Spillways Abdüsselam ALTUNKAYNAK, PhD Associate Professor,

Slides:



Advertisements
Similar presentations
Chapter 4: Non uniform flow in open channels
Advertisements

Flood Profile Modeling with Split Flows and Weirs
Change of the flow state
Roxburgh Dam Combined Discharge of Spillway and Sluice into the same Chute Peter Silvester – Civil Engineer Contact Energy Grant Webby – Principal Hydraulic.
Introduction to Long-Throated Flumes and Broad-Crested Weirs
Chapter 13: Momentum Principles in Open-Channel
Total & Specific Energy
DAMS.
Flow Over Notches and Weirs
CE 3205 Water and Environmental Engineering
Computational Modeling of Flow over a Spillway In Vatnsfellsstífla Dam in Iceland Master’s Thesis Presentation Chalmers University of Technology 2007.
Sept 4, 2008CVEN 4838/5838Slide #1 Lecture 4 Spillways and Outlet Works.
CE154 Hydraulic Design Lectures 8-9
Design of Open Channels and Culverts CE453 Lecture 26
Design of Open Channels and Culverts
HYDRAULIC 1 CVE 303.
Open Channel Flow Part 2 (cont)
CHAPTER 6: Water Flow in Open Channels
What is a Dam? A dam is a hydraulic structure of fairly impervious material built across a river or a stream to retain the water. It prevents the flow.
Hydraulic Jump.
Monroe L. Weber-Shirk S chool of Civil and Environmental Engineering Open Channel Flow June 12, 2015 
Open Channel Flow.
Broad-crested Weir.
Pertemuan Open Channel 2. Bina Nusantara VARIED FLOW IN OPEN CHANNELS.
HEC-RAS US Army Corps of Engineers Hydrologic Engineering Center
Hydraulic Jump as an application of Momentum Equation
MECH 221 FLUID MECHANICS (Fall 06/07) Chapter 10: OPEN CHANNEL FLOWS
HEC-RAS.
Monroe L. Weber-Shirk S chool of Civil and Environmental Engineering Open Channel Flow July 15, 2015 
Reservoirs, Spillways, & Energy Dissipators
Elements of Dam Engineering
Water Flow in Open Channels
Open Channel Flow.
Chapter 7 continued Open Channel Flow
PRINCIPLES OF OPEN CHANNEL FLOW
Dams Mehmet Özger (Barajlar) Department of Civil Engineering, I.T.U.
Chapter 3: Design of Dissipation Structures By Dr. Nuray Denli Tokyay
Engineering Low-Head Dams for Function and Safety Fritz R. Fiedler Department of Civil Engineering University of Idaho.
Power Plant Construction and QA/QC Section 7.2 – Dams, Spillways, Water Conductors and Power Houses Engineering Technology Division.
The Islamic University of Gaza Faculty of Engineering Civil Engineering Department Hydraulics - ECIV 3322 Chapter 6 Open Channel.
DAMS Dept. Of Civil Engineering
ERT 349 SOIL AND WATER ENGINEERING
School of Civil Engineering/Linton School of Computing, Information Technology & Engineering 1 CE 3205 Water and Environmental Engineering Stilling Basins.
Modeling Inline Structures using HEC-RAS Version 3.1
CTC 261 Culvert Basics.
Penny Coombes Sarah Wharton Gary Davies Simon White River Bee, Desing FLOOD ALLEVIATION FEASIBILITY.
Chapter 2: Total Hydrostatic Force on Surfaces
Basic Hydraulics: Culverts – I
Basic Hydraulics: Channels Analysis and design – I
Basic Hydraulics: Open Channel Flow – I
Basic Hydrology & Hydraulics: DES 601 Module 16 Open Channel Flow - II.
 It is the type of V. F. in which the width of throat is decreased to such an extent that the depth of water in throat is equal to critical depth. 
6.12a DESIGN APPROACH ON BILILO SPATE IRRIGATION PROJECT Presented by Eyob Yehayis.
Basic Hydraulics: Rating curve. Definition & terminology Rating curve, also known as stage–discharge curve, is a graph showing the relation between the.
HYDROLOGY & WATER RESOURCES ENGINEERING TYPES OF SPILLWAYS
1 Spillway Weirs and its Role in Dam Protection Husam Khaled Al Mubark Abdel Aziz Al Mesnd Roume Al Roume Abdullah Al Qashami Civil and Environmental Engineering.
Basic Hydraulics: Open Channel Flow – II
SPILLWAYS Prepared By :- Shubham Modi (13BCL054) Pintu Nakrani (13BCL055) Grishma Parmar (13BCL057) 1 2/19/2017.
Water Can Jump!!!! Hydraulic Jump Phenomena
Assoc. Prof. Dr. Tarkan Erdik
EXAMPLE Water flows uniformly in a 2m wide rectangular channel at a depth of 45cm. The channel slope is and n= Find the flow rate in cumecs.
FLUID MECHANICS.
DISCHARGE OVER A BROAD-CRESTED WEIR
ERT 349 SOIL AND WATER ENGINEERING
Suresh.R.
Hydraulic Routing in Rivers
Hydraulic Structures HYDRAULIC STRUCTURES.
HEC-RAS US Army Corps of Engineers Hydrologic Engineering Center
Module 3 Irrigation Engineering Principles Version 2 CE IIT, Kharagpur.
BAE 6333 – Fluvial Hydraulics
Presentation transcript:

