Numerical method improvement for a subchannel code
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W. J. Ding
Abstract
Previous studies showed that the subchannel codes need most CPU time to solve the matrix formed by the conservation equations. Traditional matrix solving method such as Gaussian elimination method and Gaussian-Seidel iteration method cannot meet the requirement of the computational efficiency. Therefore, a new algorithm for solving the block penta-diagonal matrix is designed based on Stone's incomplete LU (ILU) decomposition method. In the new algorithm, the original block penta-diagonal matrix will be decomposed into a block upper triangular matrix and a lower block triangular matrix as well as a nonzero small matrix. After that, the LU algorithm is applied to solve the matrix until the convergence. In order to compare the computational efficiency, the new designed algorithm is applied to the ATHAS code in this paper. The calculation results show that more than 80 % of the total CPU time can be saved with the new designed ILU algorithm for a 324-channel PWR assembly problem, compared with the original ATHAS code.
Kurzfassung
Programme zur Berechnung von Unterkanalanalysen, wie das Programm ATHAS, benötigen den Hauptteil der CPU-Zeit zur Lösung der Matrix der Erhaltungsgleichungen. Traditionelle Lösungsalgorithmen basieren auf der Gausselemination und dem Gaus-Seidel-Einzelschrittverfahren und erfüllen nicht die Anforderungen an eine effiziente Umsetzung in schnelle Lösungsalgorithemn. Daher wurde ein neuer Algorithmus zur Lösung der penta-diagonalen Gleichungsmatrix basierend auf der unvollständigen LR-Zerlegung von Stone entwickelt. Dabei wird die Original-Matrix in eine obere Dreieckmatrix und eine untere Dreieckmatrix sowie eine kleine Matrix mit Nicht-Null-Werten zerlegt. Dann wird diese bis zum Erreichen der Konvergenz gelöst. Der neue Algorithmus wurde in das Programm ATHAS eingebaut und die Verkürzung der Rechenzeit wurde im Vergleich zur ursprünglichen Version gemessen. Für eine DWRtypische Anwendung mit einem 324-Kanal-Kern zeigte sich eine Verkürzung der CPU-Zeit um 80 %.
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© 2016, Carl Hanser Verlag, München
Articles in the same Issue
- Contents/Inhalt
- Contents
- Summaries/Kurzfassungen
- Summaries
- Editorial
- Challenges in reactor core thermal-hydraulics: subchannel analysis, CFD modeling and rod bundle CHF
- Technical Contributions/Fachbeiträge
- Subchannel analysis and correlation of the Rod Bundle Heat Transfer (RBHT) steam cooling experimental data
- CFD analysis on mixing effects of spacer grids with different dimples and sizes for advanced fuel assemblies
- An experimental investigation on dynamics and heat transfer associated with a single droplet impacting on a hot surface above the Leidenfrost point temperature
- Study on effects of mixing vane grids on coolant temperature distribution by subchannel analysis
- Reflood experiments in rod bundles with flow blockages due to clad ballooning
- The effect of spacer grid critical component on pressure drop under both single and two phase flow conditions
- Numerical method improvement for a subchannel code
- Numerical investigation on the characteristics of two-phase flow in fuel assemblies with spacer grid
- Effects of axial power shapes on CHF locations in a single tube and in rod bundle assemblies
- CFD evaluation on the thermohydraulic characteristics of tube support plates in steam generator
- Analysis of heat transfer under high heat flux nucleate boiling conditions
- Review of the correlation developments and a new concept based on mixing mechanism for heat transfer enhancement of spacer grids
- A comparison of the CFD simulation results in 5 × 5 sub-channels with mixing grids using different turbulence models
- Simulation of isothermal multi-phase fuel-coolant interaction using MPS method with GPU acceleration
- RELAP5 investigation on subchannel flow instability
Articles in the same Issue
- Contents/Inhalt
- Contents
- Summaries/Kurzfassungen
- Summaries
- Editorial
- Challenges in reactor core thermal-hydraulics: subchannel analysis, CFD modeling and rod bundle CHF
- Technical Contributions/Fachbeiträge
- Subchannel analysis and correlation of the Rod Bundle Heat Transfer (RBHT) steam cooling experimental data
- CFD analysis on mixing effects of spacer grids with different dimples and sizes for advanced fuel assemblies
- An experimental investigation on dynamics and heat transfer associated with a single droplet impacting on a hot surface above the Leidenfrost point temperature
- Study on effects of mixing vane grids on coolant temperature distribution by subchannel analysis
- Reflood experiments in rod bundles with flow blockages due to clad ballooning
- The effect of spacer grid critical component on pressure drop under both single and two phase flow conditions
- Numerical method improvement for a subchannel code
- Numerical investigation on the characteristics of two-phase flow in fuel assemblies with spacer grid
- Effects of axial power shapes on CHF locations in a single tube and in rod bundle assemblies
- CFD evaluation on the thermohydraulic characteristics of tube support plates in steam generator
- Analysis of heat transfer under high heat flux nucleate boiling conditions
- Review of the correlation developments and a new concept based on mixing mechanism for heat transfer enhancement of spacer grids
- A comparison of the CFD simulation results in 5 × 5 sub-channels with mixing grids using different turbulence models
- Simulation of isothermal multi-phase fuel-coolant interaction using MPS method with GPU acceleration
- RELAP5 investigation on subchannel flow instability
