ABSTRACT

Osborne Reynolds experiment is used to investigate the characteristic of the flow of the liquid in the pipe. This experiment is also can determine the Reynolds Number for each state of the flow. In experiment A, Reynolds Number had been compute and the type of flow had been observed by the pattern of the dye either it was laminar, transitional or turbulent flow. The velocity of the flow was control by the valve to differentiate the type of the flow. The time had been calculated for each of the flow to fill the tank exactly with 2 litre. The Reynolds

Number had been calculated by using the Reynolds Number formula,R=UL

V . From the experiment it was proved that the laminar flow fall in range of 0 to 2100, transition state range between 2100 to 400 and turbulent flow had Reynolds Number more than 4000. In experiment B, upper and lower critical velocities was determined by calculating the time taken to filled the tank to 2 litre when the pattern of the flow changed. Based on the result, it was proved that that the upper and lower critical velocities approximately at 4000 and 2100.

INTRODUCTION

Osborne Reynolds Demonstration (Model: FM 11) has been designed for students experiment

on the laminar, transition and turbulent flow. It consists of a transparent header tank and a

flow visualisation pipe. The header tank is provided with a diffuser and stilling materials at

the bottom to provide a constant head of water to be discharged through a bell mouth entry to

the flow visualisation pipe. Flow through this pipe is regulated using a control valve at the

discharge end. The water flow rate through the pipe can be measured using the volumetric

tank (or measuring cylinder) of a Hydraulics Bench. Velocity of the water can therefore be

determined to allow for the calculation of Reynolds’ number. A dye injection system is

installed on top of the header tank so that flow pattern in the pipe can be visualised.

OBJECTIVE

The objectives for Experiment A are to compute the Reynold’s Number, R=UL

V and to

observe the type of flow either laminar, transitional or turbulent flow by examine the pattern

of the dye. Meanwhile, in Experiment B, the objectives are to determine the Reynold’s

Number (R) and to determine the upper and lower critical velocities at transitional flow.

THEORY

Reynolds number is a dimensionless number that gives a measure of the ratio of

inertial forces to viscous forces and consequently quantifies the relative importance of these

two types of forces for given flow conditions. The concept was introduced by George

Gabriel Stokes in 1851, but the Reynolds number is named after Osborne Reynolds (1842–

1912), who popularized its use in 1883. Osborne Reynolds is a British engineer who

discovers the variables that can be used as criterion to distinguish between laminar and

turbulent. The Reynold’s number formula is

R=ULV

For water flowing in pipe or circular conduits, L is the diameter of the pipe. For

Reynold’s number less than 2100, the flow will be distinguished as laminar flow. Turbulent

flow will occur when Reynold’s number exceeded 4000. Meanwhile, for Reynold’s number

in between 2100 and 4000, the flow will recognized as transition flow. The viscosity of the

fluid also determines the characteristic of the flow. Fluid with higher viscosity is easier to

achieve a turbulent flow condition.

Laminar flow denoted a steady flow condition were all streamline follow parallel

path, there being no mixing between shear planes. Under this condition, the dye observed

will remain as a solid, straight and easily identifiable component flow. On the other hand,

transitional flow is a mixture of laminar and turbulent with turbulent in the centre of the pipe

and laminar flow near to the edge. Each of these flow behaves a different manner in term of

their frictional energy loss while flowing and have different equations that predict their

behaviour. Meanwhile, turbulent flow denotes an unsteady flow condition where streamlines

interacting causing shear plane collapse thus mixing of the fluid. In this condition, the dye

observed will become disperse and mix with the water.

.

http://en.wikipedia.org/wiki/Reynolds_number

Stokes, George (1851). "On the Effect of the Internal Friction of Fluids on the Motion of

Pendulums". Transactions of the Cambridge Philosophical Society 9: 8–106. 

Bruce R. Munson (2010), Fundamental of Fluid Mechanics, John Wiley & Sons (Asia) Pte

Ltd, West Virginia. Page 348