Longer Fins Research Articles

Suppression of vortex rope formation and pressure fluctuation using anti-swirl fins in a Francis turbine model at part load condition with cavitation inception point

Vortex rope formation at part load (PL) with cavitation inception causes pressure fluctuations inside the draft tube (DT) of a Francis turbine which may fail the turbine due to resonance and erosion. The pressure surge can be minimized by using anti-swirl fins which ensure safe turbine operation. The present study examines the effect of fin sizes and locations on the internal flow characteristics of the Francis turbine and predicts its adverse effect on the pressure surge. Three cases are investigated in which internal flow physics are compared among DTs with longer fins, shorter fins, and no fins. At the cavitation inception point under PL conditions, the characteristics are thoroughly studied numerically using ANSYS-CFX with structured and unstructured grids. Cavitation and PL conditions are designated by Thoma number 0.266 and guide vane angle 16°. Numerical methodology is then verified by an experiment based on International Standard (IEC 60193). The vortex rope occurrence is suppressed using fins on the DT periphery and longer fins that are extended up to the elbow exhibit the lowest strength of the vortex rope. Maximum pressure recovery inside the DT is achieved using longer fins. The swirl intensity is remarkably reduced by about 94% with longer fins. The pressure peak of low frequency is about 60% suppressed using longer fins. The PL and cavitation-induced instabilities and vibrations are significantly mitigated by longer fins, while shorter fins also moderately minimize it. Hence, energy production is preferable with longer fins because of the safe and stable turbine function.

Efficacy of angled metallic fins for enhancing phase change material melting

Research on enhancing phase change material (PCM) heat transfer is concentrated in latent heat thermal energy storage (LHTES) field, especially with utilization of metallic fins. One interesting fin parameter that was less explored for a rectangular PCM system, is the metal fin's inclined angle. This research aims to experimentally validate the hypothesis and evaluate the efficacy of angled metallic fins enhancing PCM melting in a sidewall heated cuboid LHTES system. Experiments indicate that three-dimensional PCM melting in the LHTES unit can be characterized as two dimensional. The angled fins considerably influence temperature evolution of local solid PCM around fins. Compared to the horizontal fin, positive inclined fins with angles of +30° and +15° prolong the PCM melting time by 4.0% and 3.8% respectively, while the downward tilted inclined fins at −15° and −30° promote PCM melting by up to 5.2% melting fraction difference. Extending simulations with seven fin angles and three fin lengths explicate the substantial effect on PCM heat storage, melting time, and temperature uniformity. Particularly, the longest fin at the downward angle of −15° reduces the PCM melting time most. The study shows feasibility of utilizing downward angled fins to enhance PCM transient melting in the LHTES unit.

Melting Enhancement in a Triple-Tube Latent Heat Storage System with Sloped Fins.

Due to the potential cost saving and minimal temperature stratification, the energy storage based on phase-change materials (PCMs) can be a reliable approach for decoupling energy demand from immediate supply availability. However, due to their high heat resistance, these materials necessitate the introduction of enhancing additives, such as expanded surfaces and fins, to enable their deployment in more widespread thermal and energy storage applications. This study reports on how circular fins with staggered distribution and variable orientations can be employed for addressing the low thermal response rates in a PCM (Paraffin RT-35) triple-tube heat exchanger consisting of two heat-transfer fluids flow in opposites directions through the inner and the outer tubes. Various configurations, dimensions, and orientations of the circular fins at different flow conditions of the heat-transfer fluid were numerically examined and optimized using an experimentally validated computational fluid-dynamic model. The results show that the melting rate, compared with the base case of finless, can be improved by 88% and the heat charging rate by 34%, when the fin orientation is downward–upward along the left side and the right side of the PCM shell. The results also show that there is a benefit if longer fins with smaller thicknesses are adopted in the vertical direction of the storage unit. This benefit helps natural convection to play a greater role, resulting in higher melting rates. Changing the fins’ dimensions from (thickness × length) 2 × 7.071 mm2 to 0.55 × 25.76 mm2 decreases the melting time by 22% and increases the heat charging rate by 9.6%. This study has also confirmed the importance of selecting the suitable values of Reynolds numbers and the inlet temperatures of the heat-transfer fluid for optimizing the melting enhancement potential of circular fins with downward–upward fin orientations.

