Computation of the Unstable Behavior of a Hydraulic Circuit With a Centrifugal Pump Coupled to an Air Pocket

2005 ◽  
Author(s):  
Jorge Parrondo ◽  
Juan Antun˜a ◽  
Jose´ I. Prieto
Keyword(s):  
Centrifugal Pump ◽  
Compressible Liquid ◽  
Hydraulic Systems ◽  
Calculation Algorithm ◽  
Trapped Air ◽  
Air Pocket ◽  
Dead End ◽  
Entrapped Air ◽  
The One ◽  
Oscillation Instability

A theoretical and experimental study is presented on the mass oscillation instability in hydraulic systems with entrapped gas pockets and pumps with positive slope in the head curve. In order to simulate these systems, the one-dimensional unsteady equations for compressible liquid flow were solved by means of a suitable calculation algorithm, based on the method of characteristics. Additionally, a series of laboratory tests was conducted on a conventional centrifugal pump that operated in a circuit with a dead end and different amounts of entrapped air. In accordance with the predictions of the theoretical model, instability was found to develop with limit cycle pressure oscillations of frequency dependent on the trapped air amount.

A Study on the Unstable Coupling Between Pumps and Hydraulic Circuits With Entrapped Gas Pockets

2002 ◽  
Author(s):  
Jorge L. Parrondo-Gayo ◽  
Juan Antun˜a-Schu¨tze ◽  
Jose´ Gonza´lez-Pe´rez ◽  
Joaqui´n Ferna´ndez-Francos
Keyword(s):  
Critical Conditions ◽  
Pressure Amplitude ◽  
Hydraulic Systems ◽  
Positive Slope ◽  
One Dimensional ◽  
Numerical Resolution ◽  
Air Pocket ◽  
Entrapped Air ◽  
Fundamental Equations ◽  
Oscillation Instability

A theoretical and experimental study has been conducted on the mass oscillation instability in hydraulic systems with entrapped gas pockets and pumps with positive slope in the head curve. The theoretical study was composed of an analysis of the critical conditions for the instability to develop, followed by the numerical resolution of the fundamental equations that govern the phenomenon, assuming unsteady one-dimensional flow, in order to simulate the limit cycle oscillations of the unstable system. Additionally a series of laboratory tests was conducted on a conventional centrifugal pump, with variation of the initial volume of an entrapped air pocket in the circuit. As expected from the predictions of the theoretical model, instability was found to developed with pressure amplitude oscillations and frequency dependent on the amount of entrapped air.

Analysis of effects of air pocket on hydraulic failure of urban drainage infrastructure

2004 ◽  
Vol 31 (1) ◽  
pp. 86-94 ◽  
Author(s):  
F Zhou ◽  
F Hicks ◽  
P Steffler
Keyword(s):  
Air Flow ◽  
Urban Drainage ◽  
Storm Events ◽  
Pressure Oscillations ◽  
Trapped Air ◽  
Hydraulic Failure ◽  
Air Pocket ◽  
Flow Oscillations ◽  
Entrapped Air ◽  
Peak Pressures

The effects of trapped air on flow oscillations and pressure surges in a model trunk sewer–manhole system subject to rapid filling are investigated. The study reveals the detrimental impacts of entrapped air during severe storm events under which pipelines are likely overloaded. The results of the investigation indicated huge peak pressures and severe pressure oscillations inside the system.Key words: trapped air, flow transient, rapid filling, sewers.

Experimental Validation of Existing Numerical Models for the Interaction of Fluid Transients With In-Line Air Pockets

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Jane Alexander ◽  
Pedro J. Lee ◽  
Mark Davidson ◽  
Huan-Feng Duan ◽  
Zhao Li ◽  
...  
Keyword(s):  
Time Delay ◽  
Wave Speed ◽  
Numerical Models ◽  
Diagnostic Process ◽  
Air Pocket ◽  
Fluid Transients ◽  
Entrapped Air ◽  
Air Pockets ◽  
The Given ◽  
Potential Tool

Entrapped air in pipeline systems can compromise the operation of the system by blocking flow and raising pumping costs. Fluid transients are a potential tool for characterizing entrapped air pockets, and a numerical model which is able to accurately predict transient pressures for a given air volume represents an asset to the diagnostic process. This paper presents a detailed study on our current capability for modeling and predicting the dynamics of an inline air pocket, and is one of a series of articles within a broader context on air pocket dynamics. This paper presents an assessment of the accuracy of the variable wave speed and accumulator models for modeling air pockets. The variable wave speed model was found to be unstable for the given conditions, while the accumulator model is affected by amplitude and time-delay errors. The time-delay error could be partially overcome by combining the two models.

Culture and Theater as Foundation for National Identity Formation in the Russian Far East: Where Europe Meets Asia

2005 ◽  
Vol 33 (1) ◽  
pp. 59-70 ◽  
Author(s):  
Erika V. Ossipova
Keyword(s):  
Identity Formation ◽  
Russian Far East ◽  
Far East ◽  
Past Century ◽  
Cultural Interaction ◽  
Cross Cultural Communication ◽  
Dead End ◽  
The One ◽  
The Russian Far East

For several centuries the overall trend in the world development has been along the way paved by Western civilization. Hence, the predominant flow has been based on borrowed Western cultural features. The issue of cultural interaction among nations with different culture types became fairly topical in contemporary society. Humankind now faces the legacy of moral decline of the past century and is trying to find a way out of its ideological dead end through other cultures and civilizations. In addition, the globalization processes that developed towards the end of the last century have also embraced the nations' cultural ties, turning the cross-cultural communication into an integral part of humankind's existence. The unique role of Russia in Northeastern Asia calls for an answer to the following question: Is there any cultural interaction between the Russian Far East, on the one hand, and the East Asian nations, on the other? And if so, what are its manifestations and how big are they?

