Submerged flow regimes of PK-Weir

Transcription

1 Université Mohamed Khider - BISKRA - ALGERIA Laboratoire Aménagements Hydrauliques et Environnement Tel/Fax : (+213) Mobile : (+213) aouamane@yahoo.fr 2 nd International Workshop on Labyrinth and Piano Key Weirs Paris - Chatou, France November 2013 Présenté par : - Prof. A.Ouamane - Mr. F. Belaabed

2 I. Introduction Sommaire II. III. Experimental program Experimental results 1- Effect of the discharge on the submergence of the PK-Weir 2- Comparison of the results obtained on the different models 3- Mathematical relationship of the coefficient of submergence IV. Conclusion

3 I. Introduction The spillway is regarded as one of the most important hydraulic infrastructures; this returns to its multifunction, it is often used as component of discharge control and spillway in the rivers. It can be designed in several forms depending on the characteristics required, namely, the dimensions and the profile of the cross-section, the shape of the indentation, the provision in relation to the direction of flow, and the upstream and downstream conditions of the flow.

4 Based on these last; there are two types of weirs according to the conditions of their operation. The first type corresponds to the free flow weir when water level the downstream does not influence on the flow to the upstream, as well, the aquifer is assumed to be free (figure 1-a). The second type corresponds to the submerged weir when the water level downstream affects the water level upstream (figure 1-b).

5 a- Free flow b- Submerged flow Figure 1. Definition of hydraulic parameters for the weir under free and submerged flow conditions Submerged flow - H*: upstream total head; - h*: upstream piezometric head; - H d : downstream total head; - h d : downstream piezometric head. Free flow -H o : upstream total head; - h o : upstream piezometric head.

6 Gate Piezomere Flowmeter 93W2 Figure 2. The experimental facility

7 Model of weir a- PK-Weir type A2m b- PK-Weir type A1 Figure 3. Model of PK-Weir

8 Table 1. Geometrical characteristics of the experimented model Model of weir n 0 n L cm W cm W 0 cm W i cm B cm B 0 cm B i cm B b cm P 0 =P i cm PK-Weir model A A2m PK-Weir model A A a- Plan view b- Cross section a- Plan view b- Cross section Figure 4. Geometrical configuration of the model A1 Figure 5. Geometrical configuration of the model A2m

9 Experimental installations according to the upstream conditions Wc Wt Figure 6. PK-Weir with lateral contraction

10 II Experimental program Sill Q 1 PK-Weir Figure 7. Experimental program

11 III Experimental results h* hd a- Phase free flow h* hd b- Phase transition h* hd c- Phase submerged flow Figure 8 : Different phases of the flow on the PK-Weir

12 1- Effect of the discharge on the submergence of the PK-Weir 1-1 Effect of the discharge on the submergence of the PK-Weir A2m a- Phase free flow H*/H I II III 0 PK-Weir A2m Q=30.84l/s Q=46.05l/s Q=60.69l/s Q=75.31l/s Q=90.82l/s Q=104.76l/s Q=120.67l/s Q=141.01l/s Hd/H0 b- Phase transition c- Phase submerged flow Figure 9. Relative upstream head according relative downstream head (model type A2m)

13 1-2 Effect of the discharge on the submergence of the PK-Weir A1 Figure 10. Relative upstream head according relative downstream head (model type A1)

14 2- Comparison of the results obtained on the different models H*/H PK-Weir A1 Q=142.28l/s 0.5 PK-Weir A2m Q=141.01l/s Courbe de référence PK-Weir (Tullis 2012) Hd/H0 Figure 11. Comparison of the effect of submergence between the PK-Weir type A2m, A1 and model PK-Weir (Tullis 2012)

15 3- Mathematical relationship of the coefficient of submergence Figure 12. Discharge for submerged Weir

16 Rectangular Weir (Villemonte) : PK-Weir type A2m : d PK-Weir type A (Results of physical models HCM) : d

17 IV. Conclusion This study is primarily interested in the effect of the downstream level on the upstream level in submerged flow conditions. The tests carried out on two models of PK-Weir have shown that the downstream conditions can affect the upstream flow of the PK-Weir. This influence has been demonstrated that it is characterized by a proportional p variation between the upstream and the downstream whatever the importance of the discharge. It was also found that the variation of the relative downstream head compared to the relative upstream head is done in a proportional manner for the different discharge on the PK-Weir A2m.

18 The PK-Weir with overhangs continued up to the base (A2m) seems to be more exposed to the submergence that the PK-Weir standard type A. The PK-Weir has the advantage to be better adapted to function in conditions of submerged flow, however, the linear weir is more susceptible to submergence. As well, the importance of the effect of the submergence depends on the type of weir.

19 Université Mohamed Khider - BISKRA - ALGERIA Laboratoire Aménagements Hydrauliques et Environnement Tel/Fax : Mobile : aouamane@yahoo.fr