scholarly journals Quantifying the economy of flow distribution in water supply looped networks

2011 ◽  
Vol 13 (4) ◽  
pp. 687-698 ◽  
Author(s):  
Jose Bienvenido Martínez
Keyword(s):  
Water Supply ◽  
Network Optimization ◽  
Pipe Flow ◽  
Optimization Problem ◽  
Flow Distribution ◽  
Global Solutions ◽  
Clear Understanding ◽  
Decision Variables ◽  
New Concepts ◽  
Looped Network

Optimization of water supply looped networks has attracted a great deal of attention from researchers for more than 30 years. As the classical water supply looped network optimization problem is mathematically non-convex and multimodal, the resulting solution of most approaches is uncertain in the sense of how close it is to the “best” solution. In many cases, this “best” or “global” solution is invoked and pursued only intuitively without a clear understanding of its meaning. This paper discusses what is involved in “global” solutions and the role that pipe flow distribution can play to deal with non-convexity and multimodality in a new context. The author has introduced this new context recently after formulating a new objective function capable of finding a looped network that can be economically more attractive than its related branched one. Therefore, the convenience of an approach dealing with flows and heads, as relevant decision variables, is encouraged in this paper and its advantages enumerated under the new concepts. The entropy approach is studied critically and an example is provided for comparison with the proposed approach.

A Method for Distributed Optimization for Task Allocation

2009 ◽  
Author(s):  
Sheng Zhao ◽  
Baisravan HomChaudhuri ◽  
Manish Kumar
Keyword(s):  
Information Exchange ◽  
Optimization Problem ◽  
Global Solutions ◽  
Challenging Problem ◽  
Complex Environment ◽  
Dynamic Nature ◽  
Decision Variables ◽  
Wildland Firefighting

Allocation of a large number of resources to tasks in a complex environment is often a very challenging problem. This is primarily due to the fact that a large number of resources to be allocated results into an optimization problem that involves a large number of decision variables. Most of the optimization algorithms suffer from this issue of non-scalability. Further, the uncertainties and dynamic nature of environment make the optimization problem quite challenging. One of the techniques to overcome the issue of scalability that have been considered recently is to carry out the optimization in a distributed or decentralized manner. Such techniques make use of local information to carry out global optimization. However, such techniques tend to get stuck in local minima. Further, the connectivity graph that governs the sharing of information plays a role in the performance of algorithms in terms of time taken to obtain the solution, and quality of the solution with respect to the global solution. In this paper, we propose a distributed greedy algorithm inspired by market based concepts to optimize a cost function. This paper studies the effectiveness of the proposed distributed algorithm in obtaining global solutions and the phase transition phenomenon with regard to the connectivity metrics of the graph that underlies the network of information exchange. A case study involving resource allocation in wildland firefighting is provided to demonstrate our algorithm.

An In-Pipe Leak Detection Sensor: Sensing Capabilities and Evaluation

2011 ◽  
Author(s):  
Dimitris M. Chatzigeorgiou ◽  
Atia E. Khalifa ◽  
Kamal Youcef-Toumi ◽  
Rached Ben-Mansour
Keyword(s):  
Water Supply ◽  
Environmental Health ◽  
Fresh Water ◽  
Detection System ◽  
Acoustic Emissions ◽  
Leak Detection ◽  
Acoustic Signals ◽  
Clear Understanding ◽  
Water Pipes ◽  
Water Pipeline

In most cases the deleterious effects associated with the occurrence of leak may present serious problems and therefore leaks must be quickly detected, located and repaired. The problem of leakage becomes even more serious when it is concerned with the vital supply of fresh water to the community. In addition to waste of resources, contaminants may infiltrate into the water supply. The possibility of environmental health disasters due to delay in detection of water pipeline leaks has spurred research into the development of methods for pipeline leak and contamination detection. Leaks in water pipes create acoustic emissions, which can be sensed to identify and localize leaks. Leak noise correlators and listening devices have been reported in the literature as successful approaches to leak detection but they have practical limitations in terms of cost, sensitivity, reliability and scalability. To overcome those limitations the development of an in-pipe traveling leak detection system is proposed. The development of such a system requires a clear understanding of acoustic signals generated from leaks and the study of the variation of those signals with different pipe loading conditions, leak sizes and surrounding media. This paper discusses those signals and evaluates the merits of an in-pipe-floating sensor.

