The electrochemical behaviour and surface changes on AA6061-T6 alloy exposed to Caribbean seawater from the Cozumel Channel for 30 days under laminar flow (0.1 ms−1) were studied, these contrasting then with stationary conditions. Open circuit potential monitoring and electrochemical current fluctuations, considered as electrochemical noise (EN), were employed as two nondestructive methods. The calculated corrosion current, based on Rn, was one order higher in laminar flow. The fluctuations of current were transformed in the frequency domain. Their power spectral density (PSD) plots were obtained in order to gain information concerning the dynamic of the spontaneous release of energy during the corrosion process. The value of the exponent β in PSD graphs suggested that the localised corrosion on AA6061-T6 surface occurs as a persistent stationary process, which dynamic is controlled by oxygen diffusion. The changes in the morphology and elemental composition of the formed layers revealed that the localised attacks occurred in the vicinity of intermetallic particles rich in Fe and Cu, which act as cathodes.
{"title":"Effect of Laminar Flow on the Corrosion Activity of AA6061-T6 in Seawater","authors":"G. Acosta, L. Veleva, L. Chávez, J. L. Lopez","doi":"10.3390/met10020175","DOIUrl":"https://doi.org/10.3390/met10020175","url":null,"abstract":"The electrochemical behaviour and surface changes on AA6061-T6 alloy exposed to Caribbean seawater from the Cozumel Channel for 30 days under laminar flow (0.1 ms−1) were studied, these contrasting then with stationary conditions. Open circuit potential monitoring and electrochemical current fluctuations, considered as electrochemical noise (EN), were employed as two nondestructive methods. The calculated corrosion current, based on Rn, was one order higher in laminar flow. The fluctuations of current were transformed in the frequency domain. Their power spectral density (PSD) plots were obtained in order to gain information concerning the dynamic of the spontaneous release of energy during the corrosion process. The value of the exponent β in PSD graphs suggested that the localised corrosion on AA6061-T6 surface occurs as a persistent stationary process, which dynamic is controlled by oxygen diffusion. The changes in the morphology and elemental composition of the formed layers revealed that the localised attacks occurred in the vicinity of intermetallic particles rich in Fe and Cu, which act as cathodes.","PeriodicalId":123276,"journal":{"name":"Direct Numerical Simulations - An Introduction and Applications","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127694240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-13DOI: 10.5772/intechopen.90017
V. Biryukov
Combustible systems generally consist of two types of chemically interacting components during combustion: an oxidizing agent (oxygen, fluorine, chlorine, their compounds) and fuel (hydrogen, hydrocarbons, nitrogen and hydrogen compounds, aluminum, etc.). The chemical properties of the components, their phase state, and their physical structure are essential when choosing the methods for supplying the components and organizing the processes in the combustion chambers, but they relatively weakly affect the basic laws of combustion processes. In the theory of combustion, the problems of burning homogeneous, premixed, gaseous components are studied in most detail. The concepts and methods of the theory of combustion are used in other areas of science and technology when considering exothermic processes with high heat generation. The separation of the issues of flame stability into diffusion-thermal and hydrodynamic problems, which is often encountered in theoretical works, is conditional and is caused by the desire to reduce the mathematical difficulties that arise when solving the problem in the general formulation. In fact, flame instability is determined by the influence of both transport processes in the flame (diffusion-thermal processes), depending on its structure, and hydrodynamic processes, i.e., the effects of gas flow. The determination of the concentration limits of flame propagation, ignition, and extinction, spontaneous instability of the flame front, the transition of combustion to detonation, and the excitation of oscillations during combustion are practical problems of the theory of combustion. Acoustic combustion instability can be considered as a self-oscillating process in which the feedback providing the energy necessary for maintaining undamped wave motions from a nonperiodic heat source (combustion process) is realized through the action of sound (acoustic) waves on combustion; in this case, the parameters of the wave motions, amplitude, waveform, and frequency, are determined by the internal properties of the system itself. This chapter provides a sequence of parametric estimates of acoustic instability during combustion in cylindrical chambers.
{"title":"Bases of Combustion Instability","authors":"V. Biryukov","doi":"10.5772/intechopen.90017","DOIUrl":"https://doi.org/10.5772/intechopen.90017","url":null,"abstract":"Combustible systems generally consist of two types of chemically interacting components during combustion: an oxidizing agent (oxygen, fluorine, chlorine, their compounds) and fuel (hydrogen, hydrocarbons, nitrogen and hydrogen compounds, aluminum, etc.). The chemical properties of the components, their phase state, and their physical structure are essential when choosing the methods for supplying the components and organizing the processes in the combustion chambers, but they relatively weakly affect the basic laws of combustion processes. In the theory of combustion, the problems of burning homogeneous, premixed, gaseous components are studied in most detail. The concepts and methods of the theory of combustion are used in other areas of science and technology when considering exothermic processes with high heat generation. The separation of the issues of flame stability into diffusion-thermal and hydrodynamic problems, which is often encountered in theoretical works, is conditional and is caused by the desire to reduce the mathematical difficulties that arise when solving the problem in the general formulation. In fact, flame instability is determined by the influence of both transport processes in the flame (diffusion-thermal processes), depending on its structure, and hydrodynamic processes, i.e., the effects of gas flow. The determination of the concentration limits of flame propagation, ignition, and extinction, spontaneous instability of the flame front, the transition of combustion to detonation, and the excitation of oscillations during combustion are practical problems of the theory of combustion. Acoustic combustion instability can be considered as a self-oscillating process in which the feedback providing the energy necessary for maintaining undamped wave motions from a nonperiodic heat source (combustion process) is realized through the action of sound (acoustic) waves on combustion; in this case, the parameters of the wave motions, amplitude, waveform, and frequency, are determined by the internal properties of the system itself. This chapter provides a sequence of parametric estimates of acoustic instability during combustion in cylindrical chambers.","PeriodicalId":123276,"journal":{"name":"Direct Numerical Simulations - An Introduction and Applications","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128281087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-02DOI: 10.5772/intechopen.90632
Dipal M Patel, M. Agelin-Chaab
Most of practical combustion occurs in turbulent flows which involve strong coupling between turbulence and chemical processes. The heat release from combustion alters the fluid properties such as density and viscosity and in turns affects the turbulence. Direct numerical simulations (DNS) provides a tool for obtaining both temporally and spatially resolved data in three dimension (3D). This chapter presents a brief overview of importance of DNS in turbulent combustion, the role of turbulence and identifies different combustion modes. The mathematical formulation and numerical implementation for DNS are introduced. The second half of this chapter presents DNS results for ignition in both homogeneous and stratified mixtures. It has been found that minimum ignition energy is required to obtain successful ignition in different turbulence regimes. An increase in turbulent velocity fluctuation may leads to a misfire. Additionally the difference between growing flames and those which are quenched by turbulence have been discussed with the help of the reaction–diffusion balance analysis. Furthermore, the turbulence intensity and length scale of the mixture inhomogeneity have important influences on achieving self-sustained combustion following successful ignition events.
{"title":"DNS for Turbulent Premixed Combustion","authors":"Dipal M Patel, M. Agelin-Chaab","doi":"10.5772/intechopen.90632","DOIUrl":"https://doi.org/10.5772/intechopen.90632","url":null,"abstract":"Most of practical combustion occurs in turbulent flows which involve strong coupling between turbulence and chemical processes. The heat release from combustion alters the fluid properties such as density and viscosity and in turns affects the turbulence. Direct numerical simulations (DNS) provides a tool for obtaining both temporally and spatially resolved data in three dimension (3D). This chapter presents a brief overview of importance of DNS in turbulent combustion, the role of turbulence and identifies different combustion modes. The mathematical formulation and numerical implementation for DNS are introduced. The second half of this chapter presents DNS results for ignition in both homogeneous and stratified mixtures. It has been found that minimum ignition energy is required to obtain successful ignition in different turbulence regimes. An increase in turbulent velocity fluctuation may leads to a misfire. Additionally the difference between growing flames and those which are quenched by turbulence have been discussed with the help of the reaction–diffusion balance analysis. Furthermore, the turbulence intensity and length scale of the mixture inhomogeneity have important influences on achieving self-sustained combustion following successful ignition events.","PeriodicalId":123276,"journal":{"name":"Direct Numerical Simulations - An Introduction and Applications","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134020089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-18DOI: 10.5772/intechopen.90470
I. J. Shaw, J. Kildare, M. Evans, A. Chinnici, Ciaran A.M. Sparks, S. Rubaiyat, R. Chin, P. Medwell
Rotating detonation engines are a novel device for generating thrust from combustion, in a highly efficient, yet mechanically simple form. This chapter presents a detailed literature review of rotating detonation engines. Particular focus is placed on the theoretical aspects and the fundamental operating principles of these engines. The review covers both experimental and computational studies, in order to identify gaps in current understanding. This will allow the identification of future work that is required to further develop rotating detonation engines.
{"title":"A Theoretical Review of Rotating Detonation Engines","authors":"I. J. Shaw, J. Kildare, M. Evans, A. Chinnici, Ciaran A.M. Sparks, S. Rubaiyat, R. Chin, P. Medwell","doi":"10.5772/intechopen.90470","DOIUrl":"https://doi.org/10.5772/intechopen.90470","url":null,"abstract":"Rotating detonation engines are a novel device for generating thrust from combustion, in a highly efficient, yet mechanically simple form. This chapter presents a detailed literature review of rotating detonation engines. Particular focus is placed on the theoretical aspects and the fundamental operating principles of these engines. The review covers both experimental and computational studies, in order to identify gaps in current understanding. This will allow the identification of future work that is required to further develop rotating detonation engines.","PeriodicalId":123276,"journal":{"name":"Direct Numerical Simulations - An Introduction and Applications","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125226523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-21DOI: 10.5772/intechopen.90251
L. Habeeb, Riyadh S. Al-Turaihi
This chapter consists of four sections; Introduction, Boundary and initial conditions, Setting of nonuniformly spaced grid, and Simulation approach. The fields of the fluctuating velocity describe the turbulent flows. Such fluctuations blend the transported quantities, like species concentration, energy, and momentum and make the transported quantity fluctuations in addition. Because such fluctuations have a small scale and high frequency, so they are very computationally costly for simulation straightforward in the virtual engineering computations. Alternatively, the instantaneous accurate governing equations can be time-averaged, ensemble-averaged, or in different way handled for removing the small scales, causing a modified group of equations, which are computationally less costly for solving.
{"title":"Turbulent Flow Simulations","authors":"L. Habeeb, Riyadh S. Al-Turaihi","doi":"10.5772/intechopen.90251","DOIUrl":"https://doi.org/10.5772/intechopen.90251","url":null,"abstract":"This chapter consists of four sections; Introduction, Boundary and initial conditions, Setting of nonuniformly spaced grid, and Simulation approach. The fields of the fluctuating velocity describe the turbulent flows. Such fluctuations blend the transported quantities, like species concentration, energy, and momentum and make the transported quantity fluctuations in addition. Because such fluctuations have a small scale and high frequency, so they are very computationally costly for simulation straightforward in the virtual engineering computations. Alternatively, the instantaneous accurate governing equations can be time-averaged, ensemble-averaged, or in different way handled for removing the small scales, causing a modified group of equations, which are computationally less costly for solving.","PeriodicalId":123276,"journal":{"name":"Direct Numerical Simulations - An Introduction and Applications","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115258388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-19DOI: 10.5772/intechopen.89691
H. A. Al-Zubaidi, S. Wells
The hydrodynamic numerical modeling is increasingly becoming a widely used tool for simulating the surface waterbodies including rivers, lakes, and reservoirs. A challenging step in any model development is the verification tests, especially at the early stage of development. In this study, a unique approach was developed by implementing the volume balance principle in order to verify the three-dimensional hydrodynamic models for surface waterbody simulation. A developed and verified three-dimensional hydrodynamic and water quality model, called W3, was employed by setting a case study model to be verified using the volume balance technique. The model was qualified by calculating the error in the accumulated water volume within the domain every time step. Results showed that the volume balance reached a constant error over the simulation period, indicating a robust model setup.
{"title":"A Unique Volume Balance Approach for Verifying the Three-Dimensional Hydrodynamic Numerical Models in Surface Waterbody Simulation","authors":"H. A. Al-Zubaidi, S. Wells","doi":"10.5772/intechopen.89691","DOIUrl":"https://doi.org/10.5772/intechopen.89691","url":null,"abstract":"The hydrodynamic numerical modeling is increasingly becoming a widely used tool for simulating the surface waterbodies including rivers, lakes, and reservoirs. A challenging step in any model development is the verification tests, especially at the early stage of development. In this study, a unique approach was developed by implementing the volume balance principle in order to verify the three-dimensional hydrodynamic models for surface waterbody simulation. A developed and verified three-dimensional hydrodynamic and water quality model, called W3, was employed by setting a case study model to be verified using the volume balance technique. The model was qualified by calculating the error in the accumulated water volume within the domain every time step. Results showed that the volume balance reached a constant error over the simulation period, indicating a robust model setup.","PeriodicalId":123276,"journal":{"name":"Direct Numerical Simulations - An Introduction and Applications","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133568490","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-27DOI: 10.5772/INTECHOPEN.87190
I. Sochet, K. Gault, L. Hakenholz
Confined explosions represent a serious safety hazard as significant damage to humans and structures is observed, unlike in free-field explosions. An experimental small-scale study investigated the blast wave in a single-story building. The blast waves were generated by the detonation of a gaseous charge. The building was divided into two rooms by a movable wall which could be positioned at three different locations. The presence of an opening in this movable wall means that two rooms were considered: a transmitter room (TR) and a receptor room (RR). The configuration without the movable wall was also studied. Pressure profiles recorded with pressure gauges at ground level and on the wall presented numerous reflections. The damage effects were severe since the maximum overpressure never fell below 0.2 bar. Although this study is limited to a small scale and gaseous detonation charge, the results can be applied to a large scale and for a TNT charge.
{"title":"Propagation of Shock Waves in Two Rooms Communicating through an Opening","authors":"I. Sochet, K. Gault, L. Hakenholz","doi":"10.5772/INTECHOPEN.87190","DOIUrl":"https://doi.org/10.5772/INTECHOPEN.87190","url":null,"abstract":"Confined explosions represent a serious safety hazard as significant damage to humans and structures is observed, unlike in free-field explosions. An experimental small-scale study investigated the blast wave in a single-story building. The blast waves were generated by the detonation of a gaseous charge. The building was divided into two rooms by a movable wall which could be positioned at three different locations. The presence of an opening in this movable wall means that two rooms were considered: a transmitter room (TR) and a receptor room (RR). The configuration without the movable wall was also studied. Pressure profiles recorded with pressure gauges at ground level and on the wall presented numerous reflections. The damage effects were severe since the maximum overpressure never fell below 0.2 bar. Although this study is limited to a small scale and gaseous detonation charge, the results can be applied to a large scale and for a TNT charge.","PeriodicalId":123276,"journal":{"name":"Direct Numerical Simulations - An Introduction and Applications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129284824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-11-05DOI: 10.5772/INTECHOPEN.81792
M. Polatayko
The well-known formula for the flat detonation wave velocity derived from the Hugoniot system of equations faces difficulties, if being applied to a spherical reactor. A similar formula has been obtained in the framework of the theory of explosion in reacting gas media with the use of a special model describing the transition of an explosive wave in the detonation. The derived formula is very simple, being also more suitable for studying the limiting processes of volume detonation. The conditions for the transition of a shock wave to a detonation wave are studied. Initial detonation conditions required for fast chemical reactions to take place at the front of a spherical explosive wave have been determined. A simple relation describing the critical detonation temperature for various pressures in the hydrogen-oxygen mixture was obtained. Using the known formulas for a shock transition, the critical temperature was coupled with the initial conditions in a static environment, such as the pressure, temperature, and hydrogen content in the mixture.
{"title":"Determination of the Velocity of the Detonation Wave and the Conditions for the Appearance of Spherical Detonation during the Interaction of Hydrogen with Oxygen","authors":"M. Polatayko","doi":"10.5772/INTECHOPEN.81792","DOIUrl":"https://doi.org/10.5772/INTECHOPEN.81792","url":null,"abstract":"The well-known formula for the flat detonation wave velocity derived from the Hugoniot system of equations faces difficulties, if being applied to a spherical reactor. A similar formula has been obtained in the framework of the theory of explosion in reacting gas media with the use of a special model describing the transition of an explosive wave in the detonation. The derived formula is very simple, being also more suitable for studying the limiting processes of volume detonation. The conditions for the transition of a shock wave to a detonation wave are studied. Initial detonation conditions required for fast chemical reactions to take place at the front of a spherical explosive wave have been determined. A simple relation describing the critical detonation temperature for various pressures in the hydrogen-oxygen mixture was obtained. Using the known formulas for a shock transition, the critical temperature was coupled with the initial conditions in a static environment, such as the pressure, temperature, and hydrogen content in the mixture.","PeriodicalId":123276,"journal":{"name":"Direct Numerical Simulations - An Introduction and Applications","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131906263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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