EXPERIMENTAL STUDY ON DEVELOPMENT LENGTH IN A PIPE

Abstract

As fluid enters any pipe, boundary layers keep on growing till they meet after some distance downstream from the entrance region. The distance from the entrance to the point of meeting of the boundary layer at the centre of the pipe is called Development Length. Within this development length velocity profile keeps on changing. After this distance velocity profile doesn't change, flow is said to be developed flow. This region is downstream of a point beyond which the flow field’s behaviour is invariant. However, it has not been conclusively proven that a fully developed region actually exists. A literature survey found that most facilities are cited as being ‘sufficiently long’, yet no formal definition or documentary evidence of the fully developed condition is widely accepted. The aim of the study is to produce a detailed analysis of the flow from the inlet conditions through to the fully-developed, along with an accurate definition of what constitutes fully developed flow. Development length depends on the Reynolds number of the flow. For high Reynolds number of the flow, development length of the flow increases with its Reynolds number. When the flow is in the developing state i.e. within the development length the core velocity increases with increase in the distance from the entrance. Various research paper have been proposed by various scientists based on the calculation of the development length for pipe flow in different conditions such as in laminar flow, turbulent flow, using Newtonian fluid and several other conditions. Each paper gives its own formula and its own way of calculation of the development length. Knowledge of development length is required for the case when the electronic flow meters are to be installed in the pipe, because these flow meters require fully developed flow for proper functioning. Development length is required in industries where precision of flow measurement is of top priority. In such industries, the location where the electronic flow meter is to be placed is decided on the basis of flow development length.