Series of experiments was conducted variously in a towing tank, a flume am a wind tunnel to obtain steady flow coefficients for bluff-bodied workboat ROVs. The attributes of these different test facilities are contrasted, and it is suggested that variations in the coefficient values measured at the same Reynolds number in different facilities result from differences in the level of free stream turbulence in each. This appears to influence flow separation from the corner radii of the hulls, am hence the vortex shedding, with resultant variations in resistance am transverse forces, since ROVs will generally operate in high levels of freestream turbulence, it is argued that similar conditions should be created, and carefully controlled, in subsequent experimental programmes. In addition to corner radius effects, the influence of hull solidity factor am the effects of blockage to the inflow am outflow of thrusters were also investigated. A faired, enclosed hull form, developed in the light of the experimental findings, was tested in a wind tunnel, am the results are discussed.


ROVs have been in regular use now for over two decades and yet, while considerable advances have been made in the capability of the equipment fitted am their telemetry, control am diagnostic systems, the actual vehicles themselves have developed very little. The hydrodynamics of these bluff hulls remains poorly quantified with the result that they are often underpowered, especially in the transverse plane, and rely on control techniques rather than good design for dynamic stability. A number of ROVs that are regularly deployed are incapable of operating in even a moderate crosscurrent. Even their static stability is limited; they are frequently deployed with floats tied on to the structure to counter the mass of sane extra piece of equipment that has been bolted on.

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