Parallel evolution of morphological traits and body shape in littoral and pelagic brook charr, Salvelinus fontinalis, along a gradient of interspecific competition.

The parallel evolution of similar ecotypes in response to comparable environmental conditions is believed to reveal the importance of divergent selection in phenotypic diversifying processes. Systems characterized by the presence of multiple replicate populations expressing resource polymorphism thus provide an ideal opportunity to address the occurrence and factors affecting the parallel evolution of ecotypes. Previous studies have shown that brook charr (Salvelinus fontinalis) exhibit resource polymorphism in some Canadian Shield lakes, where a littoral ecotype feeds mainly on zoobenthos and a pelagic ecotype feeds mostly on zooplankton. Using morphological traits and geometric morphometric analyses on 18 native brook charr populations, we explicitly tested (i) whether brook charr ecotypes show parallel evolution across populations (i.e. the same morphological traits discriminate ecotypes among lakes) and (ii) whether interspecific competition decreases the amplitude of morphological differentiation between ecotypes, if any, because brook charr experience some level of competitive exclusion from the littoral habitat in the presence of creek chub or white sucker. We observed a low level of parallel evolution, where the littoral ecotype was overall stouter with longer fins and smaller eyes than the pelagic ecotype. Interspecific competition had no clear impacts on the amplitude of morphological differentiation. We also observed that inter-lake morphological differences are greater than between ecotypes within lakes, suggesting an important effect of local environmental factors on population morphology. Early-stage of diversification as well as phenotypic plasticity and morphological integration could explain why resource polymorphism is still subtle in brook charr populations.

Seasonal change in male reproductive investment of a fish

Many animals are sexually dimorphic, whereby males may display brighter body coloration and more distinctive ornamentation than females. Fishes in temperate regions markedly change their energy allocation toward reproduction in response to the seasonal environment. Seasonal change in reproductive investment affects the expression of sexually dimorphic traits in males through gonadal weight change. Here, we report seasonal changes in body size, testis weight and sexual dimorphism of the fins (anal fin length and dorsal fin length) in the northern medaka Oryzias sakaizumii. Fish were collected periodically from a wild population (Aomori). Gonad weight increased from May to July in both males and females, corresponding to the reproductive season. Moreover, during this period, the degree of sexual dimorphism in fin length increased. To investigate the relationship between testis weight and individual differences in male fin length, we analyzed relationships among morphological traits using structural equation modeling. In the reproductive season, increased testis weight was associated with longer fin length in males, but the relationship disappeared after the reproductive season. These observations suggest that the sexually dimorphic fin in this fish is a mating signal. Results from a mating experiment also support this view. Males with larger size and/or longer fin attracted more mates than those with smaller fins, suggesting that sexual selection operates through females choosing to mate with males having longer fins.

Effect of fin length and shape of stemless humeral components in a reverse shoulder implant system: a FEA study

The recent reverse total shoulder arthroplasty (TSA) implant designs employ shorter humeral component stems; some designs even eliminate the stem completely. The short stem provides several advantages: preserved bone, less stress shielding, ease of revision surgery, and freedom of humeral component location due to the minimal stem length and non-complex shape. However, due to the reduction in contact surface and frictional fixation, this stemless design may cause failure of the implant, especially during early stages following surgery. In this study, the effect of fin shape and fin length of stemless humeral components were investigated, and hypothesis was that stress and micromotion would decrease as the ratio of fin length to baseplate radius increases and the overall size of the humerus component increased. 15 different 3D models of stemless humeral components, 5 different lengths and 3 different shapes, within reverse TSA systems were developed. Each humerus component was analyzed using finite element analysis (FEA) to investigate the effects of stem length and fin shape on the initial stability of the component. The highest stress and micromotion were observed at the shortest fin length; lowest stress and micromotion were found at the longest fin length. Results suggest that the length of the fin affects the stress at the bone as well as the amount of micromotion; 20–30% longer fin length than baseplate radius would be ideal for the stemless humeral component design. However, the various fin shapes showed mixed effects on the results and further investigation is required.

