DOCSLIB.ORG

Transport and Dispersion of Fire Extinguishing Agents

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Transport and Dispersion of Fire Extinguishing Agents TRANSPORT AND DISPERSION OF FIRE EXTINGUISHING AGENTS DOWNSTREAM FROM CLUTTER ELEMENTS OF AIRCRAFT ENGINE NACELLES By Khaled Zbeeb A Thesis Submitted to the Faculty of The College of Engineering and Computer Science in Partial Fulfillment of the Requirements for the Degree of Master of Science Florida Atlantic University Boca Raton, Florida April 2009 ACKNOWLEDGEMENTS I would like to thank Dr. Chaouki Ghenai for his hard work and support in developing the needed resources for this thesis. Also, I would like to express my gratitude to Dr. W. Bober and Dr. D. Moslemian for their advice and contribution. I would like to thank the people who helped me reviewing this thesis. iii ABSTRACT Author: Khaled Zbeeb Title: Transport and Dispersion of Fire Extinguishing Agents Downstream From Clutter Elements of Aircraft Engine Nacelles Institution: Florida Atlantic University Dissertation Advisor: Dr. Chaouki Ghenai Degree: Master of Science Year: 2009 The combination of highly turbulent airflow, flammable fluids, and numerous ignition sources makes aircraft engine nacelles a difficult fire zone to protect. Better understanding of nacelle air flow and how it influences the spread of fires and fire extinguishing agents is needed to improve the efficiency of fire suppression. The first objective was to establish a CFD model for a flow field test section to analyze the transport and dispersion of fire extinguishing agents in the presence of various clutter elements. To validate the use of the CFD model, the simulation results of the CFD model were compared to the experimental data and they show an agreement with the experimental data. The second objective was to present parametric studies to show the effects of the coflow speed, turbulence intensity and agent droplet size on the transport and dispersion of the agent particles downstream from the clutter elements. iv TRANSPORT AND DISPERSION OF FIRE EXTINGUISHING AGENTS DOWNSTREAM FROM CLUTTER ELEMENTS OF AIRCRAFT ENGINE NACELLES LIST OF FIGURES................................................................................................... viii LIST OF TABLES ....................................................................................................... x 1. INTRODUCTION.................................................................................................... 1 1.1 Engine Nacelles Fire Extinguishing Agents ............................................................ 1 1.2 Understanding the Whole Fire Suppression Challenge............................................ 5 1.3 Nomenclature....................................................................................................... 10 1.4 Test Section and Clutter Package.......................................................................... 11 2. GOVERNING EQUATIONS................................................................................. 14 2.1 Continuity and Momentum Equations................................................................... 14 2.2 Continuous Phase Modeling ................................................................................. 16 2.3 Turbulent Flow Equations .................................................................................... 16 2.4 Discrete Phase Modeling ...................................................................................... 18 2.5 Turbulence Dispersion of Particles ....................................................................... 19 2.6 Coupling between the Discrete and Continuous Phases......................................... 19 3. NUMERICAL METHODS .................................................................................... 21 3.1 CFD Numerical Methods................................................................................. 21 3.2 Numerical Methods using Fluent ..................................................................... 24 4. VALIDATION OF THE CFD MODEL RESULTS................................................ 34 v 4.1 Experimental Results............................................................................................ 34 4.2 CFD Simulation Results ....................................................................................... 39 4.3 Validation of the CFD Simulation Results ............................................................ 43 5. FLOW SIMULATION STUDY ............................................................................. 48 5.1 Coflow Speed Effects on Agent Particles Behavior............................................... 48 5.2 Turbulence Intensity Effects on Agent Particles Behavior..................................... 51 5.3 Injected Droplet Size Effects on Agent Particles Behavior.................................... 54 6. CONCLUSION...................................................................................................... 60 6.1 CFD Model Verification....................................................................................... 60 6.2 Flow Simulation Study......................................................................................... 60 6.3 Future Work......................................................................................................... 62 7. APPENDIX............................................................................................................ 64 7.1 Phase Doppler Anemometry System (Experiment) ............................................... 64 7.2 Experimental Strategy .......................................................................................... 64 7.3 Experimental General Strategy ............................................................................. 