The advancing wave front on a sloping channel covered by a rod canopy following an instantaneous dam break
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arXiv
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| Autori principali: | , , |
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| _version_ | 1866913270424666112 |
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| author | Buono, Elia Katul, Gabriel G. Poggi, Davide |
| author_facet | Buono, Elia Katul, Gabriel G. Poggi, Davide |
| contents | The drag coefficient $C_d$ for a rigid and uniformly distributed rod canopy covering a sloping channel following the instantaneous collapse of a dam was examined using flume experiments. The measurements included space $x$ and time $t$ high resolution images of the water surface $h(x,t)$ for multiple channel bed slopes $S_o$ and water depths behind the dam $H_o$ along with drag estimates provided by sequential load cells. Analysis of the Saint-Venant Equation (SVE) for the front speed using the diffusive wave approximation lead to a front velocity $U_f=\sqrt{Γ_h 2 g ϕ_v'/(C_d m D)}$, where $Γ_h=-\partial h/\partial x$, $g$ is the gravitational acceleration, $ϕ_v'=1-ϕ_v$ is fluid volume fraction per ground area, $ϕ_v=m πD^2/4$ is the solid volume fraction per ground area, $m$ is the number of rods per ground area, and $D$ is the rod diameter. An inferred $C_d=0.4$ from the $h(x,t)$ data near the advancing front region, also confirmed by load cell measurements, is much reduced relative to its independently measured steady-uniform flow case. This finding suggests that drag reduction mechanisms associated with transients and flow disturbances are more likely to play a dominant role when compared to conventional sheltering or blocking effects on $C_d$ examined in uniform flow. The increased air volume entrained into the advancing wave front region as determined from an inflow-outflow volume balance partly explains the $C_d$ reduction from unity. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_12232 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The advancing wave front on a sloping channel covered by a rod canopy following an instantaneous dam break Buono, Elia Katul, Gabriel G. Poggi, Davide Fluid Dynamics The drag coefficient $C_d$ for a rigid and uniformly distributed rod canopy covering a sloping channel following the instantaneous collapse of a dam was examined using flume experiments. The measurements included space $x$ and time $t$ high resolution images of the water surface $h(x,t)$ for multiple channel bed slopes $S_o$ and water depths behind the dam $H_o$ along with drag estimates provided by sequential load cells. Analysis of the Saint-Venant Equation (SVE) for the front speed using the diffusive wave approximation lead to a front velocity $U_f=\sqrt{Γ_h 2 g ϕ_v'/(C_d m D)}$, where $Γ_h=-\partial h/\partial x$, $g$ is the gravitational acceleration, $ϕ_v'=1-ϕ_v$ is fluid volume fraction per ground area, $ϕ_v=m πD^2/4$ is the solid volume fraction per ground area, $m$ is the number of rods per ground area, and $D$ is the rod diameter. An inferred $C_d=0.4$ from the $h(x,t)$ data near the advancing front region, also confirmed by load cell measurements, is much reduced relative to its independently measured steady-uniform flow case. This finding suggests that drag reduction mechanisms associated with transients and flow disturbances are more likely to play a dominant role when compared to conventional sheltering or blocking effects on $C_d$ examined in uniform flow. The increased air volume entrained into the advancing wave front region as determined from an inflow-outflow volume balance partly explains the $C_d$ reduction from unity. |
| title | The advancing wave front on a sloping channel covered by a rod canopy following an instantaneous dam break |
| topic | Fluid Dynamics |
| url | https://arxiv.org/abs/2403.12232 |