Application of Polyhedral Mesh for Vortex Formation Study for Simple Single Pump Sump

CFD letters ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 13-27
Author(s):  
Mohamad Lutfi Samsudin ◽  
Hasril Hasini
Keyword(s):  
Experimental Data ◽  
Complex Geometry ◽  
Vortex Formation ◽  
Tetrahedral Mesh ◽  
Published Data ◽  
Hexahedral Mesh ◽  
The Past ◽  
Polyhedral Mesh ◽  
Pump Sump ◽  
Comparison Of The Results

Meshing of domain in CFD is an important step to ensure accuracy of the solution. In the past, hexahedral or tetrahedral mesh systems were commonly used, and both have their merits and demerits. For large and complex geometry, polyhedral is another option but its accuracy is claimed to be lacking. In this paper, the use of polyhedral mesh system by past researchers are reviewed. Evaluation on the application of polyhedral mesh system for the study of the vortex formation with a simple single pump sump model is made. Validation was made through the comparison of the results from hexahedral, tetrahedral and polyhedral mesh sizes and the experimental data from published data. The polyhedral mesh system was found to perform satisfactorily and was able to match the results from the hexahedral mesh system as well as the experimental data.

Sensitivity of the Numerical Prediction of Turbulent Combustion Dynamics in the LIMOUSINE Combustor

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Mina Shahi ◽  
Jim B. W. Kok ◽  
Artur K. Pozarlik ◽  
J. C. Roman Casado ◽  
Thomas Sponfeldner
Keyword(s):  
Experimental Data ◽  
Turbulent Combustion ◽  
Unstructured Mesh ◽  
Numerical Prediction ◽  
Tetrahedral Mesh ◽  
Numerical Dissipation ◽  
Combustion Model ◽  
Computational Domain ◽  
Hexahedral Mesh ◽  
Mesh Topology

The objective of this study is to investigate the sensitivity and accuracy of the reaction flow-field prediction for the LIMOUSINE combustor with regard to choices in computational mesh and turbulent combustion model. The LIMOUSINE combustor is a partially premixed, bluff body-stabilized natural gas combustor designed to operate at 40–80 kW and atmospheric pressure and used to study combustion instabilities. The transient simulation of a turbulent combusting flow with the purpose to study thermoacoustic instabilities is a very time-consuming process. For that reason, the meshing approach leading to accurate numerical prediction, known sensitivity, and minimized amount of mesh elements is important. Since the numerical dissipation (and dispersion) is highly dependent on, and affected by, the geometrical mesh quality, it is of high importance to control the mesh distribution and element size across the computational domain. Typically, the structural mesh topology allows using much fewer grid elements compared to the unstructured grid; however, an unstructured mesh is favorable for flows in complex geometries. To explore computational stability and accuracy, the numerical dissipation of the cold flow with mixing of fuel and air is studied first in the absence of the combustion process. Thereafter, the studies are extended to combustible flows using standard available ansys-cfx combustion models. To validate the predicted variable fields of the combustor's transient reactive flows, the numerical results for dynamic pressure and temperature variations, resolved under structured and unstructured mesh conditions, are compared with experimental data. The obtained results show minor dependence on the used mesh in the velocity and pressure profiles of the investigated grids under nonreacting conditions. More significant differences are observed in the mixing behavior of air and fuel flows. Here, the numerical dissipation of the (unstructured) tetrahedral mesh topology is higher than in the case of the (structured) hexahedral mesh. For that reason, the combusting flow, resolved with the use of the hexahedral mesh, presents better agreement with experimental data and demands less computational effort. Finally, in the paper, the performance of the combustion model for reacting flow is presented and the main issues of the applied combustion modeling are reviewed.

Sensitivity of the Numerical Prediction of Flow in the LIMOUSINE Combustor on the Chosen Mesh and Turbulent Combustion Model

2013 ◽  
Author(s):  
Mina Shahi ◽  
Jim B. W. Kok ◽  
Artur K. Pozarlik ◽  
J. C. Roman Casado ◽  
Thomas Sponfeldner
Keyword(s):  
Experimental Data ◽  
Turbulent Combustion ◽  
Unstructured Mesh ◽  
Numerical Prediction ◽  
Tetrahedral Mesh ◽  
Numerical Dissipation ◽  
Combustion Model ◽  
Hexahedral Mesh ◽  
Mesh Topology ◽  
Turbulent Combustion Model

