Department of Civil Engineering CVEN - 327 - Hydrology and Hydraulics Lab FLUID STATICS AND MANOMETRY APPARATUS INTRODUCTION The Fluid Static and Manometry Apparatus F1-29 is designed to demonstrate the properties of Newtonian fluids and their behavior under hydrostatic conditions (fluid at rest). This allows students to develop an understanding and knowledge of a wide range of fundamental principles and techniques, before studying fluids in motion. These include the use of fluids in manometers to measure head pressure and head / pressure differences in gases and liquids. Some simple exercises are included to show how the behavior of a fluid changes when flow is involved and the relevance of phenomena such as frictional losses. Equipment Diagrams o 0 0 0 0 0 0 0 Q Q o Front View of F1-29 Fluid Statics and Manometry apparatus SITY OF THE DISTRICT OF COLUMBIA gineering and Applied Sciences "Engineering 18 - ineering The apparatus is constructed from PVC and clear acrylic for durability and ease of maintenance. It consists of a vertical cylindrical reservoir (2), containing water, that is connected to a series of vertical manometer tubes (13). These tubes can be used individually or in combination for the different demonstrations of hydrostatic principles and manometry. One tube (11) incorporates changes in cross section to demonstrate that the level of a free surface is not affected by the size or the shape of the tube. The right hand manometer tube (12) is separate from the other tubes and incorporates a pivot and indexing mechanism (9) at the base that allows this tube to be inclined at fixed angles of 5°, 30°, 60° and 90° (vertical). The Reservoir incorporates a Vernier level gauge (1), sometimes called a hook and point gauge, mounted through the lid, that allows large changes in level to be measured with better precision than a simple scale. A vertical transparent piezometer tube (3) through the lid of the reservoir allows the static head above the water in the reservoir to be observed when the air space above the water is not at atmospheric pressure. Connections (15) at the top of the reservoir and each of the manometer tubes allow a plastic syringe to be connected using flexible tubing to vary the static pressure of the air positively or negatively as required for the various demonstrations. By partly opening the drain valve (10), a small flow can be induced through the interconnecting pipework between the various manometer tubes to provide a simple but clear demonstration of the effect of friction created by the motion of the fluid. This is useful to the student before performing demonstrations using more advanced Fluid Dynamics accessories. The equipment is designed to demonstrate the basic principles of hydrostatics and manometry using water for safety and convenience. The use of a safe, water soluble food dye in the water makes observation of the level changes clearer without affecting the operation of the apparatus. Alternative liquids, with different densities, can be used in the 'U' tube manometer if required to extend the range of the demonstrations Provided that health and safety concerns are observed. Base: The apparatus incorporates four height-adjustable feet (8) that can be used in conjunction with the built-in circular spirit level (6) to unsure that the unit is upright in use. Reservoir: The circular reservoir (2) is constructed from clear acrylic to allow a clear view of the contents. A scale on the front of the reservoir indicates the depth of water inside the reservoir relative to a datum that coincides with the datum for the manor eter tubes. The lid of the reservoir incorporates an 'O' ring seal where it fits into the top of reservoir and an additional sea where the shaft of the Vernier level gauge (1) passes through. These seals allow the air spac above the liquid to be pressurized or evacuated relative to atmospheric pressure as required f- some demonstrations. The reservoir can be drained after use by connecting the filling tube to t quick release connector at the base of the reservoir. The end of the filling tube should be direct to a suitable drain. A piezometer tube through the lid of the reservoir indicates when air press above the surface of the water is above or below atmospheric pressure. This also prevents reservoir from being over pressurized in use. BIA n for the > a series of maintenance. orates size Fixed Tubes: A series of vertical tubes (13) are included on the main backboard. Each tube includes a scale for measurement of the liquid level in the tube allowing direct comparison of any differences in level between the tubes and the level in the reservoir. P h. The two left hand fixed tubes are connected at the base to create a U tube manometer with a quick release connector (7) at the lowest point to allow filling or draining of the U arrangement using the appropriate flexible tube supplied . The two middle fixed tubes are independent and can be connected externally at the top as required to create different types of manometer. The right hand fixed tube (11) incorporates changes in its cross section. When compared with the level in the reservoir and the other tubes this shows that that liquid level not affected by the diameter or the shape of the tube. Inclinable Tube: One tube at the right hand end (12) has the facility to be inclined at preset angles of 5°, 30°, 60° and 90° (vertical). The angle is adjusted by pulling the indexing knob (9) at the front, moving the tube