2D numerical contributions for the study of non-cohesive sediment transport beneath tidal bores

Putra, Yoga Satria; Beaudoin, Anthony; Rousseaux, Germain; Thomas, Lionel; Huberson, S.

doi:10.1016/j.crme.2018.11.004

Cited by 7 publications

(5 citation statements)

References 28 publications

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“…Penelitian tentang fenomena tidal bores telah banyak dilakukan, baik dengan menggunakan metode analitik, numerik, eksperimental, maupun lapangan. Kajian tentang fenomena tidal bores telah dilakukan secara numerik dan analitik dengan menekankan pada perubahan kedalaman aliran, panjang gelombang, dan amplitudo gelombang yang dikorelasikan dengan bilangan Froude (Putra, Beaudoin, Rousseaux, Thomas, & Huberson, 2019). Selain itu, Treske (1994) telah melakukan studi tentang tidal bores dengan metode eksperimen dengan menganalisis permukaan bebas, kecepatan, dan tekanan dari tidal bores.…”

Section: Pendahuluanunclassified

“…Bentuk permukaan bebas pada gelombang undular bores semakin pecah seiring dengan bertambahnya nilai Fr. Berdasarkan studi oleh Putra et al, (2019), jika Fr ditingkatkan menjadi lebih besar dari 1,4 (Fr> 1,4) maka amplitudo dan panjang gelombang pada permukaan bebasnya akan semakin menurun dan tipe tidal bores akan berubah dari undular bores menjadi breaking bores dengan kedalaman rata-rata permukaan bebas (h 2 ) yang semakin besar. Kekuatan tidal bores tipe breaking ini lebih besar dalam mengerosi dasar dan tebing sungai yang dilewatinya.…”

Section: Simulasi Permukaan Bebas Undularunclassified

“…selanjutnya nilai aw dan Lw dibandingkan dengan hasil perhitungan yang telah diperoleh oleh Lemoine (1948), Andersen (1978), dan Berry (2018. Hasil perhitungan aw dan Lw juga dibandingkan dengan hasil simulasi numerik yang telah dikerjakan oleh Putra et al (2019) dan Simon (2013), serta hasil eksperimen dari beberapa literatur ilmiah seperti ditunjukan pada Gambar 7. Hasil perhitungan aw dan Lw dari lima simulasi yang dibangun memperlihatkan pola kurva yang mirip dengan hasil dari berbagai referensi ilmiah.…”

Section: E Analisis Amplitudo (Aw) Dan Panjang Gelombang (Lw) Undular Boresunclassified

“…Sebaliknya, pada Gambar 7(b), nilai Lw semakin menurun ketika Fr menuju nilai 1,4. Menurut Putra et al (2019), penurunan Lw dan peningkatan aw dipengaruhi oleh tekanan yang terjadi diantara dua aliran yang saling bertabrakan, yaitu aliran bores dari muara dan aliran sungai dari hulu. Ketika bilangan Froude semakin besar maka tekanan diantara kedua aliran ini juga semakin besar yang berdampak pada mengecilnya panjang gelombang dari undular bores.…”

Section: E Analisis Amplitudo (Aw) Dan Panjang Gelombang (Lw) Undular Boresunclassified

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KAJIAN NUMERIK FENOMENA UNDULAR TIDAL BORES DALAM MEMPENGARUHI PROSES EROSI PADA DAERAH ALIRAN SUNGAI (Numerical study of undular tidal bores phenomenon in influencing erosion processes of watersheds)

Putra¹,

Yuniar

Kushadiwijayanto

2021

JPPDAS

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Riverbank erosion is one indication of watershed damage. One of the causes is the phenomenon of tidal bores waves that occur in a river channel.The strength of tidal bores wave's can be measured based on its shear force parameter and dissipation energy. Wave shear force and dissipation energy are the parameters that play a role in a riverbank erosion process. Both of them are characterized by the Froude number (Fr) which is a function of the upstream river flow velocity (V0), the tidal bores flow velocity from the estuary (Vb), the river depth (h1), and the gravity acceleration (g). A numerical study of the phenomenon of undular tidal bores has been carried out in this article. Five undular bores simulations have been built using the open-source Computational Fluid Dynamics (CFD) software, OpenFOAM. This study aims to analyze the effect of the Froude number variations (Fr) on the magnitude of the wave shear coefficient (ϵ) and dissipation energy ( ) on undular bores cases. Five simulations of undular bores have been generated based on five Froude's numbers, Fr = 1.0, 1.1, 1.2, 1.3, and 1.4. The validation has been performed by comparing the experimental and numerical results from the scientific literature. The analysis results show that the increase in Fr has a significant effect on the increase in the ϵ and .These results indicate that the Froude number variations have influenced the wave shear coefficient and dissipation energy on the undular bores cases. Increasing the Fr values have triggered an increase in the value of ϵ linearly and exponentially. Thus, the erosion that occurs on the riverbank in the undular tidal bores phenomenon could be determined based on Froude's number.

