The dynamics of shallow water oceanographic moorings: experimental and numerical results

Large scope chain moorings which accommodate current-, tidal-, and wave-induced deformations by lifting and lowering excess chain from the sea floor are common for oceanographic applications in coastal areas. With an increasing demand for deployments on the order of a year or longer, there is a need for a better understanding of the static and dynamic response of these systems. This paper describes an engineering experiment conducted with an instrumented surface buoy and chain mooring in 40 m of water off the Massachusetts coast during a portion of the winter storm season. The instrumentation is described and select results are presented. The experimental results are compared with numerical model results from WHOI Cable, a numerical simulation program for oceanographic cable structures. The numerical model is then used to analyze the dynamics of the mooring over a range of hydrodynamic coefficients. Conclusions are drawn about the relative importance of inertial and drag effects in forming the total dynamic response.