Effects caused by obstacles in the hydrodynamics of turbidity currents: an experimental approach

Cerqueira, Arthur Costa; Manica, Rafael

doi:10.1590/2318-0331.272220220021

Arthur Costa Cerqueira

Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil

https://orcid.org/0000-0002-5166-7193

Rafael Manica

Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil

https://orcid.org/0000-0002-0527-1374

E-mails: arthurcosta.c@gmail.com (ACC), manica@iph.ufrgs.br (RM)

Authors contributions

Arthur Costa Cerqueira: Idealization of the scope of work, planning, execution and interpretation of experimental data.

Rafael Manica: Orientation in decisions, as well as in idealizing the scope of work, in planning, execution and interpretation of experimental data.

Editor-in-Chief: Adilson Pinheiro

Associated Editor: Iran Eduardo Lima Neto

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Figure 1
Lateral view of experimental apparatus.

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Figure 2
Turbidity current mean velocity through time averaging from injection point start to the complete dissipation of the current (U_c) at five measurement points along the channel. (a) series 1 of experiments with no-obstacles; (b) series 2 with 3-cm obstacles and; (c) series 3 with 6-cm obstacles.

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Figure 3
Mean velocity vertical profiles for each section obtained from UVP data through time averaging from injection point to the complete dissipation of the current: (a) Series 1 without any obstacles in the bed; (b) Series 2 with 3 cm obstacles; and (c) Series 3 with 6 cm obstacles.

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Figure 4
Non-dimensional mean velocity vertical profiles of turbidity current runs: (a) Series 1 without any obstacles in the bed (blue line); (b) Series 2 with 3 cm obstacles (red lines); and (c) Series 3 with 6 cm obstacles (green lines).

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Figure 5
Maximum Densimetric Froude number (Frd_max) values for all runs along the five measurements points the channel. Dashed vertical lines indicates the region with obstacles. The colors blue, red and green indicates the series 1, 2 and 3 (from no to 6 cm obstacles). And, the triangle, square and circle marked are the discharges (from low to high).

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Figure 6
Relationship between the non-dimensional velocity (U_c/U_max) and the spaced-average maximum densimetric Froude number (Frd_max) for the three series of experiments. The colors blue, red and green indicates the series 1, 2 and 3 (from no to 6 cm obstacles). And, the triangle, square and circle marked are the discharges (from low to high). (a) colored dashes lines were handed fit linking the same obstacles height points; (b) Black dashes lines were handed fit linking the same discharges points.

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Figure 7
Relationship between the maximum densimetric Froude number (Frd_max) and maximum non-dimensional heights (H_umax/H_ob) for the two series considering obstacles. Red points are for 3 cm obstacles and green points for 6 cm obstacles.

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Figure 8
Sediment flux (q) calculated for the five measurements point along the channel, as well as, the space-averaged sediment flux on the right. The colors blue, red and green indicates the series 1, 2 and 3 (from no to 6 cm obstacles). Black dashed lines indicating the region with obstacles.

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Figure 9
Relationships between the densimetric Froude number and the dimensionless height of the obstacle, according to the diagram proposed by Oshaghi et al. (2013)Oshaghi, M. R., Afshin, H., & Firoozabadi, B. (2013). Experimental investigation of the effect of obstacles on the behavior of turbidity currents. Canadian Journal of Civil Engineering, 40, 343-352..

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Figure 10
Images of the flow between obstacles (images taken at 220 cm from the source): (a) Subcritical Flow; (b) Partially blocked turbidity current with hydraulic jump (white dashed line). The first image considered time equal zero.

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Table 1
Predicted vs measured discharge for the runs.

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Table 2
Parameters measured on the experiments runs.

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Table 3
Time average mean velocity (U_c) and maximum velocity (U_max) for the five measurements points along the channel.

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(1)

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(2)

Predicted discharge (L. min^-1)	Measured (mean) Q (L. min^-1)	Standard deviation
5	4.89	0.08
10	9.59	0.29
25	22.60	1.70

Parameters	Series 1			Series 2			Series 3
	E1.1	E1.2	E1.3	E2.1	E2.2	E2.3	E3.1	E3.2	E3.3
	No obstacles			Obstacle (h_ob = 3 cm)			Obstacles (h_ob = 6 cm)
Q (L.min^-1)	Q1 5	Q2 10	Q3 25	Q1 5	Q2 10	Q3 25	Q1 5	Q2 10	Q3 25
Volume Injected (L)	100
Time of injection (min)	20	10	4	20	10	4	20	10	4
Cvol Mixt. Injected (%)	5.4	5.2	5.6	5.8	5.8	5.6	5.3	5.5	5.5
U_cc (mm.s^-1)	1.4	3.9	6.7	2.5	4.8	9.3	6.3	2.6	4.0
U_max (mm.s^-1)	7.7	17.6	19.8	16.3	24.4	28.1	18.5	15.6	16.8
H_t (mm)	55	85	120	50	90	130	60	90	150
H_umax (mm)	39	62	47	60	51	35	63	69	61
Frd_mean	0.01	0.03	0.04	0.02	0.03	0.05	0.06	0.02	0.02
Frd_max	0.07	0.13	0.12	0.15	0.17	0.17	0.16	0.12	0.09
Re_mean	43	222	542	83	279	784	247	158	415
Re_max	252	1035	1536	547	1387	2399	774	901	1590

	Q (L.min^-1)	H_ob _(cm)	U_c (mm/s)					U_max (mm/s)
	Q (L.min^-1)	H_ob _(cm)	105 cm	190 cm	260 cm	320 cm	370 cm	105 cm	190 cm	260 cm	320 cm	370 cm
E1.1	5	-	1.20	0.68	1.03	1.61	2.52	10.09	2.43	7.01	7.24	11.71
E1.2	10	-	4.01	4.03	1.54	8.07	1.95	24.04	18.63	10.63	19.70	14.85
E1.3	25	-	7.82	6.19	3.35	9.08	7.06	25.66	17.11	9.46	23.67	23.06
E2.1	5	3	3.65	2.70	2.15	2.85	1.24	19.52	16.06	15.96	14.75	15.33
E2.2	10	3	4.87	2.81	2.14	12.01	2.10	28.79	20.04	20.02	26.19	27.01
E2.3	25	3	11.43	7.50	3.38	12.79	11.27	46.54	23.24	15.59	28.23	27.03
E3.1	5	6	3.85	6.53	5.22	12.42	3.31	18.91	18.23	13.20	28.14	14.02
E3.2	10	6	3.15	5.24	0.89	2.45	1.43	20.08	18.05	6.80	15.03	18.24
E3.3	25	6	4.22	4.88	3.31	5.10	2.68	19.63	14.59	7.89	19.85	22.30

[1] E-mails: arthurcosta.c@gmail.com (ACC), manica@iph.ufrgs.br (RM)

Brasil

Brasil

Effects caused by obstacles in the hydrodynamics of turbidity currents: an experimental approach

Efeitos causados por obstáculos na hidrodinâmica de correntes de turbidez: uma abordagem experimental

ABSTRACT