Monday, February 10, 2020

Engineering and construction Essay Example | Topics and Well Written Essays - 3000 words

Engineering and construction - Essay Example ............................................ 30 Task 1 Laminar flow Laminar flow is a type of flow where fluids generally move at low velocity. The layers of the fluid slide by one another. There is no lateral mixing of the fluid and no formation of eddies, cross current or any swirls. Particles of the fluid move in straight line in orderly manner parallel to the boundary walls which can be seen in straight sections of pipes. It generally occurs at a Reynolds number below critical value of 2040. Turbulent flow Turbulent flow is a type of flow that occurs in large velocities characterized with the formation of eddies, swirls and other disturbances in the flow pattern. There is irregularity of flow pattern, fluctuating nature of flow, and diffusivity of particles due to rapid lateral mixing. There is a rapid change in pressure and velocity happening with respect to the space and time. The drag due to boundary layer skin friction is increasing and the overall drag often reduces due to t he changing of structure and location of boundary layers. It generally occurs at a Reynolds number greater than 2040. Uniform Flow Uniform flow occurs when the terminal velocity of the flow is reached. This phenomenon arises when the loss of potential energy in flow is equal to the work done against the channel surface friction. If flow properties are the same at every location along the channel, the flow is uniform. dy/dx = 0. The energy line, water surface and channel bottom becomes all parallel thereby creating uniform flow. So= Sf . In a uniform flow, the velocity can be expressed only as a function of time. According to Eulerian, it is described as   Non-Uniform Flow Non-uniform flow is a type of flow for fluids where the velocity and other hydrodynamic parameters at a particular instant of time is not the same at all points. Change in parameter occur both in points where flow is in the same direction and perpendicular to the direction. The perpendicular non-uniformity is enc ountered near solid boundaries where the fluid passes through. This can be explained by the no-slip condition which occurs when the viscosity tries to reduce the relative velocity of fluid to zero. Steady Flow A steady flow is a type of flow where the hydrodynamic properties of fluid do not change at particular location and time. However, this flow is restricted with space but not with time. There is a required frame of reference. For example, in a laminar flow within a sphere, the flow is kept stationary and steady with respect to the shape of the object. Using the Eulerian approach, a steady flow is described as, and Unsteady Flow An unsteady flow is a type of flow where the hydrodynamic parameters and fluid properties at a particular point changes with respect to time. Turbulent flow is generally unsteady in nature. Reynolds Number Reynolds number denoted by Re is a dimensionless number. It represents a critical quantity to determine the type of flow of fluids, whether it is lami nar or turbulent. It is a ratio of the inertial forces to the viscous forces of fluid. Laminar flow occurs at low Reynolds number while turbulent flow occurs at high Reynolds number. [4] where: = The mean velocity of the object relative to the fluid. The unit is m/s L = Characteristic linear dimension. The unit is m ? = Dynamic viscosity of the fluid. The unit is kg/(m ·s) ? = Kinematic viscosity. The unit is (m?/s) = The density of the fluid. The unit is kg/m? Bernoulli's Theorem Bernoulli's theorem states than in a flow which has no viscosity or inviscid flow, there

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