Analysis of Combined Conductive and Radiative Heat Transfer in a Two Dimensional Square Enclosure using the Finite Volume Method

An efficient tool to deal with multidimensional radiative heat transfer is in strong demand to analyse the various thermal problems combined either with other modes of heat transfer or with combustion phenomena. Combined conduction and radiation heat transfer without heat generation is investigated. Analysis is carried out for both steady and unsteady situations. Two-dimensional gray Cartesian enclosure with an absorbing, emitting, and isotropically scattering medium is considered. Enclosure boundaries are assumed at specified temperature. The finite volume method is used to solve the energy equation and the finite volume method is used to compute the radiative information required in the solution of energy equation. The Implicit scheme is used to solve the transient energy equation. Transient and steady state temperature and heat flux distributions are found for various radiative parameters. In the last two decade, finite volume method (FVM) emerged as one of the most attractive method for modeling steady as well as transient state radiative transfer. The finite volume method is a method for representing and evaluating partial differential equations as algebraic equations. Similar to the finite difference method, values are calculated at discrete places on a meshed geometry. "Finite volume" refers to the small volume surrounding each node point on a mesh. In the finite volume method, volume integrals in a partial differential equation that contain a divergence term are converted to surface integral using divergence theorem. These terms are then evaluated as fluxes at the surfaces of each finite volume. Because the flux entering a given volume is identical to that leaving the adjacent volume, these methods are conservative. In the present work the boundaries are assumed to be gray and the medium scatters isotropically. The current study examines the finite volume method (FVM) for coupled radiative and conductive heat transfer in square enclosures in which either a non-scattering or scattering medium is included. Implicit Scheme has been used for solving the coupled conductive and radiative heat transfer equation. The transient temperature distributions are studied for the effects of various parameters like the extinction coefficient, the scattering albedo and the conduction radiation parameter for both constant. The effect of radiative parameters on the system to reach the steady state is also studied

Comparison of CFBP, FFBP, and RBF Networks in the Field of Crack Detection

The issue of crack detection and its diagnosis has gained a wide spread of industrial interest. The crack/damage affects the industrial economic growth. So early crack detection is an important aspect in the point of view of any industrial growth. In this paper a design tool ANSYS is used to monitor various changes in vibrational characteristics of thin transverse cracks on a cantilever beam for detecting the crack position and depth and was compared using artificial intelligence techniques. The usage of neural networks is the key point of development in this paper. The three neural networks used are cascade forward back propagation (CFBP) network, feed forward back propagation (FFBP) network, and radial basis function (RBF) network. In the first phase of this paper theoretical analysis has been made and then the finite element analysis has been carried out using commercial software, ANSYS. In the second phase of this paper the neural networks are trained using the values obtained from a simulated model of the actual cantilever beam using ANSYS. At the last phase a comparative study has been made between the data obtained from neural network technique and finite element analysis

Crack Assessment of Beam Structures from Changes in Natural Frequencies Using Meta-heuristic Approaches

The existence of a crack in the machine and structural components has a severe impact on the performance and integrity of the engineering structure. Failure to identify cracks has several outcomes and sometimes may lead to potential failures of the whole structure. The contributed research work addresses the theoretical and experimental assessment of the influence of a surface open crack on vibration responses of cantilever aluminum beam with rectangular geometry and an inverse analysis to evaluate and to estimate the position and intensity of crack magnitude of the cracked cantilever beam using different metaheuristic approaches. In the theoretical study, variation of natural frequencies due to the presence of crack are determined using the local stiffness matrix resulting from the matrix inversion of flexibility coefficients that the crack develops in its vicinity. Several experiments are performed in the laboratory to verify results obtained from the theoretical study. The results obtained revealed that the variation of the natural frequency could be employed as a viable parameter to show the crack existence and magnitude. The focus of the present thesis work is to carry out an inverse analysis to determine the position and intensity of crack using natural frequency data. The solution of the inverse problem is to obtain crack details by minimizing an objective function based on natural frequencies. The frequency based objective function is solved by employing different simple and reliable meta-heuristic algorithms. The differential evolution (DE) and its modified version, called modified differential evolution (MDE) have been employed to estimate the position and depth of a crack. Particle swarm optimization (PSO), a population-based meta-heuristic approach, utilizes swarm intelligence to determine the position and depth of a crack. Two different variants of PSO algorithm is employed in the area of crack detection to estimate the crack details. The first variant investigates the influence of variation of inertia weight parameter in predicting the position and severity of a crack present in the cantilever beam. The second variant embedded a squeezing strategy in the PSO mechanism, called modified PSO (MPSO) to accelerate the convergence speed for obtaining optimal crack variables. The velocity update equation of PSO is further refined by employing the concept of game theory, called as game theoretic PSO (GTPSO). The last part of the thesis work presents the design of hybrid algorithm by merging the desirable characteristics of DE and PSO to alleviate their individual shortcomings. Two different strategies are adopted to integrate DE and PSO for estimation of crack position and crack depth. The first case employs a cooperative strategy between DE and PSO and called DEPSO algorithm. In the second case, a differential parameter borrowed from DE is embedded in the velocity equation of PSO and called PSODV algorithm. A comparative analysis of the proposed techniques implemented in the current research is critically examined. The outcome of comparative analysis reveals that the hybridized DEPSO algorithm outperforms other proposed techniques explored in the area of crack detection in terms of predicting the crack position and crack depth with reasonable accuracy

Common variation near CDKN1A, POLD3 and SHROOM2 influences colorectal cancer risk

We performed a meta-analysis of five genome-wide association studies to identify common variants influencing colorectal cancer (CRC) risk comprising 8,682 cases and 9,649 controls. Replication analysis was performed in case-control sets totaling 21,096 cases and 19,555 controls. We identified three new CRC risk loci at 6p21 (rs1321311, near CDKN1A; P = 1.14 × 10 -10), 11q13.4 (rs3824999, intronic to POLD3; P = 3.65 × 10 -10) and Xp22.2 (rs5934683, near SHROOM2; P = 7.30 × 10 -10) This brings the number of independent loci associated with CRC risk to 20 and provides further insight into the genetic architecture of inherited susceptibility to CRC.</p