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In fluid dynamics, total dynamic head (TDH) is the work to be done by a pump, per unit weight, per unit volume of fluid.TDH is the total amount of system pressure, measured in feet, where water can flow through a system before gravity takes over, and is essential for pump specification.
Pressure head is a component of hydraulic head, in which it is combined with elevation head. When considering dynamic (flowing) systems, there is a third term needed: velocity head. Thus, the three terms of velocity head, elevation head, and pressure head appear in the head equation derived from the Bernoulli equation for incompressible fluids:
The total hydraulic head of a fluid is composed of pressure head and elevation head. [1] [2] The pressure head is the equivalent gauge pressure of a column of water at the base of the piezometer, and the elevation head is the relative potential energy in terms of an elevation. The head equation, a simplified form of the Bernoulli principle for ...
A low pressure ratio fan (such as that used on a high bypass ratio turbofan) has a range of working lines. At high flight speeds, the ram pressure ratio factors up the cold nozzle pressure ratio, causing the nozzle to choke. Above the choking condition, the working lines tend to coalesce into a unique steep straight line.
For incompressible flow, the dynamic pressure of a fluid is the difference between its total pressure and static pressure. From Bernoulli's law, dynamic pressure is given by = where p 0 and p s are the total and static pressures, respectively.
It describes how the total head reduces due to the losses. This is in contrast with Bernoulli's principle for dissipationless flow (without irreversible losses), where the total head is a constant along a streamline. The equation is named after Jean-Charles de Borda (1733–1799) and Lazare Carnot (1753–1823).
In fluid dynamics, stagnation pressure, also referred to as total pressure, is what the pressure would be if all the kinetic energy of the fluid were to be converted into pressure in a reversable manner. [1]: § 3.2 ; it is defined as the sum of the free-stream static pressure and the free-stream dynamic pressure. [2]
Friction Head – The friction head accounts for the frictional losses in the pumping system. The value of the friction head can be found from available data-tables depending on the flow parameters such as fluid viscosity, pipe dimensions, flow rate, etc. Total Head – It is obtained by adding the friction and static heads.