65 7.4 Experimental Data Analysis Strategy.................................................................... 66 7.5 Suppressant Transport Experimental Results and Discussion................................ 67 BIBLIOGRAPHY...................................................................................................... 72 vi LIST OF FIGURES Fig. 1.2.1 (PhostrEx Agent Flame Poisoning Chemistry [11]).......................................7 Fig. 1.2.2 (Front view of the test Section where new fire agents were tested on the F-15 engine nacelle[12])...............................................................................8 Fig. 1.2.3 (Side view of the test Section where new fire agents were tested on the F-15 engine nacelle[12])...............................................................................9 Fig. 1.2.4 (Back view of the test Section where new fire agents were tested on the F-15 engine nacelle[12]).............................................................................10 Fig. 1.4.1 (Test Section and Clutter Package)..............................................................12 Fig. 1.4.2 (3D view of the Test section and clutter package) .......................................12 Fig. 1.4.3 (Top view of the Test section and clutter package)......................................13 Fig. 3.1.1 (HTF7000 Nacelle Ventilation Design Intent [13])......................................21 Fig. 3.1.2 (Surfaces modeled (pylon side) and the nozzle surfaces used for injection of Halon 1301 into the nacelle [13]) ...........................................................22 Fig. 3.1.3 (Comparison of Halon concentrations between CFD and test Data for Probe1 [13])...............................................................................................23 Fig. 3.2.1 (3D View of the mesh created for the test section) ......................................31 Fig. 3.2.2 (Side view of the mesh created for the test section) .....................................31 Fig. 3.2.3 (Side view schematic of SF2 test section) ....................................................31 Fig. 4.1.1 ((SF)2 Zone A Test Section)[4]....................................................................34 vii Fig. 4.1.2 (U Velocity Data at 2.0 D Downstream for Various UC, CS)[4] ..................35 Fig. 4.1.3 (V Velocity Data at 2.0 D Downstream for Various UC, CS)[4] ..................35 Fig. 4.1.4 (Sauter Diameter Data at 2.0 D Downstream for Various UC, CS)[4] ..........36 Fig. 4.1.5 (U Velocity Data at 5.5 D Downstream for Various UC, CS)[4] ..................36 Fig. 4.1.6 (V Velocity Data at 5.5 D Downstream for Various UC, CS)[4] ..................37 Fig. 4.1.7 (Sauter Diameter Data at 5.5 D Downstream for Various UC, CS)[4] ..........37 Fig. 4.2.1 (Particle Traces colord by Particle X-Velocity (m/s)) ..................................38 Fig. 4.2.2 (Particle Traces colord by Particle Y-Velocity (m/s)) ..................................39 Fig. 4.2.3 (Particle Traces colord by Particle Z-Velocity (m/s)) ..................................39 Fig. 4.2.4 (Particle Traces colord by Particle Diameter (m))........................................40 Fig. 4.2.5 (3D Air X-Velocity Distribution along the Centerline (m/s)).......................40 Fig. 4.2.6 (Air X-Velocity Distribution At Z=0 (Centerline) (ms/s)) ...........................41 Fig. 4.2.7 (Air X-velocity Distribution at 2D Downstream the Clutter (m/s)) ..............41 Fig. 4.3.1 (Droplet X-Velocity Comparison 2D Downstream the Clutter) ...................43 Fig. 4.3.2 (Droplet Y-Velocity Comparison 2D Downstream the Clutter) ...................44 Fig. 4.3.3 (Droplet Diameter Comparison 2D Downstream the Clutter) ......................45 Fig. 4.3.4 (Percentage Error of the Droplet Results by using Fluent)...........................46 Fig. 5.1.1 (Comparison of Particle Traces Colored by Particle X-velocity
Load more

Recommended publications
  • Who Will Win the Most Prestigious Trophy in Aviation
    National Aeronautic Association FOR IMMEDIATE RELEASE Contact: David Ivey, 703-527-0226 February 16, 2006 ECLIPSE AVIATION WINS 2005 COLLIER TROPHY Eclipse Aviation Corporation has won the 2005 Robert J. Collier Trophy "for the greatest achievement in aeronautics or astronautics in America.” The 95 year-old trophy, aviation’s most prestigious award, will be presented to the company “for leadership, innovation, and the advancement of general aviation” in the production of very light jets, specifically, the Eclipse 500. Eclipse joins past winners of the trophy including Orville Wright, Howard Hughes, Chuck Yeager, Scott Crossfield, the crew of Apollo 11, and SpaceShipOne. The award has been administered by the National Aeronautic Association (NAA) since 1911. Announcing the 2005 winner, NAA President and CEO David Ivey said the selection committee’s criteria included recognition of the rich heritage of the Collier Trophy, and “the spirit of entrepreneurship, technical innovation, and the impact on American aviation,” exemplified by the Eclipse 500. Led by Eclipse’s founder, president and CEO Vern Raburn, Eclipse is applying innovations created in the technology industry to drive down cost, increase performance, improve safety, and spur a new type of air travel—the air taxi. Innovations to the Eclipse 500 including friction stir welding, the PhostrEx™ fire suppression system, electromechanical actuators and digital electronics with integrated software. Perhaps the company’s greatest contribution is making jet technology available to a larger segment of the population. With an acquisition cost one-third of today’s small jets and the lowest operating cost per mile of any jet, the Eclipse 500 provides the lowest jet costs ever achieved.
