Computational fluid dynamics of flow regime and hydrodynamic forces generated by a gliding North Atlantic right whale (Eubalaena glacialis)

Accurate estimates of drag on marine animals are required to investigate the locomotive cost, propulsive efficiency, and the impacts of entanglement if the animal is carrying fishing gear. In this study, we performed computational fluid dynamics analysis of a 10 m (length over all) right whale to obtain baseline measurements of drag on the animal. Swimming speeds covering known right whale speed range (0.125 m/s to 8 m/s) were tested. We found a weak dependence between drag coefficient and Reynolds number. At a swimming speed of 2 m/s, we analyzed the boundary layer thicknesses, the flow regimes, and drag components. We found the thickest boundary layer at the lateral sides of the peduncle, whereas the boundary layer thickness over the outer part of the flukes was less than 1.7 cm. Laminar flow occurred over the anterior ~0.6 LoA and turbulent flow from ~0.8 LoA to the fluke notch. On the surfaces of the flukes outside of the body wake region, flow was laminar. Our most significant finding is that the drag coefficient (0.0071–0.0059) of a right whale for swimming speeds ranging from 0.25 m/s to 2 m/s is approximately twice that of many previous estimates for cetaceans.     

Effect of larval ontogeny, turbulence and light on prey attack rate and swimming activity in herring larvae

The effects of ontogeny (larval size), light and turbulence on the attack rate and swimming activity (proportion of time swimming and duration of swimming bout) of herring larvae (15-28 mm TL) have been investigated. Emphasis was put on the experimental design in order to create a set-up where the turbulence intensity distribution could be accurately measured as well as controlled in the entire experimental tank.Both larval size (ontogeny) and light had a significant positive effect on prey attack rate. Likewise, an intermediate increase in turbulence had a positive effect on prey attack rate, but this effect was dependent of light intensity and larval size.At low light (1.5 μE m² s⁻¹) intermediate turbulence increased the prey attack rate significantly for larger larvae (26 and 28 mm), while at high light (18 μE m² s⁻¹) intermediate turbulence had only a significant positive effect on the attack rate of smaller larvae 20 and 23 mm.In general, our data show a dome-shaped response of turbulence on attack rate and a U-shaped response of turbulence on swimming activity.For herring larvae >20 mm, the maximum (attack rate) and minimum (swimming activity) response of turbulence were found at intermediate turbulence intensities (energy dissipation rates between 7∗10⁻⁸ and 1∗10⁻⁶ W/kg). The highest turbulence level tested (8∗10⁻⁶ W/kg) showed only negative effects, as attack rates where at the lowest and swimming activity at the highest.Swimming activity increased with larval size or light, and decreased at intermediate turbulence. Compared to turbulent intensities under natural conditions this implies that larger herring larvae at 10 m depth have to be exposed to wind speeds of more than 17 m/s before negative effects on attack rate and swimming activity occurs.     

Numerical streamline patterns at swimmer's surface using RANS equations

The objective of this article is to perform a numerical modeling on the flow dynamics around a competitive female swimmer during the underwater swimming phase for a velocity of 2.2 m/s corresponding to national swimming levels. Flow around the swimmer is assumed turbulent and simulated with a computational fluid dynamics method based on a volume control approach. The 3D numerical simulations have been carried out with the code ANSYS FLUENT and are presented using the standard k-ω turbulence model for a Reynolds number of 6.4 × 10(6). To validate the streamline patterns produced by the simulation, experiments were performed in the swimming pools of the National Institute of Sports and Physical Education in Paris (INSEP) by using the tufts method.     

Evaluation of Adult White Sturgeon Swimming Capabilities and Applications to Fishway Design

Concern over passage of sturgeon barriers, has focused attention on fishway design that accommodates its swimming performance. In order to evaluate swimming performance, regarding fish ladder type partial barriers, wild adult sturgeons, Acipenser transmontanus; 121–76m fork length, were captured in the San Francisco Bay Estuary and Yolo Bypass toe drain. Hydrodynamic forces and kinematic parameters for swimming performance data were collected in a laboratory flume under three flow conditions through barriers and ramp. The experiments were conducted in a 24.4 m long, 2.1 m wide, and 1.62 m deep aluminum channel. Two geometric configurations of the laboratory model were designed based on channel characteristics that have been identified in natural river systems. At a given swimming speed and fish size, the highest guidance efficiencies of successful white sturgeon passage as a function of flow depth, flow velocity, turbulence intensity, Reynolds number, Froude number and shear velocity observed in the steady flow condition, tested with the horizontal ramp structure, occurred at an approach velocity of 0.33 ms^-1. The guidance efficiency of successful sturgeon passage increased both with increasing flow velocity and Froude number, and decreased both with the flow depth and the turbulence intensity. This study also provides evidence that tail beat frequency increases significantly with swimming speed, but tail beat frequency decreases with fish total length. Stride length increases both with swimming speed and fish total length. The importance of unsteady forces is expressed by the reduced frequency both with swimming speed and fish total length. Regression analysis indicates that swimming kinematic variables are explained by the swimming speed, the reduced frequency and the fish total length. The results emphasize the importance of fish ladder type patchiness when a fishway is designed for the passage of sturgeon.     

