Fluids Basics

Question 1

What is viscosity (m)?

Answer 1

Property of a fluid, due to cohesion and interaction between molecules, which offers resistance to shear deformation.

Question 2

Different fluid …. at different rates under the same….

Answer 2

…. deform…. shear stress

Question 3

Fluids with…. viscosity such as syrup, deform more …. than fluids with…. viscosity such as water.

Answer 3

…. high…. slowly…. low….

Question 4

Formula for shear stress

Answer 4

τ=μdV/dy
μ is coefficient of dynamic viscosity
dV/dy is velocity gradient or rate of shear strain

Question 5

Coefficient of dynamic viscosity

Answer 5

μ=(τ)/(dV/dy)=(force/area)/(velocity/distance)=(force×time)/(area)=(mass)/(length×time)

Question 6

Kinematic viscosity equation

Answer 6

ν=μ/ρ

Question 7

Pascal’s law

Answer 7

Pressure at a point in a fluid at rest or in motion, is independent of direction as long as there are no shearing stresses present.
pz=py=ps

Question 8

In a fluid under gravity, pressure…. with depth

Answer 8

…. increases….

P=Patm+ρgh

Question 9

Pressure guage

Answer 9

Pressure measured with respect to atmospheric pressure.

pguage=ρgh=γh

Question 10

Pressure head formula

Answer 10

h=pguage/ρg

Question 11

Formula for force on a submerged plane surface

Answer 11

FR=γhcA
γ=specific weight of fluid
hc=depth to centroid of object
A=cross sectional area of object

Question 12

Formula for distance to FR from x-axis along y-axis

Answer 12

yR=(Ixc/ycA)+yc
Ixc=second moment of area of the object around an axis praying through the centroid, parallel to x-axis
yc=orthogonal distance to centroid from the x-axis

Question 13

Resultant force formula

Answer 13

FR=√(FH²+FV²)

Question 14

Angle of inclination of FR to horizontal

Answer 14

Φ=tan⁻¹(FV/FH)

Question 15

dV/dt=

Answer 15

Av

Question 16

Continuity equation

Answer 16

A₁v₁=A₂v₂

Question 17

Bernoulli’s equation

Answer 17

P+ρgh+0.5ρv²=constant

Question 18

PV (pressure times volume)

Answer 18

W (work done)

Question 19

Force on a vertical wall

Answer 19

F=Pave×A
Pave=vertical pressure half way down the pool
A=area of wall
(Works on angles if use length of hypotenuse)

Question 20

Resultant force on a curved submerged surface

Answer 20

R=√(F²+W²)
F=horizontal force
W=weight of fluid directly above curve

Question 21

Laminar flow

Answer 21

Motion is particles very orderly work all particles moving in a strait line parallel to the pipe

Question 22

Transitional flow

Answer 22

Short burst of turbulence embedded in laminar flow

Question 23

Turbulent flow

Answer 23

Eddying or mixing action. Fluid particle’s motion is complex and involves fluctuations in velocity and direction.

Question 24

Reynolds number formula

Answer 24

Re=ρVL/μ=VL/ν
V=velocity
L=representative length
μ=absolute viscosity
ν=kinematic viscosity

Question 25

Reynolds number boundaries

Answer 25

Re<2000 - laminar flow

2000