scholarly journals Three-Dimensional Numerical Modelling of Tidal Current in Balikpapan Bay Using Delft 3D

2021 ◽  
Vol 925 (1) ◽  
pp. 012051
Author(s):  
Syarifah Fauzah ◽  
Ayi Tarya ◽  
Nining Sari Ningsih
Keyword(s):  
Shear Stress ◽  
Current Velocity ◽  
Spring Tide ◽  
Three Dimensional ◽  
Observation Point ◽  
Ocean Current ◽  
Percentage Error ◽  
Maximum Speed ◽  
Bed Shear Stress ◽  
Residential Areas

Abstract Balikpapan is one of the main port cities with residential areas, industry, trade, and vital objects scattered from north to south along the coast of Balikpapan Bay. This dense activity increases traffic in Balikpapan Bay. Thus, the hydrodynamic conditions in these waters are essential to be reviewed. The purpose of this research is to simulate hydrodynamics in Balikpapan Bay. The simulation results of the hydrodynamic model for sea-level elevation values are close to the conditions in the field, as indicated by the correlation coefficient 0.98, skill 0.99, and RMSE 0.15 m. The ocean current velocity verification includes the average correlation for x-direction and y-direction, up to 0.93, RMSE 0.05 m, and the percentage error of 6.7%. The significant current velocity is at low tide during spring tide with an average of 0.1 m/s and a maximum speed of 1.62 m/s. Temporally, the observation point at the mouth of Balikpapan Bay has the most significant Bed Shear Stress magnitude with an average of 0.05 N/m2. Spatially, the highest Bed Shear Stress magnitude is at the time of spring tide when it recedes towards the tide with an average Bed Shear Stress in the bay of 0.16 N/m2. The most dominant tidal components are M2 and S2, with a contribution value of 65.3%. The phase propagation from mouth to upstream of Balikpapan Bay for the M2 component in Balikpapan Bay is 10.5° (22.77 minutes) and 5.5° (11 minutes) for the S2 component.

scholarly journals The Effect of Habitat Structure Boulder Spacing on Near-Bed Shear Stress and Turbulent Events in a Gravel Bed Channel

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1423
Author(s):  
Amir Golpira ◽  
Fengbin Huang ◽  
Abul B.M. Baki
Keyword(s):  
Shear Stress ◽  
Habitat Structure ◽  
Open Channel ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Quadrant Analysis ◽  
Bed Shear Stress ◽  
Gravel Bed ◽  
Restoration Practices ◽  
Ejections And Sweeps

This study experimentally investigated the effect of boulder spacing and boulder submergence ratio on the near-bed shear stress in a single array of boulders in a gravel bed open channel flume. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components. Four methods of estimating near-bed shear stress were compared. The results suggested a significant effect of boulder spacing and boulder submergence ratio on the near-bed shear stress estimations and their spatial distributions. It was found that at unsubmerged condition, the turbulent kinetic energy (TKE) and modified TKE methods can be used interchangeably to estimate the near-bed shear stress. At both submerged and unsubmerged conditions, the Reynolds method performed differently from the other point-methods. Moreover, a quadrant analysis was performed to examine the turbulent events and their contribution to the near-bed Reynolds shear stress with the effect of boulder spacing. Generally, the burst events (ejections and sweeps) were reduced in the presence of boulders. This study may improve the understanding of the effect of the boulder spacing and boulder submergence ratio on the near-bed shear stress estimations of stream restoration practices.

scholarly journals Three-Dimensional Flow Characteristics in Slit-Type Permeable Spur Dike Fields: Efficacy in Riverbank Protection

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 964 ◽  
Author(s):  
Shampa ◽  
Yuji Hasegawa ◽  
Hajime Nakagawa ◽  
Hiroshi Takebayashi ◽  
Kenji Kawaike
Keyword(s):  
Shear Stress ◽  
Longitudinal Velocity ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Efficient Solutions ◽  
Staggered Grid ◽  
Bed Shear Stress ◽  
Experimental Conditions ◽  
Alluvial Rivers ◽  
Spur Dike

This paper focuses on finding efficient solutions for the design of a highly permeable pile spur (or slit type) dike field used in morphologically dynamic alluvial rivers. To test the suitability of different arrangements of this type of permeable pile spur dike field, laboratory experiments were conducted, and a three-dimensional multiphase numerical model was developed and applied, based on the experimental conditions. Three different angles to the approach flow and two types of individual pile position arrangements were tested. The results show that by using a series of slit-type spurs, the approach velocity of the flow can be considerably reduced within the spur dike zone. Using different sets of angles and installation positions, this type of permeable spur dike can be used more efficiently than traditional dikes. Notably, this type of spur dike can reduce the longitudinal velocity, turbulence intensity, and bed shear stress in the near-bank area. Additionally, the deflection of the permeable spur produces more transverse flow to the opposite bank. Arranging the piles in staggered grid positions among different spurs in a spur dike field improves functionality in terms of creating a quasi-uniform turbulence zone while simultaneously reducing the bed shear stress. Finally, the efficacy of the slit-type permeable spur dike field as a solution to the riverbank erosion problem is numerically tested in a reach of a braided river, the Brahmaputra–Jamuna River, and a comparison is made with a conventional spur dike field. The results indicate that the proposed structure ensures the smooth passing of flow compared with that for the conventional impermeable spur structure by producing a lower level of scouring (low bed shear stress) and flow intensification.

