Fundamental Hydraulic Studies Apparatus

Hydraulic Bench Unit

An integral weir tank is provided along with a volumetric measuring tank which is stepped to afford accurate measurement of both high and low flow rates. The Hydraulics Bench Unit range provides the basic services for pumping and volumetric measurement of the water supply with which all the additional accessories and experiments are used. The measuring tank discharges into a fiberglass sump tank by means of a quick acting ball valve. The working surface of all three units is molded in fiberglass and provides a recessed area on which to mount experiments. 

Experimental Capabilty:
Centrifugal pump characteristics
Bernoulli's experiment
Water flow measurement
Flow through orifices and over weirs
Hydrostatics
Free and forced vortices
Flow in pipes and pipe fittings
Pipe networks
Reynolds number
Flow in channels
Hydraulic machines

Cavitation Demonstration

The pressure through the nozzle can be controlled by a ball valve located on the discharge side of the nozzle. The Inlet, Throat and Outlet pressures are displayed on a pressure gauge via a three-way selector switch. Cavitation demonstration apparatus is a bench top unit designed for use on Hydraulics Bench. It consists of a tube through which water can be pumped by the hydraulic bench. The apparatus comprises of a clear acrylic nozzle mounted on a support plate. The throat pressure can be varied in either of two ways. The first way is to vary the discharge. Reduction of discharge causes a corresponding reduction of the pressure drop as the flow accelerates into the throat because the velocities are reduced, so that the pressure in the throat increases and cavitation ceases. The tube has an initial diameter of 25mm. It then has a linear contraction to a throat diameter of 5mm. This is followed by a 10mm length of parallel-sided tube, after which it flows through a linear diffuser until the diameter is back to 25mm. The contraction ratio (measured in terms of cross-section area) is therefore 25:1. The second way is to throttle the flow out of the apparatus using the ball valve. From a situation where there is no cavitation, increasing the discharge increases the pressure drop as the flow accelerates into the throat because the velocities are increased. 

Bends And Fittings Friction

Bends And Fittings Friction is to be used with Hydraulics Bench All bends and fittings are connected in series with pressure tappings on both sides of each device. The Bends And Fittings Friction equipment measures pressure drops at various flow rates when water flow through different pipe bends, and fittings. A water manometer with a vent valve and a hand air pump is connected to these tappings.

Mini Axial Flow Propeller Turbine

Mini Axial Flow Propeller Turbine is to be used with a submersible pump and Hydraulics Bench. The turbine fixed guide vanes direct water to the runner. Mini Axial Flow Propeller Turbine equipment demonstrates axial flow propeller turbine characteristics power and efficiency at different speeds for various heads and flow rates of water. Flow rate is measured by the Hydraulics Bench measuring tank. The apparatus has a hose for connection to the Hydraulics Bench. Inlet pressure is indicated by a manometer. Torque is measured by a prony brake with two spring balances. Speed is indicated on a portable tachometer.

Pitot Apparatus

The Pitot Apparatus consists of a total head tube and a static head tube for the Pitot, clear acrylic pipe, inlet and outlet, and an inclined manometer. Pitot Apparatus is for a study of velocity distribution across pipe section for a water flow in pipe, and for measurement of flow velocity. The total head tube can be moved up or down vertically with a scale for indication of the tube position. Differential pressure is measured by a multiple inclination manometer. Pitot Apparatus is to be used with Hydraulics Bench. 

Hydrostatics Panel

The unit can be placed on a suitable bench top and requires outside water supply to be stored in the provided storage tank. The Hydrostatics Panel equipment is a bench top unit for the study of basic properties of fluids in hydrostatic conditions. Components are placed on the panel. 

Pipe Friction

Pipe Friction is to be used with Hydraulics Bench. It consists of adjustable constant head water source of removable clear acrylic cylinder for laminar flow. Pipe Friction equipment measures pressure drop when water flows through a vertical pipe at various flow rates both laminar and turbulent. A water manometer with a vent valve, a hand air pump and a mercury manometer are provided for measurement of pressure drop. Turbulent flow may be achieved by directly connecting the pipe to the Hydraulics Bench water supply. 

