Prabodh Panindre

Technique to Improve Performance of Positive Pressure Ventilation Tactic in High-Rise Fires

Positive Pressure Ventilation (PPV) is a firefighting tactic that can assist firefighters in venting of smoke and high temperature combustion products in a more efficient manner and make the fire-rescue /suppression operation safer than without PPV. The pressure created by PPV operation must be greater than that of created by spread of fire. In real-life structures such as high-rise buildings, considering the leakages and size of stairwells, it becomes difficult to achieve the desired pressure at upper floors using PPV operation. With the help from FDNY (Fire Department of New York), on-site tests and computer simulation techniques were performed to study the behavior of PPV tactic. A technique was developed that significantly increases the positive pressure level achieved by a typical PPV operation. The efficacy of this technique was tested by conducting on-site experiments and numerical simulation methods using computational fluid dynamics software - Fluent 12.0 and NIST’s Fire dynamic simulator (FDS 5.0). The results of on-site experiments and numerical simulation methods found to be in close agreement with each other and confirmed the efficacy of this technique in improving the performance of typical PPV operation. This paper describes the results obtained from these on-site tests and numerical simulation methods. As FDNY is in the phase of implementing this instrument to ease and improve the PPV deployment operation, numerical simulation methods have been used to optimize this technique and the analysis discussed in this study also simplifies the PPV fan deployment operation for firefighters.Copyright

Optimization of Positive Pressure Ventiliation Tactic for Wind Driven High Rise Fires

Positive Pressure Ventilation (PPV) is a firefighting tactic that can mitigate the spread of fire and the combustion products to improve the safety of firefighters and civilians in wind-driven high-rise fires than without PPV. The performance of a PPV tactic in wind-driven high-rise fires depends on various parameters that include wind speed, control of stairwell doors, number of fans, fan positions and placements, fire location etc. This paper describes the influence of these parameters on the efficacy of PPV operation that was studied by simulating wind-driven high-rise fire scenarios using computational fluid dynamics softwares Fluent 12.0 and NIST’s Fire dynamic simulator (FDS 5.0). The results obtained from Fluent and FDS found to be in close agreement with each other and have been used to optimize the PPV operation for better performance.Copyright

Effect of rotation on quality factor of single-mode optical resonances in round-cornered square-shaped resonators

Recently, non-circular microresonators have been studied mainly due to their ability to provide long interaction length and ease the air-gap spacing tolerance. The use of rectangular, square-shaped, and/ or polygonal optical microresonators with sharp corners can be limited by severe energy loss at the corners. By incorporating optimum fillet (rounding of corners) design at sharp corners of such optical microresonators optical loss can be eliminated at sharp corners. This results in significantly increasing the quality factor of the round-cornered square-shaped microresonators in comparison to the conventional circular-ring resonator systems. The enhanced quality factor makes the microresonator a promising system that can be used in advanced measurement and detection applications. The two dimensional finite element analysis of the electromagnetic frequency presented in this study quantifies the effect of rotation of round-cornered square-shaped resonators about the coupling region on the quality factor of single-mode resonances in a add-drop configuration system. It is found that the quality factor of these resonators steadily increases with the rotation (0-45° angle) of resonator about the coupling point.

Technique to improve performance of positive pressure ventilation tactic in High-Rise fires

Positive Pressure Ventilation (PPV) is a firefighting tactic that can assist firefighters in venting of smoke and high temperature combustion products in a more efficient manner and make the fire-rescue/suppression operation safer than without PPV. The pressure created by PPV operation must be greater than that of created by spread of fire. In real-life structures such as high-rise buildings, considering the leakages and size of stairwells, it becomes difficult to achieve the desired pressure at upper floors using PPV operation. With the help from FDNY (Fire Department of New York), on-site tests and computer simulation techniques were performed to study the behavior of PPV tactic. A technique was developed that significantly increases the positive pressure level achieved by a typical PPV operation. The efficacy of this technique was tested by conducting on-site experiments and numerical simulation methods using computational fluid dynamics software-Fluent 12.0 and NISTs Fire dynamic simulator (FDS 5.0). The results of on-site experiments and numerical simulation methods found to be in close agreement with each other and confirmed the efficacy of this technique in improving the performance of typical PPV operation. This paper describes the results obtained from these on-site tests and numerical simulation methods. As FDNY is in the phase of implementing this instrument to ease and improve the PPV deployment operation, numerical simulation methods have been used to optimize this technique and the analysis discussed in this study also simplifies the PPV fan deployment operation for firefighters.

Design optimization of a single-mode microring resonator for label-free detection of biomarkers within a tunable spectral range of 2 nm

This computational parametric study analyzes the effect of geometrical design parameters of a microring resonator on its optical characteristics with the goal to optimize its performance for label-free detection of biomarkers. Electromagnetic frequency domain analysis was performed using finite element numerical technique for the microring resonator. Effect of the width of feed and pickup waveguides, the coupling gap between the waveguide and microring, and the outer radius of microring on the quality factor were analyzed and quantified for a narrow operational range of wavelength between 1309-1311 nm. The computational simulation showed that these parameters play an important role in avoiding the loss of electromagnetic field, while increasing the effective circulation of energy in the resonator, the ability to achieve multiple single-mode resonances within certain wavelength bandwidth, and the quality of output signal for detection. As a result, the quality factor was enhanced by an order of magnitude with the obtained optimum values of waveguide width, coupling gap, and microring radius without changing the material of resonator or waveguide, and the medium surrounding the resonator. The ability to optically detect a nanoparticle representing a cell vesicle was demonstrated. This enhanced quality factor of the resonator will allow highly sensitive and rapid detection of biomarkers and measurement of their size.

Effect of rounding corners on optical resonances in single-mode sharp-cornered microresonators

The use of microresonators with sharp corners (rectangular and square-shaped) can be limited by severe energy loss at the corners. A 2D numerical study is conducted to investigate and analyze the effect of incorporating fillet (rounding of corners) design at sharp corners of such single-mode optical microresonators. The effect on quality factor, free spectral range, and energy loss for the coupled microresonator-waveguide system in the add-drop configuration for varying values of fillet radii are quantified. It is shown that the selection of an optimum radius of the curvature of the fillet for sharp-cornered microresonators provides a higher quality factor than that of the conventional circular resonators.

Analytical Models for Radiative Heat Transfer in Radioisotope Thermophotovoltaic (RTPV) Cell

A Radioisotope Thermophotovoltaic (RTPV) Cell is a device used to convert heat energy into electrical energy. The electric generation capacity of RTPV cell depends on the radiative heat transfer between its two surfaces: the emitter surface heated by radioisotope thermal source and the receiving photovoltaic (PV) cell surface. The spectral directional surface properties and the surface temperatures of emitter and PV cell surface play important roles in quantifying the radiative heat flux of RTPV cell. This paper establishes the required analytic flat plate solutions to calculate the radiative heat flux of RTPV cell. The results obtained using the analytic solutions developed in this study have been qualitatively validated with the results of numerical simulations performed by a commercially available software. The effect of the surface temperatures and emitter surface coating on RTPV cell capacity is also studied and analyzed by both the methods. The results obtained from both the methods show that PV cell surface temperature has negligible effect on RTPV cell capacity as compared to the emitter surface temperature. Also, the radiative heat flux of RTPV cell with coated emitter is found to be significantly higher than that of RTPV cell with uncoated emitter surface. The analytical methods can be used to estimate the net radiative heat flux of RTPV cell for different surface temperatures and are independent of the dimensions of RTPV cell.Copyright