Spillways Abdüsselam ALTUNKAYNAK, PhD Associate Professor, Department of Civil Engineering, I.T.U. altunkaynak.net altunkaynak.net

Spillway: Structural component of the dam that evacuates flood wave from reservoir to river at the downstream. Is safety valve of the dam DESIGN RETURN PERIOD From 100 yrs for diversion weir to 15,000 yrs or more (Probable Maximum Flood-PMF) for earth-fill dams TYPES OF SPILLWAYS More common types are: (1) Overflow (Ogee crested) (2) Chute (3) Side Channel (4) Shaft (5) Siphon altunkaynak.net

They have large capacities They have higher hydraulic conformities 1) OVERFLOW SPILLWAYS Most of the spillways are overflow types They have large capacities They have higher hydraulic conformities They can use successfully for all types of dams Allows the passage of flood wave over its crest Used on often concrete gravity, arch and buttress dams Constructed as a separate reinforced concrete structure at one side of the fill-typed dams Classified as uncontrolled (ungated) and controlled (gated) altunkaynak.net

The underside of the nappe of a sharp-crested weir when Q=Qmax Ideal Spillway Shape The underside of the nappe of a sharp-crested weir when Q=Qmax H AIR P Ho yo ha E G L H Sharp crested weir AIR The Overflow spillway altunkaynak.net

A-Design Discharge of Spillway Design discharge of an overflow spillway can be determined by integrating velocity distribution over the cross-sectional flow area on the spillway from the crest to the free surface. The equation can be obtained as below Qo = Co L Ho3/2 where Qo is the design discharge of spillway Co is discharge coefficient L is the effective crest length Ho is total head over the spillway crest altunkaynak.net

USE Fig. to modify Co for inclined upstream face. Determined from Figures for the vertical overflow spillways as a function of P (spillway height) / Ho (total head) USE Fig. to modify Co for inclined upstream face. USE Fig. to obtain Co for heads other than design head. USE Fig 4.8 to reflect “apron effect” on Co. USE Fig. to reflect “tail-water effect” on Co. The overall Co  multiplying each effects of each case altunkaynak.net