Mini Axial Flow Impulse Turbine

Mini Axial Flow Impulse Turbine is to be used with Hydraulics Bench. The Mini Axial Flow Impulse Turbine twin nozzles with flow control valves direct water jets to the runner radial blades. Mini Axial Flow Impulse Turbine demonstrates axial flow impulse turbine characteristics i.e. torque, power and efficiency at different speeds for various heads and flow rates of water. Flow rate is measured by the Hydraulics Bench measuring tank. The apparatus has a hose for connection to the Hydraulics Bench. Nozzle pressure is indicated by a pressure gauge. Torque is measured by a prony brake with two spring balances. Speed is indicated on a portable tachometer.

Laminar Flow Apparatus

Laminar Flow Apparatus is to be used with Hydraulics Bench. Two horizontal plates are placed closely together with seals on side edges.  The top plate is transparent and has a transparent grid to help observe stream line patterns. Laminar Flow Apparatus equipment is designed to study laminar flow in two dimensions. Stream lines are produced by regulating a flow of dye from a reservoir through a series of holes at the upstream end. The set rests on adjustable screw supports with bulls eye level. This plate is removable to insert or remove models. The bottom plate has small holes which are connected by valves to a water supply or source and a drain or sink. Water is admitted through a diffuser at one end and drained at the other end.

Mini Flow Channel

The Mini Flow Channel in made of clear acrylic with an undershot weir at inlet and an overshot weir at discharge. Flow rate can be controlled by a flow control valve of the Hydraulics Bench. A dye injection system is installed at the channel inlet to observe flow patterns around models. Mini Flow Channel equipment demonstrates primary characteristics of flow in an open channel including flow patterns over or around immersed objects. It is to be used with Hydraulics Bench. Water is admitted to the channel through a cylinder with a stilling baffle to reduce turbulence. A grid on a white background is provided for easy observation of the streamlines.

Hydrostatics Set

Hydrostatics Set is a reduced version of the hydrostatics bench designed to be used with the Hydraulics Bench.

Experimental Capability of Hydrostatics Set:
Manometry and Hares Tube
Capillarity
Demonstration of Pascals Law.

The unit consists of a backboard unit, mounted directly onto the with:
Hare tube, 600 mm long
Manometer manifold block
2x Fluid manometer, 600 mm long
Pascals apparatus, comprising glass tubes of differing shapes and varying cross-sectional area sealed by a pressure disc actuated by a weighing beam  
Capillarity apparatus comprising set of capillary tubes in frame and trough  
Capillarity apparatus comprising two glass plates in frame and trough

Hydrostatics Bench

Hydrostatics Bench is styled to be a matching unit to Hydraulics Bench, which provides a range of hydro dynamic experiments. A number of the individual experiments are permanently mounted on the backboard, whilst the remaining items are conveniently stored in the cupboard along with the triple beam balance. The working surface is recessed and supplied with a drain point. The optional barometer, consists of siphon type barometer mounted on a wooden backboard supplied complete with mounting brackets for attaching to the frame of the Hydrostatics Bench. The unit is self-contained and independent of all laboratory services. The bench consists of a steel-framed unit, mounted on castors, and containing a high quality fibreglass work surface, a steel backboard and a storage cupboard and shelf under the work surface. 

Osborne Reynolds Unit

The unit is designed to be used on Hydraulics Bench which allows the volumetric measuring tank to be used for flow measurement. Alternatively the unit can be used on a laboratory bench with water supplied from a tap and with the unit discharging to a drain. Osborne Reynolds Unit comprises a reentrant bell mouthed glass experimental tube of 16 mm bore and approximately 650 mm long mounted horizontally in a 103 mm bore perspex tube. Flow control is achieved by an angled seat valve at exit from the apparatus. A dye injector probe and adjustable head dye reservoir are provided to introduce a dye filament for the observation of laminar, and turbulent flow regimes, and the transition between them. An adjustable height constant head inlet tank supplies water to the annulus so that the water flows along the annulus through a baffle into a reverse flow stilling chamber, thus providing a uniform flow with very little turbulence into the bell mouth entry of the experimental tube.

Experimental Capability:
Determination of the lower and upper Critical Velocities and Reynolds Number.
Demonstration of laminar or streamline flow, turbulent flow and the transition between these two regimes by observation of injected dye line.  

