A New Equation Solver for Modeling Turbulent Flow in Coupled Matrix‐Conduit Flow Models. Issue 4 (28th January 2016)

• Record Type: Journal Article
• Authors: Hubinger, Bernhard; Birk, Steffen; Hergarten, Stefan
• Is Part Of: Ground water. Volume 54:Issue 4(2016:Jul./Aug.)
• Page Start: 596
• Page End: 602
• Publication Date: 2016-01-28
• Subjects: Groundwater -- Periodicals; Wells -- Periodicals; Eau souterraine -- Périodiques; Puits -- Périodiques; Grondwater; Eau souterraine; Puits; Electronic journals; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 551.49
• DOI: 10.1111/gwat.12400
• Languages: English
• ISSNs: 0017-467X

Abstract

Abstract: Karst aquifers represent dual flow systems consisting of a highly conductive conduit system embedded in a less permeable rock matrix. Hybrid models iteratively coupling both flow systems generally consume much time, especially because of the nonlinearity of turbulent conduit flow. To reduce calculation times compared to those of existing approaches, a new iterative equation solver for the conduit system is developed based on an approximated Newton–Raphson expression and a Gauß–Seidel or successive over‐relaxation scheme with a single iteration step at the innermost level. It is implemented and tested in the research code CAVE but should be easily adaptable to similar models such as the Conduit Flow Process for MODFLOW‐2005. It substantially reduces the computational effort as demonstrated by steady‐state benchmark scenarios as well as by transient karst genesis simulations. Water balance errors are found to be acceptable in most of the test cases. However, the performance and accuracy may deteriorate under unfavorable conditions such as sudden, strong changes of the flow field at some stages of the karst genesis simulations. Abstract : Article impact statement : Provides a new method for solving the nonlinear equation system representing turbulent conduit flow in numerical karst groundwater models.