The expansion of floating offshore renewable energy demands reliable mooring solutions. Synthetic mooring ropes offer cost savings and performance benefits but exhibit complex, nonlinear, and frequency-dependent behavior. This study investigates their mechanical response through experimental testing, characterizing quasi-static and dynamic properties. The results inform a viscoelastic material model that captures nonlinear stiffness and dynamic response under marine loading. Based on Schapery’s formulation, this model can be integrated into a Finite Element framework to simulate real-world conditions, improving predictive capabilities for synthetic mooring lines in offshore applications.

The present study aims at providing experimental performance analysis of ducted wind turbines (DWTs) through momentum theory. To simplify the DWT model, a screen emulating the rotor is adopted by applying the actuator disc theory. Two duct models and five different screens are employed for different configurations to investigate the aerodynamic performance of the DWT in this experimental study. Duct 1 (C _{T , d u c t} = 0.91 ) is characterized by an aerofoil-shaped cross-section and duct 2 (C _{T , d u c t} = 1.17 ) has a cambered shape. Specifically, the five screens vary in porosity from low (C _{T , s c r e e n} = 0.46) to high thrust coefficient (C _{T , s c r e e n} = 1.12). Results show that the total thrust coefficient (C _{T , D W T} ) varies with screen thrusts and ducts geometry. The aerofoil-shaped duct 1, caused by the non-linear behaviour of the aerodynamic force on an aerofoil-shaped body at increasing angle of attack, is more sensitive to the screen loading compared to duct 2. Thrust on duct 1 is highly dependent on screen thrusts owning to the existence of inward oriented lift, while thrust on cambered plate duct 2 stays constant. The high thrust and solid blockage this duct creates, accelerates the flow through the lesser loaded centre where the screen is located. The data also show that the growth of duct thrust has a positive effect on the overall performance of DWT. Both high screen loading and inappropriate aerofoil shape duct may lead to flow separation which causes the momentum loss for DWT. Moreover, the optimal value of C _{T , s c r e e n} = 0.89 for a bare wind turbine doesn’t seem apply to the tested DWTs. The optimal value of C _{T , D W T} depends both on duct geometry and the screen loading. The velocity measurements further indicate that flow separation occurs at the duct 1 external (pressure) surface, and shows the presence of stalled flow around centre line inside the duct. Finally, a comparison of the pressure distribution of duct with different screen loadings reveals that adding a screen inside duct 1 leads to loss in lift and hence to mass reduction.

This paper reports an experimental investigation on the effect of the duct geometry on the aerodynamic performance of an aerofoil shaped ducted wind turbine (DWT). The tested two-dimensional model is composed of an aerofoil equipped with pressure taps and a uniform porous screen. The experimental setup is based on the assumption that the duct flow is axisymmetric and the rotor can be simulated as an actuator disc. Firstly, different tip clearances between the screen and the aerofoil are tested to point out the influence of this parameter on the DWT performance in terms of aerofoil pressure distribution, aerofoil lift and flow field features at the duct exit area. Then, the combined effect of tip clearance, of the angle of attack and of the screen position along the aerofoil chord is evaluated through a Design of Experiments (DoE) based approach. The analysis shows that, among the analysed range of design factor variation, increasing angle of attack and the tip clearance leads to a beneficial effect on the lift and back-pressure coefficients, while they show a poor dependence upon the screen axial position. Finally, the configuration characterized by the maximum value of all three main factors (15 degree of angle of attack, 5% of tip clearance and 30% backward to the nozzle plane), has the best values of lift coefficient and back-pressure coefficient.

It is well known that ducted wind turbine (DWT) captures more mass flow through the interior of the duct compared to the same size of bare wind turbine. The duct geometry is usually generated by airfoils shaped annular wings. To this end, a new high-lift airfoil for duct application is developed. This paper describes the wind tunnel testing methodology that has been applied to determine the two-dimensional characteristic of an airfoil for a Reynolds number of 1.0 × 10⁵. A particular aspect of the experiments is the presence of a screen, simulating the pressure drop over a real rotor. The experiments are performed in the 0.4 m × 0.4 m W-wind tunnel of the Delft University of Technology. The two-dimension model is composed of an airfoil and a uniform porous screen. Measurements are conducted with the varying angle of attack and wind speed. To investigate the effect of screen loading on the airfoil pressure distribution, three different screens, with thrust coefficient equals to 0.46, and 1.06, respectively, are tested. Tests on the airfoil with screens show the lift coefficient increases compared to the pure airfoil configuration. For fixed angle of attack, the airfoil pressure difference does not linearly increases with the increasing screen loading. By coupling with different screen loading has different influence on the airfoil lift, combining with the screen has C_T = 0.46 achieves the highest C_l in the vicinity of angle of attack (4° ≤ α ≤ 15°), and coupling with the high screen loading (C_T = 0.65 and 1.06) at high angle of attack (α ≥ 20°) is also beneficial for the tested airfoil in terms of C_l. The results also show the combination with screen delays the stall angle.