Journal ArticleDOI
Transient Flow in a Rapidly Filling Horizontal Pipe Containing Trapped Air
TLDR
In this paper, the pressure within a trapped air pocket in a rapidly filling horizontal pipe is investigated both experimentally and analytically, where the downstream end is either sealed to form a dead end or outfitted with an orifice to study the effects of air leakage on the pressure.Abstract:
The pressure within a trapped air pocket in a rapidly filling horizontal pipe is investigated both experimentally and analytically. The downstream end of the pipe is either sealed to form a dead end or outfitted with an orifice to study the effects of air leakage on the pressure. Three types of pressure oscillation patterns are observed, depending on the size of the orifice. When no air is released or orifice sizes are small, the cushioning effects of the air pocket prevents the water column from impacting on the pipe end and from generating high water hammer pressures. However, the maximum pressure experienced may still be several times the upstream driving pressure. When the orifice size is very large, the air cushioning effect vanishes and the water hammer pressure is dominant. For intermediate orifice sizes, the pressure oscillation pattern consists of both long-period oscillations (while the air pocket persists) followed by short-period pressure oscillations (once water hammer pressures dominate). Air leakage is observed to play a significant role in increasing the magnitude of the observed pressures during rapid filling, resulting in peak pressures up to 15 times the upstream head. An analytical model, capable of calculating the air pocket pressure and the peak pressure when the water column slams into the end of the pipe, is developed and results are compared with those of experiments. The model was successful in determining the amplitude of the peak pressure for the entire orifice range and was able to simulate the pressure oscillation pattern for the case of a negligible water hammer impact effect. Although the model was unable to simulate the pressure oscillation pattern for substantial air release, it was able to predict the type of pressure oscillation behavior and the peak pressure.read more
Citations
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Journal ArticleDOI
Improved Simulation of Flow Regime Transition in Sewers: Two-Component Pressure Approach
TL;DR: In this paper, a new modeling framework is proposed for describing the flow regime transition utilizing a shock-capturing technique that decouples the hydrostatic pressure from surcharged pressures occurring only in pressurized conditions, effectively overcoming the cited Preissmann slot limitation.
Journal ArticleDOI
State-of-the-art review on the transient flow modeling and utilization for urban water supply system (UWSS) management
TL;DR: In this article, a comprehensive review on the transient flow research for urban water supply system (UWSS) management is presented, which consists of two aspects as follows: the first aspect is about the development and progress of current transient theory, including transient flow models, unsteady friction and turbulence models, and numerical simulation methods.
Journal ArticleDOI
Experimental Investigation of Surges in a Stormwater Storage Tunnel
TL;DR: In this article, an experimental apparatus consisting of a 14.6m-long, 94mm-diameter acrylic pipe was used to observe the nature of flows in such conditions, and the results indicated that the effects of air phase pressurization should be properly included in numerical simulations if ventilation conditions are limited.
Journal ArticleDOI
Simulation of Flow Transients in a Water Filling Pipe Containing Entrapped Air Pocket with VOF Model
Ling Zhou,Deyou Liu,Chuanqi Ou +2 more
TL;DR: In this article, a volume of fluid (VOF) model is introduced to simulate the transient flow of an entrapped air pocket in a filling pipeline without air release, and experimental observations show that the air-water interface moves irregularly, and the water column near bottom pipe wall firstly reaches and impacts on pipe end wall, which could induce a sudden pressure jump.
References
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Book
Mechanics of Fluids
TL;DR: In this article, the authors present fundamental concepts and principles governing fluids in motion problems, including the Momentum Equation (ME) and the Laminar Flow between Solid Boundaries (LFL) problems.
Journal ArticleDOI
Transient conditions in the transition from gravity to surcharged sewer flow
M. A. Hamam,J. A. McCorquodale +1 more
TL;DR: A complete design of a storm sewer should consider both gravity an... as discussed by the authors, and one of the least understood aspects of flow in sewers is the nature of the transition from gravity to pressure or surcharged flow.
Journal ArticleDOI
Energy Relations in Transient Closed‐Conduit Flow
TL;DR: In this paper, a mathematical expression for the kinetic energy of the fluid, the internal energy associated with fluid compressibility and pipeline elasticity effects, the energy dissipated by friction, and the work done at the ends of the conduit is derived by mathematical manipulation of the governing continuity and momentum equations.
Journal ArticleDOI
Influence of Liquid Length Variation in Hydraulic Transients
TL;DR: In this paper, it was shown that in a system with entrapped air and without changes of potential energy at the air-water interface (horizontal pipe) the final pressure obtained in a mass oscillation in which the kinetic energy of the fluid and the liquid column length variation are neglected is the same as the final peak pressure obtained from the consideration of both effects.