scholarly journals Comparison of Methods for Bed Shear Stress Estimation in Complex Flow Field of Bend

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2753
Author(s):  
Liyuan Zhang ◽  
Faxing Zhang ◽  
Ailing Cai ◽  
Zhaoming Song ◽  
Shilin Tong
Keyword(s):  
Shear Stress ◽  
Flow Field ◽  
Single Point ◽  
Three Dimensional ◽  
Bed Shear Stress ◽  
Complex Flow ◽  
Three Dimensional Flow ◽  
Stress Estimation ◽  
Log Law ◽  
Flow Field Measurement

Bed shear stress is closely related to sediment transport in rivers. Bed shear stress estimation is very difficult, especially for complex flow fields. In this study, complex flow field measurement experiments in a 60° bend with a groyne were performed. The feasibility and reliability of bed shear stress estimations using the log-law method in a complex flow field were analyzed and compared with those associated with the Reynolds, Turbulent Kinetic Energy (TKE), and TKE-w′ methods. The results show that the TKE, Reynolds, and log-law methods produced similar bed shear stress estimates, while the TKE-w′ method produced larger estimates than the other methods. The TKE-w′ method was found to be more suitable for bed shear stress estimation than the TKE method, but the value of its constant C2 needed to be re-estimated. In a complex, strong, three-dimensional flow field, the height of the measurement point (relative or absolute) should be re-estimated when a single point measurement is used to estimate the bed shear stress. The results of this study provide guidance for experimental measurement of bed shear stress in a complex flow field.

scholarly journals Bed Shear Stress Influence on Local Scour Geometry Properties in Various Flume Development Conditions

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2346 ◽  
Author(s):  
Kiraga ◽  
Popek
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Mutual Influence ◽  
Three Dimensional ◽  
Critical Shear Stress ◽  
Water Structure ◽  
Correlation Coefficients ◽  
Bed Shear Stress ◽  
Hole Dimensions ◽  
Bed Material

Numerous approaches in sediment mobility studies highlighted the key meaning of channel roughness, which results not only from bed material granulation but also from various bed forms presence, caused by continuous sediment transport. Those forms are strictly connected with the intensity of particle transport, and they eventuate from bed shear stress. The present paper comprised of local scours geometric dimensions research in three variants of lengthwise development of laboratory flume in various hydraulic properties, both in “clear-water” and “live-bed” conditions of sediment movement. Lots of measurements of the bed conformation were executed using the LiDAR device, marked by a very precise three-dimensional shape description. The influence of the bed shear stress downstream model on scours hole dimensions of water structure was investigated as one of the key factors that impact the sediment transport intensity. A significant database of 39 experimental series, lasting averagely 8 hours, was a foundation for delineating functional correlations between bed shear stress-and-critical shear stress ratio and geometry properties of local scours in various flume development cases. In the scope of mutual influence of bed shear stress and water depth, high correlation coefficients were attained, indicating very good and good functional correlations. Also, the influence of bed shear stress and the total length of the scour demonstrated a high correlation coefficient.

Numerical Investigation on Wave Induced Vortex Dynamics Around Cylindrical Pile With Considering Varying Keulegan-Carpenter Number

2017 ◽  
Author(s):  
M. Mohammad Beigi Kasvaei ◽  
M. H. Kazeminezhad ◽  
A. Yeganeh-Bakhtiary
Keyword(s):  
Shear Stress ◽  
Vortex Shedding ◽  
Vortex Dynamics ◽  
Three Dimensional ◽  
Surface Model ◽  
Bed Shear Stress ◽  
Wave Flume ◽  
Horseshoe Vortices ◽  
Free Surface Model ◽  
Wave Induced

Three-dimensional numerical simulation of regular waves passing over cylindrical monopile has been conducted to investigate the vortex dynamics. To do so the rectangular wave flume and monopile is modeled on a solver, available in the open-source CFD toolkit OpenFOAM®. The solver applied RANS equations with VOF method for tracking free surface. Model validation has been done by comparison numerical results with the experimental ones and admissible agreement has been seen. Computations have been done for three cases with different pile diameters consequently for different Keulegan-Carpenter numbers (KC). The vorticity field around the pile was investigated as well as vortices by means of Q criterion. It was seen that by increasing KC number, horseshoe vortices will be formed and vortex shedding will be happened. Moreover, Bed shear stress around the pile has been extracted and it has been seen that, the bed shear stress is influenced by KC value which result of existence of horseshoe vortices and vortex shedding.