Approaches for expedition of discharging of PCM involving nanoparticles and radial fins

In this research, sinusoidal tank including inner circular cylinder was considered and to expedite the solidification, radial fins were installed over the inner cold cylinder. To improve the conduction, CuO nano sized material was added and effects of size of particles were involved. The governing equations consist of energy equation with one source term of solid fraction and equation for distribution of ice fraction. To fins the solution, Galerkin approach was applied and different mesh configuration in various time step helps to capture the phenomena more accurate. Validation with experimental data shows the nice accommodation. So, influence of fins length and diameter of particles were imposed. As longer fins were employed, the solidification time reduces about 3.74% when dp = 40. As dp rises from 40 to 50, temperature augments and greater energy has been achieved because of augmentation of needed time from 175.44 to 264.05 s. Impact of dp on isotherms is more significant than fins length.

Melting process of nanoparticle enhanced PCM through storage cylinder incorporating fins

This paper discusses how the arrangement of fins can affect the charging process. Mixture of paraffin and copper oxide nanomaterial has been utilized. Several configurations of fins with various position, thickness and length were discussed. Volume fraction of NEPCM in domain is constant, thus reducing melting time is criterion for good efficiency. Outputs reveal that with incorporating fins in both sides, melting process becomes more uniform. Lower melting time with using longer fins is a result of more effective buoyancy forces by dividing the whole domain into smaller blocks. Using fins over both inner and outer pipes shorten the melting time. The main purpose of current modeling is finding the optimized style of fins to gain the highest performance. Nice accommodation of outputs with empirical previous data indicates the verification of code.

Early winter foraging success, swimming performance, and morphology of juvenile landlocked Atlantic salmon reared under semi-wild and hatchery conditions

Several Finnish populations of salmonids have been maintained exclusively by stocking hatchery-reared fish for several generations, and it is crucial to know whether domestication has affected fitness-related traits and to assess how the developmental environment influences fish phenotypes. Here, we focused on Lake Saimaa landlocked salmon (Salmo salar m. sebago) and studied the role of the early rearing environment in trait formation by comparing juveniles (fingerlings) from three backgrounds: (i) semi-wild (stocked as alevins), (ii) standard hatchery, and (iii) enriched hatchery conditions We compared juvenile morphology, swimming performance, and capability of feeding on natural prey in early winter. We found no differences between standard and enriched hatchery conditions. Semi-wild fish consumed more prey items, but wet mass of stomach contents did not differ among backgrounds. Swimming endurance was comparable among backgrounds. Semi-wild fish had slenderer body shape and longer fins than hatchery-reared fish. The lack of performance differences between hatchery juveniles and their semi-wild conspecifics is possibly due to reduced phenotypic plasticity caused by extremely low levels of genetic diversity in this population.

Sexual dimorphism and dichromatism in the cyprinid fish Puntius titteya

We documented sexual dimorphism and dichromatism in the cyprinid fish Puntius titteya. We observed no sexual difference in body size, although males had longer fins than females. Male body coloration was redder and exhibited a higher saturation than that of females. However, in females, coloration in the cheek (around the gill cover) was near red and exhibited high saturation compared to coloration of the abdomen. These results clearly indicate sexual dimorphism in fin size and dichromatism in P. titteya, which suggests that this species has a high potential use as a model for studying sexual selection.

Extravagant ornaments of male threadfin rainbowfish (Iriatherina werneri) are not costly for swimming

