Karst and Cave RSS news feed Like us on Facebook! follow us on Twitter!
Community news

Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

Speleology in Kazakhstan

Shakalov on 11 Jul, 2012
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

Did you know?

That prism storage is the storage of water in a river channel or reservoir in prism above the original water level [16].?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms

What is Karstbase?



Browse Speleogenesis Issues:

KarstBase a bibliography database in karst and cave science.

Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
See all featured articles
Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
See all featured articles from other geoscience journals

Search in KarstBase

Your search for hybrid model (Keyword) returned 5 results for the whole karstbase:
A New Equation Solver for Modeling Turbulent Flow in Coupled Matrix‐Conduit Flow Models, ,

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.

Do you want to read the rest of this publication?


Karst and Early Fracture Networks in Carbonates, Turks and Caicos Islands, British West Indies, 2007, Guidry Sean A. , Grasmueck Mark, Carpenter Daniel G. , Gombos Andrew M. Jr. , Bachtel Steven L. , Viggiano David A. ,
Historically, studies of Quaternary carbonates have not adequately addressed the influence of early fracture networks on diagenesis. Because of this lack of detail, understanding and predicting fracture-related diagenetic heterogeneities and preferential fluid flow pathways in ancient carbonate successions is particularly challenging. The Pleistocene oolitic grainstones of the Caicos platform provide an excellent opportunity to evaluate the relative importance of fractures on early diagenetic alteration styles, and are a suitable analog for subsurface carbonate reservoirs. Detailed analyses of fractures (e.g., orientation, aperture, spacing, fill material) from Caicos outcrops combined with high-resolution, three-dimensional ground-penetrating radar (3D GPR), assisted in exploring the causality and distribution of fractures and relationship to karst. Four models were evaluated to explain the observed distribution of dolines: (1) gravitational, fractured-margin controlled, (2) tectonic-fracture controlled, (3) antecedent-topography controlled, and (4) a hybrid model. Based on observations of numerous fractures (n = 306) on the western Caicos platform, early fractures are abundant and dominantly margin-parallel. These fracture networks are well established in limestones prior to mineralogical stabilization, thereby indicating that diagenetic heterogeneities evolve very early in carbonate diagenesis. The spatial distribution of dolines on Providenciales is likely the result of a complex interplay between the antecedent topography, margin-parallel fracture systems, and meteoric fluids. Resultant diagenetic alteration is far more complicated than simple, unconfined, meteoric lenses associated with topographic highs. Any attempts to model early diagenesis in carbonates should not dismiss the role of fractures as diagenetic facilitators and diagenetic anisotropy templates

Arches: a Framework for Modeling Complex Terrains, 2009,

In this paper, we present a framework for representing complex terrains with such features as overhangs, arches and caves and including different materials such as sand and rocks. Our hybrid model combines a volumetric discrete data structure that stores the different materials and an implicit representation for sculpting and reconstructing the surface of the terrain. Complex scenes can be edited and sculpted interactively with high level tools. We also propose an original rock generation technique that enables us to automatically generate complex rocky sceneries with piles of rocks without any computationally demanding physically-based simulation.

The significance of turbulent flow representation in single-continuum models, 2011, Reimann T. , Rehrl C. , Shoemaker W. B. , Geyer T. , Birk S.

Karst aquifers evolve where the dissolution of soluble rocks causes the enlargement of discrete pathways along fractures or bedding planes, thus creating highly conductive solution conduits. To identify general interrelations between hydrogeological conditions and the properties of the evolving conduit systems the aperture-size frequency distributions resulting from generic models of conduit evolution are analysed. For this purpose, a process-based numerical model coupling flow and rock dissolution is employed. Initial protoconduits are represented by tubes with log-normally distributed aperture sizes with a mean ?0 = 0.5 mm for the logarithm of the diameters. Apertures are spatially uncorrelated and widen up to the metre range due to dissolution by chemically aggressive waters. Several examples of conduit development are examined focussing on influences of the initial heterogeneity and the available amount of recharge. If the available recharge is sufficiently high the evolving conduits compete for flow and those with large apertures and high hydraulic gradients attract more and more water. As a consequence, the positive feedback between increasing flow and dissolution causes the breakthrough of a conduit pathway connecting the recharge and discharge sides of the modelling domain. Under these competitive flow conditions dynamically stable bimodal aperture distributions are found to evolve, i.e. a certain percentage of tubes continues to be enlarged while the remaining tubes stay small-sized. The percentage of strongly widened tubes is found to be independent of the breakthrough time and decreases with increasing heterogeneity of the initial apertures and decreasing amount of available water. If the competition for flow is suppressed because the availability of water is strongly limited breakthrough of a conduit pathway is inhibited and the conduit pathways widen very slowly. The resulting aperture distributions are found to be unimodal covering some orders of magnitudes in size. Under these suppressed flow conditions the entire range of apertures continues to be enlarged. Hence, the number of tubes reaching aperture sizes in the order of centimetres or decimetres continues to increase with time and in the long term may exceed the number of large-sized tubes evolving under competitive flow conditions. This suggests that conduit development under suppressed flow conditions may significantly enhance the permeability of the formation, e.g. in deep-seated carbonate settings.

Effects of dynamically variable saturation and matrix-conduit coupling of flow in karst aquifers, 2011, Reimann T. , Geyer T. , Shoemaker W. B. , Liedl R. , Sauter M.

Well-developed karst aquifers consist of highly conductive conduits and a relatively  low permeability fractured and/or porous rock matrix and therefore behave as a dualhydraulic  system. Groundwater flow within highly permeable strata is rapid and transient  and depends on local flow conditions, i.e., pressurized or nonpressurized flow. The  characterization of karst aquifers is a necessary and challenging task because information  about hydraulic and spatial conduit properties is poorly defined or unknown. To investigate  karst aquifers, hydraulic stresses such as large recharge events can be simulated with hybrid  (coupled discrete continuum) models. Since existing hybrid models are simplifications of  the system dynamics, a new karst model (ModBraC) is presented that accounts for unsteady  and nonuniform discrete flow in variably saturated conduits employing the Saint-Venant  equations. Model performance tests indicate that ModBraC is able to simulate (1) unsteady  and nonuniform flow in variably filled conduits, (2) draining and refilling of conduits with  stable transition between free-surface and pressurized flow and correct storage  representation, (3) water exchange between matrix and variably filled conduits, and (4)  discharge routing through branched and intermeshed conduit networks. Subsequently,  ModBraC is applied to an idealized catchment to investigate the significance of free-surface  flow representation. A parameter study is conducted with two different initial conditions:  (1) pressurized flow and (2) free-surface flow. If free-surface flow prevails, the systems is  characterized by (1) a time lag for signal transmission, (2) a typical spring discharge pattern  representing the transition from pressurized to free-surface flow, and (3) a reduced conduitmatrix  interaction during free-surface flow.

Results 1 to 5 of 5
You probably didn't submit anything to search for