scholarly journals May a Standard VOF Numerical Simulation Adequately Complete Spillway Laboratory Measurements in an Operational Context? The Case of Sa Stria Dam

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1606
Author(s):  
Maria Grazia Badas ◽  
Riccardo Rossi ◽  
Michela Garau
Keyword(s):  
Numerical Simulation ◽  
Physical Model ◽  
Numerical Models ◽  
Relevant Information ◽  
Mitigation Measures ◽  
Laboratory Measurements ◽  
Concrete Gravity Dam ◽  
Flood Discharge ◽  
Vof Model ◽  
Under Construction

The present work aims to assess whether a standard numerical simulation (RANS-VOF model with k − ϵ closure) can adequately model experimental measurements obtained in a dam physical model. The investigation is carried out on the Sa Stria Dam, a roller compacted concrete gravity dam currently under construction in Southern Sardinia (Italy). The original project, for which a physical model was simulated, included a downstream secondary dam. However, due to both economic and technical reasons, the secondary dam may not be built. Hence, it is important to assess the flood discharge routing and energy dissipation in the modified plan. Numerical validation is performed adopting the same laboratory configuration, in presence of the downstream dam, and results show a good agreement with mean experimental variables (i.e., pressure, water level). An alternative configuration without the downstream dam is here numerically tested to understand the conditions of flood discharge and assess whether its results can give relevant information for the design of mitigation measures. The topic is of interest also from a more general perspective. Indeed, the feasibility to integrate numerical models with existing laboratory measurements can be very useful not only for new constructions but also for existing dams, which may need either maintenance or upgrading works, such as in case of flood discharge increment.

scholarly journals Two-Dimensional Numerical Modeling of Flow in Physical Models of Rock Vane and Bendway Weir Configurations

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 458
Author(s):  
Drew C. Baird ◽  
Benjamin Abban ◽  
S. Michael Scurlock ◽  
Steven B. Abt ◽  
Christopher I. Thornton
Keyword(s):  
Numerical Modeling ◽  
Physical Model ◽  
Numerical Models ◽  
Hydraulic Performance ◽  
Physical Models ◽  
Protection Measures ◽  
Design Engineers ◽  
Model Study ◽  
Study Results ◽  
Wide Range

While there are a wide range of design recommendations for using rock vanes and bendway weirs as streambank protection measures, no comprehensive, standard approach is currently available for design engineers to evaluate their hydraulic performance before construction. This study investigates using 2D numerical modeling as an option for predicting the hydraulic performance of rock vane and bendway weir structure designs for streambank protection. We used the Sedimentation and River Hydraulics (SRH)-2D depth-averaged numerical model to simulate flows around rock vane and bendway weir installations that were previously examined as part of a physical model study and that had water surface elevation and velocity observations. Overall, SRH-2D predicted the same general flow patterns as the physical model, but over- and underpredicted the flow velocity in some areas. These over- and underpredictions could be primarily attributed to the assumption of negligible vertical velocities. Nonetheless, the point differences between the predicted and observed velocities generally ranged from 15 to 25%, with some exceptions. The results showed that 2D numerical models could provide adequate insight into the hydraulic performance of rock vanes and bendway weirs. Accordingly, design guidance and implications of the study results are presented for design engineers.

Accelerating Climate Model Computation by Neural Networks: A Comparative Study

2021 ◽  
Author(s):  
Maha Mdini ◽  
Takemasa Miyoshi ◽  
Shigenori Otsuka
Keyword(s):  
Neural Networks ◽  
Computational Complexity ◽  
Statistical Model ◽  
Physical Model ◽  
Climate Model ◽  
Numerical Models ◽  
Computation Time ◽  
High Accuracy ◽  
Physical Models ◽  
Computer Resources

<p>In the era of modern science, scientists have developed numerical models to predict and understand the weather and ocean phenomena based on fluid dynamics. While these models have shown high accuracy at kilometer scales, they are operated with massive computer resources because of their computational complexity.  In recent years, new approaches to solve these models based on machine learning have been put forward. The results suggested that it be possible to reduce the computational complexity by Neural Networks (NNs) instead of classical numerical simulations. In this project, we aim to shed light upon different ways to accelerating physical models using NNs. We test two approaches: Data-Driven Statistical Model (DDSM) and Hybrid Physical-Statistical Model (HPSM) and compare their performance to the classical Process-Driven Physical Model (PDPM). DDSM emulates the physical model by a NN. The HPSM, also known as super-resolution, uses a low-resolution version of the physical model and maps its outputs to the original high-resolution domain via a NN. To evaluate these two methods, we measured their accuracy and their computation time. Our results of idealized experiments with a quasi-geostrophic model [SO3] show that HPSM reduces the computation time by a factor of 3 and it is capable to predict the output of the physical model at high accuracy up to 9.25 days. The DDSM, however, reduces the computation time by a factor of 4 and can predict the physical model output with an acceptable accuracy only within 2 days. These first results are promising and imply the possibility of bringing complex physical models into real time systems with lower-cost computer resources in the future.</p>

