A Thesis entitled A Sensor for Measuring Liquid Water Content of Wet Snow on Superstructures by Mehdi Sarayloo Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Civil Engineering ___________________________________________ Dr. Douglas K. Nims, Committee Chair ___________________________________________ Dr. Hossein Sojoudi, Committee Member ___________________________________________ Dr. Ahmed Abdelaal, Committee Member ___________________________________________ Dr. Amanda C. Bryant-Friedrich, Dean College of Graduate Studies The University of Toledo December 2019 Copyright 2019 Mehdi Sarayloo This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of A Sensor for Measuring Liquid Water Content of Wet Snow on Superstructures by Mehdi Sarayloo Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Civil Engineering The University of Toledo December 2019 Abstract One of the phenomena that has a considerable impact on many aspects of today’s world is atmospheric icing. In many cold areas around the world, such as northern Europe, Japan, Canada, and the United States, atmospheric icing causes difficulties in operating of structures or severe dam ages to them. A variety of structures, such as power lines, bridges, telecommunication towers, wind turbines, and naval structures are vulnerable to atmospheric icing problems. Previous studies done by the University of Toledo icing research team on cable- stayed bridges suffering from ice/snow shedding showed that none of the tested active or passive methods are as reliable and economic as an administrative approach. Apart from the method chosen to mitigate this problem, some parameters of frozen precipitation, especially wet snow, are needed to efficiently run the system. The liquid water content and density are the main parameters of wet snow which significantly affect the mechanical bonding between snow and a surface. One of the results of previous studies by the UT icing research team was the UT icing sensor to detect the ice accumulation on bridge cables. The UT icing sensor was a iii thin-film resistance-based sensor which also utilizes temperature to work properly. Due to the satisfactory utilization of this sensor on the VGCS bridge, and its capability of developing new functionalities, several experiments were designed and conducted to find a correlation between the liquid water content and the electrical resistance of wet snow. Based on this correlation, a new operation was developed for the UT icing sensor to measure the real-time liquid water content of wet snow. Additionally, the function previously developed for the UT icing sensor was tested and improved by implementing an algorithm to differentiate between frozen water (ice or snow), liquid water, and air. Utilizing these two capabilities together enables the sensor to be used for indicating ice or snow accumulation and shedding on a structure. In terms of design, the sensor is light, flexible, small, and inexpensive, which makes it easy to be implemented on structures such as cable-stayed bridges. Snow density is another parameter which significantly impacts the snow accumulation and shedding. In another part of this thesis, correlating the snow density to the normal velocity of snowflakes was attempted. iv Acknowledgements I would first like to thank my thesis advisor, Professor Douglas Nims of the Civil & Environmental Engineering Department at the University of Toledo, whose expertise was invaluable in the formulating of the research topic. As my teacher and mentor, he has taught me more than I could ever give him credit for here. I would like to acknowledge my co-advisor, Dr. Hossein Sojoudi of the Mechanical & Industrial Manufacturing Engineering Department at the University of Toledo, for his great support and for all the opportunities I was given to conduct my research. He taught me a great deal about scientific research and academic projects. I would especially like to acknowledge Dr. Ahmed Abdelaal of the Department of the Engineering Technology and Industrial Distribution at Texas A & M University as the committee member of this thesis, and I am gratefully indebted to him for his valuable professional guidance and comments on this thesis. I am also grateful to all of those with whom I have had the pleasure to work during this and other related projects. Finally, I must express my profound gratitude to my parents and to my lovely wife, Sara, for providing me with unfailing support and continuous encouragement throughout my years of study and through the process of researching and writing this thesis. This accomplishment would not have been possible without them. Thank you. v Table of Contents Table of Contents Abstract .............................................................................................................................. iii Acknowledgements ............................................................................................................. v Table of Contents ............................................................................................................... vi List of Tables ...................................................................................................................... x List of Figures .................................................................................................................... xi List of Abbreviations ....................................................................................................... xiv List of Symbols ................................................................................................................. xv 1 Introduction ...................................................................................................................... 1 1.1 Background .......................................................................................................... 1 1.2 Problem Statement ............................................................................................... 4 1.3 Objectives ............................................................................................................ 5 1.4 Thesis Outline ...................................................................................................... 5 2 Literature Review............................................................................................................. 7 2.1 Introduction to the Icing Problem ........................................................................ 7 2.1.1 Precipitation Icing .................................................................................... 8 2.1.2 In-cloud Icing ........................................................................................... 9 vi 2.1.3 Hoar Frost .............................................................................................. 10 2.2 History of Precipitation Icing Caused Problems on Bridges ............................. 11 2.2.1 Alex Fraser Bridge (Vancouver, BC, Canada) ...................................... 11 2.2.2 Arthur Ravenel Jr. Bridge (Charleston, SC, USA) ................................ 11 2.2.3 Leonard P. Zakim Bunker Hill Memorial Bridge (Boston, MA, USA) 12 2.2.4 Mackinac Bridge (Mackinaw City, MI, USA)....................................... 12 2.2.5 Penobscot Narrows Bridge (Stockton Springs, ME, USA) ................... 12 2.2.6 Port Mann Bridge (Vancouver, BC, Canada) ........................................ 13 2.2.7 Severn Bridge (South West England / South East Wales) ..................... 13 2.2.8 Sidney Lanier Bridge (Brunswick, GA, USA) ...................................... 14 2.2.9 Veterans’ Glass City Skyway Bridge (Toledo, OH, USA) .................... 14 2.3 Anti-icing and De-icing Technologies ............................................................... 15 2.4 Electrical Properties of Snow............................................................................. 16 2.5 University of Toledo’s Testing Facilities .......................................................... 19 2.5.1 UT Icing Tunnel ..................................................................................... 19 2.5.2 UT Icing Station ..................................................................................... 21 2.6 Snow Making Science........................................................................................ 23 2.7 Similar Sensors to UTLWC Sensor ................................................................... 25 2.7.1 Detecting Accumulation State ............................................................... 26 2.7.2 Detecting Liquid Water Content of Wet Snow ...................................... 28 vii 3 Sensor Functions and Experiments Setup ...................................................................... 34 3.1 Introduction ........................................................................................................ 34 3.2 Wet Snow vs. Dry Snow .................................................................................... 35 3.3 Importance of the UTLWC Sensor .................................................................... 37 3.3.1 Ice/Snow Accumulation Detection ........................................................ 38 3.3.2 Liquid Water Content ...........................................................................