Radial basis function (RBF)-based interpolation and spreading for the immersed boundary method

Immersed boundary methods are efficient tools of growing interest as they allow to use generic CFD codes to deal with complex, moving and deformable geometries, for a reasonable computational cost compared to classical body-conformal or unstructured mesh approaches. In this work, we propose a new immersed boundary method based on a radial basis functions framework for the spreading–interpolation procedure. The radial basis function approach allows for dealing with a cloud of scattered nodes around the immersed boundary, thus enabling the application of the devised algorithm to any underlying mesh system. The proposed method can also keep into account both Dirichlet and Neumann type conditions. To demonstrate the capabilities of our novel approach, the imposition of Dirichlet boundary conditions on a 2D cylinder geometry in a Navier–Stokes CFD solver, and the imposition of Neumann boundary conditions on an adiabatic wall in an unsteady heat conduction problem are considered. One of the most significant advantage of the proposed method lies in its simplicity given by the algorithmic possibility of carrying out the interpolation and spreading steps all together, in a single step

Design mining interacting wind turbines

© 2016 by the Massachusetts Institute of Technology. An initial study has recently been presented of surrogate-assisted evolutionary algorithms used to design vertical-axis wind turbines wherein candidate prototypes are evaluated under fan-generated wind conditions after being physically instantiated by a 3D printer. Unlike other approaches, such as computational fluid dynamics simulations, no mathematical formulations were used and no model assumptions weremade. This paper extends that work by exploring alternative surrogate modelling and evolutionary techniques. The accuracy of various modelling algorithms used to estimate the fitness of evaluated individuals from the initial experiments is compared. The effect of temporally windowing surrogate model training samples is explored. A surrogateassisted approach based on an enhanced local search is introduced; and alternative coevolution collaboration schemes are examined

On roof geometry for urban wind energy exploitation in high-rise buildings

The European program HORIZON2020 aims to have 20% of electricity produced by renewable sources. The building sector represents 40% of the European Union energy consumption. Reducing energy consumption in buildings is therefore a priority for energy efficiency. The present investigation explores the most adequate roof shapes compatible with the placement of different types of small wind energy generators on high-rise buildings for urban wind energy exploitation. The wind flow around traditional state-of-the-art roof shapes is considered. In addition, the influence of the roof edge on the wind flow on high-rise buildings is analyzed. These geometries are investigated, both qualitatively and quantitatively, and the turbulence intensity threshold for horizontal axis wind turbines is considered. The most adequate shapes for wind energy exploitation are identified, studying vertical profiles of velocity, turbulent kinetic energy and turbulence intensity. Curved shapes are the most interesting building roof shapes from the wind energy exploitation point of view, leading to the highest speed-up and the lowest turbulence intensity

Computational fluid dynamics simulation and full-scale experimental model inter-comparison of the wind flow around a university campus

In this article, results obtained from two computational fluid dynamics solvers, WindSim and OpenFOAM, have been compared for the wind flow around the University of Mauritius’ campus for different wind directions, and a reference incident wind speed at diverse height above ground level. A grid resolution study is performed for both software and the mean differences of the two solvers with multiple turbulence models (standard k-ε, k-ε with Yap correction, and renormalization group k-ε) are analyzed with onsite measured data. The article concludes that the best results for the computational fluid dynamics simulation of the wind flow around buildings are obtained using OpenFOAM with k-ε turbulence model including Yap correction

Energy Audits and Energy Efficiency in Small Wastewater Treatment Plants: A Case Study

Energy plays an important role in the water sector. In fact, energy consumption by this sector accounts for nearly 44% of municipalities’ energy costs in developed countries. To minimize adverse environmental and human health impacts wastewater can undergo three treatment levels before discharge or reuse. Since it is an energy intensive process, wastewater treatment represents the largest share of water-related electricity consumption in developed countries. According to the literature, there is a potential for improvement and energy savings in wastewater treatment facilities. Indeed, International Energy Agency states that, the energy consumption in the water sector can be reduced by 15% if this potential is harnessed. Consequently, energy audits can provide valuable information about those facilities, allowing to assess their energy performance and to identify energy-saving opportunities. In this paper the results of internal energy audits conducted in two “small” wastewater treatment plants, located in the North of Portugal, are presented and analyzed. The results, 13% and 22% savings, show that simple energy audits, which can be implemented by company members, should not be considered as a cost, but rather as a step to a more efficient energy use, reducing energy costs and environmental impacts

Immune escape of colorectal tumors via local LRH-1/Cyp11b1-mediated synthesis of immunosuppressive glucocorticoids.

Control of tumor development and growth by the immune system critically defines patient fate and survival. What regulates the escape of colorectal tumors from destruction by the immune system is currently unclear. Here, we investigated the role of intestinal synthesis of glucocorticoids in the tumor development during inflammation-induced mouse model of colorectal cancer. We demonstrate that the local synthesis of immunoregulatory glucocorticoids has dual roles in the regulation of intestinal inflammation and tumor development. In the inflammation phase LRH-1/Nr5A2-regulated and Cyp11b1-mediated intestinal glucocorticoid synthesis prevents tumor development and growth. In established tumors, however, tumor-autonomous Cyp11b1-mediated glucocorticoid synthesis suppresses anti-tumor immune responses and promotes immune escape. Transplantation of glucocorticoid synthesis-proficient colorectal tumor organoids into immunocompetent recipient mice resulted in rapid tumor growth, whereas transplantation of Cyp11b1-deleted and glucocorticoid synthesis-deficient tumor organoids was characterized by reduced tumor growth and increased immune cell infiltration. In human colorectal tumors, high expression of steroidogenic enzymes correlated with the expression of other immune checkpoints and suppressive cytokines, and negatively correlated with overall patients' survival. Thus, LRH-1-regulated tumor-specific glucocorticoid synthesis contributes to tumor immune escape and represents a novel potential therapeutic target

Towards the evolution of vertical-axis wind turbines using supershapes

© 2014, Springer-Verlag Berlin Heidelberg. We have recently presented an initial study of evolutionary algorithms used to design vertical-axis wind turbines (VAWTs) wherein candidate prototypes are evaluated under fan generated wind conditions after being physically instantiated by a 3D printer. That is, unlike other approaches such as computational fluid dynamics simulations, no mathematical formulations are used and no model assumptions are made. However, the representation used significantly restricted the range of morphologies explored. In this paper, we present initial explorations into the use of a simple generative encoding, known as Gielis superformula, that produces a highly flexible 3D shape representation to design VAWT. First, the target-based evolution of 3D artefacts is investigated and subsequently initial design experiments are performed wherein each VAWT candidate is physically instantiated and evaluated under fan generated wind conditions. It is shown possible to produce very closely matching designs of a number of 3D objects through the evolution of supershapes produced by Gielis superformula. Moreover, it is shown possible to use artificial physical evolution to identify novel and increasingly efficient supershape VAWT designs