Fluids mechanics ER ANKIT KUMAWAT ASSISTANT PROFESSOR DEPARTMENT

Fluids mechanics ER. ANKIT KUMAWAT ASSISTANT PROFESSOR DEPARTMENT OF CIVIL ENGINEERING SEMESTER III

Fluid mechanics studies the systems with fluid such as liquid or gas under static and dynamics loads. Fluid mechanics is a branch of continuous mechanics, in which the kinematics and mechanical behavior of materials are modeled as a continuous mass rather than as discrete particles. Fluid mechanics deals with the behavior of fluids at rest and in motion. It is logical to begin with a definition of fluid. Fluid is a substance that deforms continuously under the application of shear (tangential) stress no matter how small the stress may be. Alternatively, we may define a fluid as a substance that cannot sustain a shear stress when at rest. SSCE DEPARTMENT OF CIVIL ENGINEERING 2

SCOPE OF FLUID MECHANICS The design of all types of fluid machinery including pumps, fans, blowers, compressors and turbines clearly require knowledge of basic principles fluid mechanics. Other applications include design of lubricating systems, heating and ventilating of private homes, large office buildings, shopping malls and design of pipeline systems. The list of applications of principles of fluid mechanics may include many more. The main point is that the fluid mechanics subject is not studied for pure academic interest but requires considerable academic interest. SSCE DEPARTMENT OF CIVIL ENGINEERING 3

Why Study Fluid Mechanics? There are number of fluids that when burnt, produce lots of heat, which can be used for various applications. Examples of these fluids includes petrol and diesel for vehicles. Most of the civil structure rest on soil surface, so life of these structures depend upon the load carrying capacity of soil. There are some fluids like oil that have a tendency to exert very high pressure or force. These fluids can be used for lifting various heavy loads. The fluids used in hydraulic machines and hydraulic lifters are an example. For large projects such as a highway, airport, dam etc. , soil studies before design of foundation of structure Some fluids have excellent flow properties which can be used for the lubrication of various machines. fluids like water posses kinetic and potential energy, which is used for generation of electricity as in hydroelectric power plants. SSCE DEPARTMENT OF CIVIL ENGINEERING 4

Common Applications of Fluids Hydroelectric Power Plants Hydraulic machines Automobiles Refrigerators and Air Conditioners Thermal Power Plants Nuclear power plants Fluids as a Renewable Energy Source Operating Various Instruments SSCE DEPARTMENT OF CIVIL ENGINEERING 5

Topic study in Fluid mechanics Physical properties of fluid Hydrostatics Buoyancy Hydro-kinematics Application of Bernoulli’s equation Momentum equation and application Flow through pipe SSCE DEPARTMENT OF CIVIL ENGINEERING 6

Physical properties of fluid There are three physical properties of fluids that are particularly important: density, viscosity, and surface tension. Each of these will be defined and viewed briefly in terms of molecular concepts, and their dimensions will be examined in terms of mass, length, and time (M, L, and T). The physical properties depend primarily on the particular fluid. Density The density ρ of a fluid is defined as its mass per unit volume and indicates its inertia or resistance to an accelerating force. the density of an ideal gas depends on the molecular weight, absolute pressure, and absolute temperature. SSCE DEPARTMENT OF CIVIL ENGINEERING 7

viscosity. The viscosity of a fluid measures its resistance to flow under an applied shear stress, properties of fluids—including viscosity—are also discussed often involve containing the fluid in a small gap between two surfaces, moving one of the surfaces, and measuring the force needed to maintain the other surface stationary. Surface tension is the tendency of the surface of a liquid to behave like a stretched elastic membrane. There is a natural tendency for liquids to minimize their surface area. The obvious case is that of a liquid droplet on a horizontal surface that is not wetted by the liquid—mercury on glass, or water on a surface that also has a thin oil film on it. For small droplets adopts a shape that is almost perfectly spherical, because in this configuration there is the least surface area for a given volume SSCE DEPARTMENT OF CIVIL ENGINEERING 8

Hydrostatics is about the pressures exerted by a fluid at rest Any fluid is meant, not just water. It is usually relegated to Fluid Mechanics, since its results are widely used in study. such as forces on dams, buoyancy and hydraulic actuation, There are several familiar topics in hydrostatics Pressure and its measurement Atmospheric pressure and its effects Maximum height to which water can be raised by a suction pump Discovery of atmospheric pressure and invention of the barometer Hydraulic equivalent of a lever Pumps Forces on a submerged surface The Hydrostatic Paradox Buoyancy (Archimedes' Principle) Measurement of Specific Gravity SSCE DEPARTMENT OF CIVIL ENGINEERING 9

