Hydrostatic pressure refers to the pressure exerted by a fluid gas or liquid at any point in space within that fluid, assuming that the fluid is incompressible and at rest. It is the branch of fluid mechanics that deals with the behaviorresponse of fluid when they are at rest. If the pressure is same at all the points of a finite plane surface with area a, then. Pressure and fluid statics c h a p t e r 3 pressure. Explain the variation of pressure with depth in a fluid. It is necessary to discuss the type of forces that could act on fluid elements. Pressure change in any direction is proportional to the fluid density, local g, and vertical change in depth.
Because these fluids are not in motion, that means they have achieved a stable equilibrium state, so fluid statics is largely about understanding these fluid equilibrium conditions. Fluid statics study material for iit jee askiitians. Density density relates the mass and volume such that mv kg m3 pressure pressure is the result of compacting the molecules of a fluid into a smaller space than it would otherwise occupy. Pressure and fluid statics absolute, gage, and vacuum pressures actual pressure at a give point is called the absolute pressure. From around the point of interest, p in the fluid let us pull out a small wedge of dimensions dx x dz x ds. However, pressure at any point in a fluid is the same in all directions.
Fluid statics is the field of physics that involves the study of fluids at rest. Pressure has a magnitude, but not a specific direction, and thus it is a scalar quantity. Pressure and fluid statics this chapter deals with forces applied by fluids at rest or in rigidbody motion. At rest, there are no shear stresses, the only force is the normal force due to pressure is present. Compressible fluid flow calculation methods article pdf available in chemical engineering new york mcgraw hill incorporated then chemical week publishing llc 1212. What you will learn pressure is the amount of force exerted on a given area. Section 1 fluids and pressure key concept fluid is a nonsolid state of matter. The task is to find the resultant pressure force acting on a submerged surface and point of application of the resultant pressure force. Show the variation of pressure force acting on the walls of the following containers. Pressure at a point within a fluid university of cambridge. For the general case, the stress on a fluid element or at a point. Some of these derive from a unit of force divided by a unit of area. The pressure is the same at all points on a given horizontal plane in a fluid.
Some of the fluid flows over and some under the body. For a fluid at rest, pressure at a point is independent of direction, which is known as pascals law. All fluids can flow and exert pressure evenly in all directions. There is no pressure change in the horizontal direction. In the limit as the fluid wedge shrinks to a point. We define the pressure p a that point as the normal force per unit area, i. Pressure and fluid statics pressure the manometer the barometer fluid statics hydrostatic forces on plane surfaces hydrostatic forces on curved surfaces buoyancy and stability rigidbody motion pressure at a point pressure at a any point in a.
Fluid flow for chemical engineers ekc212 core course. The pressure exerted by the atmosphere on earth is atmospheric pressure. Relative density or specific gravity is defined as the ratio of the density of the given substance to the density of the water at 4c. Fluid pressure and flow phet simulation worksheet phet. Fluid statics pressure and density iit jee and neet physics. It would seem to make more sense if the pressure was greater on the top of the point than on the bottom and not at all on the sides but remember we are talking about a point. Notes lecture 2 fluid statics pressure measurement pressure. Closed bodies of fluid are either static, when the fluid is not moving, or dynamic, when the fluid can move as in either a pipe or by compressing an air gap in a closed container. For static fluid, the maximum rate of change of pressure is along the gravitational acceleration and the constant pressure line is perpendicular to the gravitational acceleration. This is consistent with the use of z as the elevation or height in many applications. P is only a function of z caused by weight force of the column of fluid above the surface. Differential manometers procedure to keep track of pressures start at a known point or at one end of the system and write the pressure there using an appropriate symbol add to this the change in pressure to the next meniscus plus if the next meniscus is lower, and minus if higher continue until the other end of the gage is reached and equate. Consider for example the velocity at a specific point in a fluid.
Find and study its derivation in your fluid mechanics book. Catastrophic breakdown can occur if this factor is not considered. Fluid statics is the part of fluid mechanics that deals with fluids when there is no relative motion between. Analyze the stability of floating and submerged bodies. Pressure at a point pressure at any point in a fluid is the same in all directions. We now regroup the factors of this expression so as to combine all those involving. Hydrostatic pressure distribution pressure in a continuously distributed uniform static fluid varies only with vertical distance and is independent of the shape of the container. In fluid mechanics we consider forces upon fluid elements. Definition of pressure pressure is defined as the amount of force exerted on a unit area of a substance. There is a new discussion of stagnation, static and dynamic pressures, and boundary.
These concepts are key to the solution of problems in fluid statics and lead to the following. Since the unit pa is too small for pressures encountered in practice, kilopascal 1 kpa 103 pa and megapascal 1 mpa 106. For the general case, the stress on a fluid element or at a point is a tensor for a static fluid. Points to remember the governing equation for static fluid is the above equation applies to static fluid where there is no relative motion between fluid particles. Calculate pressure using various kinds of manometers.
