Write the Newton’s formula for internal friction and call its members.
Newton by the internal friction of the fluid phenomenon of the law. Suppose two adjacent parallel to the flow of fluid, when its flow rate is not equal, the two of them will have fluid friction within. Newton's law of friction is : inside a two-layer fluid friction values, and two relative movement between the two tiers of speed and contact surface directly proportional to the size, that is perpendicular to the flow direction is proportional to the velocity gradient. This ratio constant (with the fluid nature of the different), or known as the coefficient of viscosity viscosity.
Newton's law of viscosity states that the shear stress between adjacent fluid layers is proportional to the negative value of the velocity gradient between the two layers, where constant of proportionality is called coefficient of viscosity. Mathematically, tau = mu*velocity gradient
Newtons law of viscosity:
This tells us that the shear stress, , in a fluid is proportional to the velocity gradient - the rate of change of velocity across the fluid path. For a "Newtonian" fluid we can write:
where the constant of proportionality, is known as the coefficient of viscosity (or simply viscosity). We saw that for some fluids - sometimes known as exotic fluids - the value of changes with stress or velocity gradient.
Write formula for calculation Reynolds number (Re). Call its members.
[5]
where:
is
the mean velocity of the object relative to the fluid (SI
units:
m/s)
is
a characteristic linear dimension, (travelled length of the
fluid; hydraulic
diameter when
dealing with river systems) (m)
is
the dynamic
viscosity of
the fluid (Pa·s
or N·s/m² or kg/(m·s))
is
the kinematic
viscosity (
)
(m²/s)
is
the density of
the fluid (kg/m³).
Note
that multiplying the Reynolds number by 
yields 
,
which is the ratio of the inertial forces to the viscous
forces.[6] It
could also be considered the ratio of the total momentum transfer to
the molecular momentum transfer.
Write the formula for calculation the speed of sound using gas temperature; and call its members.
Speed of Sound in Ideal Gases
Since the acoustic disturbance introduced in a point is very small the heat transfer can be neglected and for gases assumed isentropic. For an isentropic process the ideal gas law can be used and the speed of sound can be expressed as
c = (k p / ρ)1/2
= (k R T)1/2 (3)
where
k = ratio of specific heats (adiabatic index)
p = pressure (Pa, psi)
R = gas constant
T = absolute temperature (oK, oR)
For an ideal gas the speed of sound is proportional to the square root of the absolute temperature.
How (quality) does change dynamic coefficient of viscosity when temperature of gas changes? The same for liquid.
As an object moves through a gas, the gas molecules stick to the surface. If we have two surfaces, as shown in the figure, with one surface fixed and the other surface moving parallel to the fixed surface, a shearing force is generated in the fluid between the surfaces. An external force F must be applied to the moving surface to overcome the resistance of the fluid. If we denote the magnitude of the shearing force by the Greek letter tau. Then:
tau = F / A
where A is the area of the moving surface. It is experimentally observed that, for most gases, the shear stress is directly proportional to the gradient of the velocity between the surfaces:
tau is linearly proportional to dV/dy
where y is the distance between the surfaces and V is the velocity. The proportionality constant is called the coefficient of dynamic viscosity and assigned the Greek letter mu
tau = (mu) * (dV/dy)
The value of the dynamic viscosity coefficient is found to be a constant with pressure but the value depends on thetemperature of the gas. For air, D. M. Sutherland provides an equation for the dependence on temperature T:
mu = mu0 * ((T / T0)^1.5) * ((T0 + 198.72) / (T + 198.72))
where mu0 and T0 are reference values given at sea level stanfard conditions. The temperature is specified in degreesRankine:
mu0 = 3.62 x 10^-7 lb-sec/ft^2
T0 = 518.7 R