Buoyancy is the force that causes objects to float. It is the force exerted on an object that is partly or wholly immersed in a fluid. Buoyancy is caused by the differences in pressure acting on opposite sides of an object immersed in a static fluid. It is also known as the buoyant force. Buoyancy is the phenomena due to Buoyant The upward force applied by the fluid on the object or the body when an object is put in or submerged in the fluid. The unit of buoyant force is the Newton (N) When a body is in water, it displaces some amount of water owing to its weight. The amount of displaced water is computed by the object’s density which relates to volume. The volume of a cricket ball and beach ball can be same their different weight their density differs. The steel solid block descends in water but the steel ship does not. Therefore, the quantity of displaced water in the upward direction is elucidated in terms of Buoyant force. The point where the force of Buoyancy is applied or the point on the object where the force acts are termed as the Center of Buoyancy. SSCE DEPARTMENT OF CIVIL ENGINEERING 10

KINEMATICS OF FLOW (hydro-kinematics) Method of describing Fluid Motion : As the fluid moves on the values of the fluid properties such as density, velocity and acceleration etc. will change from one position to other positions from time to time. Two methods are possible to describe fluid motion. Lagrangian Method and Eulerian Method. Steam Line: A steam line is a continuous line in a fluid which shows the direction of the velocity of the fluid at each point along the line. The tangent to the stream line at any point on it is in the direction of the velocity at that point. Fluid particle lying on a stream line at an instant move along the stream line. Path Line: A path line means the path or a line actually described by a single fluid particle as it moves during a period of time. The path line indicates the direction of the velocity of the same fluid particle at successive instants of time. SSCE DEPARTMENT OF CIVIL ENGINEERING 11

Types of fluid flow Ideal and real flow Incompressible and compressible flow Laminar and turbulent flow Steady and unsteady flow Uniform and non uniform flow SSCE DEPARTMENT OF CIVIL ENGINEERING 12

Bernoulli’s equation First derived (1738) by the Swiss mathematician Daniel Bernoulli, theorem states, in effect, that the total mechanical energy of the flowing fluid, comprising the energy associated with fluid pressure, the gravitational potential energy of elevation, and the kinetic energy of fluid motion, remains constant Bernoulli’s theorem is the principle of energy conservation for ideal fluids in steady or streamline flow and is the basis for many engineering applications. SSCE DEPARTMENT OF CIVIL ENGINEERING 13

Application of Bernoulli’s theorem here are some example based on Bernoulli`s Theorem Siphon Effect- most widely phenomena which you can see around yours in real time. Drawing Fluids Upward: Atomizers and Chimneys , perfumes It is used to calculate pressure or velocity of the fluid Air flight Draft Venturimeter Orifice meter SSCE DEPARTMENT OF CIVIL ENGINEERING 14

Momentum equation and application The momentum equation is used to determine the resultant force exerted on the boundaries of a flow passage by a stream of flowing fluid as the flow changes its direction or the magnitude of velocity or both. Following are the practical application of momentum equation (1) Flow though bend pipes (2) Jet propulsion and propellers (3) Fluid flow though stationary and moving plates or vanes. (4) Non-uniform flow through sadden enlarged pipes. (5) Hydraulic jump in open channels SSCE DEPARTMENT OF CIVIL ENGINEERING 15

Flow through pipe It is mainly based on the frictional losses in pipe flow There are many types of losses of head for flowing liquids such as friction, inlet and outlet losses. The major loss is that due to frictional resistance of the pipe, which depends on the inside roughness of the pipe. The common formula for calculating the loss of head due to friction is Darcy’s Formula Darcy’s formula for friction loss of head: hf = 4 f L v 2 /2 g d Where hf = head loss due to friction f = frictional coefficient V = velocity in pipe g = gravitational acceleration d = diameter of pipe L = length of pipe SSCE DEPARTMENT OF CIVIL ENGINEERING 16

Objective To introduce and explain fundamentals of Fluid Mechanics, which is used in the applications of Aerodynamics, Hydraulics, Marine Engineering, Gas dynamics etc. To give fundamental knowledge of fluid, its properties and behavior under various conditions of internal and external flows. To develop understanding about hydrostatic law, principle of buoyancy and stability of a floating body and application of mass, momentum and energy equation in fluid flow. To inculcate the importance of fluid flow measurement and its applications in Industries. To determine the losses in a flow system, flow through pipes, boundary layer flow and flow past immersed bodies. SSCE DEPARTMENT OF CIVIL ENGINEERING 17

Thank you SSCE DEPARTMENT OF CIVIL ENGINEERING 18