Calculate Dynamic Viscosity of Air at 4000m Altitude

[es_joe]

How to calculate the dynamic viscosity of air at high alttitudes,i want to calculate it at height 4000m abovesea level at that height the temp. is 262 kelven degrees.

Any thoughts?

 

[FredGarvin]

Since viscosity is more or less dependent on temperature, I would start with using Sutherland's Formula:

\mu = \mu_o \left[ \frac{0.555T_o+C}{.555T+C}\right] \left[\frac{T}{T_o}\right]^{1.5}

Where:
\mu_o= .01827 cP for air (or some known value at a different known temperature)
T_o= 524.07°R for air (for the viscosity above, different if using a different value)
C= 120 for air (Sutherland's constant)
T= absolute temperature (°R)

Crane's states that the variation in viscosity is on the order of 10% when going up to 500 psi. Assuming no wierdness goes on at lower (sub atmospheric) pressures, the variation should be very small when deviating less than 15 psi.

You can then go on and calculate the dynamic viscosity through the relation \nu=\frac{\mu}{\rho}

 

[FredGarvin]

According to: http://www.bh.com/companions/034074152X/appendices/data-d/default.htm

Viscosity (kilogram per metre second)

Viscosity is needed to determine kinematic viscosity as shown in the next item.

mALT = (1.458x10-6 x TALT3/2) / TALT + 110.4

where: mALT = viscosity (kg/ms) at altitude (h)

Kinematic Viscosity (square metre per second)

The coefficient of kinematic viscosity is used in determination of Reynolds Number It is evaluated by the ratio:-

nALT = mALT / rALT

where: nALT = coefficient of kinematic viscosity at altitude (m2/s)

It looks like they use a version of Sutherland's method as shown above.

 

[es_joe]

what is rALT ?