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In this paper, we investigate flows with moving contact lines on curved solid walls on a dual-resolution grid using a diffuse-interface immersed-boundary (DIIB) method. The dual-resolution grid, on which the flows are solved on a coarse mesh while the interface is resolved on a fine mesh, was shown to significantly improve the computational efficiency when simulating multiphase flows. On the other hand, the DIIB method is able to resolve dynamic wetting on curved substrates on a Cartesian grid, but it usually requires a mesh of high resolution in the vicinity of a moving contact line to resolve the local flow. In the present study, we couple the DIIB method with the dual-resolution grid, to improve the interface resolution for flows with moving contact lines on curved solid walls at an affordable cost. The dynamic behavior of moving contact lines is validated by studying drop spreading, and the numerical results suggest that the effective slip length λ n can be approximated by 1.9 Cn , where Cn is a dimensionless measure of the thickness of the diffuse interface. We also apply the method to drop impact onto a convex substrate, and the results on the dual-resolution grid are in good agreement with those on a single-resolution grid. It shows that the axisymmetric simulations using the DIIB method on the dual-resolution grid saves nearly 60% of the computational time compared with that on a single-resolution grid. [ABSTRACT FROM AUTHOR]

This paper reports a comprehensive experimental study on evolutions of burning rate and flame tilting of medium-to-large size pool fires with cross flows. Square pool fires with length of 25, 35, 45, 60 and 70 cm were employed with heptane as fuel, whose burning behaviors are in radiation-controlled optical-thin regime in still air. The evolutions of their burning rates and flame tilt angles were measured with cross flow air speed from 0 to 4.5 m/s, in which range the data is still lacking in the literature which mostly concerned relative smaller pools (up to 25–30 cm) in laboratory or relative larger pools (> 1.0 m) by outdoor burning where the wind is hard to maintain. It was found that there were several transitions for the burning rate with increase in cross flow air speed in this range for different size pool fires. For relative smaller pools (25 and 35 cm), the burning rate increased and then decreased; meanwhile for the medium pool (45 cm), the burning rate first increased then decreased, and further increased then finally decreased. However, for the relative larger pools (60 and 70 cm), the burning rate first increased then decreased and finally increased with flow speed up to 4.5 m/s. These transitions were discussed based on physically the change of the controlling mechanisms due to heat feedback or the aerodynamic extinction at the flame leading edge (Damköhler number). The corresponding cross flow air speeds for these transitions correlated well with buoyancy induced velocity scaled by [( gD ) 0.5 ] based on Froude number. The flame tilt angles measured were compared with previous correlations to validate their applicability in this range. This work provided a comprehensive data base revealing the transitions of burning behaviors of medium-to-large pool fires with increase in cross flows air speed. [ABSTRACT FROM AUTHOR]

A wide pitch gradient covering the near infrared region (750.0–2500.0 nm) were facilely obtained by simple controlling temperature difference to LC mixtures with a twist grain boundary (TGB)–N* phase transition. After the pitch gradient formed, the structure of broad reflective bandwidth was fixed through polymerisation of monomers in mixtures by UV irradiation. It was found that the temperature difference between the up and down side of the samples was critical to form wide-pitch gradient distribution. Additionally, the reflection wavelength and bandwidth of films could be adjusted by the applied temperature difference with the widest bandwidth up to 1750 nm. This simple method for the preparation of broad reflective films was expected to be used in the fields like architectural energy conservation or infrared shield. [ABSTRACT FROM PUBLISHER]

Two types of typical thermal cycling tests are used for the evaluation of thermal cycling lifetime of thermal barrier coatings. Those are the burner cycling test with a thermal gradient and the isothermal furnace cycling test. There are diverse explanations to test results up to now. Although certain correlations should exist between the results obtained by two types of the tests, no evident parameters in two tests were directly related, possibly due to large range of difference test conditions. In this investigation, a series of TBC samples with carefully prepared AlO-based TGO of different thicknesses were used for both the burner cycling and the furnace cycling tests. The relationships between thermal cycling lifetime and TGO thickness were obtained for two types of the tests. It was found that TGO thickness presents the same influence tendency despite of different types of thermal cycling test. The results reveal the existence of the critical TGO thickness by which the transition of failure mode takes place. Moreover, the values of the critical TGO thickness for two tests are comparable. The results evidently suggest that the lifetimes during different thermal cycling tests can be correlated by TGO effects on failure behavior. However, it is clear that the apparent dominant driving factors to TBC failure are different in two types of tests. Accordingly, the burner cycling test could be used for optimizing the durability of ceramic top coat by separating the effect of individual factors through test condition design, while the furnace cycling test results represent the integrated TBC durable performance of the bond coat and top ceramic coating. [ABSTRACT FROM AUTHOR]

The finite time blow-up of solutions to a nonlinear Timoshenko-type equation with variable exponents is studied. More concretely, we prove that the solutions blow up in finite time with positive initial energy. Also, the existence of finite time blow-up solutions with arbitrarily high initial energy is established. Meanwhile, the upper and lower bounds of the blow-up time are derived. These results deepen and generalize the ones obtained in [Nonlinear Anal. Real World Appl., 61: Paper No. 103341, 2021]. [ABSTRACT FROM AUTHOR]

The construction of the reservoir has changed the nitrogen migration and transformation processes in the river, and a large amount of sediment deposition in the reservoir may also lead to the spatial differentiation of complete ammonia oxidation (comammox) bacteria. The study investigated the abundance and diversity of comammox bacteria in the sediments of three cascade reservoirs, namely, Xiaowan, Manwan, and Nuozhadu on the Lancang River in China. In these reservoirs, the average amoA gene abundance of clade A and clade B of comammox bacteria, ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB) was 4.16 ± 0.85 × 105, 1.15 ± 0.33 × 105, 7.39 ± 2.31 × 104, and 3.28 ± 0.99 × 105 copies g−1, respectively. The abundance of clade A was higher than that of other ammonia oxidizing microorganisms. The spatial variation of comammox bacteria abundance differed among different reservoirs, but the spatial variation trends of the two clades of comammox bacteria in the same reservoir were similar. At each sampling point, clade A1, clade A2, and clade B coexisted, and clade A2 was usually the dominant species. The connection between comammox bacteria in the pre-dam sediments was looser than that in non-pre-dam sediments, and comammox bacteria in pre-dam sediments exhibited a simpler network structure. The main factor affecting comammox bacteria abundance was NH 4 +-N, while altitude, temperature, and conductivity of overlying water were the main factors affecting comammox bacteria diversity. Environmental changes caused by differences in the spatial distribution of these cascade reservoirs may be the main driver of the changes of community composition and abundance of comammox bacteria. This study confirms that the construction of cascade reservoirs results in niche spatial differentiation of comammox bacteria. • Comammox bacteria clade A2 was the dominant species in Lancang cascade reservoir. • Pre-dam comammox bacteria exhibited a simpler network structure than non-pre-dam one. • NH 4 +-N was the main factor affecting comammox bacteria abundance in cascade reservoirs. [ABSTRACT FROM AUTHOR]