The frictional drag of smooth ship forms¹

Article type: Research Article

Authors: Lap, A.J.W.

Affiliations: N.S.M.B. at Wageningen, Holland

Note: [1] Part of a paper presented at the 1955 Autumn Meeting of the Institution of Naval Architects.

Abstract: The only method of deriving resistance formulae for turbulent flow along flat plates more or less theoretically is by starting from theoretical formulae for pipe flow. The latter formulae are, therefore, subjected to a detailed consideration as is also done with the assumption that these formulae may be used in the boundary layer of a flat plate. A new approximate method is developed to establish a relation between resistance coefficients for pipes and rectangular flat plates. This method proves to be in fair agreement with Schultz-Grunow’s measurements of local frictional resistance. With the aid of theoretical formulae the total frictional resistance coefficients can be determined from the local frictional resistance coefficients. Apart from this the total frictional resistance coefficients can also be derived from resistance experiments with flat plates. The agreement between the two methods is highly satisfactory. With the aid of results obtained from experiments with model families it is shown that it is not satisfactory to apply plate-friction coefficients to ship forms. A new method is indicated for calculating frictional resistance coefficients for ship forms. It appears that frictional resistance coefficients of pipes, plates (local and total) and ship forms can be represented by the general formula: χ2ζ=lnReζAn+C where: χ=universal constant=0.4144;logA0=0.000for pips;logA1=1.556for local frictional resistance coefficients of flat plates;logA2=1.980for total frictional resistance coefficients of flat plates;logA3=2.10−2.50for ship forms. Values frequently occurring for ship forms are log A3=2.35−2.40.

DOI: 10.3233/ISP-1956-32702

Journal: International Shipbuilding Progress, vol. 3, no. 27, pp. 573-587, 1956