The objective of this study is to investigate the sensitivity and accuracy of the combustible flow field prediction for the LIMOUSINE combustor with regards to choices in computational mesh and turbulent combustion model. The LIMOUSINE combustor is a partially premixed bluff body stabilized natural gas combustor designed to operate at 40–80 kW and atmospheric pressure and used to study combustion instabilities. The transient simulation of a turbulent combusting flow with the purpose to study thermo-acoustic instabilities is a very time consuming process. For that reason the meshing approach leading to accurate numerical prediction, known sensitivity, and reduced amount of mesh elements is important. Since the numerical dissipation (and dispersion) is highly dependent on, and affected by, the geometrical mesh quality, it is of high importance to control the mesh distribution and element size across the numerical model. Typically, the structural mesh topology allows using much less grid elements compared to the unstructured grid, however an unstructured mesh is favorable for flows in complex geometries. To explore computational stability and accuracy, the numerical dissipation of the cold flow with mixing of fuel and air is studied first in the absence of the combustion process. Thereafter the studies are extended to combustible flows using standard available ANSYS-CFX combustion models. To validate the predicted variable fields of the combustor’s transient reactive flows, the numerical results for dynamic pressure and temperature variations, resolved under structured and unstructured mesh conditions, are compared with experimental data. The obtained results show minor dependence on the used mesh in the velocity and pressure profiles of the investigated grids under non-reacting conditions. More significant differences are observed in the mixing behavior of air and fuel flows. Here the numerical dissipation of the (unstructured) tetrahedral mesh topology is higher than in the case of the (structured) hexahedral mesh. For that reason, the combusting flow resolved with the use of the hexahedral mesh presents better agreement with experimental data and demands less computational effort. Finally in the paper the performance of the combustion model for reacting flow as a function of mesh configuration is presented, and the main issues of the applied combustion modeling are reviewed.

scholarly journals Looking at the Nudibranch Family Myrrhinidae (Gastropoda, Heterobranchia) from a Mitochondrial ‘2D Folding Structure’ Point of View

Life ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 583
Author(s):  
Giulia Furfaro ◽  
Paolo Mariottini
Keyword(s):  
16S Rrna ◽  
Phylogenetic Analyses ◽  
Integrative Taxonomy ◽  
Point Of View ◽  
Past Study ◽  
Mitochondrial Coi ◽  
The Past ◽  
Combining Data ◽  
Folding Structure ◽  
Comparison Of The Results

Integrative taxonomy is an evolving field of multidisciplinary studies often utilised to elucidate phylogenetic reconstructions that were poorly understood in the past. The systematics of many taxa have been resolved by combining data from different research approaches, i.e., molecular, ecological, behavioural, morphological and chemical. Regarding molecular analysis, there is currently a search for new genetic markers that could be diagnostic at different taxonomic levels and that can be added to the canonical ones. In marine Heterobranchia, the most widely used mitochondrial markers, COI and 16S, are usually analysed by comparing the primary sequence. The 16S rRNA molecule can be folded into a 2D secondary structure that has been poorly exploited in the past study of heterobranchs, despite 2D molecular analyses being sources of possible diagnostic characters. Comparison of the results from the phylogenetic analyses of a concatenated (the nuclear H3 and the mitochondrial COI and 16S markers) dataset (including 30 species belonging to eight accepted genera) and from the 2D folding structure analyses of the 16S rRNA from the type species of the genera investigated demonstrated the diagnostic power of this RNA molecule to reveal the systematics of four genera belonging to the family Myrrhinidae (Gastropoda, Heterobranchia). The “molecular morphological” approach to the 16S rRNA revealed to be a powerful tool to delimit at both species and genus taxonomic levels and to be a useful way of recovering information that is usually lost in phylogenetic analyses. While the validity of the genera Godiva, Hermissenda and Phyllodesmium are confirmed, a new genus is necessary and introduced for Dondice banyulensis, Nemesis gen. nov. and the monospecific genus Nanuca is here synonymised with Dondice, with Nanuca sebastiani transferred into Dondice as Dondice sebastiani comb. nov.

scholarly journals Impact of Coronavirus Outbreaks on Science and Society: Insights from Temporal Bibliometry of SARS and COVID-19

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 626
Author(s):  
Ramya Gupta ◽  
Abhishek Prasad ◽  
Suresh Babu ◽  
Gitanjali Yadav
Keyword(s):  
Published Data ◽  
Science And Society ◽  
Time Dimension ◽  
Scientific Publications ◽  
The Past ◽  
Economic Trends ◽  
Global Events ◽  
One Year ◽  
Personal Devices ◽  
Share Information

