Constant velocity water entry is important in understanding planing and slamming of marine vessels. A test rig has been developed that drives a wedge section with end plates down guides to enter the water vertically at near constant velocity. Entry force and velocity are measured. Analysis of the test data shows that the wetting factor is about 1.6 at low deadrise angles and reduces nearly linearly to 1.3 at 451 deadrise angle. The added mass increases quadratically with immersed depth until the chines become wetted. It then continues to increase at a reducing rate, reaching a maximum value between 20% and 80% greater than at chine immersion. The flow momentum drag coefficient is estimated from the results to be 0.78 at 51 deadrise angle reducing to 0.41 at 451 deadrise angles. Constant velocity exit tests show that the momentum of the added mass is expended in driving the water above the surface level and that exit forces are low and equivalent to a drag coefficient of about 1.0-1.3. Considerable dynamic noise limits the accuracy of the results, particularly after chine immersion

The paper looks at the use of blade element-momentum theory for predicting the torque and thrust on a marine current turbine and the results of wave tank tests using a 400 mm-diameter rotor model. To include the effects of waves, linear wave theory particle velocities and accelerations were integrated into the mathematical model. Comparison with test data shows a good agreement which implies that the theory can be effective in analysing the wave-current interactions in marine current turbines. The paper also carried out parametric studies into related parameters, which include wave height, wave frequency, and tip-speed ratio. The interaction of waves with the current may increase or decrease the torque and hence power output of the turbine. The paper also explains the selection and manufacture of the rotor and the experimental setup.

The influence of waves on the dynamic properties of bending moments at the root of blades of tidal stream vertical-axis rotors is reported. Blade element-momentum theory for wind turbines is combined with linear wave theory and used to analyze this influence. Experiments were carried out with a 350 mm diameter rotor to validate the simulation and the comparison shows the ability of the theoretical approach to predict the blade root bending moments. It can be concluded that, in steep waves, linear theory underestimates the dynamic behaviour of bending moments. However, in long waves, linear theory works well. Bending moments at roots of rotor blades fluctuate with significant amplitudes (as much as 50 per cent of mean value for out-of-plane bending moment and 100 per cent of mean value for in-plane bending moment), which will be important for design of tidal stream rotors

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