Faculty Publications
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Publications by NITK Faculty
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Item Real-Time Hardware Implementation of 3D Sound Synthesis(Institute of Electrical and Electronics Engineers Inc., 2020) Sathwik, G.S.; Acharya, B.K.; Ali, B.; Deepu, S.P.; Sumam David, S.In this paper, hardware design and implementation to realize the effect of 3D sound with time-varying FIR filters are presented. 3D sound is a type of audio that encapsulates and recreates the effect identical to the way our ears normally experience. The spatial location of sound results in its three dimensional aspect. To synthesize it from a stereo recording, Head Related Transfer Functions (HRTFs), which describe the spectral behaviour of sounds coming from a particular direction are used. FIR filters derived from this transfer function are applied to the incoming sound, yielding spatial effect. The system was implemented using 180 nm technology libraries targeting an Application Specific Integrated Circuit (ASIC) and the functionality was validated in real-time on FPGA. © 2020 IEEE.Item Coupled computational fluid dynamics-discrete element method simulations of a pilot-scale batch crystallizer(American Chemical Society service@acs.org, 2015) Ali, B.; Börner, M.; Peglow, M.; Janiga, G.; Seidel-Morgenstern, A.; Thévenin, D.Computational fluid dynamics (CFD) coupled with the discrete element method (DEM) has been used to investigate numerically crystal dynamics in an existing pilot-scale batch crystallizer. The CFD-DEM combination provides a detailed description of crystal dynamics considering a four-way coupling. In a previous analysis,1 CFD had been coupled with a discrete phase model (DPM) using a simple one-way coupling. The corresponding predictions are then compared with those obtained through four-way coupling considering KH2PO4 crystals in water. From the CFD-DEM simulation, it is possible to investigate quantitatively the driving force controlling crystal growth and the interaction of crystals with reactor walls, baffles, and impellers. This delivers essential data for process improvement. Different seeding procedures were also compared. The seed crystals have been injected either within the complete liquid volume or, as in the experiments, through a funnel. By varying the most important crystallization process parameters, we found optimal conditions for a liquid phase volume in the crystallizer of 24 L, for injection through a funnel above the baffle, and for an initial seed crystal size of 0.5 mm. © 2014 American Chemical Society.Item Numerical investigation of engulfment flow at low Reynolds numbers in a T-shaped microchannel(American Institute of Physics Inc. claims@aip.org, 2020) Madana, V.S.T.; Ali, B.Microreactors play a major role in the intensification of industrial processes. The performance of microfluidic devices depends on the flow behavior and flow regimes present in such systems. In this work, single-phase flow behavior and associated flow regimes in a T-shaped microchannel are numerically analyzed using computational fluid dynamics (CFD). To predict the single-phase flow regimes, three dimensional transient CFD simulations are performed. The critical Reynolds number (Re) at which flow regime transition and onset of engulfment occur is identified (Recritical = 300). To achieve engulfment flow at lower Re, the inlet geometry of the microchannel is modified as a convergent (C)-divergent (D) section and its effect on engulfment flow is analyzed. When the C/D ratio is 9:1, the predicted pressure drop (?p) is found to be minimum (Recritical = 75, ?p = 5.4 kPa). The understanding of the engulfment flow regime is exploited through residence time distribution (RTD). The predicted RTD profiles indicate strong recirculation among vortices. The mixing index is calculated to quantify RTD, and it is found to be minimum when the C/D ratio is 9:1. The mixing performance is further verified by introducing buoyant particles in Lagrangian manner using discrete phase modeling. The predicted dynamics are qualitatively and quantitatively analyzed through Poincaré maps and Shannon's entropy for various convergent-divergent inlets to characterize mixing. Once again, the C/D ratio of 9:1 supports in enhancing mixing in the microchannel. Hence, the proposed micromixer based on geometric modifications at the inlet helps achieve the engulfment flow regime at low Re. © 2020 Author(s).Item Computational investigation of air solid flow in a spray dryer for effluent treatment(Scientific Publishers, 2020) Singh, S.K.; Ali, B.In this work, the hydrodynamics and evaporation rate of the co-current spray dryer is numerically investigated through ANSYS Fluent (CFD). The performance of the spray dryer depends on the geometry, operating conditions, and underlying hydrodynamics in such systems. To predict the air-solid flow in a spray dryer, the Euler-Lagrangian CFD model is used to track the particles in the dryer. The continuous phase turbulence is predicted using RNG version of k-turbulence model. To quantify the flow pattern, a horizontal line is considered and spatial variation of velocity profiles are analyzed. The predicted air velocity variation was found to be maximum at the center of the core. Further, the airflow pattern is analyzed for various operating temperatures and feed properties. It was found that airflow pattern influences particle behavior with minimum deposition rates on each section of the wall when air temperature is 350 K. © 2020 Scientific Publishers. All rights reserved.Item Computational investigation of hydrodynamics and drying of industrial sludge waste in a spouted bed column(Scientific Publishers, 2020) Santhosh Kumar, N.; Ali, B.The disposal of sludge from waste water treatment plants adversely affects the environment. Since sludge wastes are sticky, drying of such waste water sludge is challenging. Conventionally, these sludges are dried in open spaces where a large area of land is required which is a time-consuming process. To overcome this, spouted bed is used in the present investigation. The spouted bed is a gas-solid contactor for handling coarse particles of size greater than 1 mm with low operating pressure. In this work, hydrodynamics of waste water sludge in a conventional spouted bed is numerically investigated using Computational Fluid Dynamics (CFD). Euler-Eulerian CFD model is used to study the flow pattern in such system. The continuous phase turbulence (air) is modeled using standard - model. The spouting height and solid circulation rate are calculated to analyze spouting behavior. This is compared with a draft tube spouted bed system and found that the draft tube supports in enhancing the spouting characteristics of the bed. Further, an optimum draft tube configuration is found that promotes solid circulation rate. The drying characteristics are analyzed for various operating conditions and found that the temperature of air significantly improves the rate of drying. © 2020 Scientific Publishers. All rights reserved.