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Unsteady flow
Published in Bernard S. Massey, John Ward-Smith, Mechanics of Fluids, 2018
Bernard S. Massey, John Ward-Smith
The simple cylindrical surge tank considered here has certain disadvantages. A surge tank has two principal functions – first, to minimize water-hammer effects and, second, to act as a reservoir either taking in surplus water when the demand is reduced or meeting an increased demand while the water in the upstream pipe-line is accelerating. These two functions are in no way separated in the simple cylindrical tank, and consequently it is somewhat sluggish in operation. A number of different types of tank have therefore been devised in attempts to improve the operating characteristics for particular installations. The more complex tanks may have a cross-section varying with height, have overflow devices or have damping arrangements such as a restriction in the entrance. Compound tanks are sometimes used, and occasionally – where a great difference of level between the ends of the upstream pipe-line makes an open tank impossible – closed tanks with compressed air above the water level are employed.
Introduction
Published in Amitava Sil, Saikat Maity, Industrial Power Systems, 2022
Typical components of hydropower plants are: (i) Reservoir/Dam – to store water during excess flow period and supply during lean period. It creates an artificial head. (ii) Surge Tank – a small storage tank or reservoir required in the hydropower plants for regulating the water flow during load reduction and sudden increase in the load on the hydro generator (water flow transients in penstock) and thus reducing the pressure on the penstock. (iii) Penstocks –pipes that carry water from the reservoir to the turbines inside power station. (iv) Turbine/Generator, (v) Spillway – a way for spilling of water from dams that provide the controlled release of flows from a dam into a downstream area and (vi) Trail race – the channel into which the turbine discharges the water.
Single-Phase Incompressible Flow of Newtonian Fluid
Published in Henry Liu, Pipeline Engineering, 2017
A surge tank is a tank (column of liquid) connected to a pipeline for reducing the high pressure generated by the water hammer. When pressure in the pipe rises, the liquid in the pipe enters the surge tank. When the pressure in the pipe drops, the liquid in the pipe leaves the surge tank. Such actions damp out the pressure fluctuations in the pipe caused by the water hammer. Surge tanks are often used in penstocks (the large pipe that conveys water to a turbine for hydropower) and other pipelines. They are placed near turbines, at pumping stations on the discharge side of the pumps, in building water supply systems in which quick acting valves are installed, and at the end of a long pipeline upstream of a valve.
Development of Smoothed Particle Hydrodynamics based water hammer model for water distribution systems
Published in Engineering Applications of Computational Fluid Mechanics, 2023
Wenke Song, Hexiang Yan, Fei Li, Tao Tao, Huanfeng Duan, Kunlun Xin, Shuping Li
The surge tank is usually used to reduce and eliminate surges caused by the water hammer effect, including the open surge tank and the air chamber, as shown in Figure 6. During the transient simulation, the open surge tank connected to the pipeline stores or supplies water according to pressure changes in the system, thereby moderating pressure transients. To introduce the open surge tank as a boundary condition, the following set of equations is used: where is the flow into the open surge tank, is the water head in the tank, is the cross-sectional area of the connection pipe, is the loss coefficient of the connection pipe, is the cross-sectional area of the open surge tank. With two characteristic equations [Equations (31) to (32)], six unknowns () can be solved at each time step.
Dispersed-phase Volume Fraction and Flow Regimes in Oscillatory Liquid-Liquid Two-Phase Flow in Annuli: Comparison of Sieve-Plate and Baffle-Plate Internals
Published in Solvent Extraction and Ion Exchange, 2021
Sourav Sarkar, Mayur Darekar, K.K. Singh, K.T. Shenoy
Experimental setup consists of two glass annuli having different diameters or flow cross-sectional areas. The height of the annuli is 0.5 m. Each annulus has two phase disengagement sections, one at each end. These disengagement sections are provided for separation of the liquid phases. Disengagement sections are made of steel with glass windows in them. The schematic diagram of the experimental setup is given in Figure 1. There are two centrifugal pumps with bypass lines, rotameters and control valves to set the flow rate of the organic phase and the aqueous phase at the desired values. Oscillatory flow is generated by periodic pressurization and depressurization of the oscillation leg attached to the bottom phase disengagement section by using compressed air and a three-way valve. The air for creating oscillations is provided from a surge tank which receives compressed air from a compressor. The pressure in the surge tank is maintained at the desired value. The pressure in the surge tank is maintained by a feed-back control mechanism which regulates the flow through the flow control valve placed between the compressor surge drum and the surge tank. Pulsation amplitude is varied by varying the pressure in the surge tank. Oscillations frequency is controlled by an electronic timer. Sampling ports are provided at different axial positions along the length of the annuli.
Design criteria for a type of asymmetric orifice in a surge tank using CFD
Published in Engineering Applications of Computational Fluid Mechanics, 2018
The surge tank is a vital part of a hydraulic system and allows a reduction in the impact of a change in the operation mode. It is often designed solely for one specific project, depending on the particular hydraulic and geological boundary conditions (BCs). Stability criteria define the minimum area of the shaft (Thoma, 1910; Ye et al., 1992) and the storage capacity can be enhanced with additional chambers. Large mass oscillations between the surge tank and the upper reservoir can be further damped with the addition of a throttle (Adam et al., 2018a; Li & Brekke, 1989; Vereide et al., 2017). Such a structure can be added in the connection between the surge tank and head race tunnel or at a change of the cross section (Adam et al., 2016a; Richter et al., 2015). The use of an asymmetric geometry further allows us to limit the loss in the upward flow direction (into the surge tank) and to add a bigger damping effect on the downward flow direction. This leads to a reduction of the required volumes in the surge tank without introducing unwanted limits in the operation of the HPP. Extreme combination of losses can be reached with a vortex chamber diode, which has the disadvantage that the full throttling loss is available after an initialization time (Haakh, 2003). Hence, an asymmetric orifice is often preferred, which provides a stable behavior as well as a suitable ratio of the losses depending on the flow direction.