Estimating the relative abundance of emperor penguins at inaccessible colonies using satellite imagery

Emperor penguin (Aptenodytes forsteri) populations are useful environmental indicators due to the bird’s extreme reliance on sea ice. We used remote sensing technology to estimate relative adult bird abundance at two inaccessible emperor penguin colonies in the Ross Sea, Antarctica. We performed supervised classification of 12 panchromatic satellite images of the seven known Ross Sea colonies. We used regression to predict adult bird counts at the inaccessible colonies by relating the number of pixels classified as “penguin” in the satellite images of the accessible colonies to corresponding known adult bird counts from aerial photographs or ground counts. While our analysis was hampered by excessive guano and shadows, we used satellite imagery to differentiate between relatively small (<3,000 adult birds) and larger colonies (>5,000 adult birds). Remote sensing technology is logistically less intense and less costly than aerial or ground censuses when the objective is to document penguin presence and/or large emperor penguin population changes (e.g., catastrophic changes). Improvements expected soon in the resolution of the satellite images should allow for more accurate abundance estimates.     

Diving behaviour and energetics in breeding little penguins (Eudyptula minor)

We present data on the diving behaviour and the energetics of breeding little penguins in Tasmania, Australia. Using an 18 m long still water canal in conjunction with respirometry, we determined the energy requirements while diving. Using electronic devices measuring dive depth or swimming speed, we investigated the foraging behaviour at sea. Cost of Transport was calculated to be minimal at the speed the birds prefer at sea (1.8 m/s) and averaged 11.1 J/kg/m (power requirements at that speed: 20.0 W/kg). Metabolic rate of little penguins resting in water was found to be 8.5 W/kg. The externally-attached devices had no significant influence on the energy expenditure.
Foraging trips can be divided into four distinct phases with different diving behaviours. A mean of 500 dives was executed per foraging trip lasting about 18 hours with 60% of this time being spent swimming. The total distance travelled averaged 73 km per day, although foraging range was about 12km. Mean swimming speed of little penguins at sea was 1.8 m/s, maximum swimming speed was 3.3 m/s. More than 50% of all dives had maxima not exceeding 2 m. Maximum depth reached was 27 m. Mean dive duration was 21 s. There were inter-sex differences in diving behaviour as well as changes in foraging behaviour over the breeding period. Aerobic dive limits (ADL) in the wild were estimated between 42 and 50 s. From the swim canal experiments we derived an ADL of 44 s. Total oxygen stores were calculated to be 45 ml O₂/kg. Only 2% of all dives exceeded the ADL. FMRs at sea were calculated to be between 1280 and 1500 kJ/kg/d according to chick size. The yearly food requirements of a breeding little penguin amount to 114 kg.     

Influence of a postural change of the swimmer's head in hydrodynamic performances using 3D CFD

This study deals with recent researches undertaken by the authors in the field of hydrodynamics of human swimming. The aim of this numerical study was to investigate the flow around the entire swimmer's body. The results presented in this article focus on the combination of a 3D computational fluid dynamics code and the use of the k–ω turbulence model, in the range of Reynolds numbers representative of a swimming level varying from national to international competition. Emphasis is placed on the influence of a postural change of the swimmer's head in hydrodynamic performances, which is directly related to the reduction of overall drag. These results confirm and complete those, less accurate, of a preliminary 2D study recently published by the authors and allow the authors to optimise the swimmer's head position in underwater swimming.     

