Experimental and numerical study of flood dynamics in a river-network-floodplain set-up

2020 ◽  
Vol 22 (4) ◽  
pp. 793-814
Author(s):  
Vijay Kisan Mali ◽  
B. Veeranna ◽  
Aditya Parik ◽  
Soumendra Nath Kuiry
Keyword(s):  
Numerical Study ◽  
River Network ◽  
Channel Network ◽  
Flood Prediction ◽  
River Floodplain ◽  
Flood Simulations ◽  
Set Up ◽  
Flood Dynamics ◽  
Accurate Scheme ◽  
2D Model

Abstract Flood simulations demand mathematical models, which are rigorously calibrated and validated against benchmarking datasets. For this purpose, experiments are conducted in a river-network-floodplain set-up. Hypothetical stepped hydrographs are passed through the channel-network, and fluvial flooding situations are created. Flood depths are recorded at various locations and evolving flood extents are extracted by image processing. TELEMAC 2D is tested against the observed data. The most accurate scheme for flood prediction is identified through sensitivity analysis. Inclusion of the turbulence model is found to improve the accuracy in predicting dynamic flood extents. The model seems to slightly overpredict inundation extents during the rising limb of the hydrographs and underpredict during the falling limb. In addition, certain aspects of a flood such as river–floodplain interaction and junction hydraulics cannot be reproduced with high precision by the 2D model. The experimental datasets can be a valuable resource to mathematical modellers and are freely downloadable.

Experimental and numerical study of flood in a river-network-floodplain set-up

2020 ◽  
Vol 58 (6) ◽  
pp. 938-956 ◽  
Author(s):  
Vijay Kisan Mali ◽  
Soumendra Nath Kuiry
Keyword(s):  
Numerical Study ◽  
River Network ◽  
Set Up

scholarly journals Fast Two-Stage Computation of an Index Policy for Multi-Armed Bandits with Setup Delays

Mathematics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 52
Author(s):  
José Niño-Mora
Keyword(s):  
Numerical Study ◽  
Arithmetic Operation ◽  
Bandit Problem ◽  
Index Policy ◽  
Two Stage ◽  
Second Stage ◽  
Whittle Index ◽  
Set Up ◽  
Computing Method ◽  
Special Case

We consider the multi-armed bandit problem with penalties for switching that include setup delays and costs, extending the former results of the author for the special case with no switching delays. A priority index for projects with setup delays that characterizes, in part, optimal policies was introduced by Asawa and Teneketzis in 1996, yet without giving a means of computing it. We present a fast two-stage index computing method, which computes the continuation index (which applies when the project has been set up) in a first stage and certain extra quantities with cubic (arithmetic-operation) complexity in the number of project states and then computes the switching index (which applies when the project is not set up), in a second stage, with quadratic complexity. The approach is based on new methodological advances on restless bandit indexation, which are introduced and deployed herein, being motivated by the limitations of previous results, exploiting the fact that the aforementioned index is the Whittle index of the project in its restless reformulation. A numerical study demonstrates substantial runtime speed-ups of the new two-stage index algorithm versus a general one-stage Whittle index algorithm. The study further gives evidence that, in a multi-project setting, the index policy is consistently nearly optimal.

Load Characteristics of Steel and Concrete Tubular Members Under Jet Fire: An Experimental and Numerical Study

2010 ◽  
Author(s):  
Jeong Hyo Park ◽  
Bong Ju Kim ◽  
Jung Kwan Seo ◽  
Jae Sung Jeong ◽  
Byung Keun Oh ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Numerical Study ◽  
Fire Load ◽  
Adiabatic Wall ◽  
Fire Engineering ◽  
Ansys Cfx ◽  
Design Values ◽  
Computational Fluid Dynamics Cfd ◽  
Load Characteristics ◽  
Set Up

