A number of these parameters are used in alternative definitions below.
A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the end of a tube or other surface boundary, producing a hanging drop called a pendant drop. Drops may also be formed by the condensation of a vapor or by atomization of a larger mass of solid ...
Volumetric flow rate is defined by the limit [3] = ˙ = =, that is, the flow of volume of fluid V through a surface per unit time t.. Since this is only the time derivative of volume, a scalar quantity, the volumetric flow rate is also a scalar quantity.
The flow rate can be converted to a mean flow velocity V by dividing by the wetted area of the flow (which equals the cross-sectional area of the pipe if the pipe is full of fluid). Pressure has dimensions of energy per unit volume, therefore the pressure drop between two points must be proportional to the dynamic pressure q.
Flow coefficient. The flow coefficient of a device is a relative measure of its efficiency at allowing fluid flow. It describes the relationship between the pressure drop across an orifice valve or other assembly and the corresponding flow rate . Mathematically the flow coefficient Cv (or flow-capacity rating of valve) can be expressed as. where.
Continuum mechanics. In nonideal fluid dynamics, the Hagen–Poiseuille equation, also known as the Hagen–Poiseuille law, Poiseuille law or Poiseuille equation, is a physical law that gives the pressure drop in an incompressible and Newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant cross section.
The drop surface area density is the product of the spray drop surface area and the number of drops per unit volume. The surface area density is very important in evaporation and combustion applications since the local evaporation rate is highly correlated to the surface area density.