This can be attributed to the nearly uniform pressure distributions that occur in tube flows with a low rate of change of cross-sectional area with distance.doi:10.1080/10407799208944988Katz, Ira M.Shaughnessy, E. J.Zhang, ZongqinTaylor & Francis GroupNumerical Heat Transfer Part B Fundamentals...
With your age in years (from the first step), go toIRS Table III, and look up the distribution period for your age in years. This number is an actuarially-calculated expected distribution period for your age. IRS Table III is specifically for IRA owners who are either single, are married...