The lockers occupy a narrow hallway that, during breaks, becomes choked with people.
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In the case of upstream air pressure at atmospheric pressure and vacuum conditions downstream of an orifice, both the air velocity and the mass flow rate becomes choked or limited when sonic velocity is reached through the orifice.
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Next, consider the nozzle connected to a compressed air supply. With a pressure ratio of about 2, the flow becomes choked, and cannot exceed the speed of sound. But the density and resultant mass flow rate can be increased by increasing the inlet pressure. The greater the pressure, the greater the density, and the greater the mass flow.
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Choked flow is a compressible flow effect. The parameter that becomes "choked" or "limited" is the fluid velocity. Choked flow is a fluid dynamic condition associated with the venturi effect. When a flowing fluid at a given pressure and temperature passes through a constriction (such as the throat of a convergent-divergent nozzle or a valve in a pipe) into a lower pressure environment the fluid velocity increases.
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Dismantled valve components Automatic valves are used to release trapped air as it collects. They are not a substitute for bleeding a system manually when it is first filled during commissioning, nor for remedial bleeding if the system becomes choked with trapped air. In those cases, individual bleed screws on each radiator, or high pipe run, are opened manually. The valves are installed at a high point of the system, where trapped air collects.
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The channel provides a variety of habitats, because is passes through different soil types along its length. Near Fordham and West Dereham, the river bed is composed of Sandringham Sands with coarse pebbles and a high quartz content. In these conditions, the channel becomes choked with dense mats of the green algae Cladophora glomerata and Canadian pond weed. Near Methwold and Feltwell, the underlying rocks are chalk, resulting in the bed being covered in fine silts, on which little aquatic flora grows.
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Consequently, the nozzle exit area controls the fan match and, being larger than the throat, pulls the fan working line slightly away from surge. At higher flight speeds, the ram rise in the intake increases nozzle pressure ratio to the point where the throat becomes choked (M=1.0). Under these circumstances, the throat area dictates the fan match and, being smaller than the exit, pushes the fan working line slightly towards surge. This is not a problem, since fan surge margin is much better at high flight speeds.
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Holes or gaps have to be left in the pipes to allow water to transfer from the subsoil to the pipe and these tend to block with soil or allow silt into the pipe, so blocking it or reducing the flow of water. This can be partially overcome by surrounding the pipes with gravel. However, with time even the gravel becomes choked with soil/silt, so in the latest practice, the gravel is surrounded with a geotextile material which filters out soil particles. Ideally, land drains are laid with access points so that high pressure water jetting is possible to clear silt.
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As the pressure ratio gets to about 2, the flow through the nozzle will approach the local speed of sound, and the flow becomes choked flow. When the absolute pressure of the vacuum is decreased further, the flow speed will not increase. This is the Kantrowitz Limit, which limits the mass flow because the velocity is limited to the speed of sound, and the area, inlet pressure and density are all fixed. Aircraft jet engines are very much affected by this limit, once the inlet flow speed gets to Mach 1 the mass flow rate is limited, regardless of how much suction the engine creates.
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Downstream continues as a canyon passage which steadily enlarges, passing an inlet passage on the left where the main water enters which can be followed up to where it becomes choked with boulders underneath the stream sink. The main passage continues for about up to high and wide, under a boulder bridge wedged across the passage, to finish in a choke in a roof chamber. The water then follows a narrow meandering canyon to the first waterfall pitch of , and continues to a second pitch of at the base of which the water disappears into a choked sump pool. A traverse can be followed over the top of the pitch round to where a pitch enters from the Gavel Pot doline.
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The South Bay of Pillars is quite straight, and fairly clear for a distance of , when the bay becomes choked with islands and reefs. In the southeastern angle, an arm extends to the eastward for about , and receives the waters of a small humpback stream. On the northern side, the bay terminates in the Narrows (Skookum Chuck), which extend in a northeastern direction about , with a width of about , through which the current is quite violent during the strength of the tide. These Narrows connect with an inner bay long, in a northeast and southwest direction, by wide, which at the eastern end sends an arm at right angles to the southward about long by wide, receiving at the western terminus the waters of the Point Ellis or Kutlakoo stream.
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