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What is hydraulic jump in open channel flow?

What is hydraulic jump in open channel flow?

A hydraulic jump is a phenomenon that occurs in fast-moving open flows when the flow becomes unstable. When a jump occurs, the height of the liquid surface increases abruptly resulting in an increased depth and decreased average flow velocity downstream.

What are the surges in open channel flow?

A surge in an open channel is a sudden change of flow depth (i.e. abrupt increase or decrease in depth). An abrupt increase in flow depth is called a positive surge while a sudden decrease in depth is termed a negative surge. This picture shows an undular surge (Photo, propagation from left to right).

How does a hydraulic jump occur?

A hydraulic jump occurs when a two liquids of same fluid ( especially water) in an open channel which actually meets a sub critical flow of sufficient depth from a super critical flow with a high velocity then there is a abrupt increase in height of the downstream channel – this phenomenon of energy transfer is called …

Why gravity is important in open channel flow?

Open channel flow also called free gravity flow, is the flow of water induced by the effect of gravity. The surface of the flowing liquid is at atmospheric pressure and free to air. In open channel flow, the liquid has free surface.

What is the difference between subcritical and supercritical flow?

Subcritical flow is dominated by gravitational forces and behaves in a slow or stable way. It is defined as having a Froude number less than one. Supercritical flow is dominated by inertial forces and behaves as rapid or unstable flow. Supercritical flow has a Froude number greater than one.

What is meant by critical flow?

critical flow The flow that occurs when the flow velocity in a river channel equals the wave velocity generated by a disturbance or obstruction. In this condition the Froude number (Fr) = 1. When Fr is greater than 1 waves cannot be generated upstream and the flow is said to be supercritical, rapid, or shooting.

What is surge?

In general a surge is a transient wave of current, voltage or power in an electric circuit. Surges, or transients, are brief overvoltage spikes or disturbances on a power waveform that can damage, degrade, or destroy electronic equipment within any home, commercial building, industrial, or manufacturing facility.

What is the positive surge?

A positive surge is an unsteady, rapidly-varied and highly turbulent open channel flow, characterised by a sudden rise in water surface elevation (Henderson, 1966, Liggett, 1994, Chanson, 2004). Industrial situations include rejection surges in hydropower and water supply canals (Favre, 1935, CUNGE, 1966).

Is hydraulic jump a flow control?

A hydraulic jump is a phenomenon in the science of hydraulics which is frequently observed in open channel flow such as rivers and spillways. In an open channel flow, this manifests as the fast flow rapidly slowing and piling up on top of itself similar to how a shockwave forms.

How do you know where a hydraulic jump will occur?

A hydraulic jump occurs when the upstream flow is supercritical (F>1). To have a jump, there must be a flow impediment downstream. The downstream impediment could be a weir, a bridge abutment, a dam, or simply channel friction. Water depth increases during a hydraulic jump and energy is dissipated as turbulence.

What are the characteristics of open channel flow?

In contrast to pipe flows, open channel flows are characterized by a free surface which is exposed to the atmosphere. The pressure on this boundary thus remains approximately constant irrespective of any changes in the water depth and the flow velocity.

What is the difference between pipe flow and open channel flow?

Pipe flow Vs Open channel Flow Open Channel Flow is a type of fluid flow in a conduit with a free surface open to the atmosphere. The pipe flow is a type of flow within a closed conduit. The maximum velocity occurs at the center of the pipe.

What makes an open channel flow a stratified flow?

Such flows are free-surface flows but not open-channel flows (Figure 5-2), although they are usually called stratified flows, because the density difference between the two fluids gives rise to gravitational effects in the flow. On the other hand, open-channel flows are by their definition also free- surface flows. Figure 5-1.

What happens when you decrease the slope of a channel?

On the other hand, if you decreased the channel slope to be very gentle, you would eventually have a condition in which the flow was relatively deep at the upstream end and relatively shallow at the downstream end (Figure 5-6B). Somewhere in between those two extreme conditions there would be a slope for which the flow was nearly uniform.

Why are open channel flows called free surfaces?

1. INTRODUCTION 1Open-channel flowsare those that are not entirely included within rigid boundaries; a part of the flow is in contract with nothing at all, just empty space (Figure 5-1). The surface of the flow thus formed is called a free surface, because that flow boundary is freely deformable, in contrast to the solid boundaries.

What is the problem with a uniform open channel flow?

A uniform open-channel flow: the depth and the velocity profile is the same at all sections along the flow. 12One kind of problem that is associated with uniform flow is what the channel slope will be if discharge Q, water depth d, and bed sediment size Dare specified or imposed upon the flow.