Abstract
All progressive countries possess aerodynamical laboratories in which scientific researches into the problems of flight are undertaken. Such researches have made, and are capable of making, some contribution to the progress of hydraulic practice. Many of these researches have been carried out with the aid of small-scale models, and the basic principles on which such experiments rest are first considered. It is shown that dimensional analysis indicates the form in which relations between the various parameters which govern fluid flow can best be stated, and suggests the manner in which the governing conditions must be represented on the model to obtain results of the greatest practical value.
The similarity between flows of air and water under corresponding conditions is illustrated. Boundary layer flow is dealt with in some detail, and its influence on resistance and flow phenomena indicated. It is shown that turbulence in a boundary layer may have a beneficial effect on resistance. Methods of controlling flow by the use of guide vanes, slots, boundary jets, fairings, and other devices are described. Attention is directed to those features of wind tunnel design which favour steadiness of flow. The beneficial influence of a large contraction on steadiness is discussed.
Brief reference is made to theoretical and experimental researches undertaken to obtain an insight into the mechanism of fully developed turbulence. The latest resistance formula for a smooth flat plate is given, together with resistance curves for pipes having a specific form of surface roughness. Some modern developments of the theory of a perfect fluid, and applications to problems of a real fluid, are briefly outlined. A method of designing axial-flow reaction turbines and pumps on lines suggested by aerofoil theory is given.
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