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Roy, Subrata

Publications and source records attributed to Roy, Subrata.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Novel plasma actuator for mitigation of dynamic stall

A novel plasma actuator, the Linear Counter-flow using a Point Embedded Electrode (LCPEE), is developed for the prevention of dynamic stall for a sinusoidal pitching movement between α = 4° and α = 18°. The LCPEE is implemented on a NACA0012 airfoil and tested at a Reynolds Number of Re c = 2 × 105 and reduced frequency of k = π/16. Prior investigations using a standard linear actuator showed that the exposed electrode introduced perturbations passively which delayed dynamic stall when the actuator was off. For the LCPEE actuator, when turned off, there is least passive delay. When the LCPEE is turned on at St f = 50, the dynamic stall is prevented for the sinusoidal pitching motion of the airfoil. The LCPEE actuator is also tested for the same sinusoidal motion between α = 6° and α = 20°. Four cases are considered for the higher α range of motion: actuator off, actuator on at St f = 50 with a sinusoidal input waveform, actuator on at St f = 50 with a triangular input waveform, and actuator on at Stf = 100 with a sinusoidal input waveform. Specifically for the last case, experiment shows no flow reversal demonstrating the efficacy of LCPEE in controlling the dynamic stall. The effects of LCPEE on the flow energy distribution have also been studied by using proper orthogonal decomposition (POD) method.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2009

Electric propulsion device for high power applications

An electric propulsion device is disclosed having an anode and a cathode. The propulsion device includes a discharge annulus having the anode adjacent an end region thereof. At least one inlet aperture is adjacent the anode, the aperture(s) having propellant gas flow therethrough into the discharge annulus. The propellant gas has an ionization potential. Opposed, dielectric walls define the annulus, with at least one of the opposed dielectric walls having pores therein, the pores having cooling gas flow therethrough into the discharge annulus and substantially adjacent the opposed dielectric wall(s). The cooling gas has an ionization potential higher than the ionization energy of the propellant gas. The cooling gas is adapted to substantially prevent at least one of secondary electron emission and sputtering of the dielectric walls.

Roy, Subrata↗
NASA NTRS2005

Detached Eddy Simulation of Film Cooling over a GE Flat Plate

The detached eddy simulation of film cooling has been utilized for a proprietary GE plate-pipe configuration. The blowing ratio was 2.02, the velocity ratio was 1.26, and the temperature ratio was 1.61. Results indicate that the mixing processes downstream of the hole are highly anisotropic. DES solution shows its ability to depict the dynamic nature of the flow and capture the asymmetry present in temperature and velocity distributions. Further, comparison between experimental and DES time-averaged effectiveness is satisfactory. Numerical values of span-averaged effectiveness show better prediction of the experimental values at downstream locations than a steady state Glenn HT solution. While the DES method shows obvious promise, there are several issues that need further investigation. Despite an accurate prediction in the hole vicinity, the simulation still falls short in the region x = 10d to 100d. This should be investigated. Also the model used flat plate. Actual turbine blade should be modeled in the future if additional finding is available.

Roy, Subrata↗
NASA NTRS2004

Development of a Computationally Efficient, High Fidelity, Finite Element Based Hall Thruster Model

This report documents the development of a two dimensional finite element based numerical model for efficient characterization of the Hall thruster plasma dynamics in the framework of multi-fluid model. Effect of the ionization and the recombination has been included in the present model. Based on the experimental data, a third order polynomial in electron temperature is used to calculate the ionization rate. The neutral dynamics is included only through the neutral continuity equation in the presence of a uniform neutral flow. The electrons are modeled as magnetized and hot, whereas ions are assumed magnetized and cold. The dynamics of Hall thruster is also investigated in the presence of plasma-wall interaction. The plasma-wall interaction is a function of wall potential, which in turn is determined by the secondary electron emission and sputtering yield. The effect of secondary electron emission and sputter yield has been considered simultaneously, Simulation results are interpreted in the light of experimental observations and available numerical solutions in the literature.

Jacobson, David↗