With these different parameters, the flow rate, Reynolds number and friction factor were able to be calculated for each est.. For water and mercury. The main purpose of the process was to analyses and identify the regions of laminar flow, and turbulent flow, as well as the transitional region in between. These values enable the calculation of the friction factor of the pipes for specific flow rates. 2. 0 Background The viscosity (p) in the pipe flow of a fluid produces friction (shear stress) between lumps of fluid as they pass each other.
This causes the fluid to cling to the boundary in the flow field. Reynolds number (Re) is the ratio of fluid momentum to viscous forces. Re=PDP This ratio allows the flow of a fluid to be distinguished; this flow can either be laminar, turbulent or transitional. Laminar flow only occurs when the flow of a fluid is smooth and steady; a small Reynolds number defines a flow as laminar (less than 2300). Turbulent flow is the opposite of laminar flow; here the flow is unsteady and has random fluctuations. A large Reynolds number defines a flow as turbulent (greater than 4000).
For turbulent flow the viscous affects are negligible and turbulent flow is therefore known as invalid. Transitional flow is a mixture of the two flows, as it is neither completely steady or unsteady, and sits in between the change from laminar to transitional with a Reynolds number in between (greater than 2300 but less than 4000) Figure 1 As shown in the above figure Laminar flow is smooth and steady through the pipe whereas the turbulent flow is messy and unsteady through the pipe. Transitional flow will show a mix of both these arrows through the pipe showing the steadiness and unsteadiness mix in the flow.
The friction factor of flow through a pipe is defined as the ratio between wall shear stress and the inertial force of the flow as it interacts with the boundary or pipe walls through ruction, this friction affects the flow of the fluid. The greater the Reynolds number, hence the faster the fluid is flowing the less friction there is between the fluid and the pipe walls. The friction factor is proportional to 1/Re for laminar flow. For Laminar Flow, f= ere For turbulent flow the friction factor is defined different to laminar flow, it is still a function of Reynolds number.
For Turbulently, f=O. Eerie/4 The Moody Chart (Figure 2) is also used to calculate the friction factor of a flow with a known Reynolds number and pipe roughness as turbulent flow is a unction of the pipes roughness as well. 3. 0 Apparatus Figure 2 The apparatus used in this lab for the measurement of friction loss is a small horizontal pipe of nominal diameter 3 mm. Figure 1 shows the arrangement in which water from a supply tank is led through a flexible hose to the bell-mouthed entrance to a straight pipe, along which the frictional loss will be measured.
Viscometer tapings exist at an upstream section which lies approximately 45 pipe diameters away from the pipe entrance, and at a downstream section which lies approximately 40 pipe diameters away from the pipe exit. These clear lengths upstream and downstream of the test section are required to prevent the results from being affected by disturbances near the entrance and exit of the pipe. The viscometer tapings are connected to an inverted U-tube manometer, which reads the differential pressure. The rate of flow along the pipe is measured by timing the collection of water in a measuring cylinder. . 0 Procedure 4. 1 Water Manometer Readings (Readings 1-12) * Open the bench supply valve and adjust until there is a steady flow down the supply tank overflow pipe. * Turn the isolating tap to read the water manometer. * Use the needle valve to regulate the flow rates through the pipe so that your 12 readings cover the full extent of flow rates. Start from a low flow rate. * Take the readings of water manometer Hal and h2o. * Collect a suitable quantity of water in measuring cylinder and record the time taken for the collection.