Coronary ligation reduces maximum sustained swimming speed in Chinook salmon, Oncorhynchus tshawytscha

The maximum aerobic swimming speed of Chinook salmon (Oncorhynchus tshawytscha) was measured before and after ligation of the coronary artery. Coronary artery ligation prevented blood flow to the compact layer of the ventricular myocardium, which represents 30% of the ventricular mass, and produced a statistically significant 35.5% reduction in maximum swimming speed. We conclude that the coronary circulation is important for maximum aerobic swimming and implicit in this conclusion is that maximum cardiac performance is probably necessary for maximum aerobic swimming performance.     

不同体质量和饥饿程度对红鳍东方鲀幼鱼游泳能力的影响

为了考察不同体质量和饥饿程度红鳍东方鲀(Takifugu rubripes)幼鱼的游泳能力,利用行为生态学方法测定了不同体质量(0.22—3.31 g)和饥饿天数(1d、3d、6d和9d)下红鳍东方鲀幼鱼的绝对临界游速(U_crit,cm/s)、相对临界游速(U_crit’,体长/s,BL/s)、偏好游速(U_pref,cm/s)、6个流速区域(2—36 cm/s)下停留时间百分比(P_t,%)、偏好区域平均流速(V_mean,cm/s)和总游泳距离(D_1h,m)等游泳行为指标。结果显示,体质量和饥饿显著影响红鳍东方鲀幼鱼的U_crit、U_crit’、P_t、V_mean和D_1h。随体质量增加,实验鱼的U_crit、U_pref、V_mean和D_1h均逐渐升高,而U_crit...     

不同流速下杂交鲟幼鱼游泳状态与活动代谢研究

为研究水流速度对杂交鲟幼鱼行为和代谢的影响,探讨游泳状态与活动代谢及相关游泳运动参数之间的关系,在26℃水温下,使用特制的鱼类游泳行为和活动代谢同步测定装置,测定了杂交鲟幼鱼在0.1、0.3、0.5 m/s三种流速和静水条件下的游泳状态、趋流率、摆尾频率和耗氧率。结果表明:随着流速的增大,杂交鲟幼鱼逆流前进和逆流静止游泳状态所占时间比例显著减少,而逆流后退所占时间比例显著增加,顺流而下时间比例有所上升。在0.0—0.3 m/s的流速范围内,杂交鲟幼鱼各个时段的平均趋流率、摆尾频率和耗氧率均随着流速的增加而增大,在0.3 m/s流速下分别达到100%﹑(2.53±0.34)Hz和(490.99±164.59)mg O2/(kg.h)。当流速增加至0.5 m/s时,在趋流率仍保持100%的情况下,其耗氧率相比0.3 m/s增加了21.86%,而摆尾频率却减小了6.70%。实验过程杂交鲟幼鱼趋流率与摆尾频率呈显著线性正相关,而摆尾频率与耗氧率在大部分时段却无相关性。随着时间的延长,各流速组杂交鲟幼鱼趋流率、摆尾频率和耗氧率呈现不同的变化趋势,其趋流率均相对稳定;但摆尾频率均随时间延长呈下降趋势,而耗氧率则在实验前9h随时间延长逐渐增加,随后趋于稳定。研究结果提示:杂交鲟幼鱼游泳状态的变化与流速有关,而反映运动强度大小的摆尾频率与活动代谢率的关系受到游泳状态的显著影响,同时也与运动代谢特征的时间变化有关。       

Effect of Flow Turbulence on Swimming Speed of Fish

The effect of flow turbulence on the swimming speed was studied in perch (Perca fluviatilis) with different body length. The critical flow rate was used as an index of fish swimming performance. The longer was the fish, the higher turbulence was required to decrease the critical flow rate. The mechanism of turbulence impact on fish locomotion relied on the vortex structure of the flow. The torque produced by hydrodynamic forces in a vortex favors fish overturn and loss of balance. Such effect of turbulence was observed when the sizes of the vortex and fish body were similar. The fish uses the pectoral fins to restore the balance, which increases their hydraulic resistance and, together with energy expenditure for spatial balance control, decreases the swimming speed.     

Skin-friction drag analysis from the forced convection modeling in simplified underwater swimming

This study deals with skin-friction drag analysis in underwater swimming. Although lower than profile drag, skin-friction drag remains significant and is the second and only other contribution to total drag in the case of underwater swimming. The question arises whether varying the thermal gradient between the underwater swimmer and the pool water may modify the surface shear stress distribution and the resulting skin-friction drag acting on a swimmer's body. As far as the authors are aware, such a question has not previously been addressed. Therefore, the purpose of this study was to quantify the effect of this thermal gradient by using the integral formalism applied to the forced convection theory. From a simplified model in a range of pool temperatures (20-30 degrees C) it was demonstrated that, whatever the swimming speeds, a 5.3% reduction in the skin-friction drag would occur with increasing average boundary-layer temperature provided that the flow remained laminar. However, as the majority of the flow is actually turbulent, a turbulent flow analysis leads to the major conclusion that friction drag is a function of underwater speed, leading to a possible 1.5% reduction for fast swimming speeds above 1m/s. Furthermore, simple correlations between the surface shear stress and resulting skin-friction drag are derived in terms of the boundary-layer temperature, which may be readily used in underwater swimming situations.     