Summary Exaggeration of male sexual ornaments should be costly, in terms of metabolic expenditure, resource allocation or even locomotor function. For example, many male ornaments are predicted to affect the aerodynamics, drag or biomechanics of movement and thus inhibit the speed or manoeuvrability of individuals; but empirical support for this is equivocal. We tested the locomotor and metabolic costs of exaggerated male ornaments in the threadfin rainbowfish (Iriatherina werneri), an Australasian native fish characterized by excessively long fin streamers. We predicted that males with greater relative ornamentation would have reduced escape abilities (i.e. burst swim speeds) as well as higher metabolic costs when resting or swimming. Furthermore, we evaluated the benefits of the signal by comparing the preference of females for males with differing amounts of ornamentation. As expected, we found that females spent more time observing (i.e. preferred) males with longer relative fins. We also experimentally reduced threadfin length and found that females continued to show preference for males with longer fins, rather than a preference for particular males. Male I. werneri with longer ornaments had higher resting metabolic rates, but we found no effect of ornament size on metabolic rates during swimming. Males with longer threadfins tended to swim faster, but our manipulation of fin length had no effect on burst swimming speed, indicating swimming abilities are not causally related to threadfin length. Overall, we found no evidence that the extravagant ornaments of male threadfin rainbowfish increase the metabolic or functional costs associated with swimming. Our results are surprising, given the high viscosity of water and the extreme length of I. werneri's ornaments. We suggest that future work should focus on the fitness costs of threadfin length, relative to reproductive output or survival under more natural conditions.

Fin Effects in Flow Channels of Plate-Fin Compact Heat Exchanger Cores

The fin effects on laminar forced convection of air in the interfin passages of plate-fin heat exchangers are investigated. Steady state fully developed flows in rectangular, trapezoidal, and triangular plate-fin channels are considered. With H1 and T conditions at the partition plates, the conjugate conduction–convection fin problem is solved computationally. The fin effects on the convective Nusselt number are shown to scale by a new dimensionless parameter Ω, which accounts for the attendant fin material and size; its limits describe perfectly conducting and nonconducting fins. Ineffective fins and the consequent reduction in the convective heat transfer coefficient are most pronounced in low fin density cores with longer fins in low-conductivity metal (stainless steel). However, with increasing fin density and shorter fins, the convection performance is virtually the same as that with 100% fin efficiency; the same is the case when fins are made of very high conductivity metal (copper). These results provide design insights for optimizing the conjugate fin-conduction and fluid-flow convection performance in plate-fin compact heat exchangers.

Aspects of the ecology and life history of Alligatorfish Aspidophoroides monopterygius

The Alligatorfish (Aspidophoroides monopterygius) is one of numerous non-commercial marine fishes for which basic elements of life history and biology are poorly known. More than 200 individuals were collected from the southern Gulf of St. Lawrence, Canada, in September 2000 and 2001, during fisheries-independent surveys. The standard length of Alligatorfish averaged 10.9 cm in 2000 and 9.2 cm in 2001, and putative age ranged between 2 and 7 years. Males possessed significantly longer pelvic fins, relative to body size, than females. We hypothesize that Alligatorfish undergo internal gametic association and that spawning takes place in mid- to late-autumn. Diet was comprised primarily of amphipods and isopods; other diet items included euphausiids, mysids, copepods, pteropods and calcareous algae. Based on analysis of individuals collected in 2000, 6.8% were affected by parasites (nematodes). Our research on the life history and ecology of Alligatorfish contributes to our knowledge of the biodiversity of Canada’s sub-Arctic marine fish fauna.

Advanced Microchannel Heat Exchanger with S-shaped Fins

Fin shape effects on thermal-hydraulic characteristics were studied for a Microchannel Heat Exchanger (MCHE) with S-shaped fins using 3D-CFD and changing the fin parameters: fin angle, overlapping length, fin width, fin length, and edge roundness. The fin angle effect on the pressure drop is consistent with the equation obtained experimentally by Weisbach for a circular bent tube: the pressure drop in the S-shaped fin configuration results from bent flow. The overlap of fins with those located immediately downstream at the offset position provides a guide wing effect that reduces the pressure drop remarkably. The overlap was changed by changing the fin radial position and arc length. The pressure drop was minimized when the downstream fins are placed in the middle of the bent flow channels formed by the fins upstream, which differs from Ito's configuration obtained from experiments with a single bent duct. Regarding arc length, the pressure drop is minimized at the standard overlapping length, which was formed to have the longest arc without a change in channel width. Shorter arc lengths from the optimum value by 30 and 50%, respectively, give 2.4 and 4.6% decreases in the heat transfer rate and 17 and 13% increases in the pressure drop. Thinner fins show better thermal-hydraulic performance for fin widths of 0.2–0.8 mm. However, the pressure drop reduced by the longer fin and heat transfer rate was also reduced. Rounded fins with 0.1mm radius increased the pressure drop by about 30% compared with that of the fin designed with no roundness.

