This paper introduces a novel design of a double glazed box type solar cooker having an L-shaped absorber plate with one internal (bottom) and two external plane reflectors. A series of experiments were performed to access the cooker's thermal performance at the location of Taxila (33.74°N, 72.80°E) in Pakistan during the year 2017. The cooker's performance is evaluated in terms of maximum absorber plate temperature and other thermal performance indicators like first and second figures of merits (F1 and F2), parameter index, energy efficiency, and utilizable efficiency. The experimentally obtained values of all the performance indicators are found to be in the recommended ranges specified in the literature. An increment of about 30% in the absorber plate temperature is estimated for the case of the proposed L-shaped absorber plate along with an internal (bottom) reflector as compared to the case of no internal reflector and a conventional horizontal absorber plate. The first figure of merit of the proposed cooker is estimated to be 0.12, thus classifying it in grade A category. Furthermore, the solar cooker is manufactured at a nominal cost of ∼130 USD, making it a competitive product in the market.

The ability to accurately predict vortex shedding around wind turbine blades is paramount, particularly at high Reynolds number. Turbulence models employed in the numerical studies strongly influence flow separation and the aerodynamic loading, thus affecting the overall accuracy of numerical simulations. In this manuscript, three turbulence models (Spalart-Allmaras, k − and k − ω Shear Stress Transport model) are investigated in two and three dimensional configurations using standard Reynolds Average Navier-Strokes equations. The focus is on the NACA0015 airfoil, and the simulations are conducted at a Reynolds number of 1.96 × 10 6 to match the experimental data in the literature. The effect of flow separation and vortex shedding pattern is investigated at different angles of attack (0°≤ α ≤ 17°,) along with the prediction ability of the turbulence models. Spectral analysis is performed over the time history of aerodynamic coefficients to identify the dominant frequencies along with their even and odd harmonics. A reduced-order model based on the van der Pol equation is proposed for the aerodynamic lift calculation. The method of multiple scales (a perturbation approach) is adapted to compute the coefficients of the proposed model consisting of quadratic and cubic non-linearities at the various angle of attacks (α). The model is also tested in a predictive setting, and the results are compared against the full order model solution.

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