scholarly journals A Momentum-Conserving Scheme for Flow Simulation in 1D Channel with Obstacle and Contraction

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 26
Author(s):  
Putu Veri Swastika ◽  
Sri Redjeki Pudjaprasetya ◽  
Leo Hari Wiryanto ◽  
Revi Nurfathhiyah Hadiarti
Keyword(s):  
River Flow ◽  
Flow Simulation ◽  
Staggered Grid ◽  
Steady Flows ◽  
Flow Modeling ◽  
Dimensional Approach ◽  
Flow Simulations ◽  
Saint Venant Equations ◽  
Steady Solutions ◽  
Good Agreement

We consider the extension of the momentum conservative staggered-grid (MCS) scheme for flow simulation in channels with varying depth and width. The scheme is formulated using the conservative properties of the Saint-Venant equations. The proposed scheme was successful in handling various steady flows and achieved results that are in complete accordance with the analytical steady solutions. Different choices of boundary conditions have created steady solutions according to the mass and energy conservations. This assessment has served as a validation of the proposed numerical scheme. Further, in a channel with a contraction and a nonuniform bed, we simulate two cases of dam break. The simulation results show a good agreement with existing experimental data. Moreover, our scheme, that uses a quasi-1-dimensional approach, has shown some fair agreement with existing 2-dimensional numerical results. This evaluation demonstrates the merits of the MCS scheme for various flow simulations in channels of varying width and bathymetry, suitable for river flow modeling.

scholarly journals Flow modeling and analysis of compound channel in river network with complex floodplains and groynes

2010 ◽  
Vol 13 (3) ◽  
pp. 474-488 ◽  
Author(s):  
Hassan Ahmed ◽  
Norio Tanaka ◽  
Nobuyuki Tamai
Keyword(s):  
Water Depth ◽  
River Flow ◽  
Storage Capacity ◽  
Flow Simulation ◽  
Two Dimensional ◽  
Compound Channel ◽  
Modeling And Analysis ◽  
Flow Models ◽  
Flow Simulations ◽  
Kanto Region

Presented here are flow simulations of a network of natural rivers flanked by one or two large and complex floodplains with impermeable groynes and bridge embankments using one- and quasi-two-dimensional dynamic flow models. The effects of the large floodplain storage capacity, momentum transfer interaction and apparent shear stress at the vertical interface between the main channel and floodplain on the flow-simulated discharge and water depth values could be well explained. The two models were tested and validated in the Arakawa River basin, Kanto Region, Japan. The simulated results show that the large floodplain storage capacity greatly affected the flow discharge and water depth results and cannot be neglected. The quasi-two-dimensional river flow model was used in a flow simulation of a compound channel with complex floodplains with groynes and gave more acceptable results. In the simulated case, the average reduction in flood discharge using floodplain groynes was about 7–15%. Thus, floodplain groynes can be effective for flood protection and attenuation.

scholarly journals The Momentum Conserving Scheme Implementation for Simulating Dambreak Flow in a Channel with Various Contractions

2021 ◽  
Vol 925 (1) ◽  
pp. 012012
Author(s):  
P V Swastika ◽  
S R Pudjaprasetya
Keyword(s):  
Detrimental Effect ◽  
Point Of View ◽  
Staggered Grid ◽  
Rapid Flow ◽  
Saint Venant Equations ◽  
Grid Scheme ◽  
Life Threatening ◽  
Flow Through ◽  
Case Data ◽  
Good Agreement

Abstract Rapid flow downstream due to dambreak has a detrimental effect on the surrounding environment or, more dangerously, can be life-threatening. From a practical point of view, these flows are important to studies due to the limited dambreak real case data. This paper discusses the numerical modelling of the dambreak flow through a channel with three different contractions. Our goal here is to investigate the performance of a numerical model for solving the Saint-Venant equations using a momentum conserving staggered grid scheme (MCS). The scheme is the conservative formulation of the governing equations. Flows across channels of various widths and depths have been successfully simulated using a version of this scheme. In this work, we extend our previous work by simulating dambreak flow in a wave tank through several forms of contraction; trapezoidal and triangular. Our simulation results show good agreement with the experimental data in the literature. This assessment shows the merit of the scheme, which is suitable for dambreak flows in channels of varying width.

scholarly journals Numerical Simulation of Propagation and Run-Up of Long Waves in U-Shaped Bays

Fluids ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 146
Author(s):  
S. R. Pudjaprasetya ◽  
Vania M. Risriani ◽  
Iryanto
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Long Waves ◽  
Staggered Grid ◽  
Wave Focusing ◽  
Consistent Approximation ◽  
Saint Venant Equations ◽  
Wave Shoaling ◽  
Run Up ◽  
Good Agreement

