壁に沿ふて曲る噴流に就いて

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I. This paper describes the results of analytical and experimental investigations of jets of two dimensions deflected by various wall surfaces. To produce such a plane jet the author has deviced a simple apparatus as shown in Fig. 5,in which the jet issues horizontally from a rectangular nozzle of 5 cm wide and 1 cm thick, and the both upper and lower sides of the jet are covered with glass plates. Wooden pieces having equal thickness to the jet are used for guides and deflecting walls. Putting a section paper underneath the lower glass plate , the photographs of flows are taken to determine their outlines. II. In part A the author deals with the jet guided and deflected by two very long straight walls making corner angle. General solution for any arbitrary deflecting angle π/n is derived, and for five special cases where n=2,4/3,3/2,3 and 4,the calculations to determine the free surface, the positions of three stream lines and the pressure distribution along the deflecting wall are noted. The calculated and observed results are compared for each case. The author points out that, during any deflection, velocity drop and pressure rise are caused and consequently it necessitates the increase of the initial breadth b of the flow, which should be taken in consideration in designing of the bends of large power canals. In part B, the jet deflected by the wall having finite length l is dealt with. In this case the final direction of the jet leaving the wall deviates from the direction of the wall by angle a. The relation between a and l/b is calculated for the case where the corner angle is 90°. III. The nature of the jet deflected by a curved surface can be easily understood of the jet deflected by some straight walls. For example, from a flow as shown in Fig. 31,we can presume the flow shown in Fig. 33,which resembles the jet deflected by the bucket of a Pelton wheel. In this connection author has concluded that in order to give tho jet a deflection of just 180°, a wall of a circular are larger than π should be used. The potential flow of the perfect fluid is considered to be reversible and this is approximately true also in the actual flow as shown in Fig. 36,which is the reversed flow of that shown in Fig. 35. From this fact we easily understand that the initial direction of a jet entering deflecting wall of finite length should deviate by some angle a from that of the said wall or the tangent to the inlet of the curved wall as shown in Fig. 38. In analytical treatment of such a problem, the representation of the stream line along the curved surface in the velocity plane is assumed to be a circular arc, and the corresponding flow is found out in Z-plane. Although it seems impossible to get the exact solution for the problem of the semi-circular vane, we are able to calculate jets having various initial breadth deflected by curved surfaced of various depth and deflecting angles. The Figs. 40 and 41 show two examples of wall approximate to a semi-circle and it is easily seen that, between these two, there will be another wall, which is more approximate to the semi-circle than any of them. The author calculates the angle of deviation, the increase of the breadth of jets at the centre of deflection and the pressure distribution along the wall, which are important in designing of turbine vanes. It is also made clear that if we set the initial direction of the jet tangentially to the wall end, some part of the flow will leake outwardly from the wall tip as shown in Fig. 42,which is caused by the pressure rise due to the deflection. The above mentioned is the nature of flow concerning water jet, but it is no doubt that this holds true in some extent also in the flow of gaseous fluids, such as air, steam, etc.
一般社団法人日本機械学会の論文
1927-06-20

壁に沿ふて曲る噴流に就いて

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一般社団法人日本機械学会 | 論文

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