Modeling Gravity and Turbidity Currents: Computational Approaches and Challenges

Meiburg, Eckart; Radhakrishnan, Senthil K.; Nasr-Azadani, Mohamad M.

doi:10.1115/1.4031040

Cited by 81 publications

(80 citation statements)

References 165 publications

(227 reference statements)

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“…As opposed to simulations within closed or periodic geometries, such as the lock-exchange configuration, open flows are somewhat more challenging because attention has to be paid to minimising any numerical contamination of the flow by upstream propagation of the outflow boundary conditions. For a broader discussion of the computational challenges associated with modeling gravity currents, we refer the reader to Meiburg et al (2015).…”

Section: Introductionmentioning

confidence: 99%

Sustained gravity currents in a channel

et al. 2016

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Gravitationally-driven motion arising from a sustained constant source of dense fluid in a horizontal channel is investigated theoretically using shallow layer models and direct numerical simulations of the Navier-Stokes equations, coupled to an advectiondiffusion model of the density field. The influxed dense fluid forms a flowing layer underneath the less dense fluid, which initially filled the channel, and in this study its speed of propagation is calculated; the outflux is at the end of the channel. The motion, under the assumption of hydrostatic balance, is modelled using a two-layer shallowwater model to account for the flow of both the dense and the overlying less dense fluids. When the relative density difference between the fluids is small (the Boussinesq regime), the governing shallow layer equations are solved using analytical techniques. It is demonstrated that a variety of flow-field patterns is feasible, including those with constant height along the length of the current and contrasted with those where the height varies continuously and discontinuously. The type of solution realised in any scenario is determined by the magnitude of the dimensionless flux issued from the source and the source Froude number. Two important phenomena may occur: the flow may be choked, whereby the excess velocity due to the density difference is bounded and the height of the current may not exceed a determined maximum value, and it is also possible for the dense fluid to completely displace all of the less dense fluid originally in the channel in an expanding region close to the source. The onset and subsequent evolution of these types of motions are also calculated using analytical techniques. The same range of phenomena occurs for non-Boussinesq flows; in this scenario the solutions of the model are calculated numerically. The results of direct numerical simulations of the Navier-Stokes equations are also reported for unsteady two-dimensional flows in which there is inflow of dense fluid at one end of the channel and outflow at the other end. These simulations reveal the detailed mechanics of the motion and the bulk properties are compared with the predictions of the shallow-layer model to demonstrate good agreement between the two modelling strategies.

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Section: Introductionmentioning

confidence: 99%

Sustained gravity currents in a channel

et al. 2016

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“…Piomelli [31] argued that the cost of a calculation scales like the Reynolds number to the power 2.4 for LES. The computational cost of LES model is about 4-100-times higher than that required by the RANS model [43,44].…”

Section: Model Descriptionmentioning

confidence: 97%

Computational Fluid Dynamics for Modeling Gravity Currents in the Presence of Oscillatory Ambient Flow

Stancanelli¹,

Musumeci²,

Foti³

2018

Water

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Gravity currents generated by lock release are studied in the case of initially quiescent ambient fluid and oscillating ambient fluid (regular surface waves). In particular, the dynamics of the density currents are investigated by means of CFD numerical simulations. The aim is to evaluate the influence of the ambient fluid velocity field on the observed mixing and turbulent processes. Results of two different turbulence closure models, namely the standard k − ε turbulence model and the LES model, are analyzed. Model predictions are validated through comparison with laboratory measurements. Results show that the k − ε model is able to catch the main current propagation parameters (e.g., front velocity at the different phases of the evolution of the current, gravity current depth, etc.), but that a LES model provides more realistic insights into the turbulent processes (e.g., formation of interfacial Kelvin-Helmholtz billows, vortex stretching and eventual break up into 3D turbulence). The ambient fluid velocity field strongly influences the dynamics of the gravity currents. In particular, the presence of an oscillatory motion induces a relative increase of mixing at the front (up to 25%) in proximity of the bottom layer, and further upstream, an increase of the mixing process (up to 60%) is observed due to the mass transport generated by waves. The observed mixing phenomena observed are also affected by the ratio between the gravity current velocity v f and the horizontal orbital velocity induced by waves u w , which has a stronger impact in the wave dominated regime (v f /u w < 1).

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“…More recent reviews on the numerical modeling of turbidity current may be found in. [23][24][25] Numerical model study…”

Section: Field and Physical Model Studiesmentioning

confidence: 99%

A numerical modeling study of sediment bypass tunnels at shihmen reservoir, Taiwan

Lai

2018

IJH

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A numerical modeling study of sediment bypass tunnels at shihmen reservoir, Taiwan Submit Manuscript | http://medcraveonline.com IntroductionMany reservoirs have been constructed worldwide. After the construction, a reservoir will continue to be filled with sediment over time, causing storage loss, reducing water supply reliability, and impacting infrastructure such as marinas, outlet works, and turbine intakes.1 Reservoir sedimentation affects all levels of the reservoir and all storage allocations by use, whether it is conservation, multiuse, or flood pool.2 The rate of reservoir sedimentation is site specific and may vary from an average annual storage loss of 2.3 percent in China to 0.2 percent in North America. 3 In the western United States, half of the Reclamation's reservoirs are over 60 years old, nearly 20 percent are at least 80 years old, and 7 percent are already over the design life of 100 years.1 According to the RESSED (REServoir SEDimentation) database, 4 the 83 surveyed Reclamation reservoirs have had an average annual storage loss of 0.19 percentage since 1990. More in-depth discussions of reservoir sedimentation issues and the management measures were provided. 1,[5][6][7][8][9] This study concerns with the sedimentation issue at Shihmen reservoir, Taiwan. Topological, geological and seismological factors have increased sediment delivery to the reservoir. Due to limited desilting facilities, a large amount of fine sediments did not pass through the reservoir, leading to a significant loss of the storage capacity. Moreover, extreme typhoons produced sufficiently high sediment concentrations that water supply was interrupted, causing social and economic problems. A number of sediment management projects have been planned by the Taiwan government to extend the reservoir life and maintain water supply. In particular, multiple sediment bypass tunnels are to be designed and constructed to address the sedimentation issues. A combined field, physical model and numerical model studies are being used to assist the planning and design of the sediment bypass tunnels. However, few numerical models are found adequate to simulate the turbidity current processes in the reservoir and sediment sluicing predictions through the outlets. In this study, the aim is to develop and present a twodimensional (2D) layer-averaged turbidity current numerical model that is suitable for sediment bypass prediction in practical reservoirs. The model builds on the work of Lai et al. 10 The new contributions of this study are threefold. First, the model of Lai et al. 10 is further calibrated and validated against a practical reservoir (Shihmen) that has a combined sluicing gates and sediment bypass tunnels. The effort lends credence to the numerical model that is being considered for real-time forecast applications at the reservoir. Second, the model is extended to simulate two proposed sediment bypass plans and results are compared with the existing condition scenario. The results allow an objective evaluation of the bypass tu...

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Modeling Gravity and Turbidity Currents: Computational Approaches and Challenges

Cited by 81 publications

References 165 publications

Sustained gravity currents in a channel

Sustained gravity currents in a channel

Computational Fluid Dynamics for Modeling Gravity Currents in the Presence of Oscillatory Ambient Flow

A numerical modeling study of sediment bypass tunnels at shihmen reservoir, Taiwan

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