This paper presents an enhanced method for predicting aerodynamically generated broadband noise produced by a Vertical Axis Wind Turbine (VAWT). The method improves on existing work for VAWT noise prediction and incorporates recently developed airfoil noise prediction models. Inflow-turbulence and airfoil self-noise mechanisms are both considered. Airfoil noise predictions are dependent on aerodynamic input data and time dependent Computational Fluid Dynamics (CFD) calculations are carried out to solve for the aerodynamic solution. Analytical flow methods are also benchmarked against the CFD informed noise prediction results to quantify errors in the former approach. Comparisons to experimental noise measurements for an existing turbine are encouraging. A parameter study is performed and shows the sensitivity of overall noise levels to changes in inflow velocity and inflow turbulence. Noise sources are characterised and the location and mechanism of the primary sources is determined, inflow-turbulence noise is seen to be the dominant source. The use of CFD calculations is seen to improve the accuracy of noise predictions when compared to the analytic flow solution as well as showing that, for inflow-turbulence noise sources, blade generated turbulence dominates the atmospheric inflow turbulence.16m. For a VAWT with an equivalent swept area, this corresponds to any machine with a diameter of less than 5m and span of 10m.Preliminary design of SWT's almost exclusively incorporates the use of low-or reduced-order prediction tools to make early performance estimates. Popular design tools such as QBlade [2] utilise methods such as the Double-Multiple Streamtube (DMS) [3] approach for aerodynamic performance estimates. Noise estimates 15 may subsequently be made based on these preliminary flow calculations.experimental results are available [16,17]. Experimental campaigns are mostly used to study overall performance as opposed to looking at detailed flow structures. Li et al. [16] performed a thorough investigation of the flow features around the blade of a VAWT, verifying CFD calculations against wind tunnel test data and showed that CFD calculations performed well when an appropriate turbulence model was applied. There are, however, some outstanding issues to be addressed when using CFD for VAWT aerodynamic prediction [18]. 50An example of this is the matter of grid dependency such as the study by Almohammadi et al. [19] showing the sensitivity of the power/torque calculations to mesh types and the time step/Courant number.The primary objectives of the present study are concerned with the development of a validated computational method for the prediction of noise generated by a VAWT. Additionally the new methods will make use of CFD calculations as input data to existing noise models since CFD calculations can be used 55 to efficiently (and more accurately) predict detailed flow features including turbulence parameters which are important inputs required for noise prediction models. Models for inflow-turbulence and ...

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A novel concept (referred to as the flap extension) is implemented on the leading edge of the flap of a three element high lift device. The concept is optimised using two optimisation approaches based on Genetic Algorithm optimisations. A zero order approach which makes simplifying assumptions to achieve an optimised solution: and a direct approach which employs an optimisation in ANSYS DesignXplorer using RANS calculations. The concept was seen to increase lift locally at the flap. The solution to the zero order optimisation showed a decreased stall angle and decreased maximum lift coefficient against angle of attack due to early stall onset at the flap. The DesignXplorer optimised solution matched that of the baseline solution very closely. Computational Aeroacoustic simulations were performed using the DES (Detached Eddy Simulation) model, in 2D, on the baseline and DesignXplorer optimised solution. The De-signXplorer optimised concept steadied the shear layer that bounds the spoiler cove thus reducing noise from this vicinity by 10dB at frequencies over 7 000Hz.

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