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A novel computational tool based on the Localized Radial-basis Function (RBF) Collocation (LRC) Meshless method coupled with a Volume-ofFluid (VoF) scheme capable of accurately and efficiently solving transient multi-dimensional heat conduction problems in composite and heterogeneous media is formulated and implemented. While the LRC Meshless method lends its inherent advantages of spectral convergence and ease of automation, the VoF scheme allows to effectively and efficiently simulate the location, size, and shape of cavities, voids, inclusions, defects, or de-attachments in the conducting media without the need to regenerate point distributions, boundaries, or interpolation matrices. To this end, the Inverse Geometric problem of Cavity Detection can be formulated as an optimization problem that minimizes an objective function that computes the deviation of measured temperatures at accessible locations to those generated by the LRC-VoF Meshless method. The LRC-VoF Meshless algorithms will be driven by an optimization code based on the Simplex Linear Programming algorithm which can efficiently search for the optimal set of design parameters (location, size, shape, etc.) within a predefined design space. Initial guesses to the search algorithm will be provided by the classical 1D semi-infinite composite analytical solution which can predict the approximate location of the cavity. The LRC-VoF formulation is tested and validated through a series of controlled numerical experiments. The proposed approach will allow solving the onerous computational inverse geometric problem in a very efficient and robust manner while affording its implementation in modest computational platforms, thereby realizing the disruptive potential of the proposed multidimensional high-fidelity non-destructive evaluation (NDE) method.

<abstract> <p>Transformation of salty seawater into fresh water by the aid of solar energy is one of the solutions for overcoming the lack of these waters with an eco-friendly procedure. The use of solar stills is one of the solutions that use solar energy with a simple design to produce fresh water in small to moderate amounts. Hemispherical solar stills are one kind of still design that does not require a particle rotational orientation, and they have proved to be more efficient than traditional designs. Solar stills generally possess a low thermal efficiency, with limitations of working hours, i.e., only daytime. To overcome these problems, rocks placed in the saline water basin are used as heat storage materials to increase the working period of the design. In the present work, different amounts of river rocks are utilized to study the effect of this addition experimentally. Steady state tests are conducted to study the influence of these additive rocks on the enhancement of solar energy absorption, since increased working time is assured by published research. Two volumes of rocks (300 mL and 600 mL) were tested, and both increased water productivity, by 52% and 58%, respectively. The increases are explained by the increases in solar energy absorption, since steady state cases were used.</p> </abstract>