Discussion the froude number is the most important parameter in openchannel flow. Open channel flow florida international university. But, when flow transitions the other direction when a fastmoving supercritical flow transitions to a more tranquil subcritical condition something much more interesting happens. An experimental study of hydraulic jump in a gradually expanding. Basic hydraulic principles of openchannel flow by harvey e. Openchannel flow is a flow of liquid basically water in a conduit with a free surface. Open channel flow takes place with a free surface open to the atmosphere, so flow is due to gravity, rather than due to pressure as in pipe flow. Analysis upstream of a hydraulic jump, the upstream flow must be supercritical. Characterization of hydraulic jump over an obstacle in an. 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. Flow in open channel steady flow unsteady flow uniform flow nonuniform flow rapidly varied flow gradually varied flow temporal time spatial space classification of openchannel flows. In this transition, the water surface rises abruptly, surface rollers are formed, intense mixing occurs, air is entrained, and often a large amount of energy is dissipated. In a horizontal, rectangular channel, the sequent downstream depth is related to the. It is ratio of the channel cross section area to the wetted perimeter.
When the slope of open channel decreases from steep to mild, the depth of flow of water increases toward the critical depth and a flow instability occurs at some point. June 29, 2017 4348 low behavior and compared with the measured outcomes of an experimental lume armield model no. Hydraulic jump a rectangular horizontal channel 2m. In the case of earthlined channels or river channels, bank protection is also required if the shear stress is high enough to cause erosion or scouring. In order to describe the super critical flow and sub critical flow, there is need to define the.
In open channel networks, flow is usually approximated by the one. The depth water on the downstream side of the hydraulic jump is 1m. Hydraulic design of energy dissipators for culverts and. In an open channel when rapidly flowing stream abruptly changes to slowly flowing stream, a distinct rise or jump in the elevation of liquid surface takes, this phenomenon is known as hydraulic jump. June 29, 2017 4548 validation of the hydraulic jump model the experimental work was accomplished in the laboratory to explore the critical depth and the conjugate depths of hydraulic jump as. Energy, specific energy, and gradually varied flow closed conduit.
Hydraulic jump types and characteristics of hydraulic jump. Hydraulic jump and resultant flow choking in a circular. The classic demonstration of a hydraulic jump can be seen at the bottom of your sink. Hydraulic jump experiment in a rectangular open channel flume. The specific force equation has many applications in open channel flow problems. Critical flow occurs when v c, or more generally importantly, critical depth is independent of the channel slope. Pdf a hydraulic jump is formed in the open channel whenever supercritical flow changes to subcritical flow within a short distance. Therefore, it is clear that, the effect of gravity is very important in openchannel flow. Typical examples include rivers and canals, drainage channels, gutters, water rides at amusement parks or sewerage.
It is an intriguing and interesting phenomenon that has caught the imagination of many research workers since its first description by leonardo da vinci. The hydraulic jump occurs when flow transitions from supercritical to subcritical flow in an open channel. That is a surface on which pressure is equal to local atmospheric pressure. The document then presents open channel flow principles and design applications, followe by a parallel discussion of closed conduit principles and design applications. These two types of flow are similar in many ways but differ in one important respect.
Before defining the hydraulic jump it is necessary to describe the terms super critical flow and sub critical flow in order to clearly understand that what is hydraulic jump hydraulic jump usually occurs in super critical flow. Openchannel 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. Open channel flow geomorphology of natural channels. Compute and plot a curve showing the theoretical velocity distribution. It occurs when either the bed slope and changes to water depth are insufficient to compensate. When the slope of open channel decreases from steep to mild, the. Hydraulic design of energy dissipators for culverts and channels hydraulic engineering circular number 14, third edition. Another situation in which a hydraulic jump commonly forms is downstream of a change from a relatively steep channel slope, with which supercritical flow is. Pdf hydraulic jump in ushaped open channel researchgate. The hydraulic jump equations were discussed in chapter 2.
You might have observed the phenomenon of a hydraulic jump in your washbasin what is the science behind this. Chapter 5 specific energy, e total of depth and kinetic energy of the flow. In this work, a comparison in terms of accuracy and computational cost between a coupled 1d2d. Openchannel flows are characterized by the presence of a liquidgasinterface called the free surface. Afzal 9 investigated the streamwise flow structure of turbulent hydraulic jump, which was taken placed over a rectangular channel rough bed.
Hydraulic jump is the jump or standing wave formed when the depth of flow of water changes from supercritical to subcritical state. Various calculations related to critical, subcritical and supercritical flow conditions will be presented, including hydraulic jump calculations. The hydraulic jump as a transition from subcritical to. A hydraulic jump is a phenomenon in the science of hydraulics which is frequently observed in open channel flow such as rivers and spillways. This chapter provides guidance for designing systems with openchannel. Proper design requires that open channels have sufficient hydraulic capacity to convey. To determine the jump location in a channel, we need to use the jump equation along with the graduallyvaried flow calculations. Hydraulic jump is one subject which has extensively been studied in the field of hydraulic engineering. Hydraulic jump in a rectangular channel, also known as classical jump, is a natural phenomenon that occurs whenever flow changes from supercritical to subcritical flow. Strong decelerations to the upper level jet is verified. This equation has a direct solution only for the rectangular channels.
Hydraulic radius is the function of shape of the channel not the. 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. Also, the inluence of lo w structures on water level variation is studied to reveal shear force existence due to bed roughness 1012. Hydraulic jump experiment in a rectangular open channel. When liquid at high velocity discharges into a zone of lower velocity, a rather abrupt rise occurs in the liquid surface. In open channel networks, flow is usually approximated by the onedimensional 1d saintvenant equations coupled with an empirical junction model. A hydraulic jump is a phenomenon in the science of hydraulics which is frequently observed in open channel flow such as rivers and spillways with or without sluice gates.
It occurs for supercritical flow on a subcritical channel slope. Open channel flow mcq hydraulic jump set 1 model answer these open channel flow mcq covers the following topics points of hydraulic jump introduction to rapidly varied flow rvf hydraulic jumps momentum equation formulation for hydraulic jumps. A wide channel carries a uniform flow at a depth of 5. When channel width decreases, curve moves right and upwards, and vice versa. You must follow along the curve for a channel of constant cross section only exception is for hydraulic jumps. This paper presents a laboratory experiment for the formation of hydraulic jump in a rectangular open channel flume to accurately explore the effect of flow structures on water resources. On this episode of practical engineering, were talking about one of the most interesting. Compute the shear stress at the bed and the friction velocity. This experiment illustrates the behavior of supercritical flow under sluice gate for. Hydraulic jump a hydraulic jump is an abrupt change from a shallow highspeed flow to a deep lowspeed flow of lower energy. Open channel flow mcq hydraulic jump set 1 14 mcqs. Energy, specific energy, and gradually varied flow 10. In openchannel flow the driving force that is the force causing the motion is the component of gravity along the channel bottom.
Rapidly varied flow and hydraulic jump continuity equation x momentum equation substituting and simplifying quadratic equation for y2y1 me33. Performing organization name and address 2963 ash street denver. Thus, specific energy is the energy at a crosssection of an open channel flow with respect to the channel bed. The bottom for the channel in problem 2 is smooth and the water tempera ture is 40 f. Devices that can be used to measure open channel flow. In an open channel, a hydraulic jump is a sudden and rapid transition from a supercritical to a subcritical flow. Plot a graph of the mean velocity against and determine the manning roughness value from the slope of the graph. Energy, specific energy, and gradually varied flow.