Two finite-difference procedures are described for the computation of steady, three-dimensional boundary layers in ducts. In addition to the velocity components, one method uses pressure as the fourth dependent variable, while the other uses vorticity. Both methods take full account of shear stresses and heat fluxes on planes aligned with the main flow direction, and allow for non-uniform transport and thermodynamic properties. There is no restriction as to boundary conditions.

Two recently developed numerical procedures have been used to predict some laminar, three-dimensional flows in rectangular-sectioned ducts. These predictions are compared with experimental data and theoretical analyses wherever available and the agreement is shown to be satisfactory. Results are also presented of two classes of flow situations which do not appear to have been tackled before. From a comparison of results obtained by the two methods, it is concluded that both yield solutions of comparable accuracy and are equally versatile; there is as yet little to choose between them. However, improvements in the economy and range of their application are desirable; these are in the process of development.