Formation of Sand Ripples Under Turbulent Flow Simulated by LES

2010 ◽  
Author(s):  
Yan Cui ◽  
John C. Wells ◽  
Y. Quoc Nguyen
Keyword(s):  
Shear Stress ◽  
Numerical Model ◽  
Three Dimensional ◽  
Sand Wave ◽  
Bed Shear Stress ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Eddy Simulation ◽  
Large Eddy

To simulate the initial formation of sedimentary bedforms, constrained to be in hydraulically smooth turbulent flows under bedload conditions, a numerical model based on Large Eddy Simulation (LES) in a doubly periodic domain has been developed. The numerical model comprises three parts. Given the instantaneous bed geometry, the bed shear stress distribution is obtained from a Large-Eddy-Simulation (LES) method coupled with an Immersed-Boundary-Method (IBM). Flux is estimated by the van Rijn’s formula [1]. Finally, evolution of the bed surface is described by the Exner equation. “Two-dimensional bed” [2] and “three-dimensional bed” models employ, respectively, transversely averaged bed shear stress and instantaneous local shear stress to estimate the bedload flux. Based on this model, the evolution of an initial sand wave has been successfully computed. Compared to the “two-dimensional” [2] model, the three-dimensional model leads to a slightly slower propagation and a smaller sand wave. The tendency of the sand wave evolution in three-dimensional model is two-dimensional during the simulated interval.

Modelling of three-dimensional flow velocities in a deep hole in the East Channel of the Mackenzie Delta, Northwest Territories

2007 ◽  
Vol 34 (10) ◽  
pp. 1312-1323 ◽  
Author(s):  
Bahram Gharabaghi ◽  
Chris Inkratas ◽  
Spyros Beltaos ◽  
Bommanna Krishnappan
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Bed Shear Stress ◽  
Mackenzie Delta ◽  
Stress Distributions ◽  
Deep Hole ◽  
Flow Conditions ◽  
Scour Hole ◽  
Scour Holes ◽  
The Stability

The Mackenzie River has several anomalous deep scour holes in a number of river channels in its delta. Proposed gas pipeline crossings have renewed interest in studying the stability of these scour holes. The main goal of this research project was to study flow velocity and bed shear stress distributions for a 30 m deep hole in the East Channel of the Mackenzie Delta as a first step toward assessing the stability of the scour hole and the risk of its migration during various flow conditions. In this study, a three-dimensional (3D) finite element flow model, FLUENT, using the renormalization group (RNG) k-ε turbulence model (where k is the turbulent kinetic energy and ε is the turbulence dissipation rate) was set up for the scour hole and calibrated using detailed measurements of 3D flow velocities, obtained with an acoustic doppler current profiler. The numerical model was then applied to predict flow velocity and bed shear stress distributions in and around the scour hole for three flow conditions (720, 1000, and 1400 m3/s). Results indicate that two vortices are formed in the river elbow above the scour hole. As the flow rate changed, the sizes of the vortices varied. The region upstream of the hole experienced the greatest magnitudes of bed shear stress.Key words: computational fluid dynamics, finite element, bed shear stress, deep hole, flow reversal.

Streamlining of Bridge Piers as Scour Countermeasures

2015 ◽  
Vol 2521 (1) ◽  
pp. 162-171 ◽  
Author(s):  
Junhong Li ◽  
Junliang Tao
Keyword(s):  
Shear Stress ◽  
Cross Section ◽  
Cross Sections ◽  
Turbulence Intensity ◽  
Computational Cost ◽  
Three Dimensional ◽  
Test Cases ◽  
Bridge Scour ◽  
Bed Shear Stress ◽  
Cfd Simulations

Bridge scour is one of the most critical causes of bridge failure. Existing scour countermeasures either passively prevent the development of scour holes by stabilizing the critical shear zone or actively reduce the turbulence intensity in the vicinity of the pier surface. This paper proposes streamlining of the bridge pier as an option to reduce turbulence intensity actively in the local zone and thus decrease overall local scour potential. The effect of the curvature of the pier cross section was evaluated with computational fluid dynamics (CFD) simulations. To reduce computational cost, two-dimensional CFD simulations were conducted to model the flow fields around test cases having different pier cross sections. Simulation results were systematically analyzed and compared to evaluate the effect of streamlining on the flow field. The cross section that resulted in the smallest value of the maximum bed shear stress was selected as the optimal cross section for the subsequent three-dimensional (3-D) study, which investigated the vortex structures around the pier. Results from this 3-D simulation were compared with those from two other test cases, in which piers had cross-section shapes that are commonly seen in practice. The pier model with the optimal cross section was found to significantly reduce the downward velocity in front of the piers, the maximum bed shear stress, and the overall scour potential. These findings are expected to inform the design of optimal streamlined piers for newly proposed bridges, which could diminish the overall scour potential around piers.

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