Q = 2/3 (2g)0.5 C L (H13/2- H23/2) B-Design Discharge of Spillway If the gates are partially opened, the discharge can be computed as following Q = 2/3 (2g)0.5 C L (H13/2- H23/2) Where g is the gravitational C is the discharge coefficient for a partially open gate L is the effective crest length H1 and H2 are the heads as defined in Figure 4.4 C: Discharge Coefficient determined from Figure 4.10 altunkaynak.net

See Fig. 4.11 for Primitive types of gates. CREST GATES Provide additional storage above the crest See Fig. 4.11 for Primitive types of gates. See Fig. 4.11 for Underflow gates. Common types: radial and rolling CREST PROFILES The ideal shape of overflow spillway crest under design conditions for a vertical upstream face is recommended by USBR (1987) x y R=0.5 Ho R=0.2 Ho 0.175 Ho 0.282 Ho Origin of Coordinates altunkaynak.net

The smoothness of the crest profile. The values of “K” and “n” in the parabolic relation given in Fig. 4.12 can be determined from Figure 4.13. The pressure distribution on the bottom of the spillway face depends on The smoothness of the crest profile. Important Note: The upstream face of the crest is formed by smooth curves in order to minimize the separation For a smooth spillway face, the velocity head loss over the spillway can be ignored. altunkaynak.net

If H (head) > Ho  p < patm If H (head) > Ho  p < patm. ↔ “overflowing water” may lose contact with the spillway face, which results in the formation of a vacuum at the point of separation and CAVITATION may occur. In order to prevent cavitation, sets sets of ramps are placed on the face of overflow spillways so that the jet leaves the contact with the surface. Subatmospheric Pressure Zone Spillway Crest Flow Direction Ho H>Ho EGL Development of negative pressures at the spillway crest for H>Ho altunkaynak.net

Energy Dissipation at the Toe of Overflow Spillway Excessive turbulent energy at the toe of an overflow spillway can be dissipated by a hydraulic jump, which is a phenomenon caused by the change in the stream regime from supercritical to subcritical with considerable energy dissipation. should be done to prevent scouring at the river bed. P E1 y2 y1 E2 Ho hL ΔE EGL (O) (1) (2) altunkaynak.net

Sequent depth of the hydraulic jump, y2 can be determined from the momentum equation between sections (1) and (2). Ignoring the friction between these sections, the momentum equation for a rectangular basin can be written as with altunkaynak.net

and after simplification Where Fr1 is the flow Froude number at section (1). The energy loss through the hydraulic jump in a rectangular basin is computed from altunkaynak.net

Case 1: Flow conditions for y2=y3 altunkaynak.net If the tailwater depth, y3, is coincident with the sequent depth, y2, the hydraulic jump forms just at toe of the spillway as shown in Figure below y2=y3 y1 (1) (2) Flow conditions for y2=y3 altunkaynak.net

This case should be eliminated, because water flows at a very If the tailwater depth is less than the required sequent depth, the jump moves toward the downstream, as can be seen from Figure below. This case should be eliminated, because water flows at a very high velocity having a destructive effect on the apron. y2>y3 y1 (1) (2) Flow conditions for y2>y3 altunkaynak.net

Case 3 : Flow conditions for y2<y3 altunkaynak.net If the tailwater depth is greater than the required sequent depth as shown in Figure below y2 < y3 Flow conditions for y2<y3 altunkaynak.net

rectangular basin. REMINDERS: “y1” (depth at the toe)  a supercritical depth and determined from “Energy Eq.” between upstream of spillway and the toe 2) If “y2” (tailwater depth) is subcritical  a HYDRAULIC JUMP between y1 and y2 (toe and tailwater, see case1). 3) “y2 ” (conjugate depth)  determined from Eq. for rectangular basin. altunkaynak.net

SIDE CHANNEL SPILLWAYS SHAFT SPILLWAYS SIPHON SPILLWAYS CHUTE SPILLWAYS SIDE CHANNEL SPILLWAYS SHAFT SPILLWAYS SIPHON SPILLWAYS altunkaynak.net