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Subrata Bhattacharjee

Bio: Subrata Bhattacharjee is an academic researcher from San Diego State University. The author has contributed to research in topics: Flame spread & Combustion. The author has an hindex of 21, co-authored 76 publications receiving 1251 citations. Previous affiliations of Subrata Bhattacharjee include Washington State University & Mississippi State University.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors demonstrate that substantial changes in a reattaching flow can be produced by controlled forcing techniques, and the forcing apparently works by affecting the vortex merging process in a fashion similar to that observed in forced mixinglayer experiments.
Abstract: Recent experimental observations have shown that large-scale organized vortices are produced in reattaching separated flows. Interactions between these vortices are important in the development of these flows downstream. Experimental studies from a downstream-fac ing step flow are presented to demonstrate that substantial changes in a reattaching flow can be produced by controlled forcing techniques. The forcing apparently works by affecting the vortex merging process in a fashion similar to that observed in forced mixinglayer experiments. The separated mean flow spreading rate could be increased most effectively by forcing at a nondimensional frequency (based on step height and freestream velocity) between 0.2 and 0.4. This result was found to be relatively independent of step Reynolds numbers over the range (26,000-76,000) studied. A significant decrease in the reattachment length accompanied the increased growth of the separated shear layer. Considerable changes in the turbulence energy and the Reynolds stress levels were also observed for the forced flows.

136 citations

Journal ArticleDOI
01 Jan 1991
TL;DR: In this paper, the effects of surface and gas-phase radiation on the rate and the structure of laminar flame spread over thin fuels are investigated using a flame-spread model which consists of the continuity, momentum, species, and energy equations in the gas and the continuity and energy equation in the solid.
Abstract: The effects of surface and gas-phase radiation on the rate and the structure of laminar flame spread over thin fuels are investigated using a flame-spread model which consists of the continuity, momentum, species, and energy equations in the gas and the continuity and energy equations in the solid. Numerical calculations, complemented by scaling arguments, show that, at high velocities of the oxidizer flow, radiation effects are unimportant; the spread rate decreases with increasing opposing velocity due to finite-rate gas-phase kinetics. However, radiation becomes progressively important when the opposing velocity is below a certain value: the flame cools, shrinks in size, and its spread rate falls sharply with decreasing opposing velocity.

63 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical model is presented that can be used to predict the structure and rate of spread of an attached diffusion flame moving over a thermally thin, pyrolyzing combustible placed in a gravity-free, quiescent, oxidizing environment.
Abstract: A theoretical model is presented that can be used to predict the structure and rate of spread of an attached diffusion flame moving over a thermally thin, pyrolyzing combustible placed in a gravity-free, quiescent, oxidizing environment. The gas-phase model includes steady-state, two-dimensional momentum, energy, and species equations while the solid-phase model consists of continuity and energy equations, the solution to which provide boundary conditions for the gas-phase problem. The spread rate appears as an eigenvalue in both the gas- and solid-phase equations. The numerical procedure developed to solve the system of equations is stable even for spread rates comparable to normal velocities present at the fuel-gas interface. Solid fuel pyrolysis is modelled using a first-order Arrhenius decomposition while both finite-rate and infinite rate chemistry in the gas phase are considered. Computed spread rates increase with increasing oxygen concentration in the ambient and are generally a factor of...

59 citations

Journal ArticleDOI
01 Jan 2005
TL;DR: In this paper, a simplified analysis leading to the development of closed-form expressions for spread rate for both thin and thick fuels in the microgravity regime of opposed-flow flame spread is presented.
Abstract: The spread rate formulas of de Ris in the thermal regime of opposed-flow flame spread are inarguably the most well-known formulas in the flame spread literature. Similar easy-to-use formulas are lacking in all other regimes of flame spread. This paper presents a simplified analysis leading to the development of closed-form expressions for spread rate for both thin and thick fuels in the microgravity regime of opposed-flow flame spread. The resulting formulas, expressed in terms of the thermal limit of spread rate and a radiation number that can be evaluated from the known parameters of the problem, are shown to reproduce the experimentally and numerically observed trends quite well at both limits of fuel thickness. These formulas are utilized to develop quantitative criterion to delineate thin and thick fuels in the microgravity and thermal regimes. The transition between the microgravity and thermal regimes is also explored. The flammability maps, derived from the spread rate expressions, are the first of their kind, establishing fuel thickness as one of the critical parameters.

