The diagram shows a reach of uniform open channel flow, followed by a change in bottom slope that causes non uniform flow, ending with another reach of uniform open channel flow. Open channel flow florida international university. Depth in uniform flowis called normal depth y n uniform depth occurs when the flow depth and thus the average flow velocity remains constant common in long straight runs average flow velocity is called uniform flow velocity v0. The depth associated with uniform flow is designated y 0. This article is about means of calculating the surface profile depth vs distance down the channel for a reach of non uniform flow. Open channel flow engineering excel templates blog. Normal depth is the depth of uniform flow in an prismatic open channel.
Exp 1 steady uniform flow conditions civil engineers pk. This occurs only when the cross section is constant. Uniform flow occurs in long inclined channels of uniform cross section when the terminal velocity is reached. In this video i have tried to explain the uniform flow in an open channel and various most efficient channel sections.
In an open channel flow froude number is defined as. The cartridge meter is the first open channel flowmeter to utilize hybrid technology. Uniform flow is a necessary condition for the use of the manning equation, to be discussed in detail in the. If the depth of flow changes over a relatively long distance along the length of a channel, then the flow is called gradually varied flow. Introduction the beginning of any channel design or modification is to understand the hydraulics of the stream. Open channel flow is defined as fluid flow with a free surface open to the atmosphere. Non uniform flow calculations are needed, however, in some open channel flow situations, where the flow is clearly non uniform. Pressure flow takes place in a closed conduit such as a pipe, and pressure is the primary driving force for the flow. In open channel flow the driving force that is the force causing the motion is the component of gravity along the channel bottom. Open channel flow is characterized by a flow not completely enclosed by solid bound aries. The backwater produced by a dam or weir across a river and drawdown produced at a sudden drop in a channel are few typical examples of gvf.
The procedures for performing uniform flow calculations aid in the selection or evaluation of appropriate depths and grades for natural or manmade channels. This occurs when the loss of potential energy equals the work done against the channel surface friction. And the fluid flow is non uniform if the flow parameters vary and are different at different points on the flow path. 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 subcritical, critical and supercritical flow.
Analysis of steady non uniform flow in open channels. The differences among these three classifications of open channel flow, however, are not as obvious or intuitive as. Velocity distribution in open channelsfactors affecting velocity distribution in open channels1. Factors affecting velocity distribution in open channels. The calculation of the reynolds number for open channel flow is a bit different than for closed conduits. Analysis requires a different approach, requiring the use of the energy equation in a different form. Bureau of reclamation flumelevel system for low flow applications with the more accurate epa proven transittime chordal velocity method for high flow applications. For open channel flow, the flow is non uniform if the depth of flow does not remains constant along a certain length of the channel. An open channel flow describes the fluid motion in open channel fig. Uniform and nonuniform open channel flow supercritical, subcitical, or critical flow.
At the discharge end of the channel an adjustable undershot sluice gate is provided. Non uniform flow results from gradual or sudden changes in the cross sectional area. In this condition the water surface is parallel to the bed of the channel. Jan 16, 2014 uniform flow in open channel uniform flow is an equilibrium condition that flow tends to if the channel. Since the flow is uniform, the depth and discharge are related through mannings equation with sf so. Equation for uniform flow uniform flow occurs in a channel when the depth and velocity do not vary along its length where. In this type of flow in which flow properties discharge, velocity etc does not remain same with respect to distance as well as with respect to time. Only if an open channel flow can somehow be adjusted to be strictly uniform, in the sense that the water surface is planar and the flow depth is the same at all cross sections along. For a given value of specific energy, e1, the discharge may pass through the channel section at either depth d1 supercritical flow or d2 subcritical flow. Apr 23, 2017 in this video i have talked about the various gradually varied flow profiles and control section and its importance in finding out the flow depth at various sections in an open channel flow. Any open channel flow will be supercritical, subcritical or critical flow. In this video i have talked about the various gradually varied flow profiles and control section and its importance in finding out the flow depth at various sections in an open channel flow. Open channel flow i the manning equation and uniform flow harlan h.