    [Show full text]
  • Particulates in Your Home $9.99
    A Brief Bit of Info on Particulates in Your Home $9.99 A Brief BitB i t ofo f IInformation n f o rmationr m a t i o n o nonn Particulates in Your Home This guide provides information and guidance for homeowners on a few indoor particulates to be aware of, and how they may affect some aspects of your Indoor Air Quality. This document contains information from the EPA, Consumer Product Safety Commission, and American Lung Association including but not limited to document #402-F-04-021, #402/F-08/008, and added content. Visit www.epa.gov/iaq for more information. =================================================================== PARTICULATE SAMPLING by HomePro Inspections 904-268-8211 www.GoHomePro.com.com Other Environmental Sampling Services: Lead Paint, Water, Asbestos, and Radon Testing. Moisture Intrusion Consultations and Chinese Drywall Assessments also available! 904-268-8211 HomePro Inspections www.GoHomePro.com A Brief Bit of Info on Particulates in Your Home In the last several years, a growing body of scientific evidence has indicated that the air within homes and other buildings can sometimes be more polluted than the outdoor air. Other research indicates that people spend approximately 90 percent of their time indoors. Thus, for many people, the risks to health may be greater due to exposure to air pollution indoors rather than outdoors. In addition, people who may be exposed to indoor air Americans pollutants for the longest spend up to 90% periods of time are often those of their time most susceptible to the effects indoors! of indoor air quality. Such groups include the young, the elderly, and the chronically ill, especially those suffering from respiratory or cardiovascular disease.
    [Show full text]
  • Industrial User Inspection and Sampling Manual for Potws EPA-831-B-17-001 OECA-MANL-2017-002-R1 Industrial User Inspection and Sampling Manual Contents
    33333333333 Industrial User Inspection and Sampling Manual Disclaimer This manual is an inspection support tool provided by the U.S. Environmental Protection Agency (EPA) for use by field personnel conducting inspections under the Clean Water Act (CWA) National Pretreatment Program. The statements in this document are intended solely as guidance. The statutory provisions and EPA regulations described in this document contain legally binding requirements. This Inspection Manual is not a regulation and, therefore, does not add, eliminate or change any existing regulatory requirements. While EPA has made every effort to ensure the accuracy of the discussion in this guidance, the obligations of the regulated community are determined by statutes, regulations, or other legally binding requirements. In the event of a conflict between the discussion in this document and any statute or regulation, this document would not be controlling. This document is not intended, nor can it be relied on, to create any rights, substantive or procedural, enforceable at law by any party in litigation with the United States. This guidance may be revised without public notice to reflect changes in EPA policy. Deviations from this guidance on the part of any duly authorized official, inspector, or agent to follow its contents shall not be a defense in any enforcement action; nor shall deviation from this guidance constitute grounds for rendering the evidence obtained thereby inadmissible in a court of law. The mention of trade names or commercial products does not constitute endorsement or recommendation for their use. _____________________________________________________________________________________________________________________ EPA Industrial User Inspection and Sampling Manual for POTWs EPA-831-B-17-001 OECA-MANL-2017-002-R1 Industrial User Inspection and Sampling Manual Contents Contents ACRONYMS ...........................................................................................................................................
