Browsing by Author "De, S."

Now showing 1 - 4 of 4

Numerical simulation of a compressible vortex–wall interaction
(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Thangadurai, T.; De, S.; Sreevatsa, A.; Dutta, S.
The wall interaction of isolated compressible vortices generated from a short driver section shock tube has been simulated numerically by solving the Navier–Stokes equations in axisymmetric form. The dynamics of shock-free (incident shock Mach number M= 1.36) and shock-embedded (M= 1.57) compressible vortices near the wall has been studied in detail. The AUSM+ scheme with a fifth-order upwind interpolation formula is used for the convective fluxes. Time integration is performed using a low dissipative and dispersive fourth-order six-stage Runge–Kutta scheme. The evolution of primary and wall vortices has been shown using the velocity field, vorticity field, and numerical schlierens. The vortex impingement, shocklets, wall vortices, and their lift-off are clearly identified from the wall pressure time history. It has been observed that the maximum vorticity of the wall vortices reaches close to 30 % of the primary vortex for M= 1.36 and it reaches up to 60 % for M= 1.57. The net pressure force on the wall due to incident shock impingement is dominant compared to the compressible vortex impingement and their evolution. © 2016, Springer-Verlag Berlin Heidelberg.
Orthovanillin azine ester as a potential functional material for organic electronic devices
(Elsevier B.V., 2023) Kagatikar, S.; Acharya, S.; Mp, Y.; Dhanya, D.; Kekuda, D.; Abdul Salam, A.A.; Sudhakar, S.N.; Mn, S.; De, S.
The present study reports the synthesis of OVAE, an ester of ortho-vanillin azine, and its structural characterization using spectral and single crystal-XRD studies. Intermolecular interactions of OVAE are investigated using the Hirshfield surface analysis, 3D Hirshfield surface maps, 2D fingerprint plots, and electrostatic energy frameworks. Good thermal stability in thermogravimetric analysis, irreversible redox peaks in electrochemical studies, high carrier concentration and dielectric constant in electrical measurements, uniform films observed upon surface morphology examination, fabrication of a diode, the obtained current-voltage characteristics, dielectric constant and frequency-dependent AC conductivities directed towards the use of OVAE as a potential semiconducting functional material in suitable electronic devices. Based on cyclic voltammetry and AC impedance response, the performance of OVAE as an electrode material is explored by constructing a supercapacitor, which exhibited a specific capacitance of 56 Fg−1 at 10 mV s−1. © 2023 Elsevier B.V.
Simulation of laminar flow in a three-dimensional lid-driven cavity by lattice Boltzmann method
(2009) De, S.; Nagendra, K.; Lakshmisha, K.N.
Purpose: The purpose of this paper is to apply lattice Boltzmann equation method (LBM) with multiple relaxation time (MRT) model, to investigate lid-driven flow in a three-dimensional (3D), rectangular cavity, and compare the results with flow in an equivalent two-dimensional (2D) cavity. Design/methodology/approach: The second-order MRT model is implemented in a 3D LBM code. The flow structure in cavities of different aspect ratios (0.25-4) and Reynolds numbers (0.01- 1000) is investigated. The LBM simulation results are compared with those from numerical solution of Navier-Stokes (NS) equations and with available experimental data. Findings: The 3D simulations demonstrate that 2D models may predict the flow structure reasonably well at low Reynolds numbers, but significant differences with experimental data appear at high Reynolds numbers. Such discrepancy between 2D and 3D results are attributed to the effect of boundary layers near the side-walls in transverse direction (in 3D), due to which the vorticity in the core-region is weakened in general. Secondly, owing to the vortex stretching effect present in 3D flow, the vorticity in the transverse plane intensifies whereas that in the lateral plane decays, with increase in Reynolds number. However, on the symmetry-plane, the flow structure variation with respect to cavity aspect ratio is found to be qualitatively consistent with results of 2D simulations. Secondary flow vortices whose axis is in the direction of the lid-motion are observed; these are weak at low Reynolds numbers, but become quite strong at high Reynolds numbers. Originality/value: The findings will be useful in the study of variety of enclosed fluid flows. Emerald Group Publishing Limited.
Simulation of laminar flow in a three-dimensional lid-driven cavity by lattice Boltzmann method
(2009) De, S.; Nagendra, K.; Lakshmisha, K.N.
Purpose: The purpose of this paper is to apply lattice Boltzmann equation method (LBM) with multiple relaxation time (MRT) model, to investigate lid-driven flow in a three-dimensional (3D), rectangular cavity, and compare the results with flow in an equivalent two-dimensional (2D) cavity. Design/methodology/approach: The second-order MRT model is implemented in a 3D LBM code. The flow structure in cavities of different aspect ratios (0.25-4) and Reynolds numbers (0.01- 1000) is investigated. The LBM simulation results are compared with those from numerical solution of Navier-Stokes (NS) equations and with available experimental data. Findings: The 3D simulations demonstrate that 2D models may predict the flow structure reasonably well at low Reynolds numbers, but significant differences with experimental data appear at high Reynolds numbers. Such discrepancy between 2D and 3D results are attributed to the effect of boundary layers near the side-walls in transverse direction (in 3D), due to which the vorticity in the core-region is weakened in general. Secondly, owing to the vortex stretching effect present in 3D flow, the vorticity in the transverse plane intensifies whereas that in the lateral plane decays, with increase in Reynolds number. However, on the symmetry-plane, the flow structure variation with respect to cavity aspect ratio is found to be qualitatively consistent with results of 2D simulations. Secondary flow vortices whose axis is in the direction of the lid-motion are observed; these are weak at low Reynolds numbers, but become quite strong at high Reynolds numbers. Originality/value: The findings will be useful in the study of variety of enclosed fluid flows.© Emerald Group Publishing Limited.