scholarly journals Traveltime calculations from frequency‐domain downward‐continuation algorithms

Geophysics ◽  
2003 ◽  
Vol 68 (4) ◽  
pp. 1380-1388 ◽  
Author(s):  
Changsoo Shin ◽  
Seungwon Ko ◽  
Wonsik Kim ◽  
Dong‐Joo Min ◽  
Dongwoo Yang ◽  
...  
Keyword(s):  
Wave Equation ◽  
Frequency Domain ◽  
Downward Continuation ◽  
Calculation Algorithm ◽  
Near Surface ◽  
Absolute Value ◽  
Head Waves ◽  
First Arrival ◽  
The One ◽  
Derivatives Of

We present a new, fast 3D traveltime calculation algorithm that employs existing frequency‐domain wave‐equation downward‐continuation software. By modifying such software to solve for a few complex (rather than real) frequencies, we are able to calculate not only the first arrival and the approximately most energetic traveltimes at each depth point but also their corresponding amplitudes. We compute traveltimes by either taking the logarithm of displacements obtained by the one‐way wave equation at a frequency or calculating derivatives of displacements numerically. Amplitudes are estimated from absolute value of the displacement at a frequency. By using the one‐way downgoing wave equation, we also circumvent generating traveltimes corresponding to near‐surface upcoming head waves not often needed in migration. We compare the traveltimes computed by our algorithm with those obtained by picking the most energetic arrivals from finite‐difference solutions of the one‐way wave equation, and show that our traveltime calculation method yields traveltimes comparable to solutions of the one‐way wave equation. We illustrate the accuracy of our traveltime algorithm by migrating the 2D IFP Marmousi and the 3D SEG/EAGE salt models.

scholarly journals The joy at the Last Judgement according to the Heidelberg Catechism Question 52

2014 ◽  
Vol 70 (1) ◽  
Author(s):  
Eberhard Busch
Keyword(s):  
Reformed Tradition ◽  
Dead End ◽  
The Dead ◽  
The One

In this contribution, the author reflects on Question 52 of the Heidelberg Catechism where it asks: ‘What comfort is it to you that Christ “shall come to judge the living and the dead”?’ The author points out possible sources from which this formulation stems, that is, Articles 86 and 87 in John Calvin’s Catechism from 1545. God is described as a compassionate judge. Even more: the One who is the last judge, was also judged and had paid for our sins. In a dialectical fashion we discover a God who is just, but also merciful. The Reformed tradition did not follow a dead-end where it is taught that God shows us grace instead of righteousness. Had God proceeded in this way, he would only mean things well, but he would not make them well. The realisation of God being just and merciful leads to joy and repentance. The contribution ends with a discussion of the final separation of the just and evil.

On the Hydraulics of Downward Sloping Pipes With Entrapped Air Pockets

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
H. A. Warda ◽  
E. M. Wahba ◽  
E. N. Ahmed
Keyword(s):  
Hydraulic Jump ◽  
Open Channel ◽  
Numerical Results ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Dynamics Model ◽  
Computational Fluid Dynamics Model ◽  
Air Pocket ◽  
Entrapped Air ◽  
Air Pockets

Abstract In this study, air–water flow in a downward sloping pipe subsequent to the entrapping of an air pocket is investigated both numerically and experimentally. A transient, two-dimensional computational fluid dynamics model is applied to study the different possible flow regimes and their associated phenomena. The numerical model is based on the Reynolds-averaged Navier–Stokes (RANS) equations and the volume of fluid (VOF) method. Both numerical and experimental investigations provide visualization for the hydraulic jump, the blowback regime, and the full gas transport regime. The numerical results predict that the flow structure in the pipe downstream the toe of the hydraulic jump is subdivided into three distinct regions including the jet layer, the shear zone, and the circulation region, which agrees qualitatively with the previous investigations of the hydraulic jump characteristics in open channel flow. Numerical results are in reasonable agreement with the experimental measurements of the circulation length and the hydraulic jump head loss.

scholarly journals Rotor-Stator Interaction Induced Pressure Fluctuations: CFD and Hydroacoustic Simulations in the Stationary Components of a Multistage Centrifugal Pump

2007 ◽  
Author(s):  
Stefan Berten ◽  
Philippe Dupont ◽  
Mohamed Farhat ◽  
Francois Avellan
Keyword(s):  
Centrifugal Pump ◽  
Cfd Simulation ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Mode Shapes ◽  
Oscillation Analysis ◽  
Multistage Centrifugal Pump ◽  
Spatially Distributed ◽  
Rotor Stator Interaction ◽  
The One

In a centrifugal pump the interaction between the rotating impeller pressure field and the stationary diffuser pressure field yields pressure fluctuations as the result of a modulation process. These fluctuations may induce hydroacoustic pressure fluctuations in the exit chamber of the pump and could cause unacceptable vibrations. This paper presents a methodology for the prediction of hydroacoustic pressure fluctuations resulting from rotor-stator interaction in a multistage centrifugal pump. The method consists in the one-way coupling of incompressible CFD and hydroacoustic simulations. In a first step the rotorstator pressure fluctuations are calculated using a commercial 3D-RANS CFD-code (CFX 10) for different flow rates. The acoustic simulations are performed in two consecutive steps. Initially a free oscillation analysis using white noise pressure fluctuations is performed, which provides hydroacoustic eigen frequencies and mode shapes of the outlet casing. In a second step the spatially distributed pressure fluctuations from the CFD simulation are used to perform a forced oscillation analysis. This approach allows the prediction of possible standing waves in the hydraulic collection elements in the last stage of multistage pumps.

Sign in / Sign up

Export Citation Format

Share Document