Since the flow is uniform, the depth and discharge are related through mannings. Introduction when the surface of flow is open to atmosphere, in other terms when there is only atmospheric pressure on the surface, the flow is named as open channel flow. Open channel flow, a branch of hydraulics and fluid mechanics, is a type of liquid flow within a conduit with a free surface, known as a channel. Steady flow in a channel can be either uniform or nonuniform varied. Under which of the following conditions steady non uniform. Uniform flow in channels flow in open channels is classified as being uniform or nonuniform, depending upon the depth y. The other type of flow within a conduit is pipe flow. Classification of fluid flow uniform flow and nonuniform. Introduction flow of a liquid may take place either as open channel flow or pressure flow. Pdf turbulent nonuniform flows in straight compound open. Various factors such as channel slope, alignment, shape, roughness etc plays key role in velocity distribution. The fluid flow is a uniform flow if the flow parameters remain constant with distance along the flow path. Steady, nonuniform flow in an open channel the momentum equation can be used to derive the expression for shear stress.
Uniform flow channel flow open source scientific library. Consider an open channel of uniform width b and with a flat but sloping bed as. Steady, non uniform flow in an open channel the momentum equation can be used to derive the expression for shear stress. Normal depth is the depth of uniform flowin an prismatic open channel.
Unsteady flows are considerably more difficult to analyze than steady flows. Steady flow in a channel can be either uniform or non uniform varied. In an open channel flow, there are three types of flow. When the average velocities in successive cross sections of a channel are the same, the flow is uniform. The hydraulic jump as an example of rapidly varied nonuniform flow will be discussed. In an open channel flow, velocity distribution is non uniform which means velocity is different at different depths. Therefore, it is clear that, the effect of gravity is very important in open channel flow. Non uniform flow occurs in transitions where there is change in cross section or obstruction in channel. The governing force for the open channel flow is the gravitational force component along the channel slope. The diagram at the left shows uniform open channel flow in the upstream portion of the channel, followed by a section of non uniform flow due to a change in channel bottom slope, leading to another stretch of uniform open channel flow. This varied flow can be either gradually varied flow gvf or rapidly varied flow rvf. At a larger depth the same discharge may be delivered through the section with a smaller velocity and a higher specific energy than a critical depth. Open channel flow i the manning equation and uniform flow. Open channel flow 1 what is the difference between open channel flow and pipe flow.
An open channel is a waterway, canal or conduit in which a liquid flows with a free surface. The slope of the channel is small no air entrainment fixed velocity distribution resistance coefficient constant in the reach under consideration 22 f 43 nu s r assumptions made when solving the gradually varied flow equation. Non uniform flow steady uniform flow unsteady uniform flow steady non uniform flow unsteady non uniform flow. Uniform open channel water flow rate calculation with the. Uniform and non uniform open channel flow supercritical, subcitical, or critical flow. Introduction a steady non uniform flow in a prismatic channel with gradual changes in its watersurface elevation is named as graduallyvaried flow gvf.
Non uniform flow steady uniform flow unsteady uniform flow steady non uniform flow unsteady non uniform flow rapidly. These two types of flow are similar in many ways but differ in one important respect. Sanghamitra kundu introduction nonuniform flow is a flow for which the depth of flow is varied. For a uniform flow, by its definition, the area of the cross section. The concepts of supercritical, subcritical and critical flow, and calculations related to those three regimes of flow, are needed for non uniform open channel flow analysis and calculations. It characterizes the flow as uniform or non uniform. The governing force for the open channel flow is the gravitational force. The function of ditches and open channels is to convey stormwater runoff from, though, or around roadway rightsofway without damage to the highway, to the openchannel. In most applications, the liquid is water and the air above the flow is usually at rest and at standard atmospheric pressure. For our purposes, we will assume that transition occurs at a reynolds number of. Hydraulic jumps and nonuniform open channel flow pdh. Pdf the reported experimental study assesses the effects of flow nonuniformity on the momentum flux in straight compound channels.