This thesis presents the application of a new finite-difference calculation procedure for solving the partialdifferential equations governing the flow and heat and mass transfer in tee-junctions. Both laminar and turbulent flows are considered:​ in particular, attention is concentrated upon the combining laminar and uniformly dividing turbulent flow in tee-junctions of square and round cross-sections respectively.

The above flow situations are characterized by the appearance of only small regions of recirculating flow within the horizontal duct;​ surrounding this region there is a predominance to the flow direction. Such regions can be accounted for computationally in either of two ways:​ The whole flow may be classed as being elliptic or, alternatively, the recirculation region alone may be classified as being elliptic while the rest of the flow is considered to be partially-parabolic. In this thesis, both classifications are attended to by solving the differential equations governing each flow classification. Two distinctly different forms of one calculation procedure are used. The two forms of the calculation procedure are deemed elliptic and partially-elliptic. The elliptic procedure is described in detail;​ the partially-elliptic procedure being a derivative of the elliptic one and therefore only its distinguishing features are pointed out.

Turbulence is accounted for by using a two-equation model of turbulence. The time-mean momentum and continuity equations are solved with equations describing the transport of turbulence kinetic-energy and its volumetric rate of dissipation. The turbulence model relates the turbulence to a turbulent viscosity. In the near-wall regions, wall functions are employed.

For the laminar combining flow in tee-junctions of square cross-section, two diameter ratios and up to three momentum ratios are considered. When compared,to the limited experimental data, the predictions are found to agree reasonably well.

With respect to the turbulent, uniformly-dividing flow in tee-junctions of round cross-section, the predictions, when compared to the data obtained in a parallel program of study show fair agreement. In particular, the wall surface pressures and mean flow quantities are at variance with the data;​ the heat-transfer predictions, when compared to experimentally determined mass transfer (via the sublimation of naphthalene) shows good agreement.

The predictions of the partially-elliptic procedure were found to agree well with those predictions obtained by using the elliptic procedure. Although computational times were about the same, computer storage savings of up to 5Q% or more can be obtained by using the partially-elliptic procedure in lieu of the elliptic one.

The study has been made for the purposes of verifying the calculation procedure with particular reference to the three-dimensional flow in right-angled tee-junctions. Detailed parametric studies of the flow and heat-transfer characteristics of tee-junctions have not therefore been attempted.