Leak Detection—Transient Flow Simulation Approaches

1995 ◽  
Vol 117 (3) ◽  
pp. 243-248 ◽  
Author(s):  
J. C. P. Liou ◽  
J. Tian
Keyword(s):  
Transient Flow ◽  
Flow Simulation ◽  
Leak Detection ◽  
Field Trials ◽  
Flow Conditions ◽  
Flow Measurements ◽  
Data Noise ◽  
Flow Simulations ◽  
Moderate Size ◽  
Detection Algorithms

The basis for and field trials of two leak detection algorithms by transient flow simulations are presented. Data noise in pressure and flow measurements are considered. Noise is found to limit leak detectability. The ability of the two algorithms to reliably detect small to moderate size leaks under steady and transient flow conditions is demonstrated.

scholarly journals Physical Basis of Software-Based Leak Detection Methods

1998 ◽  
Author(s):  
Jim C. P. Liou
Keyword(s):  
Transient Flow ◽  
Detection System ◽  
Sudden Change ◽  
Leak Detection ◽  
The United States ◽  
Third Party ◽  
Detection Methods ◽  
Operational Experience ◽  
Flow Simulations ◽  
Long Time

There are many causes for a pipeline to leak. Third party punctures usually result in sizable leaks. The onset of such leaks generates a sudden change in the pipeline pressure and flow. Methods exist that rely upon these sudden changes for leak detection. Leaks previously undetected are not detectable by such methods. These pre-existing leaks are usually small in size but can exist for long time. The cumulation of leaked products may pose a greater hazard then the larger and sudden leaks. The operational experience of major pipeline company in the United States has demonstrated that all leak detection methods have their limitations, and that complementary leak detection methods should be used simultaneously (Mears 1993). Hence, we propose a leak detection system that uses, simultaneously, two independent but complementary methodologies: mass balance and transient flow simulations.

An Experimental Investigation Into Potential Nuclear Reactor Vessel Flow Instabilities

2010 ◽  
Author(s):  
Jeffrey A. Brown ◽  
James W. Rowland ◽  
H. Joseph Fernando
Keyword(s):  
Physical Model ◽  
Transient Flow ◽  
Plant Protection ◽  
Reactor Vessel ◽  
Flow Instabilities ◽  
Engineering System ◽  
Flow Conditions ◽  
Steam Generators ◽  
Pressurized Water ◽  
Flow Measurements

An investigation into the increase in Plant Protection System (PPS) alarms at a three-unit US Pressurized Water Reactor (PWR) plant has determined that the alarms are the result, in part, of a hydraulic instability that has developed within the Reactor Coolant System (RCS) following the replacement of the steam generators in all three units of the Palo Verde Nuclear Generating Station (PVNGS). An experimental effort has been established by Arizona Public Service Company and Arizona State University in an attempt to determine the cause of these instabilities. Preliminary investigations have determined that the time scale of these instabilities is consistent with larger scale transient flow processes of the reactor vessel. Accordingly, the flow characteristics were assessed and localized flow measurements made using a one-fifth scale physical model of the upper plenum region of the reactor core of the Combustion Engineering System 80 reactor vessel to verify the postulation that large vortex structures referred to as “precessing” vortices [Ref. 1] affect the core exit flow conditions resulting in the noted flow instabilities. The physical model investigation was complemented by numerical analysis based on a Computational Fluid Dynamics (CFD) code performed for the same geometry. Benchmarking of the CFD model by the scaled physical model is intended to provide increased confidence in the CFD code. If verified, the CFD code may be modified so as to establish corrective actions for this condition, where physical modeling would probably be time consuming and cost prohibitive. The initial results for the physical and computational models demonstrate very good agreement between the measured and calculated flows in the upper-plenum region. The results of the complementary experimental and analytic evaluations do not support the presence of any large scale vortices of appropriate space scales that could affect flow conditions within the upper-plenum region. The elimination of the reactor vessel as the source of the instabilities suggests that the replacement steam generators may be the root cause of the flow instabilities. There is a possibility, however, that frequencies pertinent to vortices may be triggering mechanisms for flow instabilities in the entire system.

