Publication Type:

Journal Article


Journal of Hydraulic Engineering, Volume 123, Number 7, p.656-658 (1997)



Calculations, channel flow, Flow of fluids, Functions, Mathematical techniques, Pipe flow, Shape effect, Smooth rectangular open channels


Available experimental data on friction in smooth rectangular channels were analyzed by a researcher and arrived at the relationship 1/√f′ = 2 log R√f′ - 0.8, where R = 4VR/v and f′ = f·ψp(P/R) for channels and f′ = f for smooth pipes. ψp(P/R) is a shape parameter. Values of P/R when b/y < 2 were indicated by an asterisk, and a relationship was obtained between P/R and ψp(P/R). Two researchers analyzed the same data that were used by another researcher and concluded that two functions ψ1(P/b) = √P/b and ψ2(b/y) are required to reflect the shape parameter. However, they combined and obtained ψK = ψ1/ψ2 = f/f′. ψ2(b/y) was calculated and plotted against b/y. They noted that ψK ≡ 1/ψp, but maintained that there is no good relationship between ψp and P/R. In the present study, it is shown that based on the curve, the equation connecting ψp(P/ R) and P/R could be obtained, which fits the curve within 1% error. A plot P/R versus ψp(P/R) is given for ready use.


cited By 2

Cite this Research Publication

N. N. Pillai, “Effect of shape on uniform flow through smooth rectangular open channels”, Journal of Hydraulic Engineering, vol. 123, pp. 656-658, 1997.