The aim of this study was to evaluate the load characteristics of steel and concrete tubular members under jet fire, with the motivation to investigate the jet fire load characteristics in FPSO topsides. This paper is part of Phase II of the joint industry project on explosion and fire engineering of FPSOs (EFEF JIP) [1]. To obtain reliable load values, jet fire tests were carried out in parallel with a numerical study. Computational fluid dynamics (CFD) simulation was used to set up an adiabatic wall boundary condition for the jet fire to model the heat transfer mechanism. A concrete tubular member was tested under the assumption that there is no conduction effect from jet fire. A steel tubular member was tested and considered to transfer heat through conduction, convection, and radiation. The temperature distribution, or heat load, was analyzed at specific locations on each type of member. ANSYS CFX [2] and Kameleon FireEx [3] codes were used to obtain similar fire action in the numerical and experimental methods. The results of this study will provide a useful database to determine design values related to jet fire.

Numerical Study of Methane and Air Combustion Inside Heat-Recirculating Combustors

2013 ◽  
Author(s):  
Yanxia Li ◽  
Zhongliang Liu ◽  
Yan Wang ◽  
Jiaming Liu
Keyword(s):  
Gas Flow ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Central Area ◽  
Small Scale ◽  
Inlet Velocity ◽  
Strong Convection ◽  
Simulation Results ◽  
Lean Fuel ◽  
Set Up

A numerical model on methane/air combustion inside a small Swiss-roll combustor was set up to investigate the flame position of small-scale combustion. The simulation results show that the combustion flame could be maintained in the central area of the combustor only when the speed and equivalence ratio are all within a narrow and specific range. For high inlet velocity, the combustion could be sustained stably even with a very lean fuel and the flame always stayed at the first corner of reactant channel because of the strong convection heat transfer and preheating. For low inlet velocity, small amounts of fuel could combust stably in the central area of the combustor, because heat was appropriately transferred from the gas to the inlet mixture. Whereas, for the low premixed gas flow, only in certain conditions (Φ = 0.8 ～ 1.2 when ν0 = 1.0m/s, Φ = 1.0 when ν0 = 0.5m/s) the small-scale combustion could be maintained.

scholarly journals Experimental and Numerical Study of a Thermal Expansion Gyroscope for Different Gases

Sensors ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 360 ◽  
Author(s):  
Guillaume Kock ◽  
Philippe Combette ◽  
Marwan Tedjini ◽  
Markus Schneider ◽  
Caroline Gauthier-Blum ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Gas Flow ◽  
Numerical Study ◽  
Rotational Velocity ◽  
Measurement Range ◽  
Gas Temperature ◽  
Hot Air ◽  
Working Principle ◽  
Set Up ◽  
Different Gases

A new single-axis gas thermal gyroscope without proof mass is presented in this paper. The device was designed, manufactured and experimentally characterized. The obtained results were compared to numerical simulation. The working principle of the gyroscope is based on the deflection of a laminar gas flow caused by the Coriolis effect. A bidirectional hot air flow is generated by alternating activation of two suspended resistive micro-heaters. The heated gas is encapsulated in a semi-open cavity and the gas expands primarily inside the cavity. The thermal expansion gyroscope has a simple structure. Indeed, the device is composed of a micromachined cavity on which three bridges are suspended. The central bridge is electrically separated into two segments enabling to set up two heaters which may be supplied independently from each other. The two other bridges, placed symmetrically on each side of the central bridge, are equipped with temperature detectors which measure variations in gas temperature. The differential temperature depends on the rotational velocity applied to the system. Various parameters such as the heating duty cycle, the type of the gas and the power injected into the heaters have been studied to define the optimal working conditions required to obtain the highest level of sensitivity over a measurement range of around 1000°/s. The robustness of the device has also been tested and validated for a shock resistance of 10,000 g for a duration of 400 µs.

scholarly journals Numerical study of various geometries of breakwaters for the installation of floating wind turbines

2016 ◽  
Vol 13 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Keyvan Esmaeelpour ◽  
Rouzbeh Shafaghat ◽  
Rezvan Alamian ◽  
Rasoul Bayani
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Numerical Study ◽  
Energy Resources ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Renewable Energy Resources ◽  
Time Step ◽  
Set Up ◽  
The Right

