Extracting explicit expressions for and from these equations is difficult. However, for the limiting case of and neglecting terms of order in the binomial expansion of a square root the following relations can be derived:
Here the bar denotes the time-averaged value of the appropriate velocity component.
the expressions for 
and 
reduce to 
and 
from these equations is difficult. However, for the limiting case of 
and neglecting terms of order 
in the binomial expansion of a square root the following relations can be derived:
