Evaluation of moisture sources for the Central European summer flood of May/June 2013 based on regional climate model simulations

Heavy precipitation affected Central Europe in May/June 2013, triggering damaging floods both on the Danube and the Elbe rivers. Based on a modelling approach with COSMO-CLM, moisture fluxes, backward trajectories, cyclone tracks and precipitation fields are evaluated for the relevant time period 30 May–2 June 2013. We identify potential moisture sources and quantify their contribution to the flood event focusing on the Danube basin through sensitivity experiments: Control simulations are performed with undisturbed ERA-Interim boundary conditions, while multiple sensitivity experiments are driven with modified evaporation characteristics over selected marine and land areas. Two relevant cyclones are identified both in reanalysis and in our simulations, which moved counter-clockwise in a retrograde path from Southeastern Europe over Eastern Europe towards the northern slopes of the Alps. The control simulations represent the synoptic evolution of the event reasonably well. The evolution of the precipitation event in the control simulations shows some differences in terms of its spatial and temporal characteristics compared to observations. The main precipitation event can be separated into two phases concerning the moisture sources. Our modelling results provide evidence that the two main sources contributing to the event were the continental evapotranspiration (moisture recycling; both phases) and the North Atlantic Ocean (first phase only). The Mediterranean Sea played only a minor role as a moisture source. This study confirms the importance of continental moisture recycling for heavy precipitation events over Central Europe during the summer half year

Influence of Turbulence Modeling on Velocity Profiles for Cyclone Separators

Newer aircraft engines are designed in order to obtain both the best performances and the lowest environmental impact, reducing the amount of polluting elements emitted in the atmosphere. The improvement of engine lubricating circuits is related to this task, aiming to a more efficient lubricant recycling when flowing into filtering devices. Cyclonic separators constitute one stage of the filtering phase. They are simple devices whose working principle consists in using centrifugal forces to separate two phases from one another, e.g. solid particles from a fluid or two fluids having different densities. The present work focuses on the impact of the turbulence models in the simulations of cyclone separators. The objective is to provide guidelines for future numerical analyses, paying special attention to the correct simulation of velocity profiles, which play a very important role in the particle separation process

The XDEM Multi-physics and Multi-scale Simulation Technology: Review on DEM-CFD Coupling, Methodology and Engineering Applications

The XDEM multi-physics and multi-scale simulation platform roots in the Ex- tended Discrete Element Method (XDEM) and is being developed at the In- stitute of Computational Engineering at the University of Luxembourg. The platform is an advanced multi- physics simulation technology that combines flexibility and versatility to establish the next generation of multi-physics and multi-scale simulation tools. For this purpose the simulation framework relies on coupling various predictive tools based on both an Eulerian and Lagrangian approach. Eulerian approaches represent the wide field of continuum models while the Lagrange approach is perfectly suited to characterise discrete phases. Thus, continuum models include classical simulation tools such as Computa- tional Fluid Dynamics (CFD) or Finite Element Analysis (FEA) while an ex- tended configuration of the classical Discrete Element Method (DEM) addresses the discrete e.g. particulate phase. Apart from predicting the trajectories of individual particles, XDEM extends the application to estimating the thermo- dynamic state of each particle by advanced and optimised algorithms. The thermodynamic state may include temperature and species distributions due to chemical reaction and external heat sources. Hence, coupling these extended features with either CFD or FEA opens up a wide range of applications as diverse as pharmaceutical industry e.g. drug production, agriculture food and processing industry, mining, construction and agricultural machinery, metals manufacturing, energy production and systems biology

The role of fluid catalytic cracking in process optimisation for petroleum refineries

Petroleum refining is a chemical process in which the raw material (crude oil) is converted to finished commercial products for end users. The fluid catalytic cracking (FCC) unit is a key asset in refineries, requiring optimised processes in the context of engineering design. Following the first stage of separation of crude oil in a distillation tower, an additional 40 per cent quantity is attainable in the gasoline pool with further conversion of the downgraded product of crude oil (residue from the distillation tower) using a catalyst in the FCC process. Effective removal of sulphur oxides, nitrogen oxides, carbon and heavy metals from FCC gasoline requires greater separation efficiency and involves an enormous environmental significance. The FCC unit is primarily a reactor and regeneration system which employs cyclone systems for separation. Catalyst losses in FCC cyclones lead to high particulate matter emission on the regenerator side and fines carryover into the product on the reactor side. This paper aims at demonstrating the importance of FCC unit design criteria in terms of technical performance and compliance with environmental legislation. A systematic review of state-of-the-art FCC technology was carried out, identifying its key technical challenges and sources of emissions. Case studies of petroleum refineries in Nigeria were assessed against selected global case studies. The review highlights the need for further modelling investigations to help improve FCC design to more effectively meet product specification requirements while complying with stricter environmental legislation

