Automatic calibration of a tidal estuary model of the Scheldt using data assimilation algorithm

Hydrodynamic

Scientific workflow orchestration interoperating HTC and HPC resources

8 páginas, 7 figuras.-- El Pdf del artículo es la versión pre-print.In this work we describe our developments towards the provision of a unified access method to different types of computing infrastructures at the interop- eration level. For that, we have developed a middleware suite which bridges not interoperable middleware stacks used for building distributed computing infrastructues, UNICORE and gLite. Our solution allows to transparently access and operate on HPC and HTC resources from a single interface. Using Kepler as workflow manager, we provide users with the needed integration of codes to create scientific workflows accessing both types of infrastructures.Peer reviewe

Optimization of an Externally Mixed Biogas Plant Using a Robust CFD Method

Biogas plants have to be continuously or periodically mixed to ensure the homogenization of fermenting and fresh substrate. Externally installed mixers provide easier access than submerged mixers but concerns of insufficient mixing deter many operators from using this technology. In this paper, a new approach to improve homogenization of the substrate mixture is proposed by optimizing external mixer configurations across a wide range of rheological properties. Robust optimization of a biogas reactor is coupled with CFD simulations to improve parameters for the angles of inflow and the position of the substrate outlet in a large-scale fermenter. The optimization objective is to minimize the area in the tank which is poorly mixed. We propose to define this “dead volume zone” as the region in which the velocity magnitude during mixing falls below a certain threshold. Different dry substance contents are being investigated to account for the varying rheological properties of different substrate compositions. The velocity thresholds are calculated for each dry substance content from the mixer-tank configuration of a real biogas reactor in Brandenburg, Germany (BGA Warsow GmbH & Co.KG). The robust optimization results comprising the whole range of rheological properties are compared to simulations of the original configuration and to optimization results for each individual dry substance content. The robust CFD-based optimized configurations reduce the dead volume zones significantly across all dry substance contents compared to the original configuration. The outcomes of this paper can be particularly useful for plant manufacturers and operators for optimal mixer placement in industrial size biogas fermenters.BMBF - ROENOBIO project with contract number 05M2013UTA (Germany), DFG - RTG 2126 Algorithmic Optimization (Germany

A numerical study on the influence of geometry on the rupture risk of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are local dilatations in the abdominal aorta occurring due to weakening of arterial wall. The present work investigates the influence of the ratio of maximum transverse diameter to abdominal height (DHr) on rupture risk of AAA, using hemodynamics and AAA wall mechanics simulations. We have considered two idealized AAA geometries, AAA1 of higher DHr than AAA2. Two constitutive models, namely, Newtonian and Carreau-Yasuda models have been used for modelling blood as an incompressible fluid. Additionally, in order to describe the behaviour of AAA wall, three constitutive models, namely, linear elastic, Saint Venant Kirchhoff elastic and a phenomenological finite-strain model called Raghavan-Vorp elastic have been utilised. Numerical simulations of AAA biomechanics have been performed using solids4Foam, an open source package built on finite volume framework. Hemodynamic parameteric study reveals that AAA1 has lower time-averaged wall shear stress (TAWSS) and higher oscillatory shear index (OSI) compared to AAA2. Thus, AAA1 has increased susceptibility to thrombus deposition and, therefore, higher risk of AAA rupture. Furthermore, the peak wall stress of AAA1 is about 8% higher than that of AAA2. It is concluded that higher DHr leads to greater rupture risk

Computational modeling of degradation process of biodegradable magnesium biomaterials

Despite the advantages of using biodegradable metals in implant design, their uncontrolled degradation and release remain a challenge in practical applications. A validated computational model of the degradation process can facilitate the tuning of implant biodegradation by changing design properties. In this study, a physicochemical model was developed by deriving a mathematical description of the chemistry of magnesium biodegradation and implementing it in a 3D computational model. The model parameters were calibrated using the experimental data of hydrogen evolution by performing a Bayesian optimization routine. The model was validated by comparing the predicted change of pH in saline and buffered solutions with the experimentally obtained values from corrosion tests, showing maximum 5% of difference, demonstrating the model's validity to be used for practical cases