The everyday growing populations all over the world and the necessity of increase in consumption of fossil energies have made the human to discover new energy resources, which are clean, cheap and renewable. Wind energy is one of the renewable energy resources. Considerable wind speed has made settling of wind turbines at sea beneficial and appealing. For this purpose, choosing the appropriate plates to set up wind turbines on the surface of sea is necessary. Regarding the installation condition, by choosing suitable geometry for floating breakwaters, offshore wind turbine can be mounted on them. Suitable geometry of breakwater for multifunctional usage could be selected with analyzing and comparing pressure, force and moment produced by incoming waves. In this article, we implement boundary element method to solve governing differential equations by assuming potential flow. On the other hand, for promoting free surface in each time step, we employed Euler-Lagrangian method. Finally, to find the appropriate geometry for installing the wind turbine on the breakwater, moment and wave profile next to the right and left side of breakwater body are calculated. Among simulated geometries, breakwater with trapezoid geometry which its larger base is placed in the water has more sustainability and it is the most suitable geometry for wind turbine installation.

scholarly journals Numerical Study of Smoke Propagation in a Simulated Fire in a Wagon Within a Subway Tunnel

2008 ◽  
Author(s):  
Felipe Vittori ◽  
Luis Rojas-Solo´rzano ◽  
Armando J. Blanco ◽  
Rafael Urbina
Keyword(s):  
Numerical Study ◽  
Ventilation System ◽  
Road Tunnel ◽  
Subway Tunnel ◽  
Longitudinal Ventilation ◽  
Emergency Ventilation ◽  
Tunnel Section ◽  
Fire Scenarios ◽  
Subway Stations ◽  
Set Up

This work deals with the numerical (CFD) analysis of the smoke propagation during fires within closed environments. It is evaluated the capacity of the emergency ventilation system in controlling the smoke propagation and minimizing the deadly impact of an eventual fire in a wagon within the Metro de Caracas subway tunnel on the passengers safety. For the study, it was chosen the tunnel section between Teatros and Nuevo Circo subway stations, which consists of two parallel independent twin tunnels, connected through a transverse passage. The tunnels are provided by a longitudinal ventilation system, integrated by a set of reversible fans located at both ends of the tunnels. Three stages were considered in the study: (a) Model set up; (b) Mesh sensitivity analysis; (c) Validation of the physical-numerical parameters to be used in the numerical model; and (d) Simulation of fire scenarios in Metro de Caracas subway stations. Stages (b)–(c), aimed to testing and calibrating the CFD tool (ANSYS-CFX10™), focused on reproducing experimental data from Vauquelin and Me´gret [1], who studied the smoke propagation in a fire within a 1:20 scale road tunnel. Stage (d) critical scenarios were established via a preliminary discussion with safety experts from Metro de Caracas, in order to reduce the computer memory and the number of simulations to be performed. The analyses assessed the reliability of escape routes and alternative paths for the evacuation of passengers. Additionally, the smoke front movement was particularly computed, as a function of time, in order to determine the possible presence of the “backlayering” phenomenon [5]. Results demonstrate the strengths and weaknesses of the current ventilation system in the event of a fire in the subway tunnel, and suggest new strategies to address this potentially lethal event to minimize the risks for passengers.

scholarly journals A Simplified Finite Element Approach for Modeling of Multilayer Plates

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Taiyou Liu ◽  
Xinbo Ma ◽  
Pak Kin Wong ◽  
Jing Zhao ◽  
Zhengchao Xie ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Reference Value ◽  
Fe Model ◽  
Practical Applications ◽  
Aerospace Applications ◽  
Equivalent Bending Stiffness ◽  
Element Approach ◽  
Set Up ◽  
Transverse Response

The multilayer plate has a great potential for automotive and aerospace applications. However, the complexity in structure and calculation of the response impede the practical applications of multilayer plates. To solve this problem, this work proposes a new plate finite element and a simplified finite element (FE) model for multilayer plates. The proposed new plate finite element consists of the shear and extension strains in all layers. The multilayer structure with the proposed new plate finite element is regarded as a reference to calculate the reference value of the transverse response. The simplified FE model of multilayer plates is proposed based on the equivalent bending stiffness by curve fitting of the reference value of the transverse response. Numerical study shows that this approach can be used to set up the simplified FE model of multilayer plates.

