Mechanical Properties of Fluids 2

Question 1

what is steady flow?

Answer 1

The flow of the fluid is said to be steady if at
any given point, the velocity of each passing
fluid particle remains constant in time.Each particle
follows a smooth path, and the paths of the
particles do not cross each other

Question 2

what is a streamline

Answer 2

The path taken by a fluid particle under a
steady flow is a streamline. It is defined as a
curve whose tangent at any point is in the
direction of the fluid velocity at that point.

Question 3

what is turbulent flow

Answer 3

Beyond a limiting value, called critical speed,
this flow loses steadiness and becomes
turbulent.

in turbulent velocity, the velcotiy of the particles passing through a particular point is not the same. flow becomes irregular and chaotic.

Question 4

what is continuity equation states

Answer 4

area of the cross section of the pipe/ tube is inversely proportional to the velocity of fluid flowing throuhg it.
voluemtric flow rate/ mass flow rate remains a constant.

applies for non viscous, incompressible fluids

Question 5

what are three types of energy possessed by fluid

Answer 5

i)kinetic energy= energy possessed by virtue of its motion
ii) potential energy= energy possessed by virtue of its position
iii) pressure energy= energy possessed by virtue of its pressure.

Question 6

what is bernoulli principle

Answer 6

the total energy of fluid per unit volume or per unit mass of an incompressible and non viscous fluid in steady flow remains a constant throughout the flow.

Question 7

what are the limitations of bernoulli theorem

Answer 7

• Bernoulli’s
  equation also does not hold for non-steady or
  turbulent flows, because in that situation
  velocity and pressure are constantly fluctuating
  in time.
• itis applicable only to fluids which are incompressible and non viscous.

Question 8

what is dynamic lift

Answer 8

it is the force that acts on a body by vritue of its motion through the fluid

Question 9

examples of dynamic lift in
i) ball without spin
ii) ball with spin

Answer 9

i)when a ball is moving without spin, the streamlines around the moving balls are the same ab and below the ball.. the velocity of fluid (air) above and below
the ball at corresponding points is the same
resulting in zero pressure difference. The
air therefore, exerts no upward or downward
force on the ball.

ii)A ball which is
spinning drags air along with it. If the
surface is rough more air will be dragged.The ball is moving forward
and relative to it the air is moving
backwards. Therefore, the velocity of air
above the ball relative to it is larger and
below it is smaller. The stream lines thus
get crowded above and rarified below.
This difference in the velocities of air results
in the pressure difference between the lower
and upper faces and there is a net upward force
on the ball. This dynamic lift due to spining is
called Magnus effect.

Question 10

what is aerofoil or lift on wing?

Answer 10

which is a solid piece
shaped to provide an upward dynamic lift when
it moves horizontally through air. The crosssection of the wings of an aeroplane looks
somewhat like the aerofoil shown in Fig. 10.13 (c)
with streamlines around it. When the aerofoil
moves against the wind, the orientation of the
wing relative to flow direction causes the
streamlines to crowd together above the wing
more than those below it. The flow speed on
top is higher than that below it. There is an
upward force resulting in a dynamic lift of the
wings and this balances the weight of the plane