Numerical Analysis of Evacuation from Taiwan Hsuehshan Tunnel Fire

2014 ◽  
Vol 955-959 ◽  
pp. 1840-1849
Author(s):  
Cherng Shing Lin ◽  
Kuo Da Chou
Keyword(s):  
Numerical Simulation ◽  
Fire Protection ◽  
Quantitative Data ◽  
Relevant Information ◽  
Simulation Software ◽  
Escape Time ◽  
Fire Dynamics ◽  
Fire Dynamics Simulator ◽  
Tunnel Fire ◽  
Protection Engineering

Taiwan is an island nation with numerous mountains and few plains. Consequently, the number of tunnel projects has gradually increased and tunnels are becoming longer. Because the number of large tunnels that exceed 1000 meters in length has increased, the effective escape and evacuation of people during a fire and the minimization of injury are crucial to fire protection engineers. For this study, an actual example of a fire that occurred in Hsuehshan Tunnel (12.9 kilometers and the longest tunnel in Southeast Asia) was used. A fire dynamics simulator (FDS) including numerical simulation software was applied to analyze this fire and the relevant information that was collected was compared and verified. The fire site simulation showed the escape and evacuation of people during the fire. Simulations of the original fire site and the possible escape time for people with various attributes were discussed to provide quantitative data and recommendations based on the analysis results, which can serve as a reference for fire protection engineering.

Experimental and numerical simulation of thermomechanical phenomena during a TIG welding process

2004 ◽  
Vol 120 ◽  
pp. 697-704
Author(s):  
L. Depradeux ◽  
J.-F. Jullien
Keyword(s):  
Numerical Simulation ◽  
Numerical Models ◽  
Welding Process ◽  
Central Zone ◽  
Mechanical Analysis ◽  
Tig Welding ◽  
General Ability ◽  
Reduced Dimensions ◽  
Simple Geometry ◽  
A Tig Welding

In this study, a parallel experimental and numerical simulation of phenomena that take place in the Heat Affected Zone during TIG welding on 316L stainless steel is presented. The aim of this study is to predict by numerical simulation residual stresses and distortions generated by the welding process. For the experiment, a very simple geometry with reduced dimensions is considered: the specimens are disks, made of 316L. The discs are heated in the central zone in order to reproduce thermo-mechanical cycles that take place in the HAZ during a TIG welding process. During and after thermal cycle, a large quantity of measurement is provided, and allows to compare the results of different numerical models used in the simulations. The comparative thermal and mechanical analysis allows to assess the general ability of the numerical models to describe the structural behavior. The importance of the heat input rate and material characteristics is also investigated.

scholarly journals Study on the Efficiency and Dynamic Characteristics of an Energy Harvester Based on Flexible Structure Galloping

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6548
Author(s):  
Peng Liao ◽  
Jiyang Fu ◽  
Wenyong Ma ◽  
Yuan Cai ◽  
Yuncheng He
Keyword(s):  
Numerical Simulation ◽  
Wind Speed ◽  
Physical Model ◽  
Energy Harvester ◽  
High Efficiency ◽  
Lateral Displacement ◽  
Maximum Output Power ◽  
Flexible Structure ◽  
Maximum Output ◽  
Cfd Numerical Simulation

According to the engineering phenomenon of the galloping of ice-coated transmission lines at certain wind speeds, this paper proposes a novel type of energy harvester based on the galloping of a flexible structure. It uses the tension generated by the galloping structure to cause periodic strain on the piezoelectric cantilever beam, which is highly efficient for converting wind energy into electricity. On this basis, a physical model of fluid–structure interaction is established, and the Reynolds-averaged Navier–Stokes equation and SST K -ω turbulent model based on ANSYS Fluent are used to carry out a two-dimensional steady computational fluid dynamics (CFD) numerical simulation. First, the CFD technology under different grid densities and time steps is verified. CFD numerical simulation technology is used to simulate the physical model of the energy harvester, and the effect of wind speed on the lateral displacement and aerodynamic force of the flexible structure is analyzed. In addition, this paper also carries out a parameterized study on the influence of the harvester’s behavior, through the wind tunnel test, focusing on the voltage and electric power output efficiency. The harvester has a maximum output power of 119.7 μW/mm3 at the optimal resistance value of 200 KΩ at a wind speed of 10 m/s. The research results provide certain guidance for the design of a high-efficiency harvester with a square aerodynamic shape and a flexible bluff body.

