scholarly journals Wildland fires behaviour: wind effect versus Byram’s convective number and consequences upon the regime of propagation

2018 ◽  
Vol 27 (9) ◽  
pp. 636 ◽  
Author(s):  
D. Morvan ◽  
N. Frangieh
Keyword(s):  
Wind Velocity ◽  
Wildland Fire ◽  
Short Note ◽  
Short Paper ◽  
Speed Ratio ◽  
Wind Effect ◽  
Physical Parameters ◽  
Large Set ◽  
Wildland Fires ◽  
The Relationship

With fuel moisture content and slope, wind velocity (UW) is one of the major physical parameters that most affects the behaviour of wildland fires. The aim of this short paper was to revisit the relationship between the rate of spread (ROS) and the wind velocity, through the role played by the two forces governing the trajectory of the flame front and the plume, i.e. the buoyancy of the plume and the inertia due to wind. A large set of experimental data (at field and laboratory scale) from the literature was analysed, by introducing the ratio between these two forces, namely Byram’s convective number NC and considering the relationship between the fire ROS/wind speed ratio and Byram’s number. This short note was also an opportunity to make a point on particular issues, such as the existence of two regimes of propagation of surface fires (wind-driven fire vs plume-dominated fire), the relative importance of the two modes of heat transfer (by convection and radiation) on the propagation of a fire front, and others scientific debates animating the wildland fire community.

Corrigendum 1 (published 19 Sep 2018) and Corrigendum 2 (published 11 Dec 2018) to: Wildland fires behaviour: wind effect versus Byram’s convective number and consequences upon the regime of propagation

2018 ◽  
Vol 27 (12) ◽  
pp. 857
Author(s):  
D. Morvan ◽  
N. Frangieh
Keyword(s):  
Wind Velocity ◽  
Wildland Fire ◽  
Short Note ◽  
Short Paper ◽  
Speed Ratio ◽  
Wind Effect ◽  
Physical Parameters ◽  
Large Set ◽  
Wildland Fires ◽  
The Relationship

With fuel moisture content and slope, wind velocity (UW) is one of the major physical parameters that most affects the behaviour of wildland fires. The aim of this short paper was to revisit the relationship between the rate of spread (ROS) and the wind velocity, through the role played by the two forces governing the trajectory of the flame front and the plume, i.e. the buoyancy of the plume and the inertia due to wind. A large set of experimental data (at field and laboratory scale) from the literature was analysed, by introducing the ratio between these two forces, namely Byram's convective number NC and considering the relationship between the fire ROS/wind speed ratio and Byram's number. This short note was also an opportunity to make a point on particular issues, such as the existence of two regimes of propagation of surface fires (wind-driven fire vs plume-dominated fire), the relative importance of the two modes of heat transfer (by convection and radiation) on the propagation of a fire front, and others scientific debates animating the wildland fire community.

Corrigendum to: Wildland fires behaviour: wind effect versus Byram’s convective number and consequences upon the regime of propagation

2018 ◽  
Vol 27 (9) ◽  
pp. 642
Author(s):  
D. Morvan ◽  
N. Frangieh
Keyword(s):  
Wind Velocity ◽  
Wildland Fire ◽  
Short Note ◽  
Short Paper ◽  
Speed Ratio ◽  
Wind Effect ◽  
Physical Parameters ◽  
Large Set ◽  
Wildland Fires ◽  
The Relationship

With fuel moisture content and slope, wind velocity (UW) is one of the major physical parameters that most affects the behaviour of wildland fires. The aim of this short paper was to revisit the relationship between the rate of spread (ROS) and the wind velocity, through the role played by the two forces governing the trajectory of the flame front and the plume, i.e. the buoyancy of the plume and the inertia due to wind. A large set of experimental data (at field and laboratory scale) from the literature was analysed, by introducing the ratio between these two forces, namely Byram's convective number NC and considering the relationship between the fire ROS/wind speed ratio and Byram's number. This short note was also an opportunity to make a point on particular issues, such as the existence of two regimes of propagation of surface fires (wind-driven fire vs plume-dominated fire), the relative importance of the two modes of heat transfer (by convection and radiation) on the propagation of a fire front, and others scientific debates animating the wildland fire community.

A pilot web former designed to study retention-formation relationships

2010 ◽  
Vol 25 (2) ◽  
pp. 185-194
Author(s):  
Anna Svedberg ◽  
Tom Lindström
Keyword(s):  
Pilot Scale ◽  
Operating Conditions ◽  
Montmorillonite Clay ◽  
Speed Ratio ◽  
Good Reproducibility ◽  
Total Solids ◽  
Retention Aids ◽  
Solids Content ◽  
Relationship Of ◽  
The Relationship

Abstract A pilot-scale fourdrinier former has been developed for the purpose of investigating the relationship between retention and paper formation (features, retention aids, dosage points, etc.). The main objective of this publication was to present the R-F (Retention and formation)-machine and demonstrate some of its fields of applications. For a fine paper stock (90% hardwood and 10% softwood) with addition of 25% filler (based on total solids content), the relationship between retention and formation was investigated for a microparticulate retention aid (cationic polyacrylamide together with anionic montmorillonite clay). The retention-formation relationship of the retention aid system was investigated after choosing standardized machine operating conditions (e.g. the jet-to-wire speed ratio). As expected, the formation was impaired when the retention was increased. Since good reproducibility was attained, the R-F (Retention and formation)-machine was found to be a useful tool for studying the relationship between retention and paper formation.

