Coupled Actuator Line and Finite Element Analysis Tool

Abstract

Fluid-dynamic loading of many solid bodies can be simulated using geometry resolving computational fluid dynamics methods, where the body's shape is resolved in the mesh. In some cases though slender bodies, like ropes or cables, spars, turbine blades, foils and lattice structures would require prohibitively high cell counts, since the geometrical features to be resolve are much smaller than the overall domain. Such bodies are usually made up of generic cross sections like round, square or standardised technical profiles like the famous NACA digit series for which good parametrisations of reaction forces to incoming flow exist. Actuator line methods apply inflow dependent reaction forces to the fluid domain, thus allowing the computationally efficient simulation of slender bodies and have been used extensively, for example in wind and tidal turbine simulations. Beam elements representing slender bodies are standard building blocks in structural finite element models. Combining actuator line theory with a finite element beam model allows the efficient simulation of flexible structures under fluid loads, like turbine blades or nettings used in fish farms. This paper presents an implementation of such a coupled model in OpenFOAM based on the existing turbineFoam actuator line model. The underlying numerical method is detailed and first test cases are provided.