Abstract: Urban heat island is intensified by anthropogenic activities and heat in conjunction with the built-up urban area, which absorbs more solar radiation during daytime and releases more heat during nighttime than rural areas. Air cooling systems in Singapore, as one of the anthropogenic heat sources, reject heat into the vicinity and consequently affect urban microclimate. In this paper, a new urban heat island modeling tool is developed to simulate stack effect of split type air-conditioners on high rise buildings and solar radiation induced thermal environment. By coupling the Computational Fluid Dynamics (CFD) program with the solar radiation model and perform parallel computing of conjugate heat transfer, the tool ensures both accuracy and efficiency in simulating air temperature and air relative humidity. The annual cycle of sun pathway in Singapore is well simulated and by decreasing the absorptivity or increasing the reflectivity and thermal conductivity of the buildings, the thermal environment around buildings could be improved.

Abstract: Heaving airfoils can provide invaluable physical insight regarding the flapping flight of birds and insects. We examine the thrust-generation mechanism of oscillating foils, by coupling two-dimensional simulations with multi-objective optimization algorithms. We show that the majority of the thrust originates from the creation of low pressure regions near the leading edge of the airfoil. We optimize the motion of symmetric airfoils exploiting the Knoller-Betz-Katzmayr effect, to attain high speed and lower energy expenditure. The results of the optimization indicate an inverse correlation between energy-efficiency, and the heaving-frequency and amplitude for a purely-heaving airfoil.

Abstract: We focus on a surface evolution problem where the surface is represented as a narrow-band level-set and the local surface speed is defined by a relation to the direct visibility of a source plane above the surface. A level-set representation of the surface can handle complex evolutions robustly and is therefore a frequently encountered choice. Ray tracing is used to compute the visibility of the source plane for each surface point. Commonly, rays are traced directly through the level-set and the already available (hierarchical) volume data structure is used to efficiently perform intersection tests. We present an approach that performs ray tracing on a temporarily generated explicit surface mesh utilizing modern hardware-tailored single precision ray tracing frameworks. We show that the overhead of mesh extraction and acceleration structure generation is compensated by the intersection performance for practical resolutions leading to an at least three times faster visibility calculation. We reveal the applicability of single precision ray tracing by attesting a sufficient angular resolution in conjunction with an integration method based on an up to twelve times subdivided icosahedron.

Abstract: The input workload of an irregular application must be evenly distributed among its threads to enable cutting-edge performance. To address this need in OpenMP, several loop scheduling strategies were proposed. While having this ever-increasing number of strategies at disposal is helpful, it has become a non-trivial task to select the best one for a particular application. Nevertheless, this challenge becomes easier to be tackled when existing scheduling strategies are extensively evaluated. Therefore, in this paper, we present a performance and scalability evaluation of the recently-proposed loop scheduling strategy named Smart Round-Robin (SRR). To deliver a comprehensive analysis, we coupled a synthetic kernel benchmarking technique with several rigorous statistical tools, and considered OpenMP's Static and Dynamic loop schedulers as our baselines. Our results unveiled that SRR performs better on irregular applications with symmetric workloads and coarse-grained parallelization, achieving up to 1.9x and 1.5x speedup over OpenMP's Static and Dynamic schedulers, respectively.

Abstract: Effect of small molecules, as they penetrate into a polymer system, is investigated via molecular dynamics simulations. It is found that small spherical particles reduce the glass transition temperature and thus introduce a softening of the material. Results are compared to experimental findings for the effect of different types of small molecules such as water, acetone and ethanol on the glass transition temperature of a polyurethane-based shape memory polymer. Despite the simplicity of the simulated model, MD results are found to be in good qualitative agreement with experimental data.