A global event such as the COVID-19 crisis presents new, often unexpected responses that are fascinating to investigate from both scientific and social standpoints. Despite several documented similarities, the coronavirus pandemic is clearly distinct from the 1918 flu pandemic in terms of our exponentially increased, almost instantaneous ability to access/share information, offering an unprecedented opportunity to visualise rippling effects of global events across space and time. Personal devices provide “big data” on people’s movement, the environment and economic trends, while access to the unprecedented flurry in scientific publications and media posts provides a measure of the response of the educated world to the crisis. Most bibliometric (co-authorship, co-citation, or bibliographic coupling) analyses ignore the time dimension, but COVID-19 has made it possible to perform a detailed temporal investigation into the pandemic. Here, we report a comprehensive network analysis based on more than 20,000 published documents on viral epidemics, authored by over 75,000 individuals from 140 nations in the past one year of the crisis. Unlike the 1918 flu pandemic, access to published data over the past two decades enabled a comparison of publishing trends between the ongoing COVID-19 pandemic and those of the 2003 SARS epidemic to study changes in thematic foci and societal pressures dictating research over the course of a crisis.

Modelling and simulation of ship collisions in port and coastal waters

2021 ◽  
pp. 147509022198918
Author(s):  
Chien-Chang Chou
Keyword(s):  
Coastal Waters ◽  
Maritime Transportation ◽  
Critical Factors ◽  
Ship Maneuvering ◽  
Collision Model ◽  
The Past ◽  
Sea Current ◽  
Ship Collision ◽  
Comparison Of The Results ◽  
Collision Models

Navigational safety is an important issue in maritime transportation. The most frequent type of maritime accident in the port and coastal waters is the ship collision. Although some ship collision models have been developed in the past, few have taken account of wind and sea current effects. However, wind and sea current are critical factors in ship maneuvering. Therefore, based on the previous collision model without wind and sea current effects, this study further develops a ship collision model with wind and sea current effects. Finally, a comparison of the results for the proposed collision model in this study and the ship maneuvering simulator is shown to illustrate the effectiveness of the proposed mathematical model in this paper, followed by the conclusions and suggestions given to navigators, port managers, and governmental maritime departments to improve navigational safety in port and coastal waters.

scholarly journals The Gene Ontology resource: enriching a GOld mine

2020 ◽  
Vol 49 (D1) ◽  
pp. D325-D334
Author(s):  
◽  
Seth Carbon ◽  
Eric Douglass ◽  
Benjamin M Good ◽  
Deepak R Unni ◽  
...  
Keyword(s):  
Experimental Data ◽  
Gene Ontology ◽  
Gold Mine ◽  
Gene Products ◽  
Gene Ontology Consortium ◽  
The Past ◽  
Historical Archive ◽  
File Structure

Abstract The Gene Ontology Consortium (GOC) provides the most comprehensive resource currently available for computable knowledge regarding the functions of genes and gene products. Here, we report the advances of the consortium over the past two years. The new GO-CAM annotation framework was notably improved, and we formalized the model with a computational schema to check and validate the rapidly increasing repository of 2838 GO-CAMs. In addition, we describe the impacts of several collaborations to refine GO and report a 10% increase in the number of GO annotations, a 25% increase in annotated gene products, and over 9,400 new scientific articles annotated. As the project matures, we continue our efforts to review older annotations in light of newer findings, and, to maintain consistency with other ontologies. As a result, 20 000 annotations derived from experimental data were reviewed, corresponding to 2.5% of experimental GO annotations. The website (http://geneontology.org) was redesigned for quick access to documentation, downloads and tools. To maintain an accurate resource and support traceability and reproducibility, we have made available a historical archive covering the past 15 years of GO data with a consistent format and file structure for both the ontology and annotations.

Validation of CATHARE V2.5 Thermal-Hydraulic Code Against Full-Scale PERSEO Tests for Decay Heat Removal in LWRs

2010 ◽  
Author(s):  
Giacomino Bandini ◽  
Paride Meloni ◽  
Massimiliano Polidori ◽  
Calogera Lombardo
Keyword(s):  
Experimental Data ◽  
Heat Exchangers ◽  
Heat Removal ◽  
Full Scale ◽  
Experimental Program ◽  
Decay Heat ◽  
The Past ◽  
Reserve Pool ◽  
Large Water ◽  
Safety Systems

The PERSEO experimental program was performed in the framework of a domestic research program on innovative safety systems with the purpose to increase the reliability of passive decay heat removal systems implementing in-pool heat exchangers. The conceived system was tested at SIET laboratories by modifying the existing PANTHERS IC-PCC facility utilized in the past for testing a full scale module of the GE-SBWR in-pool heat exchanger. Integral tests and stability tests were conducted to verify the operating principles, the steadiness and the effectiveness of the system. Two of the more representative tests have been analyzed with CATHARE V2.5 for code validation purposes. The paper deals with the comparison of code results against experimental data. The capabilities and the limits of the code in simulating such kind of tests are highlighted. An improvement in the modeling of the large water reserve pool is suggested trying to reduce the discrepancies observed between code results and test measurements.

scholarly journals Through what mechanisms do protected areas affect environmental and social outcomes?

