Formula Blasius

For turbulent flow (2100 < / e < 100,000) in long, smooth pipes, the Blasius formula may be used to estimate the friction factor ... 

For any given Reynolds number, one can read the value of friction factor, and then use Eq. (1) to determine the pressure drop. In the turbulent region, for Re > 2200, one correlation is the Blasius formula [Eq. (3)] ... 

Blasius formula may be used to estimate the friction factor ... 

The smooth turbulent regime corresponds to the lower envelope of the bundle of curves in the Colebrook diagram, for Re> 5 x 10. In the range lO [Pg.81]

The values of friction coefficient for turbulent flow can be calculated by the Blasius formula 1=0.316/Re°. ... 

Values for v may also be calculated from the observations of the pressure drop in cylindrical pipes, at ff = 0, within the domain of turbulent flow, seeing that an empirical formula has been derived by Blasius for this domain. The formula is... 

However, the Blasius function f(rj) is available only as the numerical solution of the Blasius equation, and it is thus inconvenient to evaluate this formula for H(r] ). A simpler alternative is to numerically integrate the Blasius equation and the thermal energy equation (11-19) simultaneously. The function H(r]), obtained in this manner, is plotted in Fig. 11-2 for several different values of the Prandtl number, 0.01 < Pr < 100. As suggested earlier, it can be seen that the thermal boundary-layer thickness depends strongly on Pr. For Pr 1, the thermal layer is increasingly thin relative to the Blasius layer (recall that / ->. 99 for rj 4). The opposite is true for Pr <[Pg.773]

Formula (1.7.8) is known as the Blasius law for the drag in longitudinal flat-plate flow. This formula can be used in laminar flow, that is, for Ret < 3.5 x 105. 

Since the forcing terms in equation (34) all vanish in this problem, we obtain equation (39), in which for simplicity we shall introduce the further assumption that C = 1—that is, p/t = [see equation (30)]. This assumption (that pp does not vary across the boundary layer) often is reasonable for gases if changes in the average molecular weight are negligible, then— because of the constancy of the pressure—the ideal-gas law implies that p 1/T, in which case constancy of pp corresponds to p T, a dependence close to the kinetic-theory predictions discussed in Appendix E. With C = 1, equation (39) is the Blasius equation [4], F " -F FF" = 0, and in view of equation (28), the boundary conditions implied by equations (48) and (49) are F co) = 1 and F (0) = 0. Use may be made of the present formula for p, C = 1, F (0) = 0, and equations (27) and (29) to ascertain the boundary condition implied by equation (50) the calculation results in... 

Comparisons of precision using Eqs. 5.220 and 5.221 and Blasius s formula (Table 5.8) in which the diameter of circular duct 2a is replaced by hydraulic diameter 4b, b being the halfspace between two plates, have been conducted by Bhatti and Shah [45]. In the range of 5000 < Re < 3 x 104, Eq. 5.220 is recommended otherwise, Eq. 5.221 should be used to obtain the friction factor for fully developed turbulent flow in a parallel plate duct. However, use of the hydraulic diameter to substitute for the circular duct diameter in the Blasius equation is reasonable for the prediction of the fraction factor [45]. 

Fig. 9. Relationship between pipe friction coeilicient X and Re3molds number for various pulp water suspensions. I depicts the theoretical equation of the flow resistance in laminar flow in pipe and II depicts the Blasius resistance formula of turbulent flow. Cp, % , 0 (Water) , 0.30 , 0.55 v, 0.72----. Adapted from Figure 9 of Ref. 166.

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