scholarly journals Current Wildland Fire Patterns and Challenges in Europe: A Synthesis of National Perspectives

2021 ◽  
Vol 14 ◽  
pp. 117862212110281
Author(s):  
Nieves Fernandez-Anez ◽  
Andrey Krasovskiy ◽  
Mortimer Müller ◽  
Harald Vacik ◽  
Jan Baetens ◽  
...  
Keyword(s):  
Land Use ◽  
Large Scale ◽  
Wildland Fire ◽  
Human Life ◽  
Local Analysis ◽  
Wildland Fires ◽  
Fire Statistics ◽  
Quantitative Evidence ◽  
Wide Range ◽  
Fire Patterns

Changes in climate, land use, and land management impact the occurrence and severity of wildland fires in many parts of the world. This is particularly evident in Europe, where ongoing changes in land use have strongly modified fire patterns over the last decades. Although satellite data by the European Forest Fire Information System provide large-scale wildland fire statistics across European countries, there is still a crucial need to collect and summarize in-depth local analysis and understanding of the wildland fire condition and associated challenges across Europe. This article aims to provide a general overview of the current wildland fire patterns and challenges as perceived by national representatives, supplemented by national fire statistics (2009–2018) across Europe. For each of the 31 countries included, we present a perspective authored by scientists or practitioners from each respective country, representing a wide range of disciplines and cultural backgrounds. The authors were selected from members of the COST Action “Fire and the Earth System: Science & Society” funded by the European Commission with the aim to share knowledge and improve communication about wildland fire. Where relevant, a brief overview of key studies, particular wildland fire challenges a country is facing, and an overview of notable recent fire events are also presented. Key perceived challenges included (1) the lack of consistent and detailed records for wildland fire events, within and across countries, (2) an increase in wildland fires that pose a risk to properties and human life due to high population densities and sprawl into forested regions, and (3) the view that, irrespective of changes in management, climate change is likely to increase the frequency and impact of wildland fires in the coming decades. Addressing challenge (1) will not only be valuable in advancing national and pan-European wildland fire management strategies, but also in evaluating perceptions (2) and (3) against more robust quantitative evidence.

scholarly journals Unmanned Aerial Vehicles for Wildland Fires: Sensing, Perception, Cooperation and Assistance

Drones ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 15
Author(s):  
Moulay A. Akhloufi ◽  
Andy Couturier ◽  
Nicolás A. Castro
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Wildland Fire ◽  
Fire Intensity ◽  
Economic Losses ◽  
Small Scale ◽  
Environmental Damage ◽  
Unmanned Aerial Systems ◽  
Wildland Fires ◽  
Natural Risk ◽  
Aerial Vehicles

Wildfires represent a significant natural risk causing economic losses, human death and environmental damage. In recent years, the world has seen an increase in fire intensity and frequency. Research has been conducted towards the development of dedicated solutions for wildland fire assistance and fighting. Systems were proposed for the remote detection and tracking of fires. These systems have shown improvements in the area of efficient data collection and fire characterization within small-scale environments. However, wildland fires cover large areas making some of the proposed ground-based systems unsuitable for optimal coverage. To tackle this limitation, unmanned aerial vehicles (UAV) and unmanned aerial systems (UAS) were proposed. UAVs have proven to be useful due to their maneuverability, allowing for the implementation of remote sensing, allocation strategies and task planning. They can provide a low-cost alternative for the prevention, detection and real-time support of firefighting. In this paper, previous works related to the use of UAV in wildland fires are reviewed. Onboard sensor instruments, fire perception algorithms and coordination strategies are considered. In addition, some of the recent frameworks proposing the use of both aerial vehicles and unmanned ground vehicles (UGV) for a more efficient wildland firefighting strategy at a larger scale are presented.

The relationship between physical parameters and wear of dental composites

Wear ◽  
2007 ◽  
Vol 263 (7-12) ◽  
pp. 1138-1146 ◽  
Author(s):  
S.D. Heintze ◽  
G. Zellweger ◽  
G. Zappini
Keyword(s):  
Dental Composites ◽  
Physical Parameters ◽  
The Relationship

Excavations of Aztec Urban Houses at Yautepec, Mexico

1999 ◽  
Vol 10 (02) ◽  
pp. 133-150 ◽  
Author(s):  
Michael E. Smith ◽  
Cynthia Heath-Smith ◽  
Lisa Montiel
Keyword(s):  
Construction Materials ◽  
Large Set ◽  
Mexican State ◽  
Residential Structures ◽  
The Relationship ◽  
House Size

Our recent excavations at the site of Yautepec in the Mexican state of Morelos have uncovered a large set of residential structures from an Aztec city. We excavated seven houses with associated middens, as well as several middens without architecture. In this paper, we briefly review the excavations, describe each house, and summarize the nature of construction materials and methods employed. We compare the Yautepec houses with other known Aztec houses and make some preliminary inferences on the relationship between house size and wealth at the site.

