This document discusses laminar and turbulent flow, boundary layer theory, and the Moody chart. It defines laminar and turbulent flow and describes Reynold's experiment. It introduces boundary layer theory, defining boundary layer thickness using nominal, displacement, momentum, and energy thicknesses. It describes how the boundary layer develops over a flat plate from laminar to turbulent. The Moody chart is introduced as relating friction factor, Reynolds number, and surface roughness to predict pressure drop in pipe flow.

1. 1
Unit-5:
Laminar and Turbulent Flow
BY
TIWARE V.S.
ASSISTANT PROFESSOR
BVCOE KOLHAPUR

2. Content
A. Laminar Flow and Turbulent Flow: Reynold's Experiment,
Hazen Poisulle's Equation for Viscous Flow through Circular
Pipes, Prandtl Mixing Length Theory, Introduction to Moody's
Chart.
B. Boundary Layer Theory: Concept, Various Thicknesses
(Nominal, Displacement, Momentum, Energy), Hydraulically
Smooth and Rough Boundaries, Separation of Boundary Layer,
Control of Separation.

6. LAMINAR FLOW:

17. LOSS OF HEAD DUE TO FRICTION IN PIPE FLOW–DARCY EQUATION

18. Moodys Chart
• In engineering, the Moody chart or Moody diagram
is a graph in non-dimensional form that relates the
Darcy-Weisbach friction factor fD, Reynolds
number Re, and surface roughness for fully
developed flow in a circular pipe. It can be used to
predict pressure drop or flow rate down such a
pipe.

21. BOUNDARY LAYER THEORY
• The concept of boundary layer was first introduced by L. Prandtl in 1904
and since then it has been applied to several fluid flow problems. When a
real fluid (viscous fluid) flows past a stationary solid boundary, a layer of
fluid which comes in contact with the boundary surface, adheres to it (on
account of viscosity) and condition of no slip occurs (The no-slip condition
implies that the velocity of fluid at a solid boundary must be same as that
of boundary itself). Thus the layer of fluid which cannot slip away from
the boundary surface undergoes retardation; this retarded layer further
causes retardation for the adjacent layers of the fluid, thereby developing
a small region in the immediate vicinity of the boundary surface in which
the velocity of the flowing fluid increases rapidly from zero at the
boundary surface and approaches the velocity of main stream. The layer
adjacent to the boundary is known as boundary layer. Boundary layer is
formed whenever there is relative motion between the boundary and the
fluid.

22. • the fluid exerts a shear stress on the boundary and
boundary exerts an equal and opposite force on
fluid known as the shear resistance. According to
boundary layer theory the extensive fluid medium
around bodies moving in fluids can be divided into
following two regions:
• (i) A thin layer adjoining the boundary is called the
boundary layer where the viscous shear takes
place.
• (ii) A region outside the boundary layer where the
flow behaviour is quite like that of an ideal fluid
and the potential flow theory is applicable

23. BOUNDARY LAYER DEFINITIONS AND CHARACTERISTICS:
Consider the boundary layer formed on a flat plate kept parallel to flow of fluid of
velocity
U (Though the growth of a boundary layer depends upon the body shape, flow
over
a flat plate aligned in the direction of flow is considered, since most of the flow
surfaces can be approximated to a flat plate and for simplicity).
— The edge facing the direction of flow is called leading edge.
— The rear edge is called the trailing edge.
— Near the leading edge of a flat plate, the boundary layer is wholly laminar. For a
laminar
boundary layer, the velocity distribution is parabolic.
— The thickness of the boundary layer (δ) increases with distance from the
leading edge x, as more and more fluid is slowed down by the viscous boundary,
becomes unstable and breaks into turbulent boundary layer over a transition
region.

25. Boundary Layer Thickness (δ)
The velocity within the boundary layer increases from zero at the
boundary surface to the
velocity of the main stream asymptotically. Therefore the thickness of
the boundary layer is arbitrarily defined as that distance from the
boundary in which the velocity reaches 99 per cent of the velocity of the
free stream (u = 0.99U). It is denoted by the symbol δ. This definition
however gives an approximate value of the boundary layer thickness and
hence δ is generally termed as nominal thickness of the boundary layer.
The boundary layer thickness for greater accuracy is defined in terms of
certain mathematical expressions which are the measure of the
boundary layer on the flow. The commonly adopted definitions of the
boundary layer thickness are:
1. Displacement thickness (δ*)
2. Momentum thickness (θ)
3. Energy thickness (δe)