The velocity field within scale models of branching coral Stylophora pistillata colonies was measured using magnetic resonance velocimetry (MRV). The models were based on digital representations of real coral skeletons derived using X-ray computed tomography (CT) and constructed using rapid-prototype manufacturing. Two morphologies of S. pistillata from the Red Sea grown in different flow regimes were used. To simplify visualization of the data, velocities were parsed into a series of spherical shells, giving the velocity distributions as functions of distance from coral center for both morphologies. The low-flow morphology distributed flow velocity relatively evenly throughout the interior. In contrast, the high-flow morphology showed a wider range of velocities with regions of flow channeling and flow stagnation.

Flows through single coral colonies were simulated with an implementation of the Immersed Boundary (IB) method in Large-Eddy Simulation (LES). The method was first validated with magnetic velocimetry experiments, which demonstrated that computational results were within approximately 7% of flow measurements. The algorithm was then applied to simulate unidirectional and wave-driven flow conditions through two morphologically distinct coral colonies that naturally grow in very different hydrodynamic environments, with detailed analysis on spatial hydrodynamic and mass transfer variability. When the hydrodynamics of each coral's native environment was simulated, the dynamics in the interior of both branching species appeared to converge, in spite of vast differences between the hydrodynamic conditions and morphologies. A correlation between local surface shear and mass transfer was derived from simulated data. The results suggest that the corals grew in such a way that mass transfer characteristics are similar despite of vast differences in their physical shapes and hydrodynamic conditions.

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