Nonlinear DOB-based explicit NMPC for station-keeping of a multi-vectored propeller airship with thrust saturation

2018 ◽  
Vol 122 (1257) ◽  
pp. 1753-1774 ◽  
Author(s):  
Y. Wen ◽  
L. Chen ◽  
Y. Wang ◽  
D. Sun ◽  
D. Duan ◽  
...  
Keyword(s):  
Control Method ◽  
Aerodynamic Force ◽  
Wind Effect ◽  
Station Keeping ◽  
Globally Asymptotically Stable ◽  
Tracking Differentiator ◽  
Propulsion Force ◽  
Predictive Controller ◽  
Dynamics Models ◽  
The Relationship

ABSTRACTA nonlinear station-keeping control method for a multi-vectored propeller airship under unknown wind field with thrust saturation is developed, which is composed of three modules: nonlinear model predictive controller (NMPC), disturbance observer (DOB) and tracking differentiator (TD). The nonlinear kinematics and dynamics models are introduced, and the wind effect is considered by the wind-induced aerodynamic force. Based on both models, an explicit NMPC is designed. Then a nonlinear DOB is introduced to estimate the wind disturbance. A TD, showing the relationship between the maximum propulsion force and the maximum flight acceleration, is proposed to handle the thrusts’ amplitude saturation. Stability analysis shows that the closed-loop system is globally asymptotically stable. Simulations for a multi-vectored propeller airship are conducted to demonstrate the robustness and effectiveness of the proposed method.

scholarly journals Supplier-initiating risk management behaviour and supply-side resilience: the effects of interpersonal relationships and dependence asymmetry in buyer-supplier relationships

2020 ◽  
Vol 40 (7/8) ◽  
pp. 971-995
Author(s):  
Yiyi Fan ◽  
Mark Stevenson ◽  
Fang Li
Keyword(s):  
Risk Management ◽  
Interpersonal Relationships ◽  
Supply Side ◽  
Large Set ◽  
Supplier Relationships ◽  
Content Type ◽  
Management Behaviour ◽  
Wide Range ◽  
Dependence Asymmetry ◽  
The Relationship

PurposeThe aim of the study is to explore how two dimensions of interpersonal relationships (i.e. size and range of relationships) affect supplier-initiating risk management behaviours (SIRMB) and supply-side resilience. Further, the study aims to explore the moderating role of dependence asymmetry.Design/methodology/approachNine hypotheses are tested based on a moderated mediation analysis of survey data from 247 manufacturing firms in China. The data are validated using a subset of 57 attentive secondary respondents and archival data.FindingsSIRMB positively relates to supply-side resilience. Further, SIRMB mediates the positive relationship between range and supply-side resilience, and this relationship is stronger at lower levels of dependence asymmetry. Yet, although dependence asymmetry positively moderates the relationship between range and SIRMB, it negatively moderates the relationship between size and SIRMB. We did not, however, find evidence that size has a conditional indirect effect on supply-side resilience through SIRMB.Practical implicationsManagers in buying firms can incentivise SIRMB to enhance supply-side resilience by developing a diverse rather than a large set of interpersonal relationships with a supplier. This might include allocating particular employees with a wide range of contacts within a supplier to that relationship, while it may be necessary to adopt different networking strategies for different supplier relationships. Firms in a highly asymmetrical relationship may seek to raise supplier expectations about the necessity to initiate risk management behaviour or look to change the dynamic of the relationship by managing contracts for fairness.Originality/valueNew knowledge on SIRMB as a mediating variable underpinning the relationship between interpersonal relationships and supply-side resilience is provided; and empirical evidence on the opposing moderation effect of dependence asymmetry is presented.

Experimental Study of Vertical Axis Wind Turbine with Wind Speed Self-Adapting

2012 ◽  
Vol 215-216 ◽  
pp. 1323-1326
Author(s):  
Ming Wei Xu ◽  
Jian Jun Qu ◽  
Han Zhang
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Velocity ◽  
Vertical Axis ◽  
Maximum Power ◽  
The Self ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Opening And Closing

A small vertical axis wind turbine with wind speed self-adapting was designed. The diameter and height of the turbine were both 0.7m. It featured that the blades were composed of movable and fixed blades, and the opening and closing of the movable blades realized the wind speed self-adapting. Aerodynamic performance of this new kind turbine was tested in a simple wind tunnel. Then the self-starting and power coefficient of the turbine were studied. The turbine with load could reliably self-start and operate stably even when the wind velocity was only 3.6 m/s. When the wind velocity was 8 m/s and the load torque was 0.1Nm, the movable blades no longer opened and the wind turbine realized the conversion from drag mode to lift mode. With the increase of wind speed, the maximum power coefficient of the turbine also improves gradually. Under 8 m/s wind speed, the maximum power coefficient of the turbine reaches to 12.26%. The experimental results showed that the new turbine not only improved the self-starting ability of the lift-style turbine, but also had a higher power coefficient in low tip speed ratio.

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