Comparison of Measured Transient Ceiling Jet Temperature and Velocity Profiles in the Presence of an Upper Layer With Predictions by LAVENT Computer Fire Model

2003 ◽  
Author(s):  
Vahid Motevalli ◽  
Siamak Riahi
Keyword(s):  
Experimental Data ◽  
Large Scale ◽  
Fire Detection ◽  
Peak Temperature ◽  
Small Scale ◽  
Radiative Loss ◽  
Fire Model ◽  
Ceiling Height ◽  
And Performance ◽  
Upper Layer Temperature

Development of an upper layer in enclosure fires has a significant effect on the characteristics of the ceiling jet and a direct influence on the placement and performance of fire detection/suppression devices. Detailed transient measurement of ceiling jet velocity and temperature profiles within an upper layer for small-scale fires (2.0 kW and ceiling height of 1 m) are used to analyze the predictions produced by the LAVENT computer fire model. While the model predictions have been compared with large-scale experimental results with fires as large as 33 MW and ceiling height of up to 22m, the large-scale measurements do not have high special resolution and the present work offers a more thorough analysis of the model prediction. Various radiative losses (10–25%) were used to produce predictions that matched the experimental data. Comparison of the small-scale experimental data with the predictions from LAVENT shows that the model, which uses unconfined ceiling jet correlations, does not capture the ceiling jet profile well and over predicts the upper layer temperature during the development of the layer. The peak temperature prediction requires a different radiative loss factor than that which matches the upper layer temperature. In general, the peak temperature measurements are within 10% of the measured value. The velocity is generally over predicted since the retardation of the jet momentum by the upper layer does not seem to be modeled accurately.

Detailed Analysis of the Wake Structure of a Straight-Blade H-Darrieus Wind Turbine by Means of Wind Tunnel Experiments and Computational Fluid Dynamics Simulations

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Alessandro Bianchini ◽  
Francesco Balduzzi ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Giacomo Persico ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Wind Turbines ◽  
Large Scale ◽  
Vertical Axis ◽  
Performance Estimation ◽  
Small Scale ◽  
Dynamics Simulations

Darrieus vertical axis wind turbines (VAWTs) have been recently identified as the most promising solution for new types of applications, such as small-scale installations in complex terrains or offshore large floating platforms. To improve their efficiencies further and make them competitive with those of conventional horizontal axis wind turbines, a more in depth understanding of the physical phenomena that govern the aerodynamics past a rotating Darrieus turbine is needed. Within this context, computational fluid dynamics (CFD) can play a fundamental role, since it represents the only model able to provide a detailed and comprehensive representation of the flow. Due to the complexity of similar simulations, however, the possibility of having reliable and detailed experimental data to be used as validation test cases is pivotal to tune the numerical tools. In this study, a two-dimensional (2D) unsteady Reynolds-averaged Navier–Stokes (U-RANS) computational model was applied to analyze the wake characteristics on the midplane of a small-size H-shaped Darrieus VAWT. The turbine was tested in a large-scale, open-jet wind tunnel, including both performance and wake measurements. Thanks to the availability of such a unique set of experimental data, systematic comparisons between simulations and experiments were carried out for analyzing the structure of the wake and correlating the main macrostructures of the flow to the local aerodynamic features of the airfoils in cycloidal motion. In general, good agreement on the turbine performance estimation was constantly appreciated.

Monitoring of dimple formation in honeycomb sandwich structures using distributed fiber optic sensors

2020 ◽  
pp. 109963622093582
Author(s):  
Juho T Siivola ◽  
Shu Minakuchi ◽  
Tadahito Mizutani ◽  
Kazuya Kitamoto ◽  
Nobuo Takeda
Keyword(s):  
Optical Fibers ◽  
Large Scale ◽  
Sandwich Structures ◽  
Beam Theory ◽  
Small Scale ◽  
Element Analysis ◽  
Thermal Expansion Coefficients ◽  
Honeycomb Sandwich ◽  
The Face ◽  
And Performance

Dimpling in the composite face sheets of honeycomb sandwich structures due to mismatch in the thermal expansion coefficients of the constituent materials was studied with emphasis on its monitoring and prediction. Strain distributions along optical fibers embedded in the face sheet were monitored during manufacturing. Dimple formation and in-plane strain distributions in the face sheets were studied using finite element analysis, and an analytical model based on the beam theory was constructed to predict the dimple depths from the strain data. A system using twin optical fiber sensors was proposed to accurately measure the dimpling-induced strains. The usability and performance of the system was evaluated using small scale specimens and finally on a more realistic large-scale specimen. The system could measure the strain changes due to dimpling of the face sheets and provided decent prediction of the dimple depth distribution along the sandwich panels.

