Modernization of Todini Global Gradient Algorithm for hydraulic analysis of networks with choked flow

The modification of well-known Global Gradient Algorithm for hydraulic network flow distribution problem is proposed. This modification is based on problem equations rewritten in “upstream” form and on modified form of linearization, and can be effectively used for piping networks with gas and multiphase gas-liquid flow with multiple choked flow.

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Hydraulic networks with pressure-dependent closure relations, under restrictions on the value of nodal pressures. Maxwell matrix properties and monotonicity of flow distribution problem solution

E3S Web of Conferences ◽

10.1051/e3sconf/201910201005 ◽

2019 ◽

Vol 102 ◽

pp. 01005 ◽

Cited By ~ 1

Author(s):

Leonid Korelstein

Keyword(s):

Existence Theorems ◽

Flow Distribution ◽

Previous Article ◽

Problem Solution ◽

Distribution Problem ◽

Matrix Properties ◽

Hydraulic Network ◽

Closure Relations ◽

Hydraulic Networks

In the article, which continues the research of article [1], the results of previous article are generalized to “abstract” hydraulic networks. Additional existence theorems are proved for classical flow distribution problem (CFDP) for hydraulic networks with pressure-dependent closure relations, under restriction on nodal pressures. Hydraulic network Maxwell matrix properties are establish, related to monotonicity of CFDP solution.

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A method of analysis of complex hydraulic networks

E3S Web of Conferences ◽

10.1051/e3sconf/202021901002 ◽

2020 ◽

Vol 219 ◽

pp. 01002

Author(s):

Leonid Duginov ◽

Michael Rozovskiy ◽

Leonid Korelstein

Keyword(s):

Loss Function ◽

Flow Rate ◽

Network Flow ◽

Solution Method ◽

Iterative Solution ◽

Distribution Problem ◽

Rate Distribution ◽

Hydraulic Network ◽

Hydraulic Networks ◽

Iterative Solution Method

A simple and reliable iterative solution method of classical hydraulic network flow rate distribution problem is described. The method is based on chord linearization of inverse branch loss function which keeps basic branch properties. It has good speed of convergency which is practically independent of initial values.

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The Location Problem of Given and Indivisible Different Units

Environment and Planning A Economy and Space ◽

10.1068/a020341 ◽

1970 ◽

Vol 2 (3) ◽

pp. 341-356

Author(s):

G. Jándy

Keyword(s):

Exact Solution ◽

Heuristic Algorithm ◽

Network Flow ◽

Location Problem ◽

Optimal Solution ◽

Type Problem ◽

Distribution Problem ◽

Enumeration Algorithm ◽

Weighted Distribution ◽

Partial Enumeration

In cases where certain simplifications are allowed, the location optimisation of given and indivisible different economic units may be modelled as a bi-value weighted distribution problem. The paper presents a heuristic algorithm for this network-flow-type problem and also a partial enumeration algorithm for deriving the exact solution. But it is also pointed out that an initial sub-optimal solution can quickly be improved with a derivation on a direct line only, if the exact solution is not absolutely essential. A numerical example is used to illustrate the method of derivation on a direct line starting with an upper bound given by a sub-optimal solution.

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Research on Influence of Different Simulation Methods of Bypass Flow in Thermal Hydraulic Analysis on Temperature Distribution in HTR-10

Science and Technology of Nuclear Installations ◽

10.1155/2020/4754589 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Shiyan Sun ◽

Youjie Zhang ◽

Yanhua Zheng

Keyword(s):

Temperature Distribution ◽

Reactor Core ◽

Flow Distribution ◽

Maximum Temperature ◽

Flow Ratio ◽

Hydraulic Analysis ◽

Bypass Flow ◽

Pebble Bed ◽

The Core ◽

Thermal Hydraulic Analysis

In pebble-bed high temperature gas-cooled reactor, gaps widely exist between graphite blocks and carbon bricks in the reactor core vessel. The bypass helium flowing through the gaps affects the flow distribution of the core and weakens the effective cooling of the core by helium, which in turn affects the temperature distribution and the safety features of the reactor. In this paper, the thermal hydraulic analysis models of HTR-10 with bypass flow channels simulated at different positions are designed based on the flow distribution scheme of the original core models and combined with the actual position of the core bypass flow. The results show that the bypass coolant flowing through the reflectors enhances the heat transfer of the nearby components efficiently. The temperature of the side reflectors and the carbon bricks is much lower with more side bypass coolant. The temperature distribution of the central region in the pebble bed is affected by the bypass flow positions slightly, while that of the peripheral area is affected significantly. The maximum temperature of the helium, the surface, and center of the fuel elements rises as the bypass flow ratio becomes larger, while the temperature difference between them almost keeps constant. When the flow ratio of each part keeps constant, the maximum temperature almost does not change with different bypass flow positions.

