Quantifying dependencies for sensitivity analysis with multivariate input sample data

We present a novel method for quantifying dependencies in multivariate datasets, based on estimating the R\'{e}nyi entropy by minimum spanning trees (MSTs). The length of the MSTs can be used to order pairs of variables from strongly to weakly dependent, making it a useful tool for sensitivity analysis with dependent input variables. It is well-suited for cases where the input distribution is unknown and only a sample of the inputs is available. We introduce an estimator to quantify dependency based on the MST length, and investigate its properties with several numerical examples. To reduce the computational cost of constructing the exact MST for large datasets, we explore methods to compute approximations to the exact MST, and find the multilevel approach introduced recently by Zhong et al. (2015) to be the most accurate. We apply our proposed method to an artificial testcase based on the Ishigami function, as well as to a real-world testcase involving sediment transport in the North Sea. The results are consistent with prior knowledge and heuristic understanding, as well as with variance-based analysis using Sobol indices in the case where these indices can be computed

Sustainability of municipal waste water treatment.

n this study the insustainability of the treatment of municipal wastewater is evaluated with the LCA-methodology. Life-Cycle Assessments (LCA) analyze and assess the environmental profile over the entire life cycle of a product or process. The LCA-methodology proved to be a proper instrument to evaluate the wastewater treatment plant on the sustainability. However, environmental impacts which are caused by sludge handling should still be classified. Besides that, the LCA should be carried out on regional level instead of on national level. In a situation of high nutrient removal the contribution of the treatment of municipal wastewater to the total insustainability level in the Netherlands is relatively low. When the sustainability of the WWTP has to be improved, the most attention has to be paid to the minimization of discharge from pollutions with the effluent and minimization of the sludge production. Because the contribution of energy consumption is relatively low, less attention can be paid to the minimization of the energy demand. The building of a WWTP and the use of chemicals are not determining the insustainability of the WWTP

CFD ANALYSIS OF A COMPLETE INDUSTRIAL LEAN PREMIXED GAS TURBINE COMBUSTOR

ABSTRACT The introduction of lean premixed combustion technology in industrial gas turbines has led to a number of interesting technical issues. Lean premixed combustors are especially prone to acoustically-coupled combustion oscillations as well as to other problems of flame stability such as flashback. Clearly it is very important to understand the physics that lies behind such behaviour in order to produce robust and comprehensive remedies, and also to underpin the future development of new combustor designs. Simulation of the flow and combustion using Computational Fluid Dynamics (CFD) offers an attractive way forward, provided that the modelling of turbulence and combustion is adequate and that the technique is applicable to real industrial combustor geometries. The paper presents a series of CFD simulations of the Rolls-Royce Trent industrial combustor carried out using the McNEWT unstructured code. The entire combustion chamber geometry is represented including the premixing ducts, the fuel injectors and the discharge nozzle. A modified k-ε model has been used together with an advanced laminar flamelet combustion model that is sensitive to variations in fuel-air mixture stoichiometry. Detailed results have been obtained for the nonreacting flow field, for the mixing of fuel and air and for the combustion process itself at a number of different operating conditions. The study has provided a great deal of useful information £ Corresponding author on the operation of the combustor and has demonstrated the value of CFD-based combustion analysis in an industrial context