Investigation of Rope Formation in Gas-Solid Flows using Flow Visualization and CFD Simulations

Coal is still one of the widely-used resources for power generation all over the world. Most of the relevant industries use pulverized coal as fuel which is delivered to the furnace by pneumatic conveying. Extensive use of coal has resulted in severe environmental problems due to emissions such as Carbon dioxide, Nitrogen and Sulphur compounds among others. It is postulated that if combustion efficiency is improved, this will lead to significant reduction in pollutant emissions. Combustion efficiency of pulverized coal power plants is influenced strongly by particle size distribution. Most industries use Cyclone Separators (or Classifiers) to separate the larger particles from the smaller ones as part of pre-combustion processes. The sizing and scaling of these classifiers are mostly based on empirical formulations. Detailed 3D numerical studies of these classifiers have not been successful in prediction of experimental observations, hence as such cannot be used as reliable tools for scale up studies. The main reason for this anomaly is believed to be failure of the models in capturing the dynamics of particle behavior in bends and ducts where particles form rope like structures with dense particle clusters. It is then imperative that more study is needed into the understanding of rope or cluster formation in gas-solid flows.;The main objective of the current study is to investigate the underlying mechanisms of rope formation phenomena. Gas-solid flow experiments have been performed in a vertical- horizontal 90o glass bend with high speed imaging of the rope formation. Also, several Computational Fluid Dynamics (CFD) simulations have been performed using the commercial CFD package Ansys FLUENT to capture the roping phenomenon, and results have well supported the experimental observations. Several factors affecting rope formation have also been studied. Roping is basically a type of particle clustering in the sense high particle concentration regions are formed in both these phenomenon. Simulations have been performed on Fluid bed risers to capture clustering phenomenon and also to study the role of vorticity in cluster and rope formation with an objective of developing a fundamental definition for roping. MFIX, a multiphase flow code developed by NETL has also been used to capture the roping phenomenon. These results showed that high particle concentration was found to be in low vorticity regions surrounded by clockwise and counter-clockwise vortices. It was observed that there is indeed a vortex roller effect behind the formation of ropes. These results can be used to provide direction in development of computational models to better handle the gas-solid flow dynamics in classifiers

Recovering the lost gold of the developing world : bibliographic database

This report contains a library of 181 references, including abstracts, prepared for Project R 7120 "Recovering the lost gold of the developing world" funded by the UK' s Department for International Development (DFID) under the Knowledge and Research (KAR) programme. As part of an initial desk study, a literature review of gold processing methods used by small-scale miners was carried out using the following sources; the lSI Science Citation Index accessed via Bath Information and Data Services (BIDS), a licensed GEOREF CD-ROM database held at the BGS's Library in Keyworth and IMMage a CD-ROM database produced by the Institution of Mining and Metallurgy held by the Minerals group ofBGS. Information on the search terms used is available from the author

The origin of centennial- to millennial-scale chronological gaps in storm emplaced beach ridge plains

Recent studies of tropical cyclone surge and wave emplaced beach ridge plains have shown that these sequences often contain centennial to millennial scale gaps in their chronologies. Two explanations for the gaps exist — they are due to erosion, or alternatively a cessation or substantial slowing of depositional processes suggestive of a quieter phase in intense storm activity. Differentiating between the two is important for uncovering reliable long-term storm histories from these sequences. We use landform morphology, sediment texture and luminescence chronology to determine the origin of substantial chronological gaps in a plain containing more than 100 shore-parallel ridges composed of fine-grained sand located in northeast Australia. We identify and describe the characteristics associated with both erosional and non-erosional gaps. The erosional gaps are associated with changes in orientation between ridge sets and often a high ridge with hummocky topography that appears to have been disturbed by aeolian activity. River floods likely caused the partial erosion of ridge sets. Non-erosional gaps do not display these morphological characteristics and are likely associated with quiescence in severe tropical cyclone activity. These geomorphic and chronological signatures can be used to identify different sorts of gaps in other ridge plains and are an important tool in the reconstruction of long-term storm histories from these coastal landforms. The data also suggests that fine-grained ridges can, like their coarse-grained counterparts, be predominantly deposited by storm waves and surge and their texture need not necessarily be indicative of the processes responsible for ridge development