Comparative squamation of the lateral line canal pores in sharks

The current study collected the first quantitative data on lateral line pore squamation patterns in sharks and assessed whether divergent squamation patterns are similar to experimental models that cause reduction in boundary layer turbulence. In addition, the hypothesis that divergent orientation angles are exclusively found in fast‐swimming shark species was tested. The posterior lateral line and supraorbital lateral line pore squamation of the fast‐swimming pelagic shortfin mako shark Isurus oxyrinchus and the slow‐swimming epi‐benthic spiny dogfish shark Squalus acanthias was examined. Pore scale morphology and pore coverage were qualitatively analysed and compared. In addition, pore squamation orientation patterns were quantified for four regions along the posterior lateral line and compared for both species. Isurus oxyrinchus possessed consistent pore scale coverage among sampled regions and had a divergent squamation pattern with multiple scale rows directed dorsally and ventrally away from the anterior margin of the pore with an average divergent angle of 13° for the first row of scales. Squalus acanthias possessed variable amounts of scale coverage among the sampled regions and had a divergent squamation pattern with multiple scale rows directed ventrally away from the anterior margin of the pore with an average angle of 19° for the first row of scales. Overall, the squamation pattern measured in I. oxyrinchus fell within the parameters used in the fluid flow analysis, which suggests that this pattern may reduce boundary layer turbulence and affect lateral line sensitivity. The exclusively ventral oriented scale pattern seen in S. acanthias possessed a high degree of divergence but the pattern did not match that of the fluid flow models. Given current knowledge, it is unclear how this would affect boundary layer flow. By studying the relationship between squamation patterns and the lateral line, new insights are provided into sensory biology that warrant future investigation due to the implications for the ecology, morphology and sensory evolution of sharks.     

Drag of suction cup tags on swimming animals: Modeling and measurement

Bio‐logging tags are widely used to study the behavior and movements of marine mammals with the tacit assumption of little impact to the animal. However, tags on fast‐swimming animals generate substantial hydrodynamic forces potentially affecting behavior and energetics adversely, or promoting early removal of the tag. In this work, hydrodynamic loading of three novel tag housing designs are compared over a range of swimming speeds using computational fluid dynamics (CFD). Results from CFD simulation were verified using tag models in a water flume with close agreement. Drag forces were reduced by minimizing geometric disruptions to the flow around the housing, while lift forces were reduced by minimizing the frontal cross‐sectional area of the housing and holding the tag close to the attachment surface. Hydrodynamic tag design resulted in an experimentally measured 60% drag force reduction in 5.6 m/s flow. For all housing designs, off‐axis flow increased the magnitude of the force on the tag. Experimental work with a common dolphin (Delphinus delphis) cadaver indicates that the suction cups used to attach the types of tags described here provide sufficient attachment force to resist failure to predicted forces at swimming speeds of up to 10 m/s.     

Effect of leg kick on active drag in front-crawl swimming: Comparison of whole stroke and arms-only stroke during front-crawl and the streamlined position

The purpose of this study was to examine the effect of leg kick on the resistance force in front-crawl swimming. The active drag in front-crawl swimming with and without leg motion was evaluated using measured values of residual thrust (MRT method) and compared with the passive drag of the streamlined position (SP) for the same swimmers. Seven male competitive swimmers participated in this study, and the testing was conducted in a swimming flume. Each swimmer performed front-crawl under two conditions: using arms and legs (whole stroke: WS) and using arms only (arms-only stroke: AS). Active drag and passive drag were measured at swimming velocities of 1.1 and 1.3 m s⁻¹ using load cells connected to the swimmer via wires. We calculated a drag coefficient to compare the resistances of the WS, AS and SP at each velocity. For both the WS and AS at both swimming velocities, active drag coefficient was found to be about 1.6–1.9 times larger than that in passive conditions. In contrast, although leg movement did not cause a difference in drag coefficient for front-crawl swimming, there was a large effect size (d = 1.43) at 1.3 m s⁻¹. Therefore, although upper and lower limb movements increase resistance compared to the passive condition, the effect of leg kick on drag may depend on swimming velocity.     