53 citations


Cited by
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01 Jan 2016
TL;DR: The numerical heat transfer and fluid flow is universally compatible with any devices to read and is available in the authors' digital library an online access to it is set as public so you can get it instantly.
Abstract: Thank you for reading numerical heat transfer and fluid flow. Maybe you have knowledge that, people have search numerous times for their favorite books like this numerical heat transfer and fluid flow, but end up in infectious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they cope with some malicious virus inside their computer. numerical heat transfer and fluid flow is available in our digital library an online access to it is set as public so you can get it instantly. Our books collection spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the numerical heat transfer and fluid flow is universally compatible with any devices to read.

1,531 citations

Book ChapterDOI
28 Jan 2005
TL;DR: The Q12-40 density: ρ ((kg/m) specific heat: Cp (J/kg ·K) dynamic viscosity: ν ≡ μ/ρ (m/s) thermal conductivity: k, (W/m ·K), thermal diffusivity: α, ≡ k/(ρ · Cp) (m /s) Prandtl number: Pr, ≡ ν/α (−−) volumetric compressibility: β, (1/K).
Abstract: Geometry: shape, size, aspect ratio and orientation Flow Type: forced, natural, laminar, turbulent, internal, external Boundary: isothermal (Tw = constant) or isoflux (q̇w = constant) Fluid Type: viscous oil, water, gases or liquid metals Properties: all properties determined at film temperature Tf = (Tw + T∞)/2 Note: ρ and ν ∝ 1/Patm ⇒ see Q12-40 density: ρ ((kg/m) specific heat: Cp (J/kg ·K) dynamic viscosity: μ, (N · s/m) kinematic viscosity: ν ≡ μ/ρ (m/s) thermal conductivity: k, (W/m ·K) thermal diffusivity: α, ≡ k/(ρ · Cp) (m/s) Prandtl number: Pr, ≡ ν/α (−−) volumetric compressibility: β, (1/K)

636 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the progress that has been made to the understanding of chemical and physical processes, which occur during combustion of solid fuels, is presented, and the effects of bubble formation on the transport of volatiles during thermal degradation of non-charring fuels, described through a one-step global reaction, have been modeled.

434 citations

Journal ArticleDOI
TL;DR: This work presents three Web services related with mass spectrometry, namely isotopic distribution simulation, peptide fragmentation simulation, and molecular formula determination, taking advantage of modern HTML5 and JavaScript libraries (ChemDoodle and jQuery).
Abstract: Web services, as an aspect of cloud computing, are becoming an important part of the general IT infrastructure, and scientific computing is no exception to this trend. We propose a simple approach to develop chemical Web services, through which servers could expose the essential data manipulation functionality that students and researchers need for chemical calculations. These services return their results as JSON (JavaScript Object Notation) objects, which facilitates their use for Web applications. The ChemCalc project http://www.chemcalc.org demonstrates this approach: we present three Web services related with mass spectrometry, namely isotopic distribution simulation, peptide fragmentation simulation, and molecular formula determination. We also developed a complete Web application based on these three Web services, taking advantage of modern HTML5 and JavaScript libraries (ChemDoodle and jQuery).

301 citations

Journal ArticleDOI
K.B. Chun1, Hyung Jin Sung1
TL;DR: In this paper, the effect of local forcing on the flow structure was scrutinized by altering the forcing amplitude (0 ⩽ A� 0.07) and forcing frequency (0⩽ St====== Hαγγαγαβαγβαβγα βαγ βαββ ββββα ββααβ β ββ βγ ββγβ βα βγββγ βγγ β βγα αββδ ββΔ βγΔβα α
Abstract: An experimental study was made of the flow over a backward-facing step. Excitations were given to separated flow by means of a sinusoidally oscillating jet issuing from a thin slit near the separation line. The Reynolds number based on the step height (H) varied 13000 ⩽ Re H ⩽ 33000. Effect of local forcing on the flow structure was scrutinized by altering the forcing amplitude (0 ⩽ A 0 ⩽ 0.07) and forcing frequency (0 ⩽ St H ⩽ 5.0). Small localized forcing near the separation edge enhanced the shear-layer growth rate and produced a large roll-up vortex at the separation edge. A large vortex in the shear layer gave rise to a higher rate of entrainment, which lead to a reduction in reattachment length as compared to the unforced flow. The normalized minimum reattachment length (x r )min/x x0 was obtained at St θ ≅ 0.01. The most effective forcing frequency was found to be comparable to the shedding frequency of the separated shear layer.

264 citations