Intraspecific taxonomy and ecology characterize morphological divergence among cutthroat trout (Oncorhynchus clarkii ssp. Richardson) populations

We compared the proportion of morphological variation accounted for by subspecies categories with the proportion encompassed by ecologically based categories in cutthroat trout (Oncorhynchus clarkii ssp.), as a means of assessing the relative importance of each approach in identifying intraspecific diversity. We used linear and geometric morphometrics to compare measures of body shape, fin length, and head features between and within subspecies of cutthroat trout. Both categories accounted for a significant proportion of the variation between and within the subspecies; however, the larger proportion was explained by subspecific differences, with the greatest morphological divergence between coastal cutthroat trout (Oncorhynchus clarkii clarkii) and interior subspecies. Ecotypic categories within each subspecies also explained significant morphological differences: stream populations had longer fins and deeper, more robust bodies than lake populations. The largest ecotypic differences occurred between stream and lake populations of Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri). Given that many cutthroat trout subspecies are of conservation concern, our study offers a better understanding of intraspecific variation existing within the species, providing precautionary evidence of incipient speciation, and a framework of describing phenotypic diversity that is correlated with ecological conditions. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 266–281.

Advanced Microchannel Heat Exchanger with S-shaped Fins

Fin shape effects on thermal-hydraulic characteristics were studied for a Microchannel Heat Exchanger (MCHE) with S-shaped fins using 3D-CFD and changing the fin parameters: fin angle, overlapping length, fin width, fin length, and edge roundness. The fin angle effect on the pressure drop is consistent with the equation obtained experimentally by Weisbach for a circular bent tube: the pressure drop in the S-shaped fin configuration results from bent flow. The overlap of fins with those located immediately downstream at the offset position provides a guide wing effect that reduces the pressure drop remarkably. The overlap was changed by changing the fin radial position and arc length. The pressure drop was minimized when the downstream fins are placed in the middle of the bent flow channels formed by the fins upstream, which differs from Ito's configuration obtained from experiments with a single bent duct. Regarding arc length, the pressure drop is minimized at the standard overlapping length, which was formed to have the longest arc without a change in channel width. Shorter arc lengths from the optimum value by 30 and 50%, respectively, give 2.4 and 4.6% decreases in the heat transfer rate and 17 and 13% increases in the pressure drop. Thinner fins show better thermal-hydraulic performance for fin widths of 0.2–0.8 mm. However, the pressure drop reduced by the longer fin and heat transfer rate was also reduced. Rounded fins with 0.1mm radius increased the pressure drop by about 30% compared with that of the fin designed with no roundness.

Fin-mutant female zebrafish (Danio rerio) exhibit differences in association preferences for male fin length

Females often choose to associate with males that have exaggerated traits. In fishes, this may reflect an overall preference for larger size in a potential mate. Female zebrafish (Danio rerio) prefer males with larger bodies but not longer fins. The availability of mutant and transgenic strains of zebrafish make this a unique model system in which to study the role of phenotypic variation in social and sexual behavior. We used mutant strains of zebrafish with truncated (short fin) and exaggerated (long fin) fins to further examine female preferences for fin length in dichotomous association tests. Wild type females showed no preferences between wild type males and short fin mutant males or between wild type males and long fin mutant males. short fin females also showed no preference for short fin males or wild type males while long fin females preferred to associate with long fin males over wild type males. These results suggest that the single gene long fin mutation that results in altered fin morphological may also be involved in a related female association preference.

