Sediment Transport Calculation Considering Laminar and Turbulent Resistance Forces Caused by Infiltration/Exfiltration and Its Application to Tsunami-Induced Local Scouring

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Tomoaki Nakamura ◽  
Norimi Mizutani
Keyword(s):  
Sediment Transport ◽  
Three Dimensional ◽  
Interaction Model ◽  
Computational Accuracy ◽  
Scour Hole ◽  
Transport Calculation ◽  
Seaward Edge ◽  
Improved Model ◽  
Resistance Forces ◽  
Load Sediment

A sediment transport calculation was proposed, which consistently considered the influence of laminar and turbulent resistance forces caused by infiltration/exfiltration. From a comparison of the nondimensional bed–load sediment transport rate, it was found to be essential to consider both laminar and turbulent resistance forces when formulating the influence of infiltration/exfiltration in sediment transport calculations. A three-dimensional coupled fluid–structure–sediment interaction model was improved using the proposed sediment transport calculation, and applied to tsunami-induced local scouring around an inland structure. Numerical results showed that consideration of infiltration/exfiltration improved the computational accuracy of the prediction of a scour hole formed around the seaward edge of the structure, and accordingly the improved model could capture the evolution of the scour hole with sufficient accuracy. This suggests that the improved model should be a useful tool for assessing tsunami-induced local scouring.

Sediment Transport Calculation Considering Laminar and Turbulent Resistance Forces due to Infiltration/Exfiltration and its Application to Tsunami-Induced Local Scouring

2013 ◽  
Author(s):  
Tomoaki Nakamura ◽  
Norimi Mizutani
Keyword(s):  
Sediment Transport ◽  
Three Dimensional ◽  
Interaction Model ◽  
Resistance Force ◽  
Computational Accuracy ◽  
Scour Hole ◽  
Transport Calculation ◽  
Seaward Edge ◽  
Improved Model ◽  
Resistance Forces

A sediment transport calculation which consistently considers the effect of laminar and turbulent resistance forces due to infiltration/exfiltration was proposed. From a comparison of the non-dimensional bed-load sediment transport rate, it is found to be essential to consider laminar resistance force as well as turbulent resistance force when formulating the effect of infiltration/exfiltration in sediment transport calculations. The proposed sediment transport calculation was incorporated to improve a three-dimensional coupled fluid-structure-sediment interaction model, and the improved model is applied to tsunami-induced local scouring around an inland structure. Numerical results show that the consideration of infiltration/exfiltration improves the computational accuracy of a scour hole formed around the seaward edge of the structure, and accordingly the improved model can capture the evolution of the scour hole with sufficient accuracy. This suggests that the improved model is expected to be a useful tool for assessing tsunami-induced local scouring.

A Nonlinear Three-Dimensional Coupled Fluid-Sediment Interaction Model for Large Seabed Deformation

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Tomoaki Nakamura ◽  
Solomon C. Yim
Keyword(s):  
Sediment Transport ◽  
Three Dimensional ◽  
Interaction Model ◽  
Navier Stokes ◽  
Coupling Scheme ◽  
Model Parameters ◽  
Interface Tracking ◽  
Beach Profile ◽  
Time Step ◽  
Profile Change

A nonlinear three-dimensional two-way coupled fluid-sediment interaction model is developed in this study. The model is composed of a generalized Navier–Stokes solver (GNS) with a volume of fluid module for air-water interface tracking and a sediment transport module (STM) for fluid-sediment interface tracking. The GNS model is based on the finite difference method with a turbulent stress model of large-eddy simulation to compute incompressible viscous multiphase flows. The STM is used to compute nonlinear sediment bed profile change due to bed-load sediment transport. A two-way coupling scheme connecting GNS with STM is implemented at each time step to ensure the fluid-sediment interaction. For validation, the fluid-sediment interaction model is applied to predict cross-shore profile change of a sloping beach due to breaking solitary waves, and the resulting predictions are examined and compared with the measured data from a set of hydraulic tests. It is found that the fluid-sediment interaction model predicts reasonably well the sediment transport and the resulting beach profile change. The sensitivity of model parameters involving the sediment transport to the beach profile change is analyzed. Finally, the fluid-sediment interaction model is applied to predict local scour in front of a quay wall due to a jet flow to demonstrate its applicability to general three-dimensional problems.