On the Nature of Critical Heat Flux in Microchannels

2005 ◽  
Vol 127 (1) ◽  
pp. 101-107 ◽  
Author(s):  
A. E. Bergles ◽  
S. G. Kandlikar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Flow Distribution ◽  
High Heat ◽  
Operating Conditions ◽  
High Heat Flux ◽  
Clear Understanding ◽  
Wide Range ◽  
Parallel Microchannels

The critical heat flux (CHF) limit is an important consideration in the design of most flow boiling systems. Before the use of microchannels under saturated flow boiling conditions becomes widely accepted in cooling of high-heat-flux devices, such as electronics and laser diodes, it is essential to have a clear understanding of the CHF mechanism. This must be coupled with an extensive database covering a wide range of fluids, channel configurations, and operating conditions. The experiments required to obtain this information pose unique challenges. Among other issues, flow distribution among parallel channels, conjugate effects, and instrumentation need to be considered. An examination of the limited CHF data indicates that CHF in parallel microchannels seems to be the result of either an upstream compressible volume instability or an excursive instability rather than the conventional dryout mechanism. It is expected that the CHF in parallel microchannels would be higher if the flow is stabilized by an orifice at the entrance of each channel. The nature of CHF in microchannels is thus different than anticipated, but recent advances in microelectronic fabrication may make it possible to realize the higher power levels.

scholarly journals A Location-Allocation Model for Seaport-Dry Port System Optimization

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Xuejun Feng ◽  
Yan Zhang ◽  
Yuwei Li ◽  
Wei Wang
Keyword(s):  
Network Optimization ◽  
Optimization Problem ◽  
System Optimization ◽  
The West ◽  
Allocation Model ◽  
Location Allocation ◽  
Port System ◽  
The Taiwan Strait ◽  
Dry Ports

Seaports participate in hinterland economic development through partnerships with dry ports, and the combined seaport-dry port network serves as the backbone of regional logistics. This paper constructs a location-allocation model for the regional seaport-dry port network optimization problem and develops a greedy algorithm and a genetic algorithm to obtain its solution. This model is applicable to situations under which the geographic distribution of demand is known. A case study involving configuration of dry ports near the west bank of the Taiwan Strait is conducted, and the model is successfully applied.

scholarly journals Theoretical perspective on the route to turbulence in a pipe

2016 ◽  
Vol 803 ◽  
Author(s):  
D. Barkley
Keyword(s):  
Pipe Flow ◽  
Theoretical Perspective ◽  
Transition Process ◽  
Turbulent Pipe Flow ◽  
Rapid Expansion ◽  
Clear Understanding ◽  
Percolation Transition ◽  
Spatiotemporal Process ◽  
Physical Features ◽  
The Relationship

The route to turbulence in pipe flow is a complex, nonlinear, spatiotemporal process for which an increasingly clear understanding has emerged in recent years. This paper presents a theoretical perspective on the problem, focusing on what can be understood from relatively few physical features and models that encompass these features. The paper proceeds step-by-step with increasing detail about the transition process, first discussing the relationship to phase transitions and then exploiting an even deeper connection between pipe flow and excitable and bistable media. In the end a picture emerges for all stages of the transition process, from transient turbulence, to the onset of sustained turbulence in a percolation transition, to the modest and then rapid expansion of turbulence, ultimately leading to fully turbulent pipe flow.

SURFACE EFFECT CORRECTION OF MOISTURE DETERMINATION BY NEUTRON PROBE USING PSO TECHNIQUE AND MCNP

2009 ◽  
Vol 06 (02) ◽  
pp. 247-255
Author(s):  
ALI ASGHAR MOWLAWI ◽  
HADI SADOGHI YAZDI ◽  
MEHDI ARGHIANI ◽  
JABER ROOHI ◽  
RAHIM KOOHI-FAYEGH ◽  
...  
Keyword(s):  
Optimization Problem ◽  
Optimization Problems ◽  
Surface Effect ◽  
Soil Surface ◽  
Moisture Determination ◽  
Swarm Optimization ◽  
Convex Optimization Problem ◽  
Neutron Probe ◽  
Decision Variables ◽  
Paraffin Block

The usefulness of the neutron meter is limited for moisture measurement near the soil surface. In this present work, optimum dimension of a paraffin block has been calculated to correct the surface effect in order to use neutron probe near the soil surface by MCNP4C code and Particle Swarm Optimization (PSO) technique. PSO is chiefly a technique to find a global or quasi-minimum for a nonlinear and non-convex optimization problem, and there have been few studies into optimization problems with discrete decision variables. The results show a paraffin block 23.55 × 23.55 cm2 square base with 4.84, 4.92, 5.10, 5.23, and 5.47 cm thickness which can correct the surface effect fairly for 0.10, 0.20, 0.30, 0.40, and 0.50 g/g moisture.

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