Unified specific energy curve lor rectangular channels. Compute water surface profiles for any open channel including bridge structures, culvert crossings and inline weirs. The specific energy reaches a minimum value es, minat some intermediate point, called the critical point, characterized by the critical depth yc and critical velocity vc. Calculation of multiple critical depths in open channels using an. The specific energy and specific force equations result in fifth degree. Open channel flow worksheet 2 energy considerations learning objectives 1. Visualization of specific energy for open channel flow in three.
Specific force and momentum oregon state university. Firstly, the concept of specific energy is very useful for solving problems where the flow or depth might change. The document then presents open channel flow principles and design applications, followe by a parallel discussion of closed conduit principles and design applications. For a given discharge, the specific energy can be calculated for various flow depths and plotted on an ey diagram. Using excel or matlab, develop a graph of an energy diagram depth versus specific energy for a 5meter wide channel that is flowing at 10 cubic meters per second, and identify the point at. The other type of flow within a conduit is pipe flow. For an open channel flow, draw a specific energy diagram and define sub critical flow, super critical flow and critical flow. Flow cannot occur with specific energy less than the.
Thus, specific energy is the energy at a crosssection of an open channel flow with respect to the channel bed. 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. Lesson 11 specific energy specific energy is defined as the energy per pound of water at any section of a channel measured with respect to the channel bottom. M specific force, q flow rate, a cross sectional area of flow, zbar distance from the water surface to the centroid of the cross sectional area of flow. State whether the flow is subcritical or supercritical d. Intelligent pump management and control software for water and wastewater pump stations. Make a plot of the specific energy curve of a rectangular channel 0. Energy and momentum principles in open channel flow. This result accounts for the wide application of the energy line hydraulic gradient line as a means of describing an open channel flow. Channel studio is software designed to be an easytouse tool for performing daytoday hydraulic analysis on open channel systems. These two depths for a given specific energy are termed as specific depths. Hydraulic design of channels conveying supercritical flow this is. In open channels, the relationship between the specific energy and the flow depth exhibits a minimum, and the corresponding flow conditions are called critical flow conditions. Dimensionless specific energy diagrams for openchannel flow.
To emphasize the importance of the unconstrained freesurface boundary, a transitional flow involving a step in a rectangular channel is considered figure 1a. To calculate these unknowns we measured the slope, flow depth, and height of water and used the energy equation, manning equation, and the head loss equation. In open channels, the relationship between the speci. This is an excel sheet that calculates the specific energy curve and its components in open channel. Momentum principles can be applied to situations that deal with a high loss of internal energy, like hydraulic jumps, which cannot be evaluated with the energy. An instruction manual of open channel hydraulic experiments for water resources engineering. E is, as the name specifies, the total energy of the fluid measured with respect to. The standard step method stm is a computational technique utilized to estimate onedimensional surface water profiles in open channels with gradually varied flow under steady state conditions. If the value of e increases, we can see that the value of y decreases in lower part of the curve. Using excel or matlab, develop a graph of an energ. Along the upper limb, specific energy is greater than minimum specific energy, ypyo, and the flow is classified as supercritical since the depth of flow, y, is greater superior to the critical depth of flow, yo in open channel flow, normal depth, ym varies with flow rate, channel geometry, channel slope, and channel roughness. The specific energy es of a liquid in an open channel is the total mechanical energy expressed as a head relative to the bottom of the channel. For the purposes of the following analysis, energy is conserved for a fluid in.
It is a summation of the velocity head and the depth of flow at a given cross section. The specific energy diagram shows that the specific energy is minimum at critical depth. Classic energy problem in openchannel flow wikiversity. Specific energy and critical depth civil engineering terms. Figure 1 shows the diagram of the flow under a sluice gate, assuming that there are no energy losses.
The specific energy diagram has three distinct reg. At a larger depth the same discharge may be delivered through the. Minimum specific energy and critical flow conditions in. Flow in open channels are discussed including classification of flow types. For simplicity, the following specific energy often referred to as specific head. In the case where the datum is the channel bed, the static pressure head or the hydraulic head is just simply the flow depth, denoted by y. It also allows the verification of the chezy equation and mannings.
