Hydromechanics Introduction PDF

Hydromechanics Introduction Basudev Biswal, Civil Engineering Department, IIT Bombay 1  About me Basudev Biswal, Associate Professor, Civil Engineering Department, IIT Bombay Worked in IIT Hydera...

Hydromechanics Introduction Basudev Biswal, Civil Engineering Department, IIT Bombay 1  About me Basudev Biswal, Associate Professor, Civil Engineering Department, IIT Bombay Worked in IIT Hyderabad (2013-2017) before joining IIT Bombay Native place: Jagatsinghpur, Odisha BE from IGIT Sarang Odisha; Mtech from IIT Guwahati PhD: University of Padova, Venice, Italy. Core academic interests: Rainfall-runoff modelling, especially in data- scarce regions; Flood inundation forecasting; Sediment transport; Landscape evolution modelling; and Self organization in nature. Other interests: Philosophy; Social science; History, and Psychology. Office: 218; Email: [email protected] 2  The hydrosphere “Britanica: Hydrosphere is the discontinuous layer of water at or near Earth’s surface. It includes all liquid and frozen surface waters, groundwater held in soil and rock, and atmospheric water vapour.” (https://www.britannica.com/science/hydrosphere) 3  Earth’s water Radius ≈ 39 km (For more details see: http://water.usgs.gov/edu/earthhowmuch.html)  What is hydromechanics? Hydromechanics is the mechanics of water, particularly in liquid and gaseous forms. It can be considered as a subset of fluid mechanics and thus both terms will be used interchangeably throughout the course. Study of mechanics of water can help us in understanding mechanics of any other fluids. Under certain circumstances mechanics of solid water (ice) can be part of hydromechanics, e.g., movement of glacier. Note that this course will focus primarily basics of hydromechanics. 5  What is mechanics? https://bahria.edu.pk/oric/cfd-computational-fluid-mechanics/ Mechanics: study of behavior of physical bodies when subjected to forces or displacement. 6  What is fluid statics? https://e360.yale.edu/features/water-warning-the-looming-threat-of-the-worlds-aging-dams Fluid Statics: study of the mechanics of fluids at rest. 7  What is fluid kinematics? https://www.pxfuel.com/en/desktop-wallpaper-pihhb Fluid Kinematics: fluid in motion without considering forces acting on them. 8  What is fluid dynamics? https://www.jove.com/v/10444/determination-impingement-forces-on-flat-plate-with-control-volume Fluid Dynamics: involves fluid in motion and considers the forces causing the flow. 9  These statements are quite valid Primarily: Statics => Geometry => Position (x,y,z). Kinematics => Position and time (x,y,z,t). Dynamics => Position, time and mass (x,y,z,t,𝜌). 10  Hydromechanis of complex systems https://energyeducation.ca/encyclopedia/Hydrologic_cycle Hydrology: typically deals with rainfall-runoff relationship. Groundwater hydrology: water flow below earth surface. Meteorology: prediction of rainfall. None of these subjects is part of this course, but a basic understanding of hydromechanics can help in mastering them. 11  Designing canals and dams https://housing.com/news/different-types-of-dams-and-their-uses/ https://en.wiktionary.org/wiki/canal  A lot happens under the water! www.capital-beltway.com https://leopard.tu- braunschweig.de/servlets/MCRFileNodeServlet/dbbs_derivate_00022866/Meyering_Final.pdf Bridge Pier Water surface Flow Sand bed; original Bed deformation due to scour  How is the ship stable? https://news.yahoo.com/why-viral-photo-massive-cruise-173319018.html In pic: the biggest cruise ship.  The two primary learning modes (Biswal et al., 2023) Our education system largely ignores the inductive learning approach. Who is the founder of hydromechanics? https://wildlife.org/wp-content/uploads/2015/11/NE-beaverdam1.jpg When it comes to hydromechanics it is hard to trace back the time period hydro-science/engineering started Beavers are perhaps the first species on the earth to have altered river flows to their advantage. The oldest known beaver dam still intact is approximately 1.25 lakh year old. The largest known beaver dam is 850 m long! 16  Past is data and inspiration for us https://wildlife.org/wp-content/uploads/2015/11/NE-beaverdam1.jpg Rouse and Ince, 1959 Humans need inspiration to make progress and achieve new heights, which is why they often glorify their