to the required inclination then pushing the knob back in to lock the position. To avoid damage to the equipment it is important to support the tube while making adjustments to prevent it from falling to the lowest position. When compared with the level in the reservoir and the other tubes this shows that that liquid level is not affected by the inclination of the tube. In more advanced demonstrations the use of the inclined tube as a manometer is demonstrated and the relationship between scale length and differential pressure. As the tube is inclined the vertical height of the zero on the scale will change so this must be accounted for when taking measurements. A lever operated valve (14) at the top of the inclinable tube can be closed to prevent loss of liquid if the level is increased in the reservoir when the tube is inclined. Connections: An outlet at the base of the reservoir is permanently connected to the different vertical and angled tubes using flexible tubing. This allows basic demonstrations to be performed without the need to configure the unit. The connection incorporates a lever operated valve (5) to isolate the connection or vary the flow to the manometer tubes to suit the required demonstration. Serrated ferrules (15) at the top of each vertical tube and the reservoir allow flexible tubing to be connected and removed to suit the various demonstrations. These fittings are permanently open so that the system remains at atmospheric pressure when the syringe is not connected A self- sealing quick-release connector (4) is fitted at the base of the reservoir to aid filling, draining etc. A similar fitting (7) is installed at the base of the U tube arrangement. These fittings are self- sealing to prevent loss of water when the fitting is disconnected. Lever operated valves are also incorporated at the top and bottom of the inclinable tube to isolate the connection or vary the flow to suit the required demonstration. Vernier Height Gauge (Hook and point gauge): A Vernier height gauge (1) is installed on top of the reservoir to accurately measure changes in the level of the water inside the reservoir. This gauge consists of a frame, with guides at top and bottom, which allows a rod to slide vertically ed to the allows ae level th the eurled face the ok ge e A scale immersed in water or attached to the side of a transparent vessel or tank can be used to measure the depth of water relative to some datum such as the base of the tank. Changes in water level can be recorded by taking repeated measurements using the scale. When taking a level measurement it is important to view the surface of the water correctly relative to the scale because of a meniscus that forms due to surface tension. The meniscus must be ignored so that the reading is taken from the true surface of the liquid. In the example below the water level corresponds to 200 mm on the scale and not 203 mm indicated by the meniscus. 220 Meniscus 210 Liquid surface 200 190 180 170 Section through reservoir Front view of scale on reservoir 2. Avoiding parallax when taking readings If the scale is not directly adjacent to the liquid then it is important to maintain eye level at the surface of the liquid to avoid parallax. If the eye is below the true liquid level, looking upwards, then the apparent reading on the scale will be lower than the true reading because of parallax as shown in the diagram below. School of Eng Civil Engineering Fall 2018 ge/Diverge Examples: CVEN-351/ Transportation Engineering Problem 1 2 lane 400 ft 2000 VPH 600 Ft 9% trucks 1500 Ft A scale immersed in measure the depth level can be When tela up and down. A linear scale attached to the frame alongside a Vernier scale attached to the vertical rod, allow height measurement with a resolution of 0.1 mm. A clamping screw allows the position of the Vernier scale to be varied on the vertical rod to change the datum for the level measurements. Coarse adjustments can be made by unclamping the rod and sliding it (with the Vernier attached) to the required position. Fine adjustments can be made using the knurled adjusting screw at the top. A hook and a point located at the bottom of the rod allow the surface of the water to be located. Accurate positioning of the gauge is obtained by observing the position where the tip and its reflection just coincide. Under normal lighting conditions the hook is used when observing the water surface from below and the point is used when observing the water surface from above. Detailed instructions on operating the Vernier level gauge are included in the demonstration of the Vernier height gauge. Exercise A: Measuring liquid level Objective To measure the level of a liquid using basic measuring techniques such as a scale, vernier depth gauge and inclined scale. Method 1. Measuring changes in liquid level using a level scale. 2. Avoiding parallax. 3. Measuring changes in liquid level using a vernier level gauge. 4. Measuring changes in liquid level using an inclined tube. 5. Magnifying small changes in level using area ratio. Equipment Required In order to complete the demonstration the following equipment is required: 1. F1-29 Fluid Statics and Manometry apparatus. 2. F1-10 Hydraulics Bench or source of water for filling the reservoir on F1-29. Optional Equipment Water soluble food dye to make observation of the level changes clearer. Theory 1. Measuring depth of a liquid using a linear scale.
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