The principle of specific energy is shown to be useful in the prediction of watersurface. Whats the purpose of developing the term of specific energy for open channel flow. The use of specific energy concepts to solve gradually varying flows, and the. To study the variation in specific energy as a function of depth of flow for a given discharge in a lab flume. According to this equation, the total energy at downstream section. Make a plot of the specific energy curve of a rect. Figures figure 61 channel crosssectional parameters 63 figure 62 specific energy vs. Dimensionless specific energy diagrams for open channel.
Determine the relationship between specific energy and depth of flow. Solution of specific energy and specific force equations. The impulsemomentum principle provides a third basic tool for the solu. This lab also showed that the critical depth is a function of the flow per width. Conclusion this lab allowed the students to derive the specific energy equation for an open channel flow for different gate openings and channel depths. Specific energy and critical depth basic definitions c slopes in open channel flow z1 v2 1 2g datu m s o y1 z2 v2 2 2g y2 hg l e l wate r level s w s. Tables 3 and 4 above summarize the data collected and analyzed from the lab. Specific energy at critical flow rectangular channel. Energydepth relationship in a rectangular channel wikipedia. Specific energy and critical depth open channel flow duration. The specific energy diagram is specific to the unit discharge for a given flow rate. This article presents the application of a specific classic energy problem in openchannel flow. In open channel flow, specific energy is the energy length, or head, relative to the channel bottom.
Definition sketch of the energy diagram for openchannel flow. These two types of flow are similar in many ways but differ in one important respect. Dimensionless specific energy diagrams for openchannel. Design charts for open channel flow fhwa us department of. Apply by may 1, 2020 to earn your masters degree online from a toprated program.
Save energy, automatically test pump efficiency, and strengthen pump asset management. It shows graphically the effect of changing specific discharge on the specific energy curve. For the purposes of the following analysis, energy is conserved for a fluid in an open channel flow, and head losses due to friction will be neglected. Flow in open channels continued hydraulics and hydrologic. To investigate the relationship between specific energy e and depth of flow y in a rectangular channel. Download scientific diagram specific energy curve for open channel flow. The form of bernoullis equation discussed here assumes the flow is. Illustration of the energy consideration in open channel flow total energy t. The bernoulli equation, which originates from a control volume analysis, is used to describe specific energy relationships in fluid dynamics. Specific energy and critical depth open channel flow.
Consider, for example, the energy of two rivers of the same size and slope but one is 10 feet above sea level and one is 5,000 feet above sea level. Specific energy is expressed in terms of kinetic energy, and potential energy, and internal energy. Bernoulli theorem, minimum specific energy, and water wave celerity in open channel flow. The term h is called the specific head, and is the height of the total head above the channel. The channel is called as deep channel for subcritical flow. Application of specific energy to an open channel flow. In this lab an open channel flow with a sluice gate is used to calculate the volumetric flow rate, head loss, theoretical head loss, and the specific energy flow moving through the channel. Alternate depths and sequent depths are calculated by solving the specific energy and specific force equations, respectively. Application of specific energy to an open channel flow problem duration. I understand specific energy is a component of the total energy by not taking account of the vertical distance from vertical datum to channel bottom. The state of rapid and shallow flow through a section is known as supercritical flow or rapid flow. Energy conservation is an important concept when analyzing open channel flows. Using graphical software, this paper displayed the specific energy function as a. It uses a combination of the energy, momentum, and continuity equations to determine water depth with a given a friction slope, channel slope, channel geometry, and also a given flow rate.
Minimum specific energy and critical flow conditions in open channels by h. Critical depth spec energy module7 university of alabama. Depthaveraged specific energy in openchannel flow and. In open channel flow, specific energy e is the energy length, or head, relative to the channel bottom. A sluice gate was raised between each trial to change the. Gates are used to regulate the level and flow in open channels and reservoirs.
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