Water Flow In Pipes and Fitting Experiments

It is also of significant interest in such diverse fields as Civil and Chemical Engineering, and Biology and Medicine. Early work in the subject was essentially empirical and despite many advances in mathematical analysis the complexity of the flow of real fluids is such that very few complete solutions of flow situations exist and therefore a large part of the topic of fluid flow in closed conduits remains an empirical science. In this area, three sets of experiments are considered which are all concerned with the flow of water through circular pipes or tubes, the head loss through pipe fittings, the loss of head at changes in pipe section, the head loss which occurs at entry and exit to pipes, the pressure loss across valves and valve characteristics. The flow of fluids in closed conduits or pipes is a major topic in the Mechanical Engineering subject of Mechanics of Fluids due to its practical importance in so many fields of study.

Open Channels Weirs

The flow pattern over a notch or weir is complex and there is no analytical solution to the relationship between discharge and head so that once again a semi-empirical approach has to be used. For small scale applications, weirs are often referred to as notches and invariably are sharp edged and manufactured from thin plate material. Hydraulics Bench incorporates a weir channel which is 158mm wide tapering to 152mm wide at the bottom, x 150mm deep x 735mm long in the working surface. The weir channel is fitted with an acrylic 60 triangular notch weir with an integral scale which can be used to provide an approximate indication of the flow rate. In open channels, weirs are commonly used to either regulate or to measure the volumetric flow rate. The Hook Gauge and Scale is an essential accessory for the accurate measurement of the upstream head. They are of particular use in large scale applications such as irrigation schemes, canals and rivers. For a detailed study of the discharge over weirs, provided two sets of weirs and a hook gauge.

Orifice Experiments

An orifice can be screwed into either of the threaded holes and the unused aperture sealed with the blanking plug provided. A scale is mounted on the side of the tank to enable the height of the water above either orifice position to be determined. This arrangement avoids excessive turbulence and enables a steady level surface to be maintained. Two threaded holes are cut into the tank in which to mount the orifice being studied, one in the tank base for 'vertical' discharge, and the other in the tank side for 'horizontal' discharge. The zero of the scale coincides with the centre of the side outlet position. The Orifice sets are used in conjunction with the Inlet Head Tank for the investigation of the flow of water through a horizontal or a vertical orifice. Water is supplied to the tank via a hose connection to the base inlet, and is then distributed within the tank by a vertical perforated sparge pipe. When an orifice is fitted in the horizontal discharge position a Trajectory Profile Hook Gauge can be used to determine the jet profile. Details of both sets of orifices are given as follows.

Impact of Jets

The apparatus is supported on a PVC base into which a vertical water supply pipe is fitted. Surrounding the supply pipe is a transparent plastic shield fitted with a top PVC flanged cover assembly. Impact of Jets apparatus enables experiments to be carried out on the reaction of a jet of water on vanes of various forms. In operation, water from the Hydraulics Bench is fed into the unit and a vertical jet is produced through the supply pipe and its interchangeable nozzle. The water from the jet is deflected by the reaction vane under test, and drains away through the large aperture in the base of the chamber. The reaction vane is held within the transparent shield approximately 20 mm above the vertical water supply pipe nozzle by a rod which passes through the top cover and supports a flat tray, onto which masses may be placed. Three different types of reaction vane are supplied with the apparatus and the types are flat, hemispherical cup and 45° cone form. The force produced by the jet impinging on the target is transmitted by the rod, to the flat tray where weights are placed in order to balance this transmitted force. Two interchangeable nozzles for the supply pipe are supplied, one of 8 mm and one of 5 mm diameter. Each vane can be secured to the pivot arm by a set screw and when not in use is stored on pegs on the unit base plate.

Bernoullis Experiment

An eleven tube static pressure manometer bank is attached to the convergent divergent duct. A dye injection system is provided which allows for a single filament of dye to be introduced into the entrance to the convergent section to enable laminar and turbulent flow regimes to be demonstrated. Bernoulli's Apparatus consists essentially of a two dimensional rectangular section convergent divergent duct designed to fit between Constant Head Inlet Tank and Variable Head Outlet Tank. The convergent divergent duct is symmetrical about the centre line with a flat horizontal upper surface into which the eleven static pressure tappings are drilled. The differential head across the test section can be varied from zero up to a maximum of 450 mm. The test section is manufactured from acrylic sheet. The height of the channel at entry and exit is 19.525 mm and the height at the throat is 6.35 mm. The static tappings are at a pitch of 25 mm distributed about the centre and therefore about the throat. The lower surface is at an angle of 4 29'. The width of the channel is 6.35 mm.

