Fluid Mechanics and Hydraulic Machinery Miscellaneous

Fluid Mechanics and Hydraulic Machinery Miscellaneous

Easy Questions
Moderate Questions
Difficult Questions

Fluid Mechanics and Hydraulic Machinery

Fluid Mechanics and Hydraulic Machinery Miscellaneous
  1. Oil (kinematic viscosity, υ oil = 1.0 × 10-6 m2/s) flows through a pipe of 0.5 m diameter with a velocity of 10 m/s. Water (kinematic viscosity, vw = 0.89 × 10-6 m2/s) is flowing through a model pipe of diameter 20 mm. For satisfying the dynamic similarity, the velocity of water (in m/s) is _______.








  1. View Hint View Answer Discuss in Forum

    oil water
    v = 1.0 × 10–5 m²/s v = 0.89 × 10– 6 m²/s
    d = 0.5 m
    d = 0.02 m
    v = 10 m/sec
    v =?
    [Re](oil) = [Re](w)

    10 × 0.5
    		 =
    V × 0.02
    1.0 × 10-58.9 × 10-6

    ⇒ v = 22.25 m/s

    Correct Option: C

    oil water
    v = 1.0 × 10–5 m²/s v = 0.89 × 10– 6 m²/s
    d = 0.5 m
    d = 0.02 m
    v = 10 m/sec
    v =?
    [Re](oil) = [Re](w)

    10 × 0.5
    		 =
    V × 0.02
    1.0 × 10-58.9 × 10-6

    ⇒ v = 22.25 m/s

  1. For a fully developed laminar flow of water (dynamic viscosity 0.001 Pa-s) through a pipe radius 5 cm, the axial pressure gradient is –10 Pa/m. The magnitude of axial velocity (in m/s) at a radial location of 0.2 cm is ________.








  1. View Hint View Answer Discuss in Forum

    u =
    -1 δP
    		(R² - r²)
    4μδx

    =
    -1
    		 × (-10)((0.05)² - (0.002)²)
    4μδx

    u = 6.24 m/s

    Correct Option: A

    u =
    -1 δP
    		(R² - r²)
    4μδx

    =
    -1
    		 × (-10)((0.05)² - (0.002)²)
    4μδx

    u = 6.24 m/s

  1. Air (ρ = 1.2 kg/m3 and kinematic viscosity, υ = 2 × 10-5 m2/s) with a velocity of 2 m/s flows over the top surface of a flat plate of length 2.5 m. If the average value of friction coefficient is
    Cf =
    1.328
    √Rex

    the total drag force (in N) per unit width of the plate is _________.








  1. View Hint View Answer Discuss in Forum

    Cf =
    1.320
    √Rex

    Rex =
    ρvd
    		 =
    vd.
    μυ

    v = 2m/s
    1 = 2.5m
    υ = 2 × 10–5 m²/s
    F = 1/2 CfρAυ²
    A = 2.5 × 1
    On substituting we get
    F = 0.0159N

    Correct Option: D

    Cf =
    1.320
    √Rex

    Rex =
    ρvd
    		 =
    vd.
    μυ

    v = 2m/s
    1 = 2.5m
    υ = 2 × 10–5 m²/s
    F = 1/2 CfρAυ²
    A = 2.5 × 1
    On substituting we get
    F = 0.0159N

  1. Couette flow is characterized by








  1. View Hint View Answer Discuss in Forum

    Couette flow is steady incompressible, laminar flow between one fixed plate and other moving with constant velocity.

    Correct Option: D

    Couette flow is steady incompressible, laminar flow between one fixed plate and other moving with constant velocity.

  1. Consider laminar flow of water over a flat plate of length 1 m. If the boundary layer thickness at a distance of 0.25 m from the leading edge of the plate is 8 mm, the boundary layer thickness (in mm), at a distance of 0.75 m, is ______








  1. View Hint View Answer Discuss in Forum

    ∴
    δ
    		 =
    k
    		, here ‘k’ is constant
    x√x

    ∴
    δ1
    		 =
    δ2
    √x1√x2

    ∴
    8
    		 =
    δ2
    		∴ δ2 = 13.86 mm.
    √0.25√0.75

    ∵
    δ
    		 =
    0.60
    x√Rex

    or
    δ
    		 =
    0.60
    		 =
    0.60√v
    x√xu∞/v√x.√u∞/v

    ∵ √v and √u∞ is constant in both the cases

    Correct Option: B

    ∴
    δ
    		 =
    k
    		, here ‘k’ is constant
    x√x

    ∴
    δ1
    		 =
    δ2
    √x1√x2

    ∴
    8
    		 =
    δ2
    		∴ δ2 = 13.86 mm.
    √0.25√0.75

    ∵
    δ
    		 =
    0.60
    x√Rex

    or
    δ
    		 =
    0.60
    		 =
    0.60√v
    x√xu∞/v√x.√u∞/v

    ∵ √v and √u∞ is constant in both the cases