    [Show full text]
  • UW Radiation Safety Manual and Administrative Procedures for the Radiation Safety Program, As Needed
    UW Radiation Safety Manual rev September 2003 Radiation Safety Office Environmental Health and Safety (EH&S) University of Washington Box 354400 Seattle WA 98195-4400 Phone: (206) 543-0463 FAX: (206) 543-3351 Radiation Safety Manual also on EH&S home page: www.ehs.washington.edu Page i Radiation Safety Manual rev January 2002 Contents Glossary........................................................................................................................ v Section 1 Emergencies Involving Radiation A. Emergency Phone Numbers ...................................................................................... 1-2 B. Personal Injury ........................................................................................................... 1-3 C. Fire............................................................................................................................. 1-3 D. Inhalation or Ingestion of Radioactive Materials ........................................................ 1-3 E. Exposure to X-ray Machines, Accelerators or Large Gamma Sources...................... 1-4 F. External Contamination to Individuals – Little or No Injury......................................... 1-4 G. Contamination or Spill of Radioactive Material .......................................................... 1-6 Section 2 Licensing and Regulatory Controls A. Regulations ................................................................................................................ 2-1 B. Radioactive Materials................................................................................................
    [Show full text]
  • Exquisite Clutter: Material Culture and the Scottish Reinvention of the Adventure Narrative
    University of Rhode Island DigitalCommons@URI Open Access Dissertations 2016 Exquisite Clutter: Material Culture and the Scottish Reinvention of the Adventure Narrative Rebekah C. Greene University of Rhode Island, [email protected] Follow this and additional works at: https://digitalcommons.uri.edu/oa_diss Recommended Citation Greene, Rebekah C., "Exquisite Clutter: Material Culture and the Scottish Reinvention of the Adventure Narrative" (2016). Open Access Dissertations. Paper 438. https://digitalcommons.uri.edu/oa_diss/438 This Dissertation is brought to you for free and open access by DigitalCommons@URI. It has been accepted for inclusion in Open Access Dissertations by an authorized administrator of DigitalCommons@URI. For more information, please contact [email protected]. EXQUISITE CLUTTER: MATERIAL CULTURE AND THE SCOTTISH REINVENTION OF THE ADVENTURE NARRATIVE BY REBEKAH C. GREENE A DISSERTATION SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN ENGLISH UNIVERSITY OF RHODE ISLAND 2016 DOCTOR OF PHILOSOPHY DISSERTATION OF REBEKAH C. GREENE APPROVED: Dissertation Committee: Major Professor Carolyn Betensky Ryan Trimm William Krieger Nasser H. Zawia DEAN OF THE GRADUATE SCHOOL UNIVERSITY OF RHODE ISLAND 2016 ABSTRACT EXQUISITE CLUTTER: MATERIAL CULTURE AND THE SCOTTISH REINVENTION OF THE ADVENTURE NARRATIVE BY REBEKAH C. GREENE Exquisite Clutter examines the depiction of material culture in adventures written by Scottish authors Robert Louis Stevenson, Arthur Conan Doyle, and John Buchan. Throughout, these three authors use depictions of material culture in the adventure novel to begin formulating a critique about the danger of becoming overly comfortable in a culture where commodities are widely available. In these works, objects are a way to examine the complexities of character and to more closely scrutinize a host of personal anxieties about contact with others, changing societal roles, and one’s own place in the world.
    [Show full text]
  • Chapter 2: History of Fire Suppression in Aircraft
    Chapter 2: HISTORY OF FIRE Donald P. Bein SUPPRESSION IN AIRCRAFTi Naval Air Systems Command TABLE OF CONTENTS 2.1 Fire Threats to Military Aircraft ........................................................................................20 2.2 Protected Compartments on Aircraft .................................................................................24 2.2.1 Engine Nacelles.......................................................................................................24 2.2.2 Other Powerplant-type Compartments....................................................................28 2.2.3 Dry Bay Compartments...........................................................................................31 2.2.4 Cargo Compartments...............................................................................................34 2.2.5 Other Compartments ...............................................................................................36 2.2.6 Fuel Tank Ullage.....................................................................................................37 2.3 Types of Fires Experienced ...............................................................................................41 2.3.1 Safety-related Fires..................................................................................................43 2.3.2 Ballistically-induced Fires.......................................................................................45 2.3.3 Spray Fires...............................................................................................................47
    [Show full text]
  • Site Remediation Technology Infobase: a Guide to Federal Programs, Information Resources, and Publications on Contaminated Site Cleanup Technologies First Edition
    EPA/542/B-98/006 August 1998 Site Remediation Technology InfoBase: A Guide to Federal Programs, Information Resources, and Publications on Contaminated Site Cleanup Technologies First Edition Prepared by the Member Agencies of the Federal Remediation Technologies Roundtable: U.S. Environmental Protection Agency Department of Defense U.S. Air Force U.S. Army U.S. Navy Department of Energy Department of Interior National Aeronautics and Space Administration Tennessee Valley Authority Coast Guard NOTICE This document has been funded by the United States Environmental Protection Agency under Contract 68-W6-0014. It has been subject to administrative review by all agencies participating in the Federal Remediation Technologies Roundtable, and has been approved for publication. Any mention of trade names or commercial products does not constitute endorsement or recommendation for use. TABLE OF CONTENTS FEDERAL CLEANUP PROGRAMS ................................................... 1 U.S. Department of Defense Cleanup Programs ........................................2 DoD Environmental Quality Mission and Challenges ................................2 DoD Environmental Quality RDT&E Process ......................................3 Defense Environmental Restoration Program.......................................4 U.S. Army Defense Environmental Restoration Program..............................5 U.S. Air Force Major Commands ................................................5 U.S. Navy Facilities Engineering Command........................................5
    [Show full text]
  • PX Operator Manual PACCAR PX-9 Engine
    2017 Emissions 2017-2018 Model Years OperatorOperator’’ss ManualManual Warranty Contents Engine Operation ..................................... 1 Engine Maintenance ..................................... 2 Engine Warranty ..................................... 3 Contents © 2018 PACCAR Inc. - All Rights Reserved This manual illustrates and describes the operation of features or equipment which may be either standard or optional on this vehicle. This manual may also include a description of features and equipment which are no longer available or were not ordered on this vehicle. Please disregard any illustrations or descriptions relating to features or equipment which are not on this vehicle. PACCAR reserves the right to discontinue, change specifications, or change the design of its vehicles at any time without notice and without incurring any obligation. The information contained in this manual is proprietary to PACCAR. Reproduction, in whole or in part, by any means is strictly prohibited without prior written authorization from PACCAR Inc. ENGINE OPERATION 1 Chapter 1 | ENGINE OPERATION Safety - Introduction ............................................................................................................................ 6 Emergency - What To Do If ............................................................................................................... 11 Operating Instructions ....................................................................................................................... 14 Y53-1185-1E1 (04/16/18)
    [Show full text]
  • UDA-Phase3.Pdf
    METROPOLITAN DESIGN CENTER University District Alliance URBAN DESIGN FRAMEWORK PHASE III Transforming the SEMI into a New Innovation District New University of Minnesota Innovation Campus The urge to preserve certain cities, or certain buildings and streets within them, has something in it of the instinct to preserve family records… [Cities] are live, changing things-–not hard artifacts in need of prettification and calculated revisions. We need to respect their rhythms and to recognize that the life of the city form must lie loosely somewhere between total control and total freedom of action. Spiro Kostof The Architect: Chapters on the History of the Profession, 1977 A Special Thanks Funding for this Direct Design Assistance project is provided through generous support from the McKnight Foundation and the Dayton Hudson Endowment. TABLE OF CONTENTS Sentinels of Memory: Maintaining the Sense of Place in a Landscape of Cultural History 02 Acknowledging the Legacy of Innovation in Minnesota’s Growth Economy 06 Thinking Beyond Property Lines: Land Reorganization and Value Capture in Transforming Post-Industrial Sites 10 Regenerative Site Plan 14 Innovation District - Detail Views 18 APPENDIX Restoring the Site: The Promise of Bio- and Phytoremediation 22 The GD III Graduate Urban Design Studio: Testing Regenerative Principles for the SEMI Area 28 Project Participants 36 References 37 Sentinels of Memory: Maintaining the Sense of Place in a Landscape of Cultural History Twin Cities, 1875 To Winnipeg, Canada To Duluth (Red River Valley) Kasota Ave SE 24th Ave SEAve 24th To Chicago 5th St SE The Urban landscape is not a text to be read, but a repository of To Breckenridge, MN (Red River Valley) SEMI Hwy 280 environmental memories far richer than any verbal code.
