Stratified Shear-Thinning Fluid Flow Past Tandem Cylinders in the Presence of Mixed Convection Heat Transfer with a Channel-Confined Configuration

The article examines the consequence of thermal buoyancy-driven cross-flow and heat transfer for shear-thinning power-law fluids on the tandem orientation of two cylinders. Finite volume methodology is used to investigate the effect of the gap ratio (2.5 ≤ S/D ≤ 5.5), power-law index (0.2 ≤ n ≤ 1) and Richardson number (0 ≤ Ri ≤ 1) on flow and thermal output parameters at Reynolds number Re ≤ 100 and Prandtl number Pr ≤ 50 in a confined channel. An unprecedented jump has been witnessed in the flow/thermal parameters at the critical gap ratio (critical spacing). At forced convection (Ri ≤ 0), this critical spacing keeps on increasing with shear-thinning character, from S/D = 3.9 (at n = 1) to 4.9 (at n = 0.2). On the contrary, an increase in shear-thinning characteristic leads to a decrease in critical spacing from S/D = 3.9 (at n = 1) to 2.8 (at n = 0.4) for Ri = 1 (mixed convection). The heat transfer rate increases with shear-thinning behavior, with a maximum heat transfer, noted at n = 0.2. A higher unprecedented increment for flow/thermal parameters is seen at critical spacing for the downstream cylinder than the upstream cylinder. At the highest gap ratio, the output parameters for the upstream cylinder approximate that of an isolated cylinder. The time-variant fluctuations in lift coefficients for a shear-thinning flow in a tandem arrangement provide a new understanding of co-shedding and extended body flow regimes.

The Role of Transient Attention in the Radial-tangential Anisotropy of Crowding

Crowding refers to the failure to identify a peripheral object due to its proximity to other objects (flankers). This phenomenon can lead to reading and object recognition impairments, and is associated with macular degeneration, amblyopia, and dyslexia. Crucially, the minimal target-flanker spacing required for the crowding interference (critical spacing) increases with eccentricity. This spacing is also larger when target and flankers appear along the horizontal meridian (radial arrangement) than when the flankers appear above and below the target (tangential arrangement). This phenomenon is known as radial–tangential anisotropy. Previous studies have demonstrated that transient attention can reduce crowding interference. However, it is still unclear whether and how attention interacts with the radial–tangential anisotropy. To address this issue, we manipulated transient attention by using a cue either at the target (valid) or fixation (neutral) location, in both radial and tangential target-flanker arrangements. Results showed that critical spacing was larger in the radial than in the tangential arrangement, and that cueing the target location improved performance and reduced the critical spacing for both radial and tangential arrangements, to the same extent. Together, our findings suggest that transient spatial attention plays an essential role in crowding but not in the radial-tangential anisotropy.

Burst Pressure Prediction of Pipes With SCC Colonies: Development of Intelligent Flaw Interaction Rules

Stress Corrosion Cracking (SCC) often occurs in clusters or colonies containing anywhere from a few cracks to hundreds of individual cracks. Multiple closely spaced cracks may interact, resulting in a burst pressure lower than what might be expected from a single crack. Most existing flaw interaction rules account for these interactions by using a single interacting crack to represent multiple cracks when the separations between them are less than a critical spacing. The length of this interacting crack is usually the sum of the individual crack length plus the spacing between them. Using this interacting length and the maximum depth in the colony could produce overly conservative burst pressure predictions which can lead to unnecessary hydrotests and/or other remediation actions. This two-paper series covers the PRCI-funded work aimed at the development of intelligent flaw interaction rules (termed PRCI-CRES SIA-1-5 rules) that can account more accurately the impact of multiple cracks without being overly conservative. This paper focuses on the development of the rules using numerical analyses. A companion paper covers the evaluation of the rules through full-scale burst tests. The PRCI-CRES SIA-1-5 rules use the principles of equivalent impact among multiple interacting cracks and represent the magnitude of the impact by a single virtual crack. The new rules do not rely on a critical spacing to determine whether there is an interaction. The magnitude of the interaction is a continuous function of the size of adjacent cracks and the spacing between them. A large number of finite element analyses (FEA) were conducted to examine the interaction among cracks for many crack configurations, including coplanar and noncoplanar cracks with different sizes and spacings. An analysis process was then developed to use the sizes and spacings of all cracks in an SCC colony to predict the equivalent virtual crack size and burst pressure.