Wave propagation and run-up in U-shaped channel bays are studied here in the framework of the quasi-1D Saint-Venant equations. Our approach is numerical, using the momentum conserving staggered-grid (MCS) scheme, as a consistent approximation of the Saint-Venant equations. We carried out simulations regarding wave focusing and run-ups in U-shaped bays. We obtained good agreement with the existing analytical results on several aspects: the moving shoreline, wave shoaling, and run-up heights. Our findings also confirm that the run-up height is significantly higher in the parabolic bay than on a plane beach. This assessment shows the merit of the MCS scheme in describing wave focusing and run-up in U-shaped bays. Moreover, the MCS scheme is also efficient because it is based on the quasi-1D Saint-Venant equations.

scholarly journals INFLUENCE OF RIVER BED ELEVATION SURVEY CONFIGURATIONS AND INTERPOLATION METHODS ON THE ACCURACY OF LIDAR DTM-BASED RIVER FLOW SIMULATIONS

2016 ◽  
Vol XLII-4/W1 ◽  
pp. 225-235 ◽  
Author(s):  
J. R. Santillan ◽  
J. L. Serviano ◽  
M. Makinano-Santillan ◽  
J. T. Marqueso
Keyword(s):  
River Flow ◽  
Interpolation Method ◽  
Flow Simulation ◽  
Flow Simulations ◽  
Bed Elevation ◽  
River Bed ◽  
Elevation Data ◽  
Data Points ◽  
Simulation Results ◽  
River Flow Simulation

In this paper, we investigated how survey configuration and the type of interpolation method can affect the accuracy of river flow simulations that utilize LIDAR DTM integrated with interpolated river bed as its main source of topographic information. Aside from determining the accuracy of the individually-generated river bed topographies, we also assessed the overall accuracy of the river flow simulations in terms of maximum flood depth and extent. Four survey configurations consisting of river bed elevation data points arranged as cross-section (XS), zig-zag (ZZ), river banks-centerline (RBCL), and river banks-centerline-zig-zag (RBCLZZ), and two interpolation methods (Inverse Distance-Weighted and Ordinary Kriging) were considered. Major results show that the choice of survey configuration, rather than the interpolation method, has significant effect on the accuracy of interpolated river bed surfaces, and subsequently on the accuracy of river flow simulations. The RMSEs of the interpolated surfaces and the model results vary from one configuration to another, and depends on how each configuration evenly collects river bed elevation data points. The large RMSEs for the RBCL configuration and the low RMSEs for the XS configuration confirm that as the data points become evenly spaced and cover more portions of the river, the resulting interpolated surface and the river flow simulation where it was used also become more accurate. The XS configuration with Ordinary Kriging (OK) as interpolation method provided the best river bed interpolation and river flow simulation results. The RBCL configuration, regardless of the interpolation algorithm used, resulted to least accurate river bed surfaces and simulation results. Based on the accuracy analysis, the use of XS configuration to collect river bed data points and applying the OK method to interpolate the river bed topography are the best methods to use to produce satisfactory river flow simulation outputs. The use of other configurations (and a choice between IDW or OK) except RBCL can also be an alternative in cases when the XS configuration is less practical or expensive to implement.

scholarly journals Hydraulic Evaluation of the Levee System Evolution on the Kurobe Alluvial Fan in the 18th and 19th Centuries

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4406
Author(s):  
Tadaharu Ishikawa ◽  
Hiroshi Senoo
Keyword(s):  
Channel Capacity ◽  
Flood Control ◽  
River Flow ◽  
Global Climate ◽  
Flow Simulation ◽  
Japan Sea ◽  
Main Channel ◽  
Alluvial Fan ◽  
Flood Peak ◽  
Levee System

The development process and flood control effects of the open-levee system, which was constructed from the mid-18th to the mid-19th centuries, on the Kurobe Alluvial Fan—a large alluvial fan located on the Japan Sea Coast of Japan’s main island—was evaluated using numerical flow simulation. The topography for the numerical simulation was determined from an old pictorial map in the 18th century and various maps after the 19th century, and the return period of the flood hydrograph was determined to be 10 years judging from the level of civil engineering of those days. The numerical results suggested the followings: The levees at the first stage were made to block the dominant divergent streams to gather the river flows together efficiently; by the completed open-levee system, excess river flow over the main channel capacity was discharged through upstream levee openings to old stream courses which were used as temporary floodways, and after the flood peak, a part of the flooded water returned to the main channel through the downstream levee openings. It is considered that the ideas of civil engineers of those days to control the floods exceeding river channel capacity, embodied in their levee arrangement, will give us hints on how to control the extraordinary floods that we should face in the near future when the scale of storms will increase due to the global climate change.

