Numerical simulation of river-bed variations: Sensitivity analyses with respect of the initial hydraulic roughness

2020 ◽  
pp. 309-316
Author(s):  
D. Termini
Keyword(s):  
Numerical Simulation ◽  
Sensitivity Analyses ◽  
Hydraulic Roughness ◽  
River Bed

Preliminary results of numerical simulation of submarine landslide-generated waves

2021 ◽  
Author(s):  
Ramtin Sabeti ◽  
Mohammad Heidarzadeh
Keyword(s):  
Numerical Simulation ◽  
Numerical Modelling ◽  
Numerical Solutions ◽  
Numerical Technique ◽  
Source Region ◽  
Three Dimensional ◽  
Terminal Velocity ◽  
Sensitivity Analyses ◽  
Physical Experiments ◽  
Set Up

<p>Landslide-generated waves have been major threats to coastal areas and have led to destruction and casualties. Their importance is undisputed, most recently demonstrated by the 2018 Anak Krakatau tsunami, causing several hundred fatalities. The accurate prediction of the maximum initial amplitude of landslide waves (<em>η<sub>max</sub></em>) around the source region is a vital hazard indicator for coastal impact assessment. Laboratory experiments, analytical solutions and numerical modelling are three major methods to investigate the (<em>η<sub>max</sub></em>). However, the numerical modelling approach provides a more flexible and cost- and time-efficient tool. This research presents a numerical simulation of tsunamis due to rigid landslides with consideration of submerged conditions. In particular, this simulation focuses on studying the effect of landslide parameters on <em>η<sub>max</sub>.</em> Results of simulations are compared with our conducted physical experiments at the Brunel University London (UK) to validate the numerical model.</p><p>We employ the fully three-dimensional computational fluid dynamics package, FLOW-3D Hydro for modelling the landslide-generated waves. This software benefit from the Volume of Fluid Method (VOF) as the numerical technique for tracking and locating the free surface. The geometry of the simulation is set up according to the wave tank of physical experiments (i.e. 0.26 m wide, 0.50 m deep and 4.0 m). In order to calibrate the simulation model based on the laboratory measurements, the friction coefficient between solid block and incline is changed to 0.41; likewise, the terminal velocity of the landslide is set to 0.87 m/s. Good agreement between the numerical solutions and the experimental results is found. Sensitivity analyses of landslide parameters (e.g. slide volume, water depth, etc.) on <em>η<sub>max </sub></em>are performed. Dimensionless parameters are employed to study the sensitivity of the initial landslide waves to various landslide parameters.</p>

scholarly journals A fast direct numerical simulation method for characterising hydraulic roughness

2015 ◽  
Vol 773 ◽  
pp. 418-431 ◽  
Author(s):  
D. Chung ◽  
L. Chan ◽  
M. MacDonald ◽  
N. Hutchins ◽  
A. Ooi
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Computational Cost ◽  
Simulation Method ◽  
Reynolds Numbers ◽  
Proof Of Concept ◽  
Hydraulic Roughness ◽  
Velocity Shift ◽  
High Reynolds ◽  
Reynolds Number Flows

We describe a fast direct numerical simulation (DNS) method that promises to directly characterise the hydraulic roughness of any given rough surface, from the hydraulically smooth to the fully rough regime. The method circumvents the unfavourable computational cost associated with simulating high-Reynolds-number flows by employing minimal-span channels (Jiménez & Moin, J. Fluid Mech., vol. 225, 1991, pp. 213–240). Proof-of-concept simulations demonstrate that flows in minimal-span channels are sufficient for capturing the downward velocity shift, that is, the Hama roughness function, predicted by flows in full-span channels. We consider two sets of simulations, first with modelled roughness imposed by body forces, and second with explicit roughness described by roughness-conforming grids. Owing to the minimal cost, we are able to conduct direct numerical simulations with increasing roughness Reynolds numbers while maintaining a fixed blockage ratio, as is typical in full-scale applications. The present method promises a practical, fast and accurate tool for characterising hydraulic resistance directly from profilometry data of rough surfaces.

scholarly journals Effect of pile driving on ground vibration in clay soil: Numerical and experimental study

2021 ◽  
Author(s):  
Hirad Shamimi Noori ◽  
Reza Shirinabadi ◽  
Ehsan Moosavi
Keyword(s):  
Numerical Simulation ◽  
Experimental Study ◽  
Clayey Soil ◽  
Ground Vibration ◽  
Friction Angle ◽  
Sensitivity Analyses ◽  
Finite Element Software ◽  
Particle Velocities ◽  
Geotechnical Tests ◽  
The Impact