    [Show full text]
  • Selection of Sustainability Indicators for Wastewater Treatment
    Selection of Sustainability Indicators for Wastewater Treatment Technologies Anupama Regmi Chalise A Thesis in The Department of Building, Civil and Environmental Engineering Presented in Partial Fulfillment of the Requirements for the Degree of Master of Applied Science (Civil Engineering) at Concordia University Montreal, Quebec, Canada 2014 © Anupama Chalise, 2014 CONCORDIA UNIVERSITY School of Graduate Studies This is to certify that the thesis prepared By: Anupama Regmi Chalise Entitled: Selection of Sustainability Indicators for Wastewater Treatment Technologies And submitted in partial fulfillment of the requirements for the degree of Master of Applied Science (Civil and Environment Engineering) Complies with the regulations of the University and meets the accepted standards with respect to originality and quality. Signed by the final examining committee: ________________________________________Chair/ BCEE Examiner Dr. R. Zmeureanu ________________________________________BCEE, Supervisor Dr. C. Mulligan ________________________________________ CES, External-to-Program Dr. G. Gopakumar ________________________________________ BCEE Examiner Dr. Z. Chen Approved By_____________________________________________________________ Chair of the BCEE Department ____________2012________________________________________________________ Dean of Engineering ABSTRACT Selection of Sustainability Indicators for Wastewater Treatment Technologies Anupama Regmi Chalise, 2014 Wastewater treatment systems must be measured and assessed in terms of its
    [Show full text]
  • School Environmental Health Inspection ______
    ___________________________________________________ SCHOOL ENVIRONMENTAL HEALTH INSPECTION _____________________________ GUIDANCE DOCUMENT _____________________________________________________ Indoor Environments Section Bureau of Environmental Health Ohio Department of Health 246 N. High Street Columbus, Ohio 43215 ODH School Environmental Health Program Inspection Guidance Forward The Ohio Department of Health (ODH), Bureau of Environmental Health (BEH), Indoor Environments Section (IES) began the process of revising the school inspection manual in 2002 because many sanitarians from local health departments around the state expressed a desire for an updated, more comprehensive inspection manual to use while conducting the annual inspection of the school building and its environment. This manual is the culmination of years of research, meetings, drafts, edits, pilot programs and revisions. In 2004, a survey was distributed to all local health departments regarding their school inspection program. The survey asked questions about the number of school inspections conducted each year, the length of time involved in school inspections, the importance of inspecting different items in the school environment and the equipment used to conduct the inspection. This survey was returned by 97 percent of all local health departments. Many of the respondents indicated a need for updated school inspection guidance. The revision process began with staff from the ODH and local health departments meeting to discuss what the new school inspection manual
    [Show full text]
  • View PDF(940
    FactSheet National Aeronautics and Space Administration Langley Research Center Hampton, Virginia 23681-0001 FS-2004-07-94-LaRC ________________________________________________________________________________________ SMALL AIRCRAFT TRANSPORTATION SYSTEM NASA-led technologies could increase air travel access NASA is preparing to demonstrate how the latest technologies could significantly enhance operating capabilities of small aircraft, allowing, for example, flights into and out of small airports without radar or towers. This Cirrus SR-22 is being used as a flying testbed for SATS research at NASA’s Langley Research Center. The SATS concept would support propeller and jet aircraft for business and personal transportation for on-demand, point-to-point trips, as well as scheduled service. Travel concept to be demonstrated The SATS concept offers an on-demand, point-to-point, NASA, the Federal Aviation Administration (FAA) and widely distributed transportation system. It relies on the National Consortium for Aviation Mobility (NCAM) advanced four to ten passenger aircraft using new are working toward a June, 2005 demonstration of a operating capabilities. Such a system promises improved supplemental system to congested interstate highways and safety, efficiency, reliability and affordability for small major "hub" airports. aircraft operating within the nation's 5,400 public-use- landing facilities. Nearly all of the U.S. population lives By enhancing the capabilities of small aircraft and small within a 30-minute drive of at least one of
    [Show full text]