Modelling solid transport in building drainage systems

1996 ◽  
Vol 33 (9) ◽  
pp. 9-16 ◽  
Author(s):  
John A. Swaffield ◽  
John A. McDougall
Keyword(s):  
Decision Making ◽  
Boundary Conditions ◽  
Numerical Solution ◽  
Water Conservation ◽  
Transient Flow ◽  
Drainage System ◽  
System Model ◽  
Flow Depth ◽  
Flow Conditions ◽  
Solid Transport

The transient flow conditions within a building drainage system may be simulated by the numerical solution of the defining equations of momentum and continuity, coupled to a knowledge of the boundary conditions representing either appliances discharging to the network or particular network terminations. While the fundamental mathematics has long been available, it is the availability of fast, affordable and accessible computing that has allowed the development of the simulations presented in this paper. A drainage system model for unsteady partially filled pipeflow will be presented in this paper. The model is capable of predicting flow depth and rate, and solid velocity, throughout a complex network. The ability of such models to assist in the decision making and design processes will be shown, particularly in such areas as appliance design and water conservation.

Numerical Studies on Trapped-Vortex Concepts for Stable Combustion

1998 ◽  
Vol 120 (1) ◽  
pp. 60-68 ◽  
Author(s):  
V. R. Katta ◽  
W. M. Roquemore
Keyword(s):  
Drag Coefficient ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Third Order ◽  
Cold Flow ◽  
Flow Simulations ◽  
Numerical Studies ◽  
Dynamic Flows ◽  
Experimental Findings ◽  
Trapped Vortex

Spatially locked vortices in the cavities of a combustor aid in stabilizing the flames. On the other hand, these stationary vortices also restrict the entrainment of the main air into the cavity. For obtaining good performance characteristics in a trapped-vortex combustor, a sufficient amount of fuel and air must be injected directly into the cavity. This paper describes a numerical investigation performed to understand better the entrainment and residence-time characteristics of cavity flows for different cavity and spindle sizes. A third-order-accurate time-dependent Computational Fluid Dynamics with Chemistry (CFDC) code was used for simulating the dynamic flows associated with forebody-spindle-disk geometry. It was found from the nonreacting flow simulations that the drag coefficient decreases with cavity length and that an optimum size exists for achieving a minimum value. These observations support the earlier experimental findings of Little and Whipkey (1979). At the optimum disk location, the vortices inside the cavity and behind the disk are spatially locked. It was also found that for cavity sizes slightly larger than the optimum, even though the vortices are spatially locked, the drag coefficient increases significantly. Entrainment of the main flow was observed to be greater into the smaller-than-optimum cavities. The reacting-flow calculations indicate that the dynamic vortices developed inside the cavity with the injection of fuel and air do not shed, even though the cavity size was determined based on cold-flow conditions.

scholarly journals On the Scope of Lagrangian Vortex Methods for Two-Dimensional Flow Simulations and the POD Technique Application for Data Storing and Analyzing

Entropy ◽  
2021 ◽  
Vol 23 (1) ◽  
pp. 118
Author(s):  
Kseniia Kuzmina ◽  
Ilia Marchevsky ◽  
Irina Soldatova ◽  
Yulia Izmailova
Keyword(s):  
Flow Simulation ◽  
Internal Flow ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Vortex Methods ◽  
Flow Simulations ◽  
Additional Information ◽  
Two Dimensional Flow ◽  
Different Shapes ◽  
Problem Formulations

The possibilities of applying the pure Lagrangian vortex methods of computational fluid dynamics to viscous incompressible flow simulations are considered in relation to various problem formulations. The modification of vortex methods—the Viscous Vortex Domain method—is used which is implemented in the VM2D code developed by the authors. Problems of flow simulation around airfoils with different shapes at various Reynolds numbers are considered: the Blasius problem, the flow around circular cylinders at different Reynolds numbers, the flow around a wing airfoil at the Reynolds numbers 104 and 105, the flow around two closely spaced circular cylinders and the flow around rectangular airfoils with a different chord to the thickness ratio. In addition, the problem of the internal flow modeling in the channel with a backward-facing step is considered. To store the results of the calculations, the POD technique is used, which, in addition, allows one to investigate the structure of the flow and obtain some additional information about the properties of flow regimes.