Three-Dimensional Flow Structures and Suspended-Sediment Transport in the Dam Area of Large Reservoir

2014 ◽  
Vol 501-504 ◽  
pp. 1981-1985
Author(s):  
Dong Dong Jia ◽  
Jian Yin Zhou ◽  
Xue Jun Shao ◽  
Xi Bao Zhang
Keyword(s):  
Sediment Transport ◽  
Three Dimensional ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Transport Processes ◽  
Flow Structures ◽  
Suspended Sediment Transport ◽  
Large Reservoir ◽  
Secondary Currents ◽  
Load Sediment

The three-dimensional (3-D) flow structures and suspended-load sediment transport processes in the dam area of the Three Gorges Project (TGP) with large water depth were simulated by a 3-D mathematical model. The characteristics of flow structures and suspended-load concentration distribution were analyzed based on the simulated results. Strong 3-D features of flow structures can be found in the dam area, the secondary currents are significant. The suspended-load sediment concentration reduced much faster in wider valley areas, where deposits accumulated. Due to impact of secondary currents, the maximum concentration of suspended-load occurs at the convex side while the minimum at the concave side. It demonstrates that the 3-D numerical modeling is a useful prediction technique and research tool to enhance our understanding of flow structures and mass transport processes in natural rivers with complex boundary.

scholarly journals Three-Dimensional Elastodynamic Analysis Employing Partially Discontinuous Boundary Elements

Algorithms ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 129
Author(s):  
Yuan Li ◽  
Ni Zhang ◽  
Yuejiao Gong ◽  
Wentao Mao ◽  
Shiguang Zhang
Keyword(s):  
Side Effect ◽  
Domain Boundary ◽  
Three Dimensional ◽  
Boundary Integral ◽  
Integration Scheme ◽  
Computational Accuracy ◽  
Time Step ◽  
Corner Points ◽  
Discontinuous Elements ◽  
The Time Domain

Compared with continuous elements, discontinuous elements advance in processing the discontinuity of physical variables at corner points and discretized models with complex boundaries. However, the computational accuracy of discontinuous elements is sensitive to the positions of element nodes. To reduce the side effect of the node position on the results, this paper proposes employing partially discontinuous elements to compute the time-domain boundary integral equation of 3D elastodynamics. Using the partially discontinuous element, the nodes located at the corner points will be shrunk into the element, whereas the nodes at the non-corner points remain unchanged. As such, a discrete model that is continuous on surfaces and discontinuous between adjacent surfaces can be generated. First, we present a numerical integration scheme of the partially discontinuous element. For the singular integral, an improved element subdivision method is proposed to reduce the side effect of the time step on the integral accuracy. Then, the effectiveness of the proposed method is verified by two numerical examples. Meanwhile, we study the influence of the positions of the nodes on the stability and accuracy of the computation results by cases. Finally, the recommended value range of the inward shrink ratio of the element nodes is provided.

Thermomechanical Coupling of a Hyper-viscoelastic Truck Tire and a Pavement Layer and its Impact on Three-dimensional Contact Stresses

2021 ◽  
pp. 036119812110171
Author(s):  
Angeli Jayme ◽  
Imad L. Al-Qadi
Keyword(s):  
Contact Stress ◽  
Contact Area ◽  
Three Dimensional ◽  
Interaction Model ◽  
Rolling Resistance ◽  
Contact Stresses ◽  
Thermomechanical Coupling ◽  
Temperature Profiles ◽  
Near Surface ◽  
Truck Tire

A thermomechanical coupling between a hyper-viscoelastic tire and a representative pavement layer was conducted to assess the effect of various temperature profiles on the mechanical behavior of a rolling truck tire. The two deformable bodies, namely the tire and pavement layer, were subjected to steady-state-uniform and non-uniform temperature profiles to identify the significance of considering temperature as a variable in contact-stress prediction. A myriad of ambient, internal air, and pavement-surface conditions were simulated, along with combinations of applied tire load, tire-inflation pressure, and traveling speed. Analogous to winter, the low temperature profiles induced a smaller tire-pavement contact area that resulted in stress localization. On the other hand, under high temperature conditions during the summer, higher tire deformation resulted in lower contact-stress magnitudes owing to an increase in the tire-pavement contact area. In both conditions, vertical and longitudinal contact stresses are impacted, while transverse contact stresses are relatively less affected. This behavior, however, may change under a non-free-rolling condition, such as braking, accelerating, and cornering. By incorporating temperature into the tire-pavement interaction model, changes in the magnitude and distribution of the three-dimensional contact stresses were manifested. This would have a direct implication on the rolling resistance and near-surface behavior of flexible pavements.

