What is free surface in open channel flow?

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. The boundary conditions at the free surface of an open-channel flow are always that both the pressure and the shear stress are zero everywhere.

What is the material used in the open channel?

Vegetated linings include grass with mulch, sod and lapped sod, and wetland channels. Riprap and some forms of flexible man-made linings or gabions are examples of flexible linings, while rigid linings are generally concrete or rigid block.

What is surge 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).

What are the three types of open channel flow?

Types of Open Channel Flow

• 1 Steady Flow. Flow is said to be steady when discharge does not change along the course of the channel flow.
• 2 Unsteady Flow. Flow is said to be steady when discharge changes with time.
• 3 Uniform flow.
• 4 Gradually Varied Flow.
• 5 Rapidly Varied Flow.
• 6 Spatially Varied Flow.

What is a free surface flow?

In fluid mechanics a free surface flow, also called open channel flow, is the gravity driven flow of a fluid under a free surface, typically water flowing under air in the atmosphere.

What is bed slope in open channel?

The depth–slope product is used to calculate the shear stress at the bed of an open channel containing fluid that is undergoing steady, uniform flow. It is widely used in river engineering, stream restoration, sedimentology, and fluvial geomorphology.

What is steady flow?

A steady flow is one in which all conditions at any point in a stream remain constant with respect to time. The exact term use for this is mean steady flow. Steady flow may be uniform or non-uniform. Uniform flow. A truly uniform flow is one in which the velocity is same at a given instant at every point in the fluid.

What is a 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).

Why is open channel flow important?

An open channel is the flow of liquids that flows with a free surface, and are at some point “open” to the atmosphere. more important that open channel flows are metered effectively and efficiently – minimizing the overall margin of error.

What are the types of open channel flow?

The flow of liquid through the open channel can be of several types like steady and unsteady flow, laminar or turbulent flow or uniform or non-uniform flow and finally sub-critical, critical and supercritical flow.

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.

How to control subcritical flow in an open channel?

For subcritical flow in an open channel, the control section for gradually varied flow profiles is The normal depth in a wide rectangular channel is increased by 10%. The percentage increase in the discharge in the channel is: A trapezoidal channel is 10.0 m wide at the base and has a side slope of 4 horizontal to 3 vertical.

How is the critical flow of a channel determined?

The depth of flow (in m) in the channel is For a given discharge, the critical flow depth in an open channel depends on The flow in a horizontal, frictionless rectangular open channel is supercritical. A smooth hump is built on the channel floor. As the height of hump is increased, choked condition is attained.

What are the profiles of gradually varied flow in the channel?

The profiles of gradually varied flow in the channel are The flow in a rectangular channel is subcritical.if the width of the channel is reduced at a certain section, the water surface under no-choke condition will

How is liquid flow measured in open channels?

LIQUID FLOW MEASUREMENT IN OPEN CHANNELS USING THIN PLATE WEIRS ( First Reprint MAY 1998 ) UDC 532.57 : 681.121.873 532.543 0 Copyright 1980 BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002 Gr 9 Mum-y 1980 ls : 9108 – 1979 Indian Standard