INTRODUCTION

The experiment is conducted mainly to study the criterion of laminar, transition and turbulent flow. In fluid mechanics, internal flow is defined as a flow for which the fluid is confined by a surface. The flow may be laminar or turbulent. Osborne Reynolds (23 August 1832 – 21 February 1912) was a prominent innovator in the understanding of fluid dynamics and mechanics.

Osborne Reynolds Apparatus consists of water resource for the system supply, fix-head water input to big and small transparent pipes, dye input by injection unit, and water output unit to determine water flow rate. The laminar, transition and turbulent flows can be obtained by varying the water flow rate using the water outlet control valve. Water flow rate and hence the flow velocity is measured by the volumetric measuring tank. The supply tank consists of glass beads to reduce flow disturbances. Flow patterns are visualized using dye injection through a needle valve. The dye injection rate can be controlled and adjusted to improve the quality of flow patterns.

AIMS / OBJECTIVES

- To observe the characteristics of laminar, transition and turbulent flow.
- To prove that the Reynolds number is dimensionless by using the formula;

THEORY

In fluid mechanics, Reynolds Number (Re) is a dimensionless number that is expressed as the ratio of inertial forces (pV2/L) to viscous forces (µV/L2). Thus, the Reynolds number can be simplified as followings;

Re = (pV2/L) / (µV/L2)

= pVL/µ

Where p is the density of the fluid, V is the mean fluid velocity, L is a characteristic linear dimension, and µ is the dynamic viscosity of the fluid.

When a fluid flows through a pipe the internal roughness (e) of the pipe wall can create local eddy currents within the fluid adding a resistance to flow of the fluid. Pipes with smooth walls such as glass, copper, brass and polyethylene have only a small effect on the frictional resistance. Pipes with less smooth walls such as concrete, cast iron and steel will create larger eddy currents which will sometimes have a significant effect on the frictional resistance. The velocity profile in a pipe will show that the fluid at the centre of the stream will move more quickly than the fluid towards the edge of the stream. Therefore friction will occur between layers within the fluid. Fluids with a high viscosity will flow more slowly and will generally not support eddy currents and therefore the internal roughness of the pipe will have no effect on the frictional resistance. This condition is known as laminar flow.