MODELING OF BEDROCK CHANNEL AND CAVE EVOLUTION USING COMPUTATIONAL FLUID DYNAMICS

In most numerical speleogenesis models conduit segments are treated in a simplified way. Most typically, they are described by two parameters, such as length and diameter. Additionally, almost all such models study the early stages of speleogenesis, do not progress beyond the point when full pipe flow switches to free surface flow, and ignore erosion mechanisms other than dissolution. Thus existing models are not suitable for explaining cave morphology on the reach scale. To examine dynamics such as cross-section evolution, changing channel wall roughness, channel width variation, and the role of sediment and mechanical erosion, we introduce a computational fluid dynamics (CFD) framework for speleogenesis modeling.

Using CFD, a solution for water flow in a three-dimensional segment of a conduit is obtained. Information on the flow, in particular shear stress at the wall, can be used to calculate dissolution, erosion, sediment transport, and evolution of the channel that accounts for all of these factors. Since cave passages often preserve long records of channel incision, we are using the CFD model to explore the controls on channel width. Ultimately, such analysis may aid interpretation of cave passage morphologies as they relate to past discharge, climate, and sediment load.