Numerical Simulation of Blast Effects on Fibre Grout Strengthened RC Panels

2017 ◽  
Vol 755 ◽  
pp. 18-30
Author(s):  
Corneliu Cismaşiu ◽  
Hugo Bento Rebelo ◽  
Válter J.G. Lúcio ◽  
Manuel T.M.S. Gonçalves ◽  
Gabriel J. Gomes ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
High Speed ◽  
Numerical Models ◽  
Blast Load ◽  
Measurement Equipment ◽  
Speed Measurement ◽  
Experimental Campaign ◽  
Blast Effects ◽  
Applied Element Method

The present paper aims to examine the potential of the Applied Element Method (AEM) in simulating the blast effects in RC panels. The numerical estimates are compared with the results obtained in an experimental campaign designed to investigate the effectiveness of fibre grout for strengthening full scale RC panels by comparing the effects that a similar blast load produces in a reference and the strengthened panel. First, a numerical model of the reference specimen was created in the software Extreme Loading for Structures and calibrated to match the experimental results. With no further calibration, the fibre reinforced grout strengthening was added and the resulting numerical model subjected to the same blast load. The experimental blast effects on both reference and strengthened panels, despite the lack of high speed measurement equipment (pressure, strains and displacements sensors), compare well with the numerical estimates in terms of residual and maximum displacements, showing that, once calibrated, the AEM numerical models can be successfully used to simulate blast effects in RC panels.

scholarly journals Impact Anlysis of Bow Flap on LHA-1 Ship Airwake

2018 ◽  
Vol 179 ◽  
pp. 03007
Author(s):  
Jinling Wang ◽  
Guangwen Jiang ◽  
Jun Shen ◽  
Chujun Hu
Keyword(s):  
Numerical Simulation ◽  
Simulation Method ◽  
Equation Model ◽  
Separation Region ◽  
Operating Environment ◽  
Study Results ◽  
Helicopter Landing ◽  
Hybrid Grid ◽  
Under Construction ◽  
The Impact

The sharp 90°corner of bow found on American Tarawa class general amphibious assault ship LHA-1 will produce large separated region in the airwake over the ship, and the turbulence in the separation region seriously affects the operation safety of the helicopter. In order to reduce the separation in bow region of the LHA-1, and optimize the helicopter operating environment, the numerical simulation method is used to study the influence of the bow flap on the airwake of LHA-1. The study results show that: the ANSYS k-ε two equation model based on the hybrid grid can be used to predict the steady-state characteristics of the ship airwake; the bow flap can improve the flow field downwind of the flap installation position, and the impact range can cover two spots; in headwind, the optimal installation angle of the bow flap is 15°~25°. The research results of this paper can provide modification and improvement reference for the amphibious assault ship in-service and under construction, so as to achieve the purpose of optimizing the ship airwake, thereby improving the safety of helicopter landing process and extending the service life.

scholarly journals An Improved Empirical Model for Flood Discharge Atomization and Its Application to Optimize the Flip Bucket of the Nazixia Project

2019 ◽  
Vol 16 (3) ◽  
pp. 316 ◽  
Author(s):  
Jijian Lian ◽  
Junling He ◽  
Fang Liu ◽  
Danjie Ran ◽  
Xiaoqun Wang ◽  
...  
Keyword(s):  
Physical Model ◽  
Model Test ◽  
Empirical Model ◽  
Rainfall Intensity ◽  
Droplet Diameter ◽  
Heavy Rain ◽  
Physical Model Test ◽  
Rain Area ◽  
Left Wall ◽  
Flood Discharge

Flood discharge atomization is a serious challenge that threatens the daily lives of the residents around the dam area as well as the safety of the water conservancy project. This research aims to improve the prediction accuracy of the stochastic splash model. A physical model test with four types of flip bucket is conducted to obtain the hydraulic parameters of the impinging outer edge of the water jet, the relationship of the splashing droplet diameter with its corresponding velocity, and the spatial distribution of the downstream nappe wind. The factors mentioned above are introduced to formulate the empirical model. The rule obtained from the numerical analyses is compared with the results of the physical model test and the prototype observations, which yields a solid agreement. The numerical results indicate that the powerhouse is no longer in the heavy rain area when adopting the flip bucket whose curved surface is attached to the left wall. The rainfall intensity of the powerhouse is significantly weaker than that of other types under the designed condition, so we choose it as the recommended bucket type. Meanwhile, we compare the rainfall intensity distribution of the original bucket and the recommended bucket under different discharge which rates ranging from 150.71 to 1094.9 m3/s. It is found that the powerhouse and the owner camp are no longer in the heavy rain area under all of the working conditions. Finally, it is shown that the atomization influence during the flood discharge can be reduced by using the recommended bucket.

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