New giant penguin bones from Antarctica: Systematic and paleobiological significance

A tarsometatarsus and a fragmented humerus of striking dimensions recently collected in the Late Eocene locality DPV 13/84 Submeseta Formation-level 38 Submeseta II-, Seymour (Marambio) Island, Antarctic Peninsula were both assigned to Palaeeudyptes klekowskii. According to estimates, the tarsometatarsus would belong to the largest and most massive penguin described so far. This bird was probably a piscivorous penguin, with high diving ability for catching prey. Although the humerus is not an appropriate element for body mass or body length assessments, it also belonged to a huge penguin.     

Reproductive ecology of cultured fish in the wild

Domestication has been shown to have an effect on morphology and behaviour of Atlantic salmon ( Salmo salar ). We compared swimming costs of three groups of juvenile Atlantic salmon subject to different levels of domestication: (1) wild fish; (2) first generation farmed fish origination from wild genitors; and (2) seventh generation farmed fish originating from Norwegian aquaculture stocks. We assessed swimming costs under two types of turbulent flow (one mean flow velocity of 23 cm s⁻¹ and two standard deviations of flow velocity of 5 and 8 cm s⁻¹). Respirometry experiments were conducted with fish in a mass range of 5–15 g wet at a water temperature of 15° C. Our results confirm (1) that net swimming costs are affected by different levels of turbulence such that, for a given mean flow velocity, fish spent 1·5‐times more energy as turbulence increased, (2) that domesticated fish differed in their morphology (having deeper bodies and smaller fins) and in their net swimming costs (being up to 30·3% higher than for wild fish) and (3) that swimming cost models developed for farmed fish may be also be applied to wild fish in turbulent environments.     

Turbulent flow evaluation of the venous needle during hemodialysis

Arteriovenous (AV) grafts and fistulas used for hemodialysis frequently develop intimal hyperplasia (IH) at the venous anastomosis of the graft, leading to flow-limiting stenosis, and ultimately to graft failure due to thrombosis. Although the high AV access blood flow has been implicated in the pathogenesis of graft stenosis, the potential role of needle turbulence during hemodialysis is relatively unexplored. High turbulent stresses from the needle jet that reach the venous anastomosis may contribute to endothelial denudation and vessel wall injury. This may trigger the molecular and cellular cascade involving platelet activation and IH, leading to eventual graft failure. In an in-vitro graft/needle model dye injection flow visualization was used for qualitative study of flow patterns, whereas laser Doppler velocimetry was used to compare the levels of turbulence at the venous anastomosis in the presence and absence of a venous needle jet. Considerably higher turbulence was observed downstream of the venous needle, in comparison to graft flow alone without the needle. While turbulent RMS remained around 0.1 m/s for the graft flow alone, turbulent RMS fluctuations downstream of the needle soared to 0.4-0.7 m/s at 2 cm from the tip of the needle and maintained values higher than 0.1 m/s up to 7-8 cm downstream. Turbulent intensities were 5-6 times greater in the presence of the needle, in comparison with graft flow alone. Since hemodialysis patients are exposed to needle turbulence for four hours three times a week, the role of post-venous needle turbulence may be important in the pathogenesis of AV graft complications. A better understanding of the role of needle turbulence in the mechanisms of AV graft failure may lead to improved design of AV grafts and venous needles associated with reduced turbulence, and to pharmacological interventions that attenuate IH and graft failure resulting from turbulence.     

Differences in the energetic cost of swimming in turbulent flow between wild,farmed and domesticated juvenile Atlantic salmon Salmo salar

Domestication has been shown to have an effect on morphology and behaviour of Atlantic salmon (Salmo salar). We compared swimming costs of three groups of juvenile Atlantic salmon subject to different levels of domestication: (1) wild fish; (2) first generation farmed fish origination from wild genitors; and (2) seventh generation farmed fish originating from Norwegian aquaculture stocks. We assessed swimming costs under two types of turbulent flow (one mean flow velocity of 23 cm s^?1 and two standard deviations of flow velocity of 5 and 8 cm s^?1). Respirometry experiments were conducted with fish in a mass range of 5–15 g wet at a water temperature of 15° C. Our results confirm (1) that net swimming costs are affected by different levels of turbulence such that, for a given mean flