Recherches expérimentales sur l'écoulement par déversoir-puits

Professeur émérite de l'Université de Liège.

Résumé

The problem consists in studying the relationship between discharge Q, the head at the column H and column diameter and length D and L, or between the non-dimensional factors H/D, L/Dand Froude number Q/ racine carrée 2 g D5 (see Fig. 1). The test results are shown in Figure 16, from which it is seen that, depending on Froude number, the following cases are possible : - (i) Weir flow giving a parabolic curve with a horizontal axis. The author suggests simplified formulae 2 and 3 for this flow, both of which are independant of L/D ; (ii) Alternatively, pressure pipe flow giving a parabola with a vertical axis in the diagram in Figure 16, with its peak at a distance L/D below the origin. The author suggests formula 1 for this flow, which depends on L/D. The critical H/D values in terms of L/D at which the weir flow goes over to pressure pipe flow are shown in Figure 18. Given certain discharge conditions and a Froude number of about 0.5, conventional orifice flow can be obtained (Fig. 20). At decreasing discharge the clischarge coefficient falls below 0.66 (Fig. 21). A momentary outside factor-which, apparently, may be only very small-will cause difrerent orifice fiow, for which values of the contraction coefficient are given in Figure 22 and 23. For given values of H/D, these coefficients are the same at both increasing and decreasing discharge. They are also the same as that in diagram 21. This type of flow is fairly unstable and not always easy to achieve. Once this orifice flow incluced by an outside effect is achieved, weir flow can be restored by momentarily imparting swirl to the water in the feed tank.