Free-surface behaviour of shallow turbulent flows

Abstract

Over the last two decades, interest in the free-surface behaviour of gravity-driven shallow turbulent flows has increased considerably. It is believed that observation of free-surface behaviour can provide useful information about the hydrodynamic characteristics of the flow and enable remote retrieval of these characteristics to non-invasively and rapidly monitor river flows. At the current state the literature presents scattered knowledge and also exhibits non-uniformity in the terminology used. This paper is a review of the state-of-art of this area of research and was created with two objectives: to gather the information relevant to understand the linkages between the free-surface behaviour and underpinning hydrodynamic processes while using a uniform terminology, and to analyse the gaps in our knowledge of this critical topic.

The Influence of In‐Channel Obstacles on River Sound

“…Our data (Figures 7 and 8) suggest we see this blindness, with nearly identical data paths from the taller REs (Figure 14). We see kinks in the data when the flow reaches the point where it encounters the top of The free-surface is the dynamic and turbulent surface of the rivers' flow, and therefore is affected by flow disturbing REs (Muraro et al, 2021). Flammer et al (1970) observed that as relative submergence increased, the flow transitions between three phases of pronounced, gradual and negligible free-surface effects.…”

“…The free‐surface is the dynamic and turbulent surface of the rivers' flow, and therefore is affected by flow disturbing REs (Muraro et al., 2021). Flammer et al.…”

Using Noncontact Measurement of Water Surface Dynamics to Estimate River Discharge

“…Despite a growing interest by the scientific community, the research on the interaction between a turbulent flow and its free surface is still a relatively young and largely unexplored topic (Muraro et al., 2021). This work has confirmed the existence of a link between the water surface dynamics and macroscopic flow parameters such as surface velocity and water depth at a field scale, and has demonstrated the potential to monitor river discharge entirely remotely, with a physics‐based approach.…”

“…All waves with ω = 0 are stationary waves. Among these, the stationary waves with the crest perpendicular to the flow (k 2 = 0) are of importance because they define the representative scale of water surface deformations for turbulent flows over rough beds in the laboratory and in the field (Dolcetti & García Nava, 2019b;Dolcetti et al, 2016;Muraro et al, 2021). The wavenumber of these stationary waves, k 0 , is found from the solution of Ω GW (k, U 0 , d) = 0 for a case with k 0 ⋅ U 0 = −k 0 U 0 , which results in…”

“…All waves with ω = 0 are stationary waves. Among these, the stationary waves with the crest perpendicular to the flow ( k 2 = 0) are of importance because they define the representative scale of water surface deformations for turbulent flows over rough beds in the laboratory and in the field (Dolcetti & García Nava, 2019b; Dolcetti et al., 2016; Muraro et al., 2021). The wavenumber of these stationary waves, k 0 , is found from the solution of Ω GW ( k , U 0 , d ) = 0 for a case with k 0 ⋅ U 0 = − k 0 U 0 , which results in $$${k}_{0}d=\left[m+\frac{1}{{\mathsf{F}}^{2}}\frac{(1+\mathsf{B})}{\mathsf{B}}\right]\mathrm{tanh}\left({k}_{0}d\right),\hspace{14.22636pt}\to \hspace{14.22636pt}\frac{{\lambda }_{0}}{d}=\frac{2\pi {\mathsf{F}}^{2}}{\left[(1+\mathsf{B})/\mathsf{B}+m{\mathsf{F}}^{2}\right]\mathrm{tanh}\left(2\pi d/{\lambda }_{0}\right)},$$$ where λ 0 = 2 π / k 0 is a characteristic wavelength.…”