oil types t 1 160 ms and t 1 640 ms for polarization lengths l 1 0 5 m and l 2 0 9 m fig3 shows an enlargement of fig2 at velocities from 0 1 to 1 5 m s as can be seen in fig3 the signal intensity at the end of the pre polarization stage undergoes significant changes when using a pre polarization stage of 50 cm or 90 cm long these changes are more noticeable in the case of those fluid components which relaxation times do not satisfy l pol vt 1 lt lt 1 taking into account the pre polarization factor f u03b1 v the expression 12 is finally transformed into i u2061 v t f a u2061 v u2062 m 0 a u2062 v a u2061 0 u2062 u2147 t t 2 u2062 u2062 eff a f b u2061 v u2062 m 0 b u2062 v b u2061 0 u2062 u2147 u2062 t u2062 t 2 u2062 u2062 eff b u2062 1 v l eff u2062 t 14 wherein m 0 u03b1 denotes m u03b1 0 equation 14 and behavior of pre polarization factors f u03b1 v suggest two possible methods for approaching the problem of the simultaneous determination of the mean velocity of fluid and phase fractions present in a fluid of two phases determination of fluid mean velocity an important remark as regards equation 14 is that in the case of values satisfying simultaneously conditions t t.