Measurement of Heat Transfer and Flow Structures in a Closed Rotating Cavity

Buoyancy-induced flow occurs inside the rotating compressor cavities of gas turbines. These cavities are usually open at the inner radius, but in some industrial gas turbines, they are effectively closed. This paper presents measurements of the disc heat transfer and rotating flow structures in a closed cavity over a wide range of engine relevant conditions. These experimentally derived distributions of disc temperature and heat flux are the first of their kind to be published. The radial distribution of the non-dimensional disc temperature virtually collapsed onto a single curve over the full experimental range. There was a small, monotonic departure from this common curve with increasing Reynolds number; this was attributed to compressibility effects where the core temperature increases as the rotational speed increases. These results imply that, if compressibility effects are negligible, all rotating closed cavities should have a disc temperature distribution uniquely related to the geometry and disc material; this is of important practical use to the engine designer. Unsteady pressure sensors detected either three or four vortex pairs across the experimental range. The number of pairs changed with Grashof number, and the structures slipped relative to the rotating discs by less than 1% of the disc speed.

Measurement of Heat Transfer and Flow Structures in a Closed Rotating Cavity

Buoyancy-induced flow occurs inside the rotating compressor cavities of gas turbines. These cavities are usually open at the inner radius, but in some industrial gas turbines, they are effectively closed. This paper presents measurements of the disc heat transfer and rotating flow structures in a closed cavity over a wide range of engine relevant conditions. These experimentally derived distributions of disc temperature and heat flux are the first of their kind to be published. The radial distribution of the non-dimensional disc temperature virtually collapsed onto a single curve over the full experimental range. There was a small, monotonic departure from this common curve with increasing Reynolds number; this was attributed to compressibility effects where the core temperature increases as the rotational speed increases. These results imply that, if compressibility effects are negligible, all rotating closed cavities should have a disc temperature distribution uniquely related to the geometry and disc material; this is of important practical use to the engine designer. Unsteady pressure sensors detected either three or four vortex pairs across the experimental range. The number of pairs changed with Grashof number, and the structures slipped relative to the rotating discs by less than 1% of the disc speed.

Selection on growth rate and local adaptation drive genomic adaptation during experimental range expansions in the protist Tetrahymena thermophila

Populations that expand their range can undergo rapid evolutionary adaptation, which can be aided or hindered by sexual reproduction and gene flow. Little is known about the genomic causes and consequences of such adaptation. We studied genomic adaptation during experimental range expansions of the protist Tetrahymena thermophila in landscapes with a uniform environment or a pH-gradient, both in the presence and absence of gene flow and sexual reproduction. We used pooled genome sequencing to identify genes subject to selection caused by the expanding range and by the pH-gradient. Adaptation to the range expansion affected genes involved in cell divisions and DNA repair, whereas adaptation to the pH gradient additionally affected genes involved in ion balance, and oxidoreductase reactions. These genetic changes may result from selection on growth and adaptation to low pH. Sexual reproduction affected both de novo mutation and standing genetic variation, whereas gene flow and the presence of a pH-gradient affected only standing variation. Sexual reproduction may have aided genetic adaptation during range expansion, but only in the absence of gene flow, which may have swamped expanding populations with maladapted alleles.

PSV-14 Influence of monsoon rainfall events on movement patterns of Angus crossbred vs. Raramuri Criollo cattle on desert rangeland

The Chihuahuan Desert averages 247 mm of precipitation annually, 53% of which occurs between July and September. Our objective was to examine movement, activity, pasture use, and watering patterns of Angus x Hereford (AH) and Raramuri Criollo (RC) cows on days with precipitation events (PE, ≥ 1.3 mm rain recorded) vs. days with no precipitation (NP) at the Jornada Experimental Range in southern New Mexico during the summers of 2015, 2016, and 2017. Breeds grazed two adjacent pastures (12A = 1190 ha; 12C = 1165 ha) separately in a crossover design for 4 weeks each year. Seven to nine randomly selected cows per breed were collared with Lotek 3300-LR GPS set to log position every 10 min. An average of 7.6 PE occurred during the 4-week trials each year. On PE days, cows traveled farther (PE = 6.95 vs. NP = 6.43 km, P < 0.01), spent more time grazing (PE = 9.07 vs. NP = 8.76 h/day, P = 0.07) and less time resting (PE = 13.90 vs. NP = 14.38 h/day, P = 0.01), and traveled similar distances from watering points (PE = 0.84 vs. NP = 0.80 km, P = 0.41) compared to NP days. On PE days, cows spent less time within 200 m (PE = 1.32 vs. NP = 2.95 h, P < 0.01) and 100 m (PE = 0.79 vs. NP = 1.90 h, P < 0.01) of drinkers regardless of breed. We detected no rainfall x breed interaction (P > 0.05). Overall, RC cows traveled farther, at higher velocities, spent more time grazing, less time resting, and explored areas with greater radius than AH counterparts (P < 0.05). Precipitation appeared to relax environmental constraints on activity of both breeds, likely due to availability of ephemeral watering sources and a transient drop in temperature.