Free and Open Source Software Codes for Antenna Design: Preliminary Numerical Experiments

In both industrial and scientific frameworks, free and open source software codes create novel and interesting opportunities in computational electromagnetics. One of the possible applications, which usually requires a large set of numerical tests, is related to antenna design. Despite the well-known advantages offered by open source software, there are several critical points that restrict its practical application. First, the knowledge of the open source programs is often limited. Second, by using open source packages it is sometimes not easy to obtain results with a high level of confidence, and to integrate open source modules in the production workflow. In the paper, a discussion about open source programs for antenna design is carried out. Furthermore, some preliminary numerical tests are presented and discussed, also in comparison with those obtained by means of commercial software. Results are related to the simulation of various typologies of antennas in order to assess the capabilities of open source software in different configurations. The presented comparisons show that, despite the abovementioned limitations, the examined open source packages have similar performance with respect to their commercial counterparts

A Non-Intrusive Reduced Basis Method for Urban Flows Simulation

In this work, we present a non-intrusive method using the Reduced Basis framework in order to diminish the cost of numerical simulation arising from the computation of parameters-dependent Partial Differential Equations (PDE). This method involves the computation of less expensive (but less accurate) solutions of the PDE during the online stage, and a RB-based rectification step. It represents a good substitute for standard Reduced Basis methods when it is applied to urban flows modelling. This approach speeds up the CFD simulation while remaining non-intrusive in relation to the high fidelity model, which can allow to avoid practical problems (e.g. non-affine parametric dependence) associated to model reduction for complex air flows involved in many sophisticated methods of urban air quality modeling. Our focus here is on the validation of the non-intrusive method applied to the backward-facing step 2D benchmark

Design and Techno-Economic Analysis of a Novel Hybrid Offshore Wind and Wave Energy System

In the past few years, advanced technologies such as floating offshore wind turbines (FOWT) and wave energy converters (WECs) have been developed. As demonstrated by the innovative hybrid platform Poseidon, the feasibility of combining floating wind turbines and wave energy converters has already been explored. Furthermore, diversification of offshore renewable energy technologies reduces power fluctuations and lowers investment costs. This paper focuses on the development of an integrated wind and wave platform and the creation of a numerical model to evaluate the system performance for the Belmullet site. The novel concept consists of the semi-submersible Nautilus platform, integrated with four-point absorbers. A hydro-servo-aero time-domain model, combining WEC-Sim with an in-house wind turbine model, simulated the device motion and estimated the power generated. The performance of the Wave Energy Converters (WECs) was optimised based on their Power Take Off (PTO) damping. Finally, the hybrid concept was compared with the simple FOWT concerning the energy produced, Levelized Cost of Energy (LCOE) and hydrodynamic stability. The hybrid configuration proved to be a promising solution with 10% lower LCOE and improved hydrodynamic stability evaluated in terms of nacelle acceleration and platform pitch motion. These results show that wind and wave could be one of the best solutions for the future of the marine energy sector and the energy transition

Interoperability and computational framework for simulating open channel hydraulics: application to sensitivity analysis and calibration of Gironde Estuary model

Water resource management is of crucial societal and economic importance, requiring a strong capacity for anticipating environmental change. Progress in physical process knowledge, numerical methods and computational power, allows us to address hydro-environmental problems of growing complexity. Modeling of river and marine flows is no exception. With the increase in IT resources, environmental modeling is evolving to meet the challenges of complex real-world problems. This paper presents a new distributed Application Programming Interface (API) of the open source TELEMAC-MASCARET system to run hydro-environmental simulations with the help of the interoperability concept. Use of the API encourages and facilitates the combination of worldwide reference environmental libraries with the hydro-informatic system. Consequently, the objective of the paper is to promote the interoperability concept for studies dealing with such issues as uncertainty propagation, global sensitivity analysis, optimization, multi-physics or multi-dimensional coupling. To illustrate the capability of the API, an operational problem for improving the navigation capacity of the Gironde Estuary is presented. The API potential is demonstrated in a re-calibration context. The API is used for a multivariate sensitivity analysis to quickly reveal the most influential parameters which can then be optimally calibrated with the help of a data assimilation technique