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The present paper presents fluid flow and mixed convective heat transfer characteristics past a semi-circular cylinder at incidence with a tandem square cylinder in cross flow. Using air ( Pr = 0.71 ) as an operating medium, numerical simulations are performed for the range of Reynolds numbers, 10 ≤ Re ≤ 45 and incidence angles, 0 0 ≤ α ≤ 180 0 . The effect of thermal buoyancy is brought about by varying the Richardson number in the range 0 ≤ R i ≤ 2 . The mathematical model is firstly validated with the experimental and numerical results from the literature and found to be in good agreement. The steady separated flow is observed to become unsteady periodic under the superimposed thermal buoyancy. Furthermore, apart from thermal buoyancy effect, angle of incidence is found to play a pivotal role in bringing hydrodynamic instabilities and thereby vortex shedding for such steady mixed convective flows. Functional dependence of drag ( C D ) , lift ( C L ) , and moment ( C M ) coefficients on the combined influence of α and R i , is explored and analysed in detail. Additionally, other global quantities, such as local and average Nusselt number distribution, Strouhal number ( S t ) are determined with respect to the various ranges of parameters considered in the present investigation. [ABSTRACT FROM AUTHOR]

Abstract: Propagation of uncertainty through the physical model has been investigated in the present paper by solving two specific simple stochastic problems using the Non-Intrusive Spectral Projection method. The uncertain parameters are described by either a Gaussian or a LogNormal probability distribution function. For each of the problems, the stochastic and the deterministic mean solutions have been compared and the respective confidence intervals have been obtained. For the deterministic problems, the confidence intervals have been estimated using both one-dimensional and multi-dimensional bound methods. From the results it has been observed that the differences between the stochastic and the deterministic mean solutions are apparent only when large uncertainties are introduced in the random variables. For both the specific problems, considered in the present study, the confidence intervals for the stochastic problems have been exactly predicted by the deterministic limits when uncertainty is introduced only in one of the parameters. For more than one uncertain parameters, the multi-dimensional bound method produces better agreement with the stochastic confidence intervals than the one-dimensional bound method. The findings are expected to be applicable to problems in heat and mass transfer with similar characteristics or input–output relations. [Copyright &y& Elsevier]

Abstract: In the present paper, a numerical model of spot pulsed current GTA welding for partially and fully penetrated weld pools is presented. Heat transfer and fluid flow in the weld pool driven by the combination of electromagnetic force, buoyancy force, surface tension gradient and latent heat are included in our model. A new formulation of the electromagnetic problem is introduced to take into account eddy current in the weld pool. The shape of the free deformable surface under the action of pulsed arc force is also handled after the magneto-hydrodynamic calculation. The numerical model was applied to 304 stainless steel welding. We compare the influence of various pulsed welding parameters such as pulse frequency and current ratio on the weld quality. Experimental study is conducted to compare our numerical prediction with welding macrographies. It shows a good agreement of the model. [Copyright &y& Elsevier]