scholarly journals On the Scope of Lagrangian Vortex Methods for Two-Dimensional Flow Simulations and the POD Technique Application for Data Storing and Analyzing

Entropy ◽  
2021 ◽  
Vol 23 (1) ◽  
pp. 118
Author(s):  
Kseniia Kuzmina ◽  
Ilia Marchevsky ◽  
Irina Soldatova ◽  
Yulia Izmailova
Keyword(s):  
Flow Simulation ◽  
Internal Flow ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Vortex Methods ◽  
Flow Simulations ◽  
Additional Information ◽  
Two Dimensional Flow ◽  
Different Shapes ◽  
Problem Formulations

The possibilities of applying the pure Lagrangian vortex methods of computational fluid dynamics to viscous incompressible flow simulations are considered in relation to various problem formulations. The modification of vortex methods—the Viscous Vortex Domain method—is used which is implemented in the VM2D code developed by the authors. Problems of flow simulation around airfoils with different shapes at various Reynolds numbers are considered: the Blasius problem, the flow around circular cylinders at different Reynolds numbers, the flow around a wing airfoil at the Reynolds numbers 104 and 105, the flow around two closely spaced circular cylinders and the flow around rectangular airfoils with a different chord to the thickness ratio. In addition, the problem of the internal flow modeling in the channel with a backward-facing step is considered. To store the results of the calculations, the POD technique is used, which, in addition, allows one to investigate the structure of the flow and obtain some additional information about the properties of flow regimes.

scholarly journals Model Verification and Error Sensitivity of Turbulence-Related Tensor Characteristics in Pulsatile Blood Flow Simulations

Fluids ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 11
Author(s):  
Magnus Andersson ◽  
Matts Karlsson
Keyword(s):  
Blood Flow ◽  
Model Verification ◽  
Patient Specific ◽  
Flow Modeling ◽  
Spatiotemporal Resolution ◽  
Flow Simulations ◽  
Phase Averaging ◽  
Confidence Levels ◽  
Cardiovascular Flow ◽  
Computational Fluid Dynamics Cfd

Model verification, validation, and uncertainty quantification are essential procedures to estimate errors within cardiovascular flow modeling, where acceptable confidence levels are needed for clinical reliability. While more turbulent-like studies are frequently observed within the biofluid community, practical modeling guidelines are scarce. Verification procedures determine the agreement between the conceptual model and its numerical solution by comparing for example, discretization and phase-averaging-related errors of specific output parameters. This computational fluid dynamics (CFD) study presents a comprehensive and practical verification approach for pulsatile turbulent-like blood flow predictions by considering the amplitude and shape of the turbulence-related tensor field using anisotropic invariant mapping. These procedures were demonstrated by investigating the Reynolds stress tensor characteristics in a patient-specific aortic coarctation model, focusing on modeling-related errors associated with the spatiotemporal resolution and phase-averaging sampling size. Findings in this work suggest that attention should also be put on reducing phase-averaging related errors, as these could easily outweigh the errors associated with the spatiotemporal resolution when including too few cardiac cycles. Also, substantially more cycles are likely needed than typically reported for these flow regimes to sufficiently converge the phase-instant tensor characteristics. Here, higher degrees of active fluctuating directions, especially of lower amplitudes, appeared to be the most sensitive turbulence characteristics.

River parametrisation of the JULES land surface model for improved runoff routing at the global scale.

2021 ◽  
Author(s):  
Aristeidis Koutroulis ◽  
Manolis Grillakis ◽  
Camilla Mathison ◽  
Eleanor Burke
Keyword(s):  
Spatial Resolution ◽  
Land Surface ◽  
River Flow ◽  
Land Surface Model ◽  
Flow Simulation ◽  
Surface Model ◽  
Routing Scheme ◽  
Basin Scale ◽  
River Flow Simulation ◽  
River Routing

