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I am a PhD Candidate at FLAME Lab in Department of Computational and Data Sciences , IISc . |
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| IIT Madras 2018-2020 |
IISc 2020-present |
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Large-eddy simulation of a planar offset wall-jet with heat transfer: Characterization, turbulent kinetic energy and Reynolds shear stress budgets
Planar wall-attaching offset jets can be found in a variety of engineering applications. In the present work, a planar turbulent offset wall-jet, at a Reynolds number of 7500 and an offset-ratio of 5, with heat transfer is numerically studied using large-eddy simulation (LES). First, a grid sensitivity study is performedand the quality of the mesh used is assessed using LES index of quality of resolution and an appropriate mesh is selected. Next, the solver is validated for mean streamwise velocity, streamwise Reynolds normal stress, and the evolution of coefficient of pressure on the wall, using reference experimental data from the literature. Thereafter, the unsteady flow features of the jet, maximum velocity decay and jet-spread, statistical features of flow and temperature, and turbulent kinetic energy (TKE) budgets and in-plane component of Reynolds shear stress are studied. The streamwise evolution of Nusselt number on the wall shows three distinct peaks and the location of these peaks correlates with a change-of-sign of the wall skin-friction coefficient. The domain can be categorized into three distinct regions namely, the re- circulation, impingement and wall-jet regions. Distinct flow and thermal characteristics are observed de- pending on the region of interest. The peak magnitudes of Reynolds normal and shear stresses increase as one moves from the recirculation region to the impingement region and decreases thereafter attaining a lowest value in the wall-jet region. The heat transfer from the wall is observed to be most effective in the recirculation region. The production of TKE is dominant in all the three regions of the flow, whereas the Reynolds shear stress budgets indicate that the production and velocity–pressure-gradient terms are dominant and balance each other in all the three regions of the flow DOI: [https://doi.org/10.1016/j.ijheatmasstransfer.2022.122847] |
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Large-eddy simulation of a planar offset-jet with heat transfer: The effects of ventilation
Several industrial and engineering applications employ ventilated offset-jets such as flow separation con- trol devices, upper surface blowing used in short take-off and landing aircraft, drying processes, and fuel injection systems. The design and efficient operation of these devices relies on controlling the turbulence levels, heat transfer rates, and the locations of flow reattachment points. Therefore, an understanding of the flow and thermal characteristics of ventilated offset-jets helps in the design and operation of these devices. The present study aims to address this by performing large-eddy simulations (LES) of a planar turbulent offset-jet for different velocities of the ventilated-jet. To understand and quantify the effects of ventilation on the offset-jet, a range of velocity-ratios of 0, 0.1, 0.14, and 0.18 are considered for a primary offset-jet Reynolds number of 14,0 0 0. First, a grid-sensitivity study is performed to establish the convergence of the solver and the LES index of quality of resolution is obtained to ascertain the quality of the mesh. Thereafter, the mean and second-order statistics of the streamwise component of velocity are compared with reference data from the literature to validate the numerical solver. The effects of ventilation on the offset-jet are studied using the decay of streamwise velocity, jet-spread, the evolution of pressure coefficient, friction coefficient, the mean Nusselt number, and the unsteady characteristics. As the velocity-ratio increases, the suction pressure in the initial region of the domain decreases, which causes the jet to spread away from the bottom wall. Further the peak magnitudes of the mean Nusselt number and coefficient of pressure decrease exponentially with an increase in the velocity-ratio. The peak magnitude of the mean Nusselt number for the unventilated-jet case – the offset-jet without the ventilated-jet – is the largest and its value for the ventilated-jet cases decreases as the velocity-ratio is increased. It is concluded that in the initial region, the ventilated-jet has a profound effect on the offset-jet flow and as the flow develops into a wall-jet the effects of ventilation vanish. DOI: [https://doi.org/10.1016/j.ijheatmasstransfer.2023.124061] |
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Cloned from Jon Barron. |