Abstract In this study, peak particle velocity (PPV) values for driving three piles with 40 cm, 50 cm, and 70 cm in a clayey soil through the impact piling method are investigated by an experimental study and a numerical simulation. An experimental study is carried out on a scale of 1:20 of the operation. Numerical simulation is performed by using an axisymmetric model in PLAXIS 2D finite element software. Properties of the soil and the piles used in the experimental study are obtained from geotechnical tests and employed in the numerical simulation. The model has been verified by comparing the acquired PPV values with those measured in the experimental study. The results show a good agreement between the computed values and the field data. Moreover, measured peak particle velocities in the experimental study indicate that an increase in the diameter of the pile can increase the level of ground vibration. Some sensitivity analyses have been performed by numerical modeling to determine the effect of soil and pile properties on the changes of PPV. The results indicate that increase in friction angle of the soil and pile diameter and reduction in elastic modulus of soil will increase the level of ground vibration.

scholarly journals Well Screen and Optimal Time of Refracturing: A Barnett Shale Well

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Shayan Tavassoli ◽  
Wei Yu ◽  
Farzam Javadpour ◽  
Kamy Sepehrnoori
Keyword(s):  
Numerical Simulation ◽  
Shale Gas ◽  
Fracture Network ◽  
Gas Production ◽  
Sensitivity Analyses ◽  
Optimal Time ◽  
Barnett Shale ◽  
Vast Number ◽  
Access To Data ◽  
The Right

Gas-production decline in hydraulically fractured wells in shale formations necessitates refracturing. However, the vast number of wells in a field makes selection of the right well challenging. Additionally, the success of a refracturing job depends on the time to refracture a shale-gas well during its production life. In this paper we present a numerical simulation approach to development of a methodology for screening a well and to determine the optimal time of refracturing. We implemented our methodology for a well in the Barnett Shale, where we had access to data. The success of a refracturing job depends on reservoir characteristics and the initial induced fracture network. Systematic sensitivity analyses were performed so that the characteristics of a shale-gas horizontal well could be specified as to the possibility of its candidacy for a successful refracturing job. Different refracturing scenarios must be studied in detail so that the optimal design might be determined. Given the studied trends and implications for a production indicator, the optimal time for refracturing can then be suggested for the studied well. Numerical-simulation results indicate significant improvement (on the order of 30%) in estimated ultimate recovery (EUR) after refracturing, given presented screen criteria and optimal-time selection.

scholarly journals Numerical Simulation of Velocity Field around Two Columns of Tandem Piers of the Longitudinal Bridge

Fluids ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 32
Author(s):  
Hongliang Qi ◽  
Junxing Zheng ◽  
Chenguang Zhang
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Velocity Field ◽  
Average Velocity ◽  
Cfd Simulations ◽  
Velocity Change ◽  
River Bed ◽  
Computational Fluid Dynamics Cfd ◽  
Lateral Range

This research explores the effects of different spans of two columns of tandem piers on the characteristics of x-velocity near the river bed based on computational fluid dynamics (CFD) simulations. With a span shorter than 27.5D (D is the diameter of piers), the shape and the lateral range of the x-velocity increases with the increase of distance downwards the x-direction. For the area between the tandem piers and the wall, the VRi/VR1 (the ratio of the x-velocity at the i-th row to the x-velocity of the first row in each model) near the wall increases up to 1.26. For the area between the two columns of tandem piers, the profile of VRi/VR1 changes from a “∩-shape” to an “M-shape” in each model. RAVC (average velocity change ratio) of different spans increases gradually and tends to be stable with the increases of the span. The largest RAVC is about −17.66% with a span of 0.52 m. The RMV (the ratio of the maximum x-velocity among piers in each row in different models to the maximum x-velocity of the two piers arranged side by side) of piers in the first row of different models is around 0.95. The RMV becomes 0.82 at the second pier in each model when the span is shorter than 27.5D, and increases to 0.91 if the span is longer than 27.5D. If the span is longer than 27.5D, the RMV of different piers are close to each other from the 2nd pier to the last one.

scholarly journals An Analysis of the Impact Exerted on Bearing Capacity of Pier and Pile after Increasing Pile Cap Height

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Xianbin Huang ◽  
Chenyang Liu ◽  
Song Hou ◽  
Chunyang Chen ◽  
Yahong Wangren ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Bearing Capacity ◽  
Seismic Waves ◽  
Bending Moment ◽  
Simulation Method ◽  
Ground Acceleration ◽  
Numerical Simulation Method ◽  
River Bed ◽  
Pile Cap ◽  
The Impact

An analysis was carried out in this paper on the bearing capacity of pier pile and seismic performance rule when the low-pile cap is increased by 1 meter, 2 meters, and 3 meters. The bottom of the pile cap of pier no. 11 of Minjiang River bridge faces three “lows”: 7.6 meters lower than island, 4.6 meters lower than natural river bed, and 6.5 meters lower than low water level. The numerical simulation method is adopted to input three seismic waves of Wolong, Bajiao, and EL to evaluate the bearing capacity of pier and pile under strong earthquakes. Using the standard formula and numerical simulation method, it is observed that the bending moment and axial force of bridge pier show an insignificant change under different seismic waves when the pile cap is increased by 0–3 meters. With peak ground acceleration increased to 0.35 g, the vertical bearing capacity and flexural capacity of pier and pile gratify the requirements; however, the pile foundation will be subject to compression and bending damage.

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