2015 ◽  
Vol 370 (1681) ◽  
pp. 20140267 ◽  
Author(s):  
Paul J. Ferraro ◽  
Merlin M. Hanauer
Keyword(s):  
Experimental Data ◽  
Protected Areas ◽  
Empirical Evidence ◽  
Strong Evidence ◽  
Protected Area ◽  
Evidence Base ◽  
Social Outcomes ◽  
Causal Effects ◽  
The Past ◽  
Made In

To develop effective protected area policies, scholars and practitioners must better understand the mechanisms through which protected areas affect social and environmental outcomes. With strong evidence about mechanisms, the key elements of success can be strengthened, and the key elements of failure can be eliminated or repaired. Unfortunately, empirical evidence about these mechanisms is limited, and little guidance for quantifying them exists. This essay assesses what mechanisms have been hypothesized, what empirical evidence exists for their relative contributions and what advances have been made in the past decade for estimating mechanism causal effects from non-experimental data. The essay concludes with a proposed agenda for building an evidence base about protected area mechanisms.

A review on tribological performance of ionic liquids as additives to bio lubricants

2020 ◽  
pp. 135065012097380
Author(s):  
Tehreem Naveed ◽  
Rehan Zahid ◽  
Riaz Ahmad Mufti ◽  
Muhammad Waqas ◽  
Muhammad Talha Hanif
Keyword(s):  
Ionic Liquids ◽  
Friction And Wear ◽  
Combustion Engine ◽  
Tribological Performance ◽  
Environmental Concerns ◽  
Published Data ◽  
Oil Reserves ◽  
Mineral Oils ◽  
The Past ◽  
Interacting Surfaces

All the moving components in an internal combustion engine require a lubricant that allows smooth sliding and/or rolling of interacting surfaces. Lubricant not only minimizes the friction and wear but also dissipates the heat generated due to friction and removes debris from the area of contact. Environmental concerns, decreasing mineral oil reserves and difficult disposal of nonbiodegradable conventional lubricants have urged the researchers to shift towards environmental-friendly lubricants. Number of tribological studies carried out in the past have proved that ionic liquid-based bio-lubricants are sustainable and biodegradable alternative to mineral oils. This paper presents a brief review of properties of ionic liquids and their ability to reduce friction and wear between the interacting surfaces. Tribological performance and compatibility of ionic liquids with various base-oils have been compared under boundary lubrication. The results reveal that phosphonium-based ionic liquids namely tetra-decyl tri-hexyl phosphonium bis(2,4,4-trimethylpentyl) phosphinate (P66614)i(C8)2PO2 and tri-hexyl tetra-decyl phosphonium bis(2-ethylhexyl) phosphate (P-DEHP) are more suitable for tribological applications. Since, ionic liquids can be tailored according to the application and millions of combinations are possible therefore, there is a need to summarize the published data in a more systematic and logical way.

Le parlement européen : Comparaison des résultats de juin 1979 et portrait de l'Assemblée élue

Res Publica ◽  
1980 ◽  
Vol 22 (3) ◽  
pp. 471-501
Author(s):  
Dusan Sidjanski
Keyword(s):  
United Kingdom ◽  
European Community ◽  
European Parliament ◽  
General Distribution ◽  
The Political ◽  
European Elections ◽  
Minor Parties ◽  
The Past ◽  
Democratic Control ◽  
Comparison Of The Results

The results of the first European elections reflect the general distribution of the European electorate slightly center-right oriented, even if the abstentionism of almost 40 % caused some distorsions as in the case of United Kingdom. After the comparison of the results, state by state, it appears globally that the socialists ( 113) and liberals (40) regressed, the gaullists and their allies (22) suffered a serious defeat, white the christian democrats ( 107) and the communists (44) progressed and some minor parties (leftists and regionalists) entered the European Parliament.The second part contains a portrait of the new European Parliament which is younger than its predecessor, has more women including its president and has many high personnalities. As in the past, the political groupsplay a central and dynamic role. The question is to know if they will be capable of maintaining their cohesion. The examined cases give no evidence of the existence of the center-right majority in front of the left opposition. In fact, there were changing coalitions and voting constellations according to different problems, ideological options or concrete choices. The recent vote rejecting the proposed budget expresses a will of the European Parliament to impose its style and its democratic control on the European Community.

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