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BREE 305 (1)
Lecture

Fluid Lab 2_Group4_RodgerLiu.docx

10 Pages
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Department
Bioresource Engineering
Course Code
BREE 305
Professor
Vijaya Raghavan

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BERNOULLI VERIFICATION & FLOW PATH FRICTION LOSSES BREE 305 FLUID MECHANICS 10/12/2012 -Lab Group 4- Nada Kahn 260479292 Mark Kim 260426887 Caro Jang 260410441 Raquel Labranche 260480722 Rodger Liu 260399475 Gianni Montanaro 260418092 Chris Panaritis260480361 Introduction: Bernoullis theorem is the principle of energy conservation for ideal fluids, allowing engineers to describe, characterize, and model fluid flow allowing for numerous engineering applications. The theorem states 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. Additionally, the mathematical expression of the Bernoulli equation relates pressure, velocity, and elevation in a steady laminar flow to a fixed constant. However, Bernoullis theorem is limited to the following conditions: flow is steady, friction is negligible, the fluid holds constant density, and the two points in question lie on the same stream line. In this lab, a special apparatus consisting of the flow of water through a tapering circular duct is designed to verify Bernoullis Theorem. The apparatus mimics the aforementioned conditions as closely as possible while providing for a way to measure the pressure head via probe and tapping points. By recording various measurements, and relating them through equations, we can expect an increase in fluid velocity for converging flow as the fluid moves into a narrower cross sectional area, and a decrease in fluid velocity for diverging flow as the fluid moves into a wider cross sectional area. The results of which, will have predictable outcomes on the total pressure head. For a practical situation (where Bernoullis conditions are not met) of pumping liquid from one point to another, it is crucial to account for friction losses in a flow path. Both the size and length of pipes can be adjusted to compensate for pressure loss/head loss in the pipes due to frictional forces. Not only does head loss occur in the straight sections of pipe, but also bending sections of pipe which have additional contributions to pressure head loss. In designing a functional system involving pipes and liquid, the calculated amount of pressure required is directly related to the amount of pressure lost due to friction along the pipe. To quantify and better understand frictional loss through pipes, both the Reynolds number and frictional factor are calculated. Primarily, head loss is directly proportional to the amount of friction present and is described with the friction factor. Using the, Darcy-Weisbach equation it is possible to calculate the friction factor which is dependent on the both the type of fluid flow and the roughness coefficient of the pipe. While the roughness coefficient is a constant dependent on the pipe material, the type of fluid flow is a calculated value called Reynolds number. To continue, Reynolds number is a dimensionless number that determines the characteristics of whether a flowing fluid is laminar, transitional or turbulent. If a flow is found to be laminar, then the friction factor is only dependent on the Re number. When a flow is found to be turbulent, then the friction factor is dependent on Re number and roughness of the pipe coefficient of the pipe. Transitional flow is a combination of turbulent and laminar flow, when 2300 < Re < 4000; a state in which the frictional factor cannot be found due to the variation of flow patterns from turbulent to laminar. When the head loss is calculated using the Darcy-Weisbach equation, it accounts for the velocity head, pressure head and elevation head. The velocity head is the pressure felt at a point placed in front of a flowing fluid. The pressure head corresponds to a height read on a manometer of a pressure at a point of a fluid at rest. The elevation head is the pressure exerted from the gravitational forces of the fluid on the pipe.Objectives: The objective of the first part of the experiment is to use the Bernoullis theorem verification apparatus to verify water flow, allowing students to test whether the Bernoullis theorem is being obeyed. The water flow that is being measured flows through a tapering circular duct that is divided into two sections in a pipe. The objectives for the second part of the experiment are to determine the friction loss of water flow through a circular pipe and to observe and discussing the resulting graph of friction factor vs. the Reynolds number. Another objective of this experiment is to estimate and observe the head loss coefficient in the bend of the circular pipe. Materials & Methods: Materials 2.1 & 2.2 Hydraulic bench F1-10 Bernoulli's Theorem demonstration apparatus F1-15 Stopwatch Buckets Weigh scale Procedure 2.1 - Bernoullis Theorem Verification Apparatus 1. The apparatus was leveled on the hydraulic bench using the adjustable feet. 2. The apparatus nanometer tubes were filled w
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