scholarly journals Gas transfer under breaking waves: experiments and an improved vorticity-based model

2008 ◽  
Vol 26 (8) ◽  
pp. 2131-2142 ◽  
Author(s):  
V. K. Tsoukala ◽  
C. I. Moutzouris
Keyword(s):  
Experimental Data ◽  
Oxygen Transfer ◽  
Large Scale ◽  
Breaking Waves ◽  
Small Scale ◽  
Gas Transfer ◽  
Transfer Coefficients ◽  
Wave Flume ◽  
Proposed Model ◽  
Sloping Beach

Abstract. In the present paper a modified vorticity-based model for gas transfer under breaking waves in the absence of significant wind forcing is presented. A theoretically valid and practically applicable mathematical expression is suggested for the assessment of the oxygen transfer coefficient in the area of wave-breaking. The proposed model is based on the theory of surface renewal that expresses the oxygen transfer coefficient as a function of both the wave vorticity and the Reynolds wave number for breaking waves. Experimental data were collected in wave flumes of various scales: a) small-scale experiments were carried out using both a sloping beach and a rubble-mound breakwater in the wave flume of the Laboratory of Harbor Works, NTUA, Greece; b) large-scale experiments were carried out with a sloping beach in the wind-wave flume of Delft Hydraulics, the Netherlands, and with a three-layer rubble mound breakwater in the Schneideberg Wave Flume of the Franzius Institute, University of Hannover, Germany. The experimental data acquired from both the small- and large-scale experiments were in good agreement with the proposed model. Although the apparent transfer coefficients from the large-scale experiments were lower than those determined from the small-scale experiments, the actual oxygen transfer coefficients, as calculated using a discretized form of the transport equation, are in the same order of magnitude for both the small- and large-scale experiments. The validity of the proposed model is compared to experimental results from other researchers. Although the results are encouraging, additional research is needed, to incorporate the influence of bubble mediated gas exchange, before these results are used for an environmental friendly design of harbor works, or for projects involving waste disposal at sea.

scholarly journals Unsteady aerodynamic analysis for offshore floating wind turbines under different wind conditions

2015 ◽  
Vol 373 (2035) ◽  
pp. 20140080 ◽  
Author(s):  
B. F. Xu ◽  
T. G. Wang ◽  
Y. Yuan ◽  
J. F. Cao
Keyword(s):  
Experimental Data ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Large Scale ◽  
Aerodynamic Performance ◽  
Small Scale ◽  
Floating Platform ◽  
Unsteady Aerodynamic ◽  
Blade Root ◽  
Platform Motions

A free-vortex wake (FVW) model is developed in this paper to analyse the unsteady aerodynamic performance of offshore floating wind turbines. A time-marching algorithm of third-order accuracy is applied in the FVW model. Owing to the complex floating platform motions, the blade inflow conditions and the positions of initial points of vortex filaments, which are different from the fixed wind turbine, are modified in the implemented model. A three-dimensional rotational effect model and a dynamic stall model are coupled into the FVW model to improve the aerodynamic performance prediction in the unsteady conditions. The effects of floating platform motions in the simulation model are validated by comparison between calculation and experiment for a small-scale rigid test wind turbine coupled with a floating tension leg platform (TLP). The dynamic inflow effect carried by the FVW method itself is confirmed and the results agree well with the experimental data of a pitching transient on another test turbine. Also, the flapping moment at the blade root in yaw on the same test turbine is calculated and compares well with the experimental data. Then, the aerodynamic performance is simulated in a yawed condition of steady wind and in an unyawed condition of turbulent wind, respectively, for a large-scale wind turbine coupled with the floating TLP motions, demonstrating obvious differences in rotor performance and blade loading from the fixed wind turbine. The non-dimensional magnitudes of loading changes due to the floating platform motions decrease from the blade root to the blade tip.

