Effect of Linearly Stratified Environment and Submerged Vegetation on Hydrodynamic Characteristics of Downslope Gravity Currents

doi:10.16183/j.cnki.jsjtu.2019.228

Abstract

Abstract:

A series of lock-exchange experiments of slope gravity currents were conducted to analyze the development and evolution characteristics of rigid vegetations in uniform and linear stratified environments. The development of gravity currents was recorded by using a digital camera, and the local flow field structure was obtained by particle image velocimetry (PIV). The results show that the head velocity of gravity currents with submerge vegetation experience the processes of acceleration, deceleration, second acceleration, and second deceleration. As the stratification degree increases, the transition points among the four stages move ahead, but the vegetation density does not significantly impact that point. In the stratified environments with the submerged vegetation patches, the phenomena of “first separated then advanced and finally separated from the slope” is observed. Vegetation can restrain the development of vorticity fields of gravity currents. When the vegetation densens, the vorticity of gravity currents will decrease more significantly. Both stratified environments and submerged vegetation patches can inhibit the development of vorticity fields of gravity currents, and the stratified water environment plays a more important role in this inhibition.

Key words: stratified environment, submerged vegetation, slope, gravity currents

CLC Number:

TV145

LIU Yayu, LIN Yingtien, YUAN Yeping, HE Zhiguo. Effect of Linearly Stratified Environment and Submerged Vegetation on Hydrodynamic Characteristics of Downslope Gravity Currents[J]. Journal of Shanghai Jiao Tong University, 2021, 55(4): 412-420.

Figures/Tables 9

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工况	H_v/ cm	g'/ (m·s^-2)	S	φ/ %	U/ (m·s^-1)	Re	Fr
N1	0	0.113	0	0	4.53	4077	0.45
N2	0	0.090	0.85	0	3.29	2961	0.37
N3	0	0.087	1.14	0	2.88	2592	0.33
A1	3	0.113	0	4.5	4.23	3807	0.42
A2	3	0.097	0.85	4.5	3.18	2862	0.34
A3	3	0.091	1.14	4.5	2.74	2466	0.30
B1	3	0.113	0	9.0	3.84	3456	0.38
B2	3	0.095	0.85	9.0	2.76	2484	0.30
B3	3	0.091	1.10	9.0	1.96	1764	0.22
C1	3	0.113	0	18	3.68	3312	0.36
C2	3	0.091	0.85	18	2.66	2394	0.29
C3	3	0.086	1.12	18	1.81	1629	0.21

工况	u_b/ (cm·s^-1)	u_v/ (cm·s^-1)	u_a/ (cm·s^-1)	R₁/%	R₂/%
A1	4.02	3.93	3.48	2.24	13.43
A2	3.57	3.46	2.90	3.08	18.77
A3	3.11	2.79	2.19	10.29	29.58
B1	4.08	3.72	3.33	8.82	18.38
B2	3.49	3.12	2.65	10.60	24.07
B3	3.03	2.54	1.94	16.17	35.97
C1	4.09	3.42	3.08	16.38	24.69
C2	3.51	3.08	2.27	12.25	35.33
C3	3.02	2.37	1.47	21.52	51.32

工况	H_v/cm	S	φ/%	H_s1/h₀	H_s2/h₀
N1	0	0	0	N.A.	N.A.
N2	0	0.85	0	N.A.	N.A.
N3	0	1.14	0	1.92	1.92
A1	3	0	4.5	N.A.	N.A.
A2	3	0.85	4.5	2.57	2.63
A3	3	1.14	4.5	1.81	2.00
B1	3	0	9.0	N.A	N.A
B2	3	0.85	9.0	2.47	N.A
B3	3	1.10	9.0	1.88	2.04
C1	3	0	18	N.A.	N.A.
C2	3	0.85	18	2.44	N.A.
C3	3	1.12	18	1.99	2.30