The document discusses various concepts related to fluid flow resistance including: 1. Viscosity is a measure of a fluid's resistance to flow and deformation, with more viscous fluids like honey having greater resistance than water. 2. Laminar and turbulent flow occur at low and high Reynolds numbers respectively, with laminar flow being smooth and turbulent flow being chaotic. 3. Parameters like drag coefficient, Froude number, Chezy equation, and Manning equation can be used to express resistance to fluid flow. 4. The Darcy-Weisbach equation relates head loss due to friction along a pipe to average fluid velocity.

1. Resistance to flow
Jyoti Khatiwada
Roll no 10

2. State of flow

6. Effect of fluid viscosity
• The viscosity of a fluid is a measure of its resistance to gradual deformation
by shear stress or tensile stress.For liquids, it corresponds to the informal
concept of "thickness"; for example, honey has a much higher viscosity
than water.
• Viscosity is a property arising from collisions between neighboring particles
in a fluid that are moving at different velocities. When the fluid is forced
through a tube, the particles which compose the fluid generally move more
quickly near the tube's axis and more slowly near its walls; therefore some
stress (such as a pressure difference between the two ends of the tube) is
needed to overcome the friction between particle layers to keep the fluid
moving. For a given velocity pattern, the stress required is proportional to
the fluid's viscosity.
• A fluid that has no resistance to shear stress is known as an ideal or inviscid
fluid. Zero viscosity is observed only at very low temperatures in
superfluids. Otherwise, all fluids have positive viscosity, and are technically
said to be viscous or viscid. In common parlance, however, a liquid is said
to be viscous if its viscosity is substantially greater than that of water, and
may be described as mobile if the viscosity is noticeably less than water. A
fluid with a relatively high viscosity, such as pitch, may appear to be a solid.

10. • laminar flow occurs at low Reynolds numbers,
where viscous forces are dominant, and is
characterized by smooth, constant fluid motion;
• turbulent flow occurs at high Reynolds numbers
and is dominated by inertial forces, which tend
to produce chaotic eddies, vortices and other
flow instabilities.
• In practice, matching the Reynolds number is
not on its own sufficient to guarantee similitude.
Fluid flow is generally chaotic, and very small
changes to shape and surface roughness can
result in very different flows.

11. Drag coefficient
The drag coefficient express the drag of an
object in a moving fluid.

12. Effect of gravity: froude number

14. Chezy equation

16. Manning equation

18. Darcy weisbach equation
• In fluid dynamics, the Darcy–Weisbach equation is a
phenomenological equation, which relates the head
loss, or pressure loss, due to friction along a given
length of pipe to the average velocity of the fluid
flow for an incompressible fluid. Theequation is
named after Henry Darcy and Julius Weisbach

22. Hydraulic flow resistant factors
• There are two types of hydraulic resistance: friction
resistance and local resistance. In the former case
hydraulic resistance is due to momentum transfer to
the solid walls. In the latter case the resistance is
caused by dissipation of mechanical energy when the
configuration or the direction of flow is sharply
changed, by the formation of vortices and secondary
flows as a result of the flow breaking away, by the
centrifugal forces, etc. To categorize local resistances,
we usually refer the resistances of adapters, nozzles,
extension pieces, diaphragms, pipeline accessories,
swivel knees, pipe entrances, etc.

24. Cowan’s method of estimating
roughness
• The most important factors that affect the selection of channel n values
are:
• 1. the type and size of the materials that compose the bed and banks of
the channel
• 2. the shape of the channel.
• Cowan (1956) developed a procedure for estimating the effects of these
factors to determine the value of n for a channel. The value of n may be
computed by
• n=(nb +n1 +n2 +n3 +n4)m
• where : nb =a base value of n for a straight, uniform, smooth channel in
natural materials
• n1 =a correction factor for the effect of surface irregularities
• n2 = a value for variations in shape and size of the channel cross section,
• n3 =a value for obstructions
• n4 =a value for vegetation and flow conditions
• m=a correction factor for meandering of the channel