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Extending the Global-Gradient Algorithm to Solve Pressure-Control Valves

Journal of Water Resources Planning and Management ◽

10.1061/(asce)wr.1943-5452.0001247 ◽

2020 ◽

Vol 146 (8) ◽

pp. 04020055

Author(s):

Gioia Foglianti ◽

Stefano Alvisi ◽

Marco Franchini ◽

Ezio Todini

Keyword(s):

Pressure Control ◽

Gradient Algorithm ◽

Control Valves ◽

Global Gradient Algorithm

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A control method for flow distribution in fuel-cooled plate based on choked flow effect

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2018.06.065 ◽

2018 ◽

Vol 142 ◽

pp. 127-137 ◽

Cited By ~ 4

Author(s):

Yu Chen ◽

Bin Liu ◽

Zhiliang Lei ◽

Qiyi Zhang ◽

Quan Zhu ◽

...

Keyword(s):

Control Method ◽

Flow Distribution ◽

Flow Effect ◽

Choked Flow

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Deposition of aerosol particles and flow resistance in mathematical and experimental airway models

Journal of Applied Physiology ◽

10.1152/jappl.1983.55.1.154 ◽

1983 ◽

Vol 55 (1) ◽

pp. 154-163 ◽

Cited By ~ 61

Author(s):

C. S. Kim ◽

L. K. Brown ◽

G. G. Lewars ◽

M. A. Sackner

Keyword(s):

Flow Resistance ◽

Airway Resistance ◽

Flow Distribution ◽

Aerosol Deposition ◽

Lung Model ◽

Straight Tube ◽

Small Airways ◽

Two Phase ◽

Gas Liquid Flow ◽

Airway Walls

Aerosol deposition and flow resistance in obstructed airways were determined from five mathematical and experimental airway models. The first three models were theoretical and based upon Weibel's symmetrical lung model with 1) uniform reduction of airway diameter in various groups of airway generations; 2) obstruction of a few major airways such that a severe uneven flow distribution occurs in the lung; 3) focal constriction of selected large airways. In model 3, an empirical formula was utilized to assess deposition and resistance in the constricted airways. The remaining two models were tested experimentally; 4) oscillation of a compliant wall in a straight tube and 5) two-phase gas-liquid flow utilizing human sputum in a rigid branching tube. In models 1, 2, and 3, airway resistance increased to a greater extent than did the increase of aerosol deposition except when small airways were obstructed in model 1. Here, the increase of aerosol deposition was slightly higher than the rise in airway resistance. A sharp increase of aerosol deposition with a minimal increase of flow resistance was demonstrated in models 4 and 5. These data indicate that aerosol deposition may be a more sensitive indicator of airway abnormalities than overall airway resistance in small airways obstruction, during oscillation of large and medium airway walls, and when excessive secretions within the airways move with a wave or slug motion.

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Testing linear solvers for global gradient algorithm

Journal of Hydroinformatics ◽

10.2166/hydro.2014.136 ◽

2014 ◽

Vol 16 (5) ◽

pp. 1178-1193 ◽

Cited By ~ 4

Author(s):

Orazio Giustolisi ◽

Naser Moosavian

Keyword(s):

Linear System ◽

Water Distribution ◽

Direct Method ◽

Mathematical Problem ◽

Network Models ◽

Water Distribution Network ◽

Mass Conservation ◽

Gradient Algorithm ◽

Global Gradient Algorithm ◽

Pressure Driven

Steady-state Water Distribution Network models compute pipe flows and nodal heads for assumed nodal demands, pipe hydraulic resistances, etc. The nonlinear mathematical problem is based on energy and mass conservation laws which is solved by using global linearization techniques, such as global gradient algorithm (GGA). The matrix of coefficients of the linear system inside GGA belongs to the class of sparse, symmetric and positive definite. Therefore a fast solver for the linear system is important in order to achieve the computational efficiency, especially when multiple runs are required. This work aims at testing three main strategies for the solution of linear systems inside GGA. The tests are performed on eight real networks by sampling nodal demands, considering the pressure-driven and demand-driven modelling to evaluate the robustness of solvers. The results show that there exists a robust specialized direct method which is superior to all the other alternatives. Furthermore, it is found that the number of times the linear system is solved inside the GGA does not depend on the specific solver, if a small regularization to the linear problem is applied, and that pressure-driven modelling requires a greater number which depends on the size and topology of the network and not only on the level of pressure deficiency.

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