Alveolar walls of emphysema victims deteriorate, and the sacs combine to form larger sacs. Units of pressure are nm2, which is called a pascal pa. This is proprietary material solely for authorized instructor use. Chapter 3 pressure and fluid statics proprietary material. Bahrami ensc 283 spring 2009 2 in the limit when the wedge shrinks to a point, fluid statics. Gauge pressure also spelled gage pressure is the pressure relative to the ambient pressure various units are used to express pressure. Phet sims are based on extensive education research and engage students through an intuitive, gamelike environment where students learn through exploration and discovery. Pressure at a point is independent of orientation, 3.
The fluid property responsible for those forces is pressure, which is a normal force exerted by a fluid per unit area. In a moving fluid there will be both static and dynamic pressure definitions. Founded in 2002 by nobel laureate carl wieman, the phet interactive simulations project at the university of colorado boulder creates free interactive math and science simulations. For a static uid, pressure is independent of the orientation of any. Pressure force per unit area 4 m 3 m 2 m w mg p 1 wa 1 48 n 6 m2 8 nm2 8 pa p 2 wa 2 48 n 8 m2 6 nm2 6 pa p 3 wa 3 48 n 12 m2 4 nm2 4 pa example. As indicated by the dye filaments in the water flowing past a streamlined object, the velocity decreases as the fluid approaches the stagnation point. Jul 27, 20 pressure at a point pressure at any point in a fluid is the same in all directions. Most pressuremeasuring devices are calibrated to read zero in the atmosphere, and therefore indicate gage pressure, p gagep absp atm. Pressure at a point pressure is the compressive forceper unit area, and it gives the impression of being a vector.
Chapter 3 fluid statics national university of singapore. Also shows that p is isotropic, one value at a point which is independent of direction, a. Pressure and fluid statics c h a p t e r 3 pressure fluid. Notes lecture 2 fluid statics pressure measurement. Vah pressure and depth examine the darker region, assumed to be a fluid it has a cross sectional area a extends to a depth h below the surface three external forces act on the region a balance them. In some of the derivations we chose z to be the vertical coordinate. That is, it has magnitude but not a specific direction, and thus it is a scalar quantity. Pressure and fluid statics pressure for a static fluid, the only stress is the normal stress since by definition a fluid subjected to a shear stress must deform and undergo motion. Because of the vacuum there is no pressure developed at the point and pressure at the two points of the lower level is equal because they are at the same heights. From the point of view of fluid mechanics, all matter consists of only two states, fluid and solid. Pressure is the force per unit area acting on a surface.
A primer on the geomechanics behind fracturing pressure in this post, i will break an idealized pressure curve like what is recorded during hydraulic fracturing or pressurize fracturing tests in different segments and explain the geomechanics. Pressure at any point in a fluid is the same in all directions and is transmitted through static fluids without loss pascals principle 2. From 1, the pressure at the wall of any vessel is perpendicular to the wall 3. In this lecture we introduce the concepts of pressure and density for a fluid and demonstrate how pressure acts in all directions. For a static fluid, pressure varies only with elevation within the fluid. Pressure and fluid statics pressure pressure is defined as a normal force exerted by a fluid per unit area. The pressure at any given point of a nonmoving static fluid is called the hydrostatic pressure.
Fluid statics contents in fluid mechanics we consider forces upon fluid elements. Such conditions conform with principles of fluid statics. Posted on december 21, 2015 updated on february 29, 2016. The dividing line the stagnation streamline terminates at the stagnation point on the body. Mohsin siddique assistant professor 1 fluid mechanics 2. Dec 19, 2014 density and pressure are the two important physical quantities that we learn in fluids statics.
A primer on the geomechanics behind fracturing pressure curves. Pressure within a liquid depends only on the density of the liquid, the acceleration due to gravity, and the depth within the liquid. Determine a liquids level by the use of general and most commonly used measuring techniques such as vernier depth gauge, inclined scale and scale. Calculate the forces exerted by a fluid at rest on plane or curved submerged surfaces. Discussion in the limit of an infinitesimal cube, we have a fluid particle, with pressure p defined at a point. Fluid statics me 305 fluid mechanics i part 2 fluid statics. Pa m n area force p 2 direction of fluid pressure on boundaries furnace duct pipe or tube heat exchanger dam pressure is a normal force acts perpendicular to surfaces it is also called a surface force absolute and. The difference in liquid level represents the applied pressure. For low pressure differences well above the vapour pressure of water. Fluid statics, static pressure1 two types of forces act on a fluid volume element.
191 1662 1442 2 1258 779 667 1293 1022 912 1520 337 1444 1245 908 3 938 1643 917 804 326 232 102 940 1086 1154 1116 791 292 202 893