ancestors' achievements. Text books on fluid mechanics discuss history, they often begin and end with ancient Greeks. However, many civilizations flourished before Greece. The left picture above is of an Indus seal, which shows a boat. The right picture depicts use of siphons in ancient Egypt 17  The foundation of science http://hakobsandbox.openetext.utoronto.ca/part/chapter-10/ One of the questions that has always bothered humans is if natural phenomena are governed by a conscious being or result merely from the interaction between matters. The latter, materialistic, viewpoint had a profound impact on the development of the scientific field what we call now physics. 18  Indian contribution to atomism https://www.vyasaonline.com/wp-content/uploads/2016/09/aruni.png Many ancient Indian schools of thought advocated ‘atomism,’ a theory which suggests the physical world is made up of indivisible particles. Aruni (8th century BCE) is likely the first in recorded history to have proposed ‘atomism’. The most well-known atomist of ancient India perhaps Kanada (the name literally means atom eater). 19  Atomic theory culminating in Europe https://upload.wikimedia.org/wikipedia/commons/thumb/d/d4/John_Dalton_by_Charles_Turner.jpg/440px- John_Dalton_by_Charles_Turner.jpg Our current understanding of atoms owes substantially to Dalton, although it is know speculated that he plagiarized parts of work by Bryan Higgins. However, Dalton’s idea of relative atomic mass was original. Dalton also contributed to hydromechanics by proposing a theory on evaporation. Well thought experimental designs were the reasons why the atomic theory eventually found widespread acceptance. 20  What is the use of atomism here? https://chem.libretexts.org/@api/deki/files/60948/564bc010bc72eacccc974f9573b7cbf0.jpg?revision=1&size=bestfit&width=524&height=572 As fluids like any other matter are made up of atoms or molecules, all fluid properties are result of atomic/molecular interactions. We will see here how atomic theory is useful in understanding fluid properties without much effort. 21  Fluid property: definition https://www.grc.nasa.gov/www/k-12/airplane/Images/state.jpg A fluid property is an observable quantity or quality which remains the same in every experimental observation conducted under the same set of conditions. 22  The three forms of matter https://qph.fs.quoracdn.net/main-qimg-d80a93f3d77156f9da47acbe7c2a94e2 For a nice animation, see https://www.chem.purdue.edu/gchelp/liquids/character.html. In this course we will focus on fluids (liquids and gases) only. 23  Scale https://www.amazon.in/Dreamy-Steel-Scale-Set-Pcs/dp/B0756WNDJS https://en.wikipedia.org/wiki/Stopwatch Scale refers to a particular size, extent or length in either space (e.g. 1 m) or time (e.g., 1 hr). Scale can also be qualitative. How much happy are you today? a) very much, b) somewhat or c) not at all? We will stick to quantitative stuffs only. 24  Scaling https://journals.humankinetics.com/view/journals/krj/7/1/kr.2017-0061/kr.2017-0061/graphic/full-f1.jpg Transfer of information from one scale to another is called scaling. We develop equations for scaling purposes. To do good science, one needs to develop skills to know when scaling is possible and when not. 25 Scale issues and the continuum concept http://www.civil.uct.ac.za/sites/default/files/image_tool/images/72/ccm.png In fluid mechanics, actual molecule structure is ignored in favor of a continuous medium, which is called the fluid continuum. Nevertheless, understanding of molecular behaviors is important as many fluid properties arise due to molecule-scale processes. 26  A hypothetical example box/vol. of the box) Density (mass in the Box size is smaller than the continuum scale The hypothetical box used Box size is larger than the for sampling continuum scale Distance from the left wall to the center of the box Imagine a hypothetical box which is used for sampling. The box collects water sample from a container filled with water. When the box’s size is bigger than the continuum scale, density should be constant everywhere no matter where we perform sampling. However, if the box’s size is closer to molecular scale, density will depend on the position of the box. 27  What I expect from you? It is a perfectly likable course if you can develop a bit of curiosity. 28