A study of fluid flow manifolds by numerical simulation and experimentation

A synergistic study encompassing numerical simulations and experiments has been performed to devise means for creating uniform-mass-flowrate jets exiting from a manifold. The initial focus of the work was to identify a turbulence model that is appropriate for the accurate numerical simulation of the fluid flow within the manifold. The selection process involved the collection of manifold pressure data and a side-by-side comparison of the data with corresponding prediction from numerical simulations. Two modalities were employed with the goal of tailoring the nature of the jets produced by the fluid exiting the manifold via an array of apertures. One of these modalities is to vary the ratio of the total cross-sectional area of the exit apertures to the cross-sectional area of the manifold. It was found that jet-to-jet mass flowrate uniformity to within +/- 2% was achieved for an area ratio of 0.135. The other modality is based on affixing tubes to each exit aperture, thereby creating a pressure drop downstream of the manifold. Parametric variations of the length of the outflow tubes enabled control of the downstream pressure drop. Although adding downstream pressure loading increased the degree of uniformity of the jet-to-jet mass flowrates, it was not as effective as was the variation of the area ratio of the first modality. The degree of jet-to-jet uniformity of jets of different cross section was also investigated. The three situations examined were (a) an array of round jets, (b) an array of rectangular jets, and (c) a continuous slot. Among these, the slot produced the most uniform outflow from the manifold.