COVID-19 Pandemic and Problems of Micro-enterprises in Dibrugarh District of Assam: An Empirical Study

2021 ◽  
pp. 097084642110424
Author(s):  
Rubab Fatema Nomani
Keyword(s):  
Large Scale ◽  
Raw Materials ◽  
Small Scale ◽  
Skilled Labour ◽  
Manufacturing Enterprises ◽  
Institutional Marketing ◽  
The Government ◽  
Obsolete Technology ◽  
And Performance ◽  
Training Programmes

Small-scale industries play a crucial role in industrialisation of India. These industries face numerous problems, some of which are peculiar to them, while others are common to both small-scale and large-scale industries. The COVID-19 pandemic has unleashed unprecedented threats as well as opportunities on this sector. This article tries to analyse the problems affecting the entrepreneurs associated with 141 micro-manufacturing enterprises in the Dibrugarh district of Assam and puts forward some policy suggestions. In order to identify the most pressing problem faced by the entrepreneurs, the Garrett ranking method is employed in the study. It is found that dearth of skilled labour is the most acute problem encountered by the sector. Lack of proper marketing arrangements, shortage of quality and cheap raw materials, obsolete technology and lack of timely finance are other important hindrances. The significance of skilled labour points to the intense need for continuous skill development of the local workforce by establishing more technical institutes, training programmes, etc. Furthermore, the government should provide special assistance for technological upgradation, develop institutional marketing facilities, and supply cheap and quality raw materials. Further, simplification of procedures in banks’ lending policies, relaxation of requirements like collateral security and margin money may go a long way in enhancing both confidence and performance of small entrepreneurs.

This Too is Music

2019 ◽  
Author(s):  
Rena Upitis
Keyword(s):  
Large Scale ◽  
Point Of View ◽  
Small Scale ◽  
Classroom Environments ◽  
Approaches To Teaching ◽  
Music Making ◽  
And Performance ◽  
And Mathematics ◽  
Traditional Approaches ◽  
Teaching Ideas

This Too Is Music guides and motivates teachers to foster classroom conditions that enable elementary students to thrive as improvisers, critical listeners, performers, and composers. Using anecdotes and illustrated with musical examples, the book explores how these aspects of music making are intertwined and quells any doubts teachers may have regarding their abilities to create an environment where children can improvise, dance, compose, and notate their musical offerings. While the book acknowledges the importance of traditional approaches to teaching notation and performance, its emphasis is on the student’s point of view, illustrating how young musicians can learn when their musical ideas are honored and celebrated. Various teaching ideas are presented; some are exploratory in nature, and others involve direct instruction. Regardless of their nature, all of the activities arise from research on children’s musical development in general and their development of notational systems in particular, and they have been tested in multiple elementary-classroom environments and preservice settings. The activities center on engaging with music through movement, performing, singing, improvising, composing, developing notational skills, and appealing to children across subjects, including language, drama, and mathematics. Activities encompass both small-scale classroom lessons and large-scale productions. This pedagogy has a timeless quality; even in our digital age, this musical environment appeals to children. The book invites readers to adapt the ideas to their own teaching settings, showing both preservice and established teachers that they can teach music creatively to build community and to inspire all who enter there.

Detailed Analysis of the Wake Structure of a Straight-Blade H-Darrieus Wind Turbine by Means of Wind Tunnel Experiments and CFD Simulations

2017 ◽  
Author(s):  
Alessandro Bianchini ◽  
Francesco Balduzzi ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Giacomo Persico ◽  
...  
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Wind Turbines ◽  
Large Scale ◽  
Vertical Axis ◽  
Performance Estimation ◽  
Small Scale ◽  
Horizontal Axis Wind Turbines ◽  
Floating Platforms ◽  
Physical Phenomena

Darrieus Vertical Axis Wind Turbines (VAWTs) have been recently identified as the most promising solution for new types of applications, such as small-scale installations in complex terrains or offshore large floating platforms. To improve their efficiencies further and make them competitive with those of conventional horizontal axis wind turbines, a more in depth understanding of the physical phenomena that govern the aerodynamics past a rotating Darrieus turbine is needed. Within this context, Computational Fluid Dynamics (CFD) can play a fundamental role, since it represents the only model able to provide a detailed and comprehensive representation of the flow. Due to the complexity of similar simulations, however, the possibility of having reliable and detailed experimental data to be used as validation test cases is pivotal to tune the numerical tools. In this study, a two-dimensional U-RANS computational model was applied to analyze the wake characteristics on the mid plane of a small-size H-shaped Darrieus VAWT. The turbine was tested in a large-scale, open-jet wind tunnel, including both performance and wake measurements. Thanks to the availability of such a unique set of experimental data, systematic comparisons between simulations and experiments were carried out analyzing the structure of the wake, and correlating the main macro-structures of the flow to the local aerodynamic features of the airfoils in cycloidal motion. In general, good agreement on the turbine performance estimation was constantly appreciated.

