Chapter 2 Static Fluid and Pressure Measurements

Fundamental Fluid Mechanics for the Practicing Engineer, 2018

Fluid statics is that branch of mechanics of fluids that deals primarily with fluids at rest. Since individual elements of fluid do not move relative to one another, shear forces are not involved and all forces due to the pressure of the fluid are normal to the surfaces on which they act. With no relative movement between the elements, the viscosity of the fluid is of no concern. At first it will be examined the variation of pressure throughout an expanse of fluid.Then it will be studied the forces caused by pressure on solid surfaces in contact with the fluid, and also the effects (such as buoyancy) of these forces in certain circumstances.

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. Normal stresses are referred to as pressure p. For the general case, the stress on a fluid element or at a point is a tensor For a static fluid,  ij = 0 ij shear stresses = 0  ii = p =  xx =  yy =  zz  i = j normal stresses =-p Also shows that p is isotropic, one value at a point which is independent of direction, a scalar. *Tensor: A mathematical object analogus to but more general than a vector, represented by an array of components that are functions of the coordinates of a space (Oxford)  ij = stress tensor* =  xx  xy  xz  yx  yy  yz  zx  zy  zz i = face j = direction

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Journal of ocean engineering and marine energy, 2015

Pressure, Manometer, and Barometer 3-1C The pressure relative to the atmospheric pressure is called the gage pressure, and the pressure relative to an absolute vacuum is called absolute pressure. 3-2C The atmospheric air pressure which is the external pressure exerted on the skin decreases with increasing elevation. Therefore, the pressure is lower at higher elevations. As a result, the difference between the blood pressure in the veins and the air pressure outside increases. This pressure imbalance may cause some thin-walled veins such as the ones in the nose to burst, causing bleeding. The shortness of breath is caused by the lower air density at higher elevations, and thus lower amount of oxygen per unit volume. 3-3C No, the absolute pressure in a liquid of constant density does not double when the depth is doubled. It is the gage pressure that doubles when the depth is doubled. 3-4C If the lengths of the sides of the tiny cube suspended in water by a string are very small, the magnitudes of the pressures on all sides of the cube will be the same. 3-5C Pascal's principle states that the pressure applied to a confined fluid increases the pressure throughout by the same amount. This is a consequence of the pressure in a fluid remaining constant in the horizontal direction. An example of Pascal's principle is the operation of the hydraulic car jack. 3-6C The density of air at sea level is higher than the density of air on top of a high mountain. Therefore, the volume flow rates of the two fans running at identical speeds will be the same, but the mass flow rate of the fan at sea level will be higher. 3-7 The pressure in a vacuum chamber is measured by a vacuum gage. The absolute pressure in the chamber is to be determined. Analysis The absolute pressure in the chamber is determined from 24 kPa P abs kPa 68 = − = − = 24 92 vac atm abs P P P P atm = 92 kPa PROPRIETARY MATERIAL.

Revista Gobierno y Políticas Públicas, 2023

El artículo muestra el estado del arte del mismo en la región y sugiere que esto supone un nuevo modelo de gobernanza que encaja perfectamente con el llamado paradigma de innovación pública (IP), Estados más flexibles, abiertos y transparentes son claramente compatibles con modelos de relacionamiento Estado-sociedad que busca mayor involucramiento en los asuntos públicos por parte de los ciudadanos. Las soluciones a los problemas públicos no son fórmulas sacralizadas en procedimientos normativo-institucionales y en rutinas burocráticas, sino la construcción conjunta entre diferentes actores donde el sector público juega un rol de legitimación que empieza por información oportuna, útil y accesible para la ciudadanía.