The expression of secondary sexual characteristics in recruit- and repeat-spawning farmed and wild Atlantic cod (Gadus morhua)

Abstract Skjæraasen, J. E., Meager, J. J., and Karlsen, Ø. 2008. The expression of secondary sexual characteristics in recruit- and repeat-spawning farmed and wild Atlantic cod (Gadus morhua). – ICES Journal of Marine Science, 65: 1710–1716. We examined the expression of the two known secondary sexual characteristics of Atlantic cod, the pelvic fin and the drumming muscle, in farmed and wild cod stemming from the same population. Farmed and wild males had longer pelvic fins and larger drumming muscles than females, but wild cod had longer fins than farmed cod. The size of the drumming muscle of males was similar among wild and farmed cod, but farmed females had smaller muscles than their wild counterparts. Repeat-spawning wild males tended to invest less in drumming-muscle mass and more in pelvic-fin growth than recruit-spawning fish, whereas the reverse was true for farmed males. Males use pelvic fins to embrace females during ventral mounts, a key mating behaviour, and display them to other males during agonistic interactions. The drumming muscle is used by males to produce sound during courtship and aggressive displays, whereas females only use sound outside the spawning season, for agonistic and defensive behaviours that are unlikely to be as important in the farming environment. The results are discussed in the context of the reproductive success of farmed escapees in the wild.

A new species of Chondrostoma Agassiz, 1832 (Cypriniformes: Cyprinidae) with sexual dimorphism from the lower Rio Tejo Basin, Portugal

Chondrostoma olisiponensis sp. nov. is described from the lower Rio Tejo Basin. It is a small species (all specimens examined less than 105mm SL) distinguished from the other species of Chondrostoma s.l. by the following combination of characters. Chondrostoma olisiponensis lacks a horny blade on the lower jaw, has a pronouncedly arched mouth, and lacks an intense reddish coloration at the base of the fins. It has elongated pelvic fins that reach the anus and often pass the anal-fin insertion in males, and dorsal, pelvic and anal fins usually have 8 branched rays. The new species has 36 to 43 scales in the lateral line, 7.0 to 8.5 scales above the lateral line, 13 to 16 circumpeduncular scales, denticulated (vs. smooth) grinding teeth surfaces, 6-5/5 pharyngeal teeth and 15 to 19 gill rakers. Chondrostoma olisiponensis is further distinguished from C. lusitanicum, a phylogenetically close species that lives in the same area, by having a higher body, a relatively longer head, and a larger eye. The origins of anal and pelvic fins are displaced anteriorly, while the origin of pectoral fins is displaced posteriorly. Pelvic and pectoral fins and last anal-fin ray are longer in the new species. Unlike the other species in the genus, C. olisiponensis shows external sexual dimorphism, with males having longer pelvic fins whose extremities pass the anus and often overlap with the anal fin. This description raises concerns on the recently proposed splitting of Chondrostoma s.l. since the morphological traits deemed characteristic of some genera are unsuitable for their diagnosis. The species should be considered Critically Endangered (CR) according to IUCN criteria B1ab(ii,iii,iv)c(iv)+2ab(ii,iii,iv)c(iv).

Spray Cooling of High Aspect Ratio Open Microchannels

Direct spraying of dielectric liquids has been shown to be an effective method of cooling high-power electronics. Recent studies have illustrated that even higher heat transfer can be obtained by adding extended structures, particularly straight fins, to the heated surface. In the current work, spray cooling of high-aspect-ratio open microchannels was explored, which substantially increases the total surface area and allows more residence time for the incoming liquid to be heated by the wall. Five such heat sinks were constructed, and their thermal performance was investigated. These heat sinks featured a projected area of 1.41×1.41cm2, channel width of 360μm, a fin width of 500μm, and fin lengths of 0.25mm, 0.50mm, 1.0mm, 3.0mm, and 5.0mm. The five enhanced surfaces and a flat surface with the same projected area were sprayed with a full cone nozzle using PF-5060 at 30°C and nozzle pressure differences from 1.36–4.08atm(69–121ml∕min). In all cases, the enhanced surfaces improved thermal performance compared to the flat surface. Longer fins were found to outperform shorter ones in the single-phase regime. Adding fins also resulted in the onset of two-phase effects (and higher-heat transfer) at lower wall temperatures than the flat surface. The two-phase regime was characterized by a balance between added area, changing flow flux, flow channeling, and added conduction resistance. Spray efficiency calculations indicated that a much larger percentage of the liquid sprayed onto the enhanced surface evaporated than with the flat surface. Fin lengths between 1mm and 3mm appeared to be optimum for heat fluxes as high as 124W∕cm2 (based on projected area) and the range of conditions studied.