Solar Chimney Cycle Analysis With System Loss and Solar Collector Performance

2000 ◽  
Vol 122 (3) ◽  
pp. 133-137 ◽  
Author(s):  
Anthony J. Gannon ◽  
Theodor W. von Backstro¨m
Keyword(s):  
Experimental Data ◽  
Simple Model ◽  
Power Plant ◽  
Kinetic Energy ◽  
Solar Collector ◽  
Large Scale ◽  
Small Scale ◽  
Energy Losses ◽  
Solar Chimney ◽  
Solar Chimney Power Plant

An ideal air standard cycle analysis of the solar chimney power plant gives the limiting performance, ideal efficiencies and relationships between main variables. The present paper includes chimney friction, system, turbine and exit kinetic energy losses in the analysis. A simple model of the solar collector is used to include the coupling of the mass flow and temperature rise in the solar collector. The method is used to predict the performance and operating range of a large-scale plant. The solar chimney model is verified by comparing the simulation of a small-scale plant with experimental data. [S0199-6231(00)00503-7]

scholarly journals STUDY THE GROWTH KINETICS OF PEDIOCOCCUS ACIDILACTICI WITH ESTIMATION OF KINETIC PARAMETERS AND APPLIED IN LARGE SCALE PEDIOCIN PRODUCTION

2016 ◽  
Vol 9 (5) ◽  
pp. 130
Author(s):  
Barnali Mandal
Keyword(s):  
Experimental Data ◽  
Lactic Acid ◽  
Kinetic Parameters ◽  
Growth Kinetics ◽  
Large Scale ◽  
Scale Up ◽  
Small Scale ◽  
Pediococcus Acidilactici ◽  
Monod Model ◽  
Kinetics Of

ABSTRACTObjectives: The aim of the study was to determine the growth kinetics of Pediococcus acidilactici using a mathematical model for large scale pediocinproduction.Methods: Growth kinetics of P. acidilactici has been studied for pediocin production in small scale batch fermenter (Erlenmeyer flask) using meatprocessing waste medium. The experiments have been conducted with varying the concentrations of glucose, protein, and lactic acid. A mathematicalmodel has been developed to describe growth rate, products (pediocin and lactic acid) formation rate, and substrates (glucose and protein) utilizationrate. Monod model for dual substrates (glucose and protein) has been used with considering lactic acid inhibition. Luedeking-Piret model has beenintroduced to describe the production of pediocin and lactic acid.Results: The values of kinetic parameters have been determined using experimental data and model equations. The model prediction has beencompared satisfactorily with the experimental data for the validation of the model.Conclusions: The developed model was satisfactorily validated to scale up the production of pediocin.Keywords: Pediococcus acidilactici, Pediocin, Meat processing waste, Monod model, Luedeking-Piret model, Kinetic parameters.

scholarly journals Modeling and Observer-Based Monitoring of RAFT Homopolymerization Reactions

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 768 ◽  
Author(s):  
Patrick M. Lathrop ◽  
Zhaoyang Duan ◽  
Chen Ling ◽  
Yossef A. Elabd ◽  
Costas Kravaris
Keyword(s):  
Experimental Data ◽  
Large Scale ◽  
Raft Polymerization ◽  
Reaction Times ◽  
Real Data ◽  
Size Exclusion ◽  
Rate Coefficients ◽  
Small Scale ◽  
Late Reaction ◽  
Exclusion Chromatography

Reversible addition–fragmentation chain–transfer (RAFT) polymerization of methyl methacrylate (MMA) is modeled and monitored using a multi-rate multi-delay observer in this work. First, to fit the RAFT reaction rate coefficients and the initiator efficiency in the model, in situ 1 H nuclear magnetic resonance (NMR) experimental data from small-scale (<2 mL) NMR tube reactions is obtained and a least squares optimization is performed. 1 H NMR and size exclusion chromatography (SEC) experimental data from large-scale (>400 mL) reflux reactions is then used to validate the fitted model. The fitted model accurately predicts the polymer properties of the large-scale reactions with slight discordance at late reaction times. Based on the fitted model, a multi-rate multi-delay observer coupled with an inter-sample predictor and dead time compensator is designed, to account for the asynchronous multi-rate measurements with non-constant delays. The multi-rate multi-delay observer shows perfect convergence after a few sampling times when tested against the fitted model, and is in fair agreement with the real data at late reaction times when implemented based on the experimental measurements.

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