1,721,094 research outputs found
Jayathi Y. Murthy, head and shoulders portrait
No full textPurdue University Faculty. Jayathi Y. Murthy, appointed the Robert V. Adams Professor of Mechanical Engineerin
Jayathi Y. Murthy and student working on computer simulation
No full textJayathi Y. Murthy (standing), a professor in Purdue's School of Mechanical Engineering, works with graduate student Dipali Pradhan on a computer simulation to analyze how heat is transferred through a carbon nanotube. Murthy will lead a new center based at Purdue's Discovery Park to develop advanced simulations for commercial and defense.applications.College of Engineering
Computational Heat Transfer in Complex Systems: A Review of Needs and Opportunities
No full textDuring the few decades, computational techniques for simulating heat transfer in complex industrial systems have reached maturity. Combined with increasingly sophisticated modeling of turbulence, chemistry, radiation, phase change and other physics, powerful computational fluid dynamics (CFD) and computational heat transfer (CHT) solvers have been developed which are beginning to enter the industrial design cycle. In this paper, an overview of emerging simulation needs is first given, and currently-available CFD techniques are evaluated in light of these needs. Emerging computational methods which address some of the failings of current techniques are then reviewed. New research opportunities for computational heat transfer, such as in sub-micron and multiscale heat transport, are reviewed. As computational techniques and physical models become mature, there is increasing demand for predictive simulation, that is, simulation which is not only verified and validated, but whose uncertainty is also quantified. Current work in the area of sensitivity computation and uncertainty propagation is described.</jats:p
Buoyancy-Driven Flow Transitions in Deep Cavities Heated From Below
No full textA numerical investigation has been conducted of flow transitions in deep three-dimensional cavities heated from below. The first critical Rayleigh number, RaI, below which the flow is at rest, and the second critical Rayleigh number, RaII, for transition from steady state to oscillatory flow, have been found for cavities of aspect ratios Ar in the range 1–5. Transition to chaos has also been examined for these cases. The results show that RaI=3583,2.545×104 and 5.5×105 and RaII=4.07×105,1.65×106 and 1.30×107 for aspect ratios of 1, 2, and 5 respectively. The route to chaos is PPeriodic→QP2(Quasi-periodic with two incommensurate frequencies)→QP3(Quasi-periodic with three incommensurate frequencies)→NChaotic for Ar=1 with the Rayleigh number varying from 4.07×105 to 4.89×105. The route is PPeriodic→P2(Periodic doubling)→I(Intermittent)→P(Periodic)→N(Chaotic) for Ar=2 over a Ra range of 1.65×106 to 1.83×106. The interval between periodic and chaotic flow is very short for Ar=5.</jats:p
Interfacial Thermal Transport in Carbon Nanotubes
No full textThere is significant amount of research to analyze the thermal, electrical and other physical properties of carbon nanotubes (CNTs). However, the energy transport mechanism at the contact of two tubes is still not well understood. This study investigates the interfacial thermal interaction between two carbon nanotubes using molecular dynamics simulation and wavelet methods. We place the tubes in a crossed configuration and pass a high temperature pulse along one of the CNTs while keeping other ends fixed, and analyze the interaction of this pulse with other nanotube. We apply this technique for nanotubes of chirality in the range of (5,0) to (10,0) to observe the response of tubes with changing diameter. This thermal pulse analysis shows that the coupling between the two tubes is very weak and may be dominated by the slow moving phonon modes with high energy. We perform a wavelet analysis of thermal pulse propagation along a CNT and its impact on another CNT in cross contact. Wavelet transformations of the heat pulse show how different phonon modes are excited and how they evolve and propagate along the tube axis depending on its chirality.</jats:p
A Numerical Technique for Computing Effective Thermal Conductivity of Fluid-Particle Mixtures
No full textImproved Phonon Transport Modeling Using Boltzmann Transport Equation With Anisotropic Relaxation Times
No full textA sub-micron thermal transport model based on the phonon Boltzmann transport equation (BTE) is developed using anisotropic relaxation times. A previously-published model, the full-scattering model, developed by Wang, directly computes three-phonon scattering interactions by enforcing energy and momentum conservation. However, it is computationally very expensive because it requires the evaluation of millions of scattering interactions during the iterative numerical solution procedure. The anisotropic relaxation time phonon BTE model employs a single-mode relaxation time idea, but the relaxation time is a function of wave-vector. The resulting model is significantly less expensive than the full-scattering model, but incorporates directional and dispersion behavior as well as relaxation times satisfying conservation rules. A critical issue in the model development is the accounting for the role of three-phonon N scattering processes. Direct inclusion of N processes into the anisotropic relaxation time model is not possible because such an inclusion would engender thermal resistance. Following Callaway, the overall relaxation rate is modified to include the shift in the phonon distribution function due to N processes. The relaxation times so obtained are compared with the data extracted from equilibrium molecular dynamics simulation by Henry and Chen. The anisotropic relaxation time phonon BTE model is validated by comparing the predicted bulk thermal conductivities of silicon and silicon thin-film thermal conductivities with experimental measurements.</jats:p
Solution of the Phonon Boltzmann Transport Equation Employing Rigorous Implementation of Phonon Conservation Rules
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