Energy migration in the aromatic vinyl polymers. 7. Application of a one-dimensional electronic excitation transport model for transient fluorescence of poly(2-vinylnaphthalene) in alkylbenzene solution and polystyrene blends

1989 ◽  
Vol 93 (2) ◽  
pp. 776-784 ◽  
Author(s):  
William C. Tao ◽  
Curtis W. Frank
Keyword(s):  
Electronic Excitation ◽  
Transport Model ◽  
Energy Migration ◽  
One Dimensional ◽  
Vinyl Polymers

Energy migration in the aromatic vinyl polymers. 1. A one-dimensional random walk model

1982 ◽  
Vol 15 (3) ◽  
pp. 733-741 ◽  
Author(s):  
Patrick D. Fitzgibbon ◽  
Curtis W. Frank
Keyword(s):  
Random Walk ◽  
Energy Migration ◽  
Random Walk Model ◽  
One Dimensional ◽  
Vinyl Polymers

Energy migration in the aromatic vinyl polymers. 5. Poly(2-vinyl naphthalene) and polystyrene

1985 ◽  
Vol 63 (6) ◽  
pp. 1328-1332 ◽  
Author(s):  
Steven N. Semerak ◽  
Curtis W. Frank
Keyword(s):  
Nearest Neighbor ◽  
Transport Model ◽  
Homogeneous System ◽  
Electronic Energy ◽  
Energy Migration ◽  
Periodic Lattice ◽  
Single Chain ◽  
Vinyl Polymers ◽  
Chain Fraction ◽  
Ring Pair

Electronic energy migration in pure poly(2-vinyl naphthalene) (P2VN) is analyzed in terms of a theory for three-dimensional transport and trapping in a homogeneous system of randomly distributed chromophores. A simpler theory for 3-D transport on a spatially periodic lattice, which was applied previously to polystyrene (PS) gave self-contradictory results for P2VN because of higher transport rates in P2VN. The fraction of rings in excimer-forming sites (EFS) in pure P2VN, analyzed by the former theory, is found to be 0.072 – moderately larger than the single-chain fraction of 0.026. In contrast, the EFS ring fraction in pure PS was 0.33, much larger than the single-chain fraction of 0.051. This reflects the reduced probability, relative to a phenyl ring pair, of packing a naphthyl ring pair into the necessary sandwich arrangement in the pure polymers. Energy migration in very dilute, miscible blends containing P2VN is analyzed by a one-dimensional transport model, which was applied previously to similar blends containing PS. The nearest-neighbor migration rates obtained from the data for both P2VN and PS are about one hundred times higher than the expected dipole–dipole rates. This suggests that (1) migration is not limited to nearest-neighbor rings, (2) the morphology of the dilute blends does not consist of isolated chains of the aromatic vinyl polymers, or (3) short-range electronic interactions other than dipole–dipole are involved in energy migration.

scholarly journals Interaction of equivalence ratio fluctuations and flow fluctuations in acoustically forced swirl flames

2021 ◽  
pp. 175682772110155
Author(s):  
Vincent Kather ◽  
Finn Lückoff ◽  
Christian O. Paschereit ◽  
Kilian Oberleithner
Keyword(s):  
Equivalence Ratio ◽  
Transfer Functions ◽  
Transport Model ◽  
Mode Conversion ◽  
Fuel Injector ◽  
One Dimensional ◽  
Flow Fluctuations ◽  
Non Linear ◽  
Non Local ◽  
Acoustic Forcing

The generation and turbulent transport of temporal equivalence ratio fluctuations in a swirl combustor are experimentally investigated and compared to a one-dimensional transport model. These fluctuations are generated by acoustic perturbations at the fuel injector and play a crucial role in the feedback loop leading to thermoacoustic instabilities. The focus of this investigation lies on the interplay between fuel fluctuations and coherent vortical structures that are both affected by the acoustic forcing. To this end, optical diagnostics are applied inside the mixing duct and in the combustion chamber, housing a turbulent swirl flame. The flame was acoustically perturbed to obtain phase-averaged spatially resolved flow and equivalence ratio fluctuations, which allow the determination of flux-based local and global mixing transfer functions. Measurements show that the mode-conversion model that predicts the generation of equivalence ratio fluctuations at the injector holds for linear acoustic forcing amplitudes, but it fails for non-linear amplitudes. The global (radially integrated) transport of fuel fluctuations from the injector to the flame is reasonably well approximated by a one-dimensional transport model with an effective diffusivity that accounts for turbulent diffusion and dispersion. This approach however, fails to recover critical details of the mixing transfer function, which is caused by non-local interaction of flow and fuel fluctuations. This effect becomes even more pronounced for non-linear forcing amplitudes where strong coherent fluctuations induce a non-trivial frequency dependence of the mixing process. The mechanisms resolved in this study suggest that non-local interference of fuel fluctuations and coherent flow fluctuations is significant for the transport of global equivalence ratio fluctuations at linear acoustic amplitudes and crucial for non-linear amplitudes. To improve future predictions and facilitate a satisfactory modelling, a non-local, two-dimensional approach is necessary.

scholarly journals A coupled modelling effort to study the fate of contaminated sediments downstream of the Coles Hill deposit, Virginia, USA

2015 ◽  
Vol 367 ◽  
pp. 272-280 ◽  
Author(s):  
C. F. Castro-Bolinaga ◽  
E. R. Zavaleta ◽  
P. Diplas
Keyword(s):  
Sediment Transport ◽  
Transport Model ◽  
Uranium Deposit ◽  
Ground Surface ◽  
Ansys Fluent ◽  
Mining Site ◽  
One Dimensional ◽  
Coupled Modelling ◽  
Modelling Effort ◽  
Modelling Process

Abstract. This paper presents the preliminary results of a coupled modelling effort to study the fate of tailings (radioactive waste-by product) downstream of the Coles Hill uranium deposit located in Virginia, USA. The implementation of the overall modelling process includes a one-dimensional hydraulic model to qualitatively characterize the sediment transport process under severe flooding conditions downstream of the potential mining site, a two-dimensional ANSYS Fluent model to simulate the release of tailings from a containment cell located partially above the local ground surface into the nearby streams, and a one-dimensional finite-volume sediment transport model to examine the propagation of a tailings sediment pulse in the river network located downstream. The findings of this investigation aim to assist in estimating the potential impacts that tailings would have if they were transported into rivers and reservoirs located downstream of the Coles Hill deposit that serve as municipal drinking water supplies.

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