<p>The JULES land surface model has a wide ranging application in studying different processes of the earth system including hydrological modeling [1]. Our aim is to tune the existing configuration of the global river routing scheme at 0.5<sup>o</sup> spatial resolution [2] and improve river flow simulation performance at finer temporal scales. To do so, we develop a factorial experiment of varying effective river velocity and meander coefficient, components of the Total Runoff Integrating Pathways (TRIP) river routing scheme. We test and adjust best performing configurations at the basin scale based on observations from GRDC 230 stations that exhibiting a variety of hydroclimatic and physiographic conditions. The analysis was focused on watersheds of near-natural conditions [3] to avoid potential influences of human management on river flow. The HydroATLAS database [4] was employed to identify basin scale descriptive hydro-environmental indicators that could be associated with the components of the TRIP. These indicators summarize hydrologic and physiographic characteristics of the drainage area of each flow gauge. For each basin we select the best performing set of TRIP parameters per basin resulting to the optimal efficiency of river flow simulation based on the Nash–Sutcliffe and Kling–Gupta efficiency metrics. We find that better performance is driven predominantly by characteristics related to the stream gradient and terrain slope. These indicators can serve as descriptors for extrapolating the adjustment of TRIP parameters for global land configurations at 0.5<sup>o</sup> spatial resolution using regression models.</p><p> </p><p>[1] Papadimitriou et al 2017, Hydrol. Earth Syst. Sci., 21, 4379–4401</p><p>[2] Falloon et al 2007. Hadley Centre Tech. Note 72, 42 pp.</p><p>[3] Fang Zhao et al 2017 Environ. Res. Lett. 12 075003</p><p>[4] Linke et al 2019, Scientific Data 6: 283.</p>

scholarly journals Accuracy of Wind Observations from Open-Ocean Buoys: Correction for Flow Distortion

2020 ◽  
Vol 37 (4) ◽  
pp. 687-703 ◽  
Author(s):  
Michael Schlundt ◽  
J. Thomas Farrar ◽  
Sebastien P. Bigorre ◽  
Albert J. Plueddemann ◽  
Robert A. Weller
Keyword(s):  
Flow Distortion ◽  
Error Sources ◽  
Neutral Winds ◽  
Flow Simulations ◽  
Temporal Sampling ◽  
Empirical Correction ◽  
The Individual ◽  
Wind Vane ◽  
Subsequent Comparison ◽  
Good Agreement

AbstractThe comparison of equivalent neutral winds obtained from (i) four WHOI buoys in the subtropics and (ii) scatterometer estimates at those locations reveals a root-mean-square (RMS) difference of 0.56–0.76 m s−1. To investigate this RMS difference, different buoy wind error sources were examined. These buoys are particularly well suited to examine two important sources of buoy wind errors because 1) redundant anemometers and a comparison with numerical flow simulations allow us to quantitatively assess flow distortion errors, and 2) 1-min sampling at the buoys allows us to examine the sensitivity of buoy temporal sampling/averaging in the buoy–scatterometer comparisons. The interanemometer difference varies as a function of wind direction relative to the buoy wind vane and is consistent with the effects of flow distortion expected based on numerical flow simulations. Comparison between the anemometers and scatterometer winds supports the interpretation that the interanemometer disagreement, which can be up to 5% of the wind speed, is due to flow distortion. These insights motivate an empirical correction to the individual anemometer records and subsequent comparison with scatterometer estimates show good agreement.

scholarly journals River flow and sediment transport simulation based on a curvilinear and rectilinear grid modelling approach – a comparison study

2017 ◽  
Vol 17 (5) ◽  
pp. 1325-1334 ◽  
Author(s):  
G. G. Morianou ◽  
N. N. Kourgialas ◽  
G. P. Karatzas ◽  
N. P. Nikolaidis
Keyword(s):  
Sediment Transport ◽  
River Flow ◽  
Morphological Changes ◽  
Field Measurements ◽  
Grid Model ◽  
Curvilinear Grid ◽  
Saint Venant Equations ◽  
Flow And Sediment Transport ◽  
Downstream Section ◽  
The Difference

In the present work, a two-dimensional (2D) hydraulic model was used for the simulation of river flow and sediment transport in the downstream section of the Koiliaris River Basin in Crete, Greece, based on two different structured grids. Specifically, an important goal of the present study was the comparison of a curvilinear grid model with a rectilinear grid model. The MIKE 21C model has been developed to simulate 2D flows and morphological changes in rivers by using either an orthogonal curvilinear grid or a rectilinear grid. The MIKE 21C model comprises two parts: (a) the hydrodynamic part that is based on the Saint-Venant equations and (b) the morphological change part for the simulation of bank erosion and sediment transport. The difference between the curvilinear and the rectilinear grid is that the curvilinear grid lines follow the bank lines of the river, providing a better resolution of the flow near the boundaries. The water depth and sediment results obtained from the simulations for the two different grids were compared with field observations and a series of statistical indicators. It was concluded that the curvilinear grid model results were in better agreement with the field measurements.

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