choked flow


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Choked flow

Fluid flow through a restricted area whose rate reaches a maximum when the fluid velocity reaches the sonic velocity at some point along the flow path. The phenomenon of choking exists only in compressible flow and can occur in several flow situations. See Compressible flow

Through varying-area duct

Choked flow can occur through a convergent flow area or nozzle attached to a huge reservoir. Flow exits the reservoir through the nozzle if the back pressure is less than the reservoir pressure. When the back pressure is decreased slightly below the reservoir pressure, a signal from beyond the nozzle exit is transmitted at sonic speed to the reservoir. The reservoir responds by sending fluid through the nozzle. Further, the maximum velocity of the fluid exists at the nozzle throat where the area is smallest.

When the back pressure is further decreased, fluid exits the reservoir more rapidly. Eventually, however, the velocity at the throat reaches the sonic velocity. Then the fluid velocity at the throat is sonic, and the velocity of the signal is also sonic. Therefore, further decreases in back pressure are not sensed by the reservoir, and correspondingly will not induce any greater flow to exit the reservoir. The nozzle is thus said to be choked, and the mass flow of fluid is a maximum. See Mach number, Sound

With friction

Choked flow can also occur through a long constant-area duct attached to a reservoir. As fluid flows through the duct, friction between the fluid and the duct wall reduces the pressure acting on the fluid. As pressure is reduced, other fluid properties are affected, such as sonic velocity, density, and temperature. The maximum Mach number occurs at the nozzle exit, and choked flow results when this Mach number reaches 1.

With heat addition

A reservoir with a constant-area duct attached may also be considered in the case that the flow through the duct is assumed to be frictionless but heat is added to the system along the duct wall. See FLuid flow, Gas dynamics

choked flow

[¦chōkt ′flō]
(fluid mechanics)
Flow in a duct or passage such that the flow upstream of a certain critical section cannot be increased by a reduction of downstream pressure.
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References in periodicals archive ?
In addition, flow through an orifice is identified as choked flow if the following condition is valid [33]:
Earlier in the day, the defence minister also said that the move to scrap high-value currency notes choked flow of funds to the terrorists and reduced stone-pelting incidents in the Jammu and Kashmir.
Figure 10(a) shows that the choked flow in the convergent part of the nozzle is still clear and no bubbles can be observed.
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Within the actual nozzle, two cases can exist: Choked Flow or Non-Choked Flow [20].
The HEM has been applied in determining the choked flow rate of flashing liquid releases, but refrigerant releases have not been found in the literature.
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The operator base has shrunk drastically and an almost unmanageable liquidity crisis has ensued from the choked flow of new investment funds.
Equation 2 by itself cannot recognize a choked flow condition.
Choked flow lasts approximately 0.1 sec until the magazine pressurizes.