2D and 3D CFD Investigations of Seabed Shear Stresses Around Subsea Pipelines

2013 ◽  
Author(s):  
Wenwen Shen ◽  
Terry Griffiths ◽  
Mengmeng Xu ◽  
Jeremy Leggoe
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Interaction Model ◽  
Suspended Sediment Transport ◽  
Shear Stresses ◽  
Parametric Function ◽  
Ample Evidence ◽  
North West ◽  
Wide Range ◽  
Subsea Pipelines

For well over a decade it has been widely recognised that existing models and tools for subsea pipeline stability design fail to account for the fact that seabed soils tend to become mobile well before the onset of pipeline instability. Despite ample evidence obtained from both laboratory and field observations that sediment mobility has a key role to play in understanding pipeline/soil interaction, no models have been presented previously which account for the tripartite interaction between the fluid and the pipe, the fluid and the soil, and the pipe and the soil. There are numerous well developed and widely used theories available to model pipe-fluid and pipe-soil interactions. A challenge lies in the way to develop a satisfactory fluid-soil interaction algorithm that has the potential for broad implementation under both ambient and extreme sea conditions due to the complexity of flow in the vicinity of a seabed pipeline or cable. A widely used relationship by Shields [1] links the bedload and suspended sediment transport to the seabed shear stresses. This paper presents details of computational fluid dynamics (CFD) research which has been undertaken to investigate the variation of seabed shear stresses around subsea pipelines as a parametric function of pipeline spanning/embedment, trench configuration and wave/current properties using the commercial RANS-based software ANSYS Fluent. The modelling work has been undertaken for a wide range of seabed geometries, including cases in 3D to evaluate the effects of finite span length, span depth and flow attack angle on shear stresses. These seabed shear stresses have been analysed and used as the basis for predicting sediment transport within the Pipe-Soil-Fluid (PSF) Interaction Model [2] in determining the suspended sediment concentration and the advection velocity in the vicinity of pipelines. The model has significant potential to be of use to operators who struggle with conventional stabilisation techniques for the pipelines, such as those which cross Australia’s North West Shelf, where shallow water depths, highly variable calcareous soils and extreme metocean conditions driven by frequent tropical cyclones result in the requirement for expensive and logistically challenging secondary stabilisation measures.

scholarly journals Towards an Improved Model of the Galaxy

1998 ◽  
Vol 11 (1) ◽  
pp. 570-570
Author(s):  
Johan Holmberg ◽  
Lennart Lindegren ◽  
Chris Flynn
Keyword(s):  
Three Dimensional ◽  
Direct Determination ◽  
Galactic Structure ◽  
Open Clusters ◽  
Selection Effects ◽  
Observational Errors ◽  
Red Giant ◽  
Improved Model ◽  
First Time ◽  
Hr Diagram

We use the Hipparcos survey to derive an improved model of the local galactic structure. The availability of parallaxes for all the stars permits direct determination of stellar distributions, eliminating the basic indeterminacy of classical methods based on star counts. Hipparcos gives for the first time a truly three-dimensional view of the solar vicinity, and a complete, homogeneous and highly accurate set of magnitudes and colours. This means that new techniques can be applied in the treatment of the data which place strong constraints on a model that tries to describe the local Galactic structure. Here we investigate how well a static model of low complexitycan describe the Hipparcos observations. The interpretation of the Hipparcos data is complicated by various observational errors and selection effects that are hard to treat correctly. We do not try to correct the data, but instead use a model and subject this model to the same observational errors and selection effects. A model catalogue is created that can be compared with the observed catalogue directly in the observational domain, thereby eliminating the effects from various biases. Many features in the HR diagram are for the first time seen in field stars thanks to Hipparcos, such as the slanted red giant clump, previously seen in rich old open clusters such as Berkeley 18. This and other features ofthe observed HR diagram are well reproduced by the model thanks to the rather detailed modelling of the joint Mv/B — V distribution. Actually, separate distributions were derived for the three different components, disk, thick disk and halo, using the kinematic characteristics of the components to discriminate between them.

scholarly journals Relative Transportability for Non-uniform Bed Load Sediment Transport

2018 ◽  
Vol 153 ◽  
pp. 042006
Author(s):  
Li Zhijing ◽  
Li Dazhi ◽  
Liu Xiaobin ◽  
Jin Zhongwu ◽  
Chen Dasong
Keyword(s):  
Sediment Transport ◽  
Bed Load ◽  
Load Sediment

An Octree Method for Interference Detection in Computer Aided 3-D Packing

1994 ◽  
Author(s):  
Zuo Dai ◽  
Jianzhong Cha
Keyword(s):  
Real Time ◽  
Three Dimensional ◽  
Detection Algorithm ◽  
Time Response ◽  
Interference Detection ◽  
Computer Memory ◽  
Computational Accuracy ◽  
Data Space ◽  
Computer Aided ◽  
Packing Process

Abstract In simulating the three dimensional packing process with arbitrary shaped objects, the task of detecting interference between objects is important and very difficult. This paper, representing the three dimensional packing space and objects with an octree, presents an effective interference detection algorithm, which can overcome the performance shortcomings that the conventional methods have in terms of real-time response, computer memory and computational accuracy. By recording the distribution status of packing space in the “bits” of short integers, the data space can be compressed to 1/16 of that used by conventional algorithms.

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