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Characteristics of Undular Surges Propagating in Still Water

  • Hydraulic Engineering
  • Published:
KSCE Journal of Civil Engineering Aims and scope

Abstract

In this study, physical experiments were performed in a horizontal rectangular channel to investigate the evolution of undular surges that propagate in still water and the reflection of these surges on a vertical wall. The generated undular surges were located in the intermediate water depth wave regime. The results demonstrated that the maximum wave steepness attained by undular surges was close to the breaking limit of progressive waves at intermediate water depths. Nevertheless, the dispersion relationship was inconsistent with the wave dispersion trend for intermediate gravity waves and strongly depended on the initial flow conditions and surge type. Furthermore, it was found that the longitudinal current velocity was governed primarily by water surface displacement. A novel and universal formula based on the experimental results was proposed to describe the velocity distributions in different types of undular surge flows. In addition, a non-breaking undular surge behaved as a solitary wave regarding its reflection on a vertical wall. Overall, the findings highlighted the effects of the initial flow conditions on the hydrodynamic characteristics of undular surges and demonstrated the unique features of undular surges that propagate in still water.

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Abbreviations

a w :

Wave amplitude (m)

C :

Dispersion coefficient: 2πg*tanh(2πhw/Lw)/Lw

Fr 0 :

Surge Froude number: Fr0=S/(gh0)0.5

g :

Gravitational acceleration (m s−2)

H :

Drop height (m)

h :

Water depth (m)

h 0 :

Initial water depth (m)

h 1c :

Water depth (m) at the first wave crest

h 1t :

Water depth (m) at the first wave trough

K conj :

Conjugate water depth (m) behind the surge front

h i :

Incident wave height (m)

h r :

Reflected wave height (m)

H w :

Wave height (m)

h w :

Mean water depth (m) behind the surge front

K :

Reflection coefficient: K=hr/hi

L w :

Wave length (m)

R 2 :

Correlation coefficient

S :

Absolute surge velocity (m s−1), positive downstream

t :

Time (s) from gate opening

t 1c :

Typical moment (s): t1c=t1ct1c1t

t ic :

Time (s) corresponding to the passage of the ith wave crest

t icit :

Typical moment (s): ticit=(tic + tit)/2

t it :

Time (s) corresponding to the passage of the ith wave trough

t it(i+1)c :

Typical moment (s): (tit + t(i+1)c)/2

t v :

Time (s) needed to fully open the gate

T w :

Wave period (s)

Ur :

Ursell parameter: Ur=(awLw2)/hw3

V x :

Instantaneous longitudinal velocity component (m s−1), positive downstream

V y :

Instantaneous transverse velocity component (m s−1), positive towards the left sidewall

V z :

Instantaneous vertical velocity component (m s−1), positive upwards

x :

Longitudinal distance (m)

y :

Transverse distance (m)

z :

Vertical distance (m)

π :

3.141592654

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Acknowledgments

This work was sponsored by the Natural Science Foundation of Chongqing, China (Grant No. cstc2020jcyj-bshX0043) and the National Key R&D Program of China (Grant No. 2018YFB1600403).

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Correspondence to Yun Li.

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Zheng, F., Wang, P., An, J. et al. Characteristics of Undular Surges Propagating in Still Water. KSCE J Civ Eng 25, 3359–3368 (2021). https://doi.org/10.1007/s12205-021-0858-3

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  • DOI: https://doi.org/10.1007/s12205-021-0858-3

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