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The upstream and downstream water levels

and

(Figure 1, Table 1) were measured using point gauges. The experiments used

(or submerged exit condition). The water-level difference

gave the energy head for the siphon flow. The characteristic velocity of the flow is

⁠, and the theoretical discharge is

⁠. The actual discharge Q for the flow is given by Equation (1). The discharge coefficient C_d was determined as the ratio of the actual to the theoretical discharge

(2)

Table 1

Hydraulic conditions and values of C_d

Case	Q	Δh/d	h₁/d		h₂/d		Re		Fr		C_d
Case	(m³/s)	Δh/d	Exp^a	CFD^b	Exp	CFD	Exp	CFD	Exp	CFD	Exp	CFD
1	0.024	6.340	9.019	13.012	2.680	6.673	247,943	247,943	0.08	0.05	0.628	0.628
2	0.025	5.762	8.879	12.872	3.117	7.128	236,372	236,012	0.09	0.05	0.687	0.688
3	0.024	6.340	8.196	12.207	1.856	5.867	247,943	247,943	0.10	0.05	0.628	0.628
4	0.022	5.412	9.089	13.100	3.678	7.671	229,075	229,445	0.07	0.04	0.623	0.622
5	0.024	5.902	9.842	13.853	3.940	7.933	239,228	239,583	0.07	0.05	0.651	0.650
6	0.024	6.165	9.229	13.240	3.065	7.075	244,494	244,494	0.08	0.05	0.637	0.637

Case	Q	Δh/d	h₁/d		h₂/d		Re		Fr		C_d
Case	(m³/s)	Δh/d	Exp^a	CFD^b	Exp	CFD	Exp	CFD	Exp	CFD	Exp	CFD
1	0.024	6.340	9.019	13.012	2.680	6.673	247,943	247,943	0.08	0.05	0.628	0.628
2	0.025	5.762	8.879	12.872	3.117	7.128	236,372	236,012	0.09	0.05	0.687	0.688
3	0.024	6.340	8.196	12.207	1.856	5.867	247,943	247,943	0.10	0.05	0.628	0.628
4	0.022	5.412	9.089	13.100	3.678	7.671	229,075	229,445	0.07	0.04	0.623	0.622
5	0.024	5.902	9.842	13.853	3.940	7.933	239,228	239,583	0.07	0.05	0.651	0.650
6	0.024	6.165	9.229	13.240	3.065	7.075	244,494	244,494	0.08	0.05	0.637	0.637

Measurements of flow depth and siphon conduit width were true to mm. Discharge measurement errors were limited to 3%.

^aFor the laboratory experiments.

^bFor the numerical simulations using the CFD model.

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