FEM Comparative Analysis of Synchronous Rotor with Different Helix Angle in the Process of Mixing

2012 ◽  
Vol 501 ◽  
pp. 388-392
Author(s):  
Hui Guang Bian ◽  
Wei Shuai Lv ◽  
Chuan Sheng Wang
Keyword(s):  
Comparative Analysis ◽  
Theoretical Basis ◽  
Production Efficiency ◽  
Transient Flow ◽  
Flow Simulation ◽  
Helix Angle ◽  
Original Performance ◽  
Mixing Performance ◽  
Axial Tensile ◽  
Flow Mixing

The paper is used to analyze the structure of traditional synchronous rotor from the perspective which the helix angle between long edge and short edge has some difference. The specialized viscoelastic fluid software--Polyflow is used to dynamic simulation analyze the two different kinds of rotors during the process of flow mixing, and then to analyze the two kinds of rotor performance through the result of transient flow simulation which mixed for one second. The analysis revealed that the improved synchronous rotor had better axial tensile properties in the case of remaining the original performance basically unchanged. And that could improve mixing performance and the production efficiency of mixer more effectively. There will provide a theoretical basis for the optimization of the rotor configuration in future.

Local characteristic of horizontal air–water two-phase flow by wire-mesh sensor

2016 ◽  
Vol 40 (3) ◽  
pp. 746-761 ◽  
Author(s):  
Weiling Liu ◽  
Chao Tan ◽  
Feng Dong
Keyword(s):  
Void Fraction ◽  
Transient Flow ◽  
Two Phase Flow ◽  
Wire Mesh ◽  
Local Characteristic ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Local Flow

Two-phase flow widely exists in many industries. Understanding local characteristics of two-phase flow under different flow conditions in piping systems is important to design and optimize the industrial process for higher productivity and lower cost. Air–water two-phase flow experiments were conducted with a 16×16 conductivity wire-mesh sensor (WMS) in a horizontal pipe of a multiphase flow facility. The cross-sectional void fraction time series was analysed by the probability density function (PDF), which described the void fraction fluctuation at different flow conditions. The changes and causes of PDFs during a flow regime transition were analysed. The local structure and flow behaviour were characterized by the local flow spectrum energy analysis and the local void fraction distribution (horizontal, vertical and radial direction) analysis. Finally, three-dimensional transient flow fluctuation energy evolution and characteristic scale distribution based on wavelet analysis of air–water two-phase flow were presented, which revealed the structural features of each phase in two-phase flow.

Sailing Yacht Design Using Advanced Numerical Flow Techniques

1999 ◽  
Author(s):  
Mario Caponnetto ◽  
Alessandro Castelli ◽  
Philippe Dupont ◽  
Bernard Bonjour ◽  
Pierre-Louis Mathey ◽  
...  
Keyword(s):  
Computer Technology ◽  
Flow Simulation ◽  
Numerical Techniques ◽  
Flow Simulations ◽  
Competitive Edge ◽  
Numerical Flow Simulation ◽  
Sailing Yacht ◽  
America’S Cup ◽  
École Polytechnique ◽  
First Time

The 30th America's Cup will be held in New Zealand, commencing in October 1999. For the first time a Swiss team, the FAST2000 Challenge of the Club Nautique Morgien, will compete. Three laboratories of the EPFL (Ecole Polytechnique Federale de Lausanne) are collaborating with FAST2000 in the design of the boat that will race in the Cup challenges. Present-day design of IACC racing yachts relies on the use of numerical flow simulations to obtain a competitive edge. The computation of the complex hydrodynamic and aerodynamic flows around sailing yachts provides valuable information to supplement the more conventional empirical and experimental design techniques. Such flow simulations, however, are extremely challenging and thus often require state­of-the-art numerical techniques and computer technology. A number of the issues critical to IACC yacht design are discussed, and various approaches described to address them through the use of advanced numerical flow simulation.

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