City College has made a large investment in the provision of laboratory equipment for Construction and Civil Engineering students.  This equipment is used for practical demonstrations and experimental work carried out by the students.

Most of the equipment we use is developed and manufactured by Armfield .  It  is self-contained and semi portable  and  requires the minimum of preparation time, allowing more 'hands-on' student work to be achieved within a typical laboratory period.

Without a doubt, students develop a higher level of interest and improved understanding, if practical work can be seen to relate to textbook theory.

HYDRODYNAMICS

A lot of the experiments are carried out on the basic hydraulics bench.

It is a portable and self-contained service module of lightweight construction from corrosion resistant materials with quick release pipe couplings to speed the assembly of accessories.

Each accessory we use is complete, needing only connection to the bench.
F1-10 Basic Hydraulics Bench

The bench top incorporates an open channel with side channels to support the accessory on test.  Volumetric measurement is integral and has been chosen in preference to other methods of flow measurement for its ease of use, accuracy and safety in use (no heavy weights for students to drop).

The volumetric measuring tank is stepped to accommodate low or high flow rates.  A stilling baffle reduces turbulence and a remote sight tube with scale gives an instantaneous indication of water level.

The sight tube is evident to the left of the On/Off switch and circuit breaker.

A measuring cylinder is also available for measurement of very small flow rates.

A dump valve in the base of the volumetric tank is operated by a remote actuator. Opening the dump valve returns the measured volume of water to the sump in the base of the bench for recycling.   An overflow in the volumetric tank avoids possible flooding.

Water is drawn from the sump tank by a centrifugal pump and a panel mounted control valve regulates the flow.  An easy-to-use quick release pipe connector situated in the bench top allows for the rapid exchange of accessories without the need for hand tools.

TECHNICAL DETAILS
Pump: ...................................... centrifugal type max. head 21m H2O max. flow 1.35 litres/sec

Motor rating: ............................ 0.37kW

Sump tank capacity: ............... 250 litres

High flow volumetric tank: ...... 40 litres

Low flow volumetric tank: ....... 6 litres

Height of working surface: ..... 1 metre above floor level

HYDROSTATICS

The Hydrostatics Bench is designed to demonstrate the properties of fluids and their behaviour 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.

The experiments and demonstrations which can be carried out on this piece of apparatus includes the following:

Studying the operation and application of pressure gauges and manometers:

Investigating the buoyancy force and stability of floating bodies:

The equipment is mounted on a steel-framed bench fitted with castors allowing it to be stored away when not in use.  This is particularly useful as the laboratory is also used for other class activities and it is not unknown for small pieces of apparatus to go missing via someone's pocket or bag. 

A variety of measuring devices is incorporated, either fastened to the back of the bench or freestanding.  Water is stored in a polythene tank situated on the lower shelf of the bench.  The water can be transferred by two positive displacement hand pumps either to an elevated open storage tank connected to a number of glass tubes for free surface studies, or to a plastic sink recessed into the working surface so that bench top experiments may be conducted without spillage.  All excess water is returned to the storage tank via the sink drain.

OPEN CHANNEL FLOW

Prior to this year, the students carried out their open channel experiments on a college made 4.0 m flume.  Shown below.

Despite the lack of variable adjustments for bed slope etc, this piece of apparatus gave very accurate results for various notch weirs and a Crump weir.  Flow through a sluice gate and through a  syphon could also be demonstrated.  Its one big disadvantage was that it required a large sump in the floor and a three phase electric motored pump for the water circulation.   This disadvantage came to be very important when the college planned to demolish the old building in which the laboratory is located and refused to pay for building a new sump and transferring the large pumps into new accommodation.

In the circumstances, we went to Armfield for a self-contained flume as shown below.

It is a  small cross-section open channel comprising a clear acrylic working section with GRP inlet and discharge tanks mounted on a rigid framework.  The flume can be tilted by use of a calibrated screw jack which allows accurate slope adjustment of the channel.
Bed pressure tappings and fixing points for models are provided.  A longitudinal scale positioned at the top of the channel allows depth gauges and Pitot-static tubes to be positioned along the channel length.

The flume is available in two standard lengths of 2.5m and 5.0m.  We chose the 5m flume to provide a greater scope experiments.

The water supply and flow measuring system is provided from a service module. similar to the basic hydraulics bench.  Water is drawn from a sump tank by a submersible pump and delivered via a shunt type flow-meter and flow control valve into the inlet tank.  A suitable stilling arrangement diffuses the water flow prior to entry into the channel, ensuring smooth, uniform flow.

The level in the working section of the flume may be controlled by an overshot weir arrangement.  Flow-rates can be measured either by using the volumetric tank (maximum flow-rate 1.2 l/sec), a set of notched weirs or by the direct reading flow-meter.

The flume was supplied with the following basic equipment:

In addition to the basic equipment, we purchased the following extras:

FRICTION LOSS APPARATUS

The Armfield Fluid Friction Measurements unit provides facilities for the detailed study of fluid friction head losses which occur when an incompressible fluid flows through pipes, fittings and flow metering devices.  The unit is designed for use with the Armfield F1-10 Hydraulics bench as shown above.

A wide range of measurements, demonstrations and training exercises are possible with the equipment:

Pipe friction is one of the classic laboratory experiments and has always found a place in the practical teaching of fluid mechanics.  Prior to the purchase of this equipment, students carried out their experiments on rather old lengths of copper pipe attached to one of the walls in the laboratory.

The copper pipes are fixed below the window cills.  Here you can see the students doing volumetric flow readings into the blue bin on the left and head loss readings from the pressure difference manometers fixed just in front of the window.

Unfortunately laminar flow would not occur through this apparatus, so the students were able to use a very small diameter plastic pipe running along the opposite wall of the laboratory.

With the unit from Armfield,  friction head losses in straight pipes of very different sizes can be investigated over a range of Reynolds' numbers from 10³ to nearly 10⁵, thereby covering the laminar, transitional and turbulent flow regimes in smooth pipes.  In addition an artificially roughened pipe is supplied which, at the higher Reynolds' numbers, shows a clear departure from the typical smooth bore pipe characteristics.

In addition to the equipment for the study of losses in straight pipes, a wide range of accessories are standard including pipe fittings and control valves, a Venturi tube, an orifice plate assembly and a Pitot tube.

An arrangement of six pipes provides facilities for testing the following:

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