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Section: Pendahuluanunclassified

Section: Simulasi Permukaan Bebas Undularunclassified

Section: E Analisis Amplitudo (Aw) Dan Panjang Gelombang (Lw) Undular Boresunclassified

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KAJIAN NUMERIK FENOMENA UNDULAR TIDAL BORES DALAM MEMPENGARUHI PROSES EROSI PADA DAERAH ALIRAN SUNGAI (Numerical study of undular tidal bores phenomenon in influencing erosion processes of watersheds)

Putra¹,

Yuniar

Kushadiwijayanto

2021

JPPDAS

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“…Turbulence impulses play a vital role in the sediment particle dislodgement at the inception of bedload motion (Diplas et al, 2008;Celik et al, 2013). Both bedload and suspended particles can be advected upstream by the bore-induced turbulent flow motion (Chanson & Tan, 2010, 2011Berchet et al, 2018;Putra et al, 2019). Therefore, the passage of tidal bores in open channels may trigger strong bed erosion and deformation, as well as upstream sediment transport.…”

Section: Presentationmentioning

confidence: 99%

Hydrodynamics of tidal bores: turbulent propagation and sediment transport

Li¹

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A tidal bore normally occurs in an estuarine zone, as a combined result of the spring tide and the trumpet-shaped river mouth. During flood tide, the inland flow is amplified by the graduallynarrowing funnelled estuary, forcing the leading edge to grow steeper until forming an upstream propagating discontinuous wave that is the tidal bore. Tidal bores in natural rivers usually contain enormous energy and induce intense turbulent mixing, posing a threat to hydraulic structures and seriously affecting the fluvial environment. The current study of tidal bores focused on the physical modelling of their turbulent propagation and transformation as well as the bore-induced sediment transport. The experiments were conducted in a 15 m long 0.5 m wide rectangular channel, with ten flow conditions encompassing various flow rates, channel slopes and bed materials (smooth PVC, fixed/mobile gravel). High-frequency sampling of instantaneous unsteady free-surface elevation and turbulent velocity was realised using acoustic displacement meters and acoustic Doppler velocimeters at 200 Hz. High-definition video recording and photographic observation were applied to track the bore propagation and transformation along the test section. Ultra-high-speed video camera recordings were undertaken at 1,200 fps, to capture the bore-induced sediment particle motion from the side view. For each series of flow conditions, the experiment was repeated at least 25 times to derive some ensemble-averaged results of flow turbulence properties and sediment particle motion characteristics. Two different kinds of decelerating bores were recorded in the inclined channel: (a) decelerating bores transformed into stationary hydraulic jumps (arrested bores) when propagating against supercritical flows; (b) decelerating bores vanished when travelling opposite to subcritical flows. The arrival of bores induced an abrupt free-surface rise and a rapid decrease of streamwise velocity. The near-bed flow was observed to reverse direction towards upstream beneath breaking bores. The instantaneous free-surface and all flow velocity components experienced some drastic fluctuations during the bore front passage. Large-amplitude Reynolds stresses and extreme Reynolds stress fluctuations occurred in the same phase during and after the passage of decelerating bores.The sediment transport in the bore-induced rapidly-varied flows was investigated focusing on the bed particle motion and diffusion processes. The frame-by-frame analysis of slow-motion videos demonstrated three basic motion modes of individual pebbles: rotation, rolling and saltation. More complicated pebble motion included a combination of 2 or 3 basic modes. Most moving particles were entrained underneath the bore front between the bore roller toe and the first crest. Based upon a Lagrangian approach, more than 550 complete trajectories of the moving bed particles were extracted from the videos recorded at 1,200 fps. These particles were set into motion by bore passages and shortly reposed into the static gr...

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