Free and Forced Vortex Unit

The profile of the vortex formed at the top of the vessel is determined by a gauge, housed on a diametrically mounted bridge piece, which measures the diameter of the vortex at various depths. Free and Forced Vortex Unit for the study of the shape of 'free and forced vortices' consists of a 250 mm diameter cylindrical, transparent vessel 180 mm depth, having two pairs of diametrically opposed inlet tubes of 9.0 mm and 12.5 mm diameter. The 12.5 mm diameter inlet tubes which are angled at 15° to the diameter, so that a swirling motion is imparted to the liquid entering the vessel, are used as entry tubes for the free vortex experiment. The input water from these tubes impinges on a simple two blade paddle which acts as a stirrer/flow straightener. The water 'leaves' the vessel via the 12.5 mm diameter angled tubes which are used as the 'entry' tubes for the free vortex experiment. The two bladed paddle rotates on a vertical shaft supported by a bushed plug, in the hole used as the outlet for the free vortex experiment, and located at the top by a suitable hole in the bridge piece fitting across the diameter of the vessel. A smooth outlet is centrally positioned in the base of the vessel and a set of push-in orifices of 24, 16, 12 and 8 mm diameter is supplied to reduce the outlet diameter to a suitable value. This gives the co-ordinate points required to plot the vortex profile. The forced vortex is created in the vessel described above by using as the inlet the 9 mm bore tubes which are angled at 60° to the diameter. This bridge piece also houses the probes required to determine the co-ordinates of the vortex profile to be measured.

Hydrostatics Experiments

The apparatus, which is illustrated in Fig. 1, consists of a valve base and a bronze barrel which has a precision machined bore into which fits a stainless steel piston. Calibration of Pressure Gauges is used for the calibration of the Bourdon type pressure gauge supplied with the Cussons Hydraulic Bench and other gauges of a similar rating using the dead weight method. Fitted to the valve base are two connections and a blanking plug. A connection for the pressure gauge under test is pre-fitted and supplied with a length of plastic pipe suitable for connection to the pressure gauge via the auxiliary tapping on the Hydraulics Bench. The piston is fitted with a platform which can carry calibration weights the weights supplied with the apparatus are equivalent to pressures of 0.5 bar and 1 bar. The piston and platform have a total weight equivalent to 0.5 bar pressure. A non-return connection for the water supply from the hydraulics bench is fitted on one side of the valve block. A spill-pipe is fitted into the barrel which prevents the piston being ejected by excess pressure. The Bourdon gauge, fitted on the Bench, is a simple device and normally very reliable in service. On the third side of the block is a blanking plug which is removed to allow the apparatus to be drained of water. The apparatus is mounted on a plastic base for stability. After an extended period of use, slight deviations of value are likely to occur and for "accurate" work a calibration curve for the instrument is necessary. The basic element of the gauge is a curved, elastic-metal tube, usually of brass or stainless steel, which changes its geometry when filled with fluid under pressure. This distortion is transmitted by linkage to the gauge pointer. The dead weight tester is not subject to variations and can, therefore, be used as a reliable.

Water Flow Measurement

Four flowmeters are described below which operate on the principle of either head loss, impulse or velocity. A fifth flowmeter, Rotameter working on the variable area principle, is described separately in the Hydraulics Bench leaflet. The measurement of flow rate is a fundamental topic to which a considerable degree of attention has been paid with the result that there are flow meters available using a wide variety of principles. Chosen five types of flowmeter, which are all in common industrial use, to provide experiments in comparative flow measurement. 

Experimental Capabilities:
Establishment of the relationship that flow is proportiona to the square root of the pressure drop between entry and the venturi throat.  
Observation of degree of pressure recovery at the end of the divergent section of the Venturi Tube.
Demonstration of use of Venturi Tube as a water flow meter and determination of the flow coefficient.