Numerical Simulation of Accident Scenario in High Temperature Gas Cooled (Pebble Bed) Nuclear Reactors

2012 ◽  
Author(s):  
Geoffrey J. Peter
Keyword(s):  
Numerical Simulation ◽  
High Temperature ◽  
Boundary Conditions ◽  
Nuclear Reactors ◽  
Numerical Study ◽  
Packed Bed ◽  
Pebble Bed ◽  
Accident Scenario ◽  
Set Up ◽  
High Temperature Gas

The accident scenario resulting from blockages due to the retention of dust in the coolant gas or from the rupture of one or more fuel particles used in the High Temperature Gas Cooled (Pebble Bed) Nuclear Reactors considered for the next generation of Advanced High Temperature Reactors (AHTR), for nuclear power production, and for high-temperature hydrogen production using nuclear reactors to reduce the carbon footprint is examined in this paper. Blockages can cause local variations in flow and heat transfer that may lead to hot spots within the bed that could compromise reactor safety. Therefore, it is important to know the void fraction distribution and the interstitial velocity field in the packed bed. The blockage for this numerical study simulated a region with significantly lower void than that in the rest of the bed. Finite difference technique solved the simplified continuity, momentum, and energy equations. Any meaningful outcome of the solution depended largely upon the validity of the boundary conditions. Among them, the inlet and outlet velocity profiles required special attention. Thus, a close approximation to these profiles obtained from an experimental set-up established the boundary conditions. This paper presents the development of the elliptic-partial differential equation for a bed of pebbles, and the solution procedure. The paper also discusses velocity and temperature profiles obtained from both numerical and experimental setup, with and without effect of blockage. In addition, the paper compares the results obtained from the experimental set-up with numerical simulation using a commercially available code that uses finite element techniques.

scholarly journals A Hybrid BEM-CFD Virtual Blade Model to Predict Interactions between Tidal Stream Turbines under Wave Conditions

2020 ◽  
Vol 8 (12) ◽  
pp. 969
Author(s):  
Nicolo’ Lombardi ◽  
Stephanie Ordonez-Sanchez ◽  
Stefania Zanforlin ◽  
Cameron Johnstone
Keyword(s):  
Numerical Study ◽  
Experimental Tests ◽  
Full Scale ◽  
Small Scale ◽  
Ansys Fluent ◽  
Narrow Channels ◽  
Tidal Turbine ◽  
Performance Deterioration ◽  
Set Up ◽  
Blade Model

Tidal turbine array optimization is crucial for the further development of the marine sector. It has already been observed that tidal turbines within an array can be heavily affected by excessive aerodynamic interference, thus leading to performance deterioration. Small-scale experimental tests aimed at understanding the physical mechanisms of interaction and identifying optimal distances between machines can be found in the literature. However, often, the relatively narrow channels of laboratories imply high blockage ratios, which could affect the results, making them unreliable if extrapolated to full-scale cases. The main aim of this numerical study was to analyze the effects of the blockage caused by the laboratory channel walls in cases of current and also current surface waves. For this purpose, the performance predictions achieved for two turbines arranged in line for different lateral offsets in case of a typical laboratory scale were compared to the predictions obtained for a full scale, unconfined environment. The methodology consisted in the adoption a hybrid Blade Element Momentum–Computational Fluid Dynamics (BEM-CFD) approach, which was based on the Virtual Blade Model of ANSYS-Fluent. The results indicate that (1) the performance of a downstream turbine can increase up to 5% when this has a lateral separation of 1.5D from an upstream device in a full-scale environment compared to a misleading 15% calculated for the laboratory set-up, and (2) the relative fluctuations of power and thrust generated by waves are not significantly affected by the domain dimensions.

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