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Stochastic Analysis of Strip Footings on Elastic Layered Soil
P. Pradeep Kumar,Priti Maheshwari 대한토목학회 2013 KSCE Journal of Civil Engineering Vol.17 No.7
In the present work, Monte Carlo simulation assisted analysis of strip footings resting on elastic layered soil has been carried out. The elastic modulii of soil layers have been treated as a stationary stochastic field characterized by mean, variance, Autocorrelation Function (ACF) and the Autocorrelation Distance (ACD). Realizations of elastic modulii (E), generated by solving a stochastic differential equation, have been fed to a deterministic distributed parameter model to generate realizations of dependent stochastic fields viz. settlement of footing and interfacial vertical stresses. Subsequently these realizations have been analyzed to evolve probability distribution functions, variance and ACF of the dependent stochastic fields. It is revealed that ACF of these fields are independent of the ACF of E. The variance of settlement has been found to increase as the ACD of E increases, implying requirement of a larger factor of safety when random soils display low frequency (macro level) variations. On the other hand variance of the vertical stress is larger at smaller ACD of E, indicating that for vertical stress, larger factor of safety is required when the random soils display high frequency (micro level) variations.
Applications of Dynamic Mode Decomposition to Unstable Shock-Induced Combustion
P. Pradeep Kumar,Jeong-Yeol Choi(최정열),Jinwoo Son(손진우),Chae Hoon Sohn(손채훈) 한국추진공학회 2017 한국추진공학회지 Vol.21 No.2
Dynamic mode decomposition (DMD) method was applied for the further study of periodical characteristics of the unsteady shock-induced combustion. The case of Lehr’s experiments was numerically simulated using 4 levels of grids. FFT result reveals that almost all the grid systems oscillate at frequencies around 430-435 kHz and the measureed one is around 425 kHz. To identify more resonant modes with low frequencies, DMD method is adopted for 4 grid systems. Several major frequencies are extracted and their damping coefficients are calculated at the same time, which is a quantification parameter for combustion stabilization.
Characteristics of Detailed Hydrogen Reaction Mechanisms for Shock Induced Combustion
P.Pradeep Kumar,Jeong-Yeol Choi(최정열) 한국연소학회 2013 KOSCOSYMPOSIUM논문집 Vol.2013 No.12
Hydrogen is one of the best propellant available today, because of its high reactivity, high performance and a green propellant with very low molecular weight, and is widely used in Rockets and Scramjet engines. Detailed Reaction mechanisms have been proposed in the past decades but direct comparison of these mechanisms are very hard to find for combustion especially at high pressure conditions. In this study, we intended for a basic comparison study of the detailed Hydrogen mechanisms for Shock Induced Combustions.
P. Pradeep Kumar,Jeong-Yeol Choi 한국추진공학회 2013 한국추진공학회 학술대회논문집 Vol.2013 No.12
Hydrogen is used as propellants for liquid rockets and scramjet engines for its superior propulsion performance from the light molecular weight. Detailed reaction mechanisms of hydrogen combustion has been established very well because of its simplest chemical composition. Various combustion mechanisms has been published but it is hard to find the direct comparison of those mechanisms. In the present study the basic comparison of laminar flame speed and induction time has been carried out and compared with an available experimental data as a reference for the future application in the combustion analysis of propulsion system and industrial applications.
Numerical Simulation of Detonation with Detailed H2/O2 Reaction Mechanisms
P.Pradeep Kumar,Jeong-Yeol Choi 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.11
Detonation propagation studies is recently getting more attention in these days for its feasibility in aerospace application. Another motivation for this study is the safety concern in industries, since the detonation can cause failure to the mechanical components particularly when the flame accelerates within a pipe or tubes. In this study we numerically simulated a Moderately unstable detonation case with various grid systems and fluid dynamic length scales and have compared in the contents. Moderately Unstable detonation case was selected for this study and detailed Hydrogen-Air Reaction Mechanisms proposed by Jachimowski was used in this study with N2 as inert species.
Analysis of H2/CO Reaction Mechanisms for the Performance prediction of Advanced Propulsion Systems
P. Pradeep Kumar,Kui-Soon Kim,Sejong Oh,Jeong-Yeol Choi 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.11
In High speed propulsion systems such as Dual Combustion Ramjet (DCR) engine and Regeneratively cooled engines, the combustion of syngas is very critical in the prediction of the propulsion systems. Utilization of the fuel for the combustion applications needs a comprehensive understanding of the reaction taking place to accurately predict the propulsive performance of the device. Also, the reaction steps of H2/CO forms the elementary reaction step for many hydrocarbon fuels such as RP-1, methane, etc and this makes the analysis of reaction mechanisms vital for the selection of an appropriate model for the numerical study of propulsive devices. In this study, performance of various reaction model were compared and found that USC model is best suited for wide range of operating conditions.
Comparison of Hydrogen combustions mechanisms for the Analysis of Shock-Induced Combustion
P.Pradeep Kumar,Jeong-Yeol Choi 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.5
Shock Induced Combustion is still an area of interest because of atleast two major reasons: detonation wave research, to determine the structure and stability of detonation waves and supersonic combustion research, to develop a hypersonic air breathing engine in which the supersonic flow is maintained at all points within the device. Various hydrogen reaction models are proposed which itself is in research phase. In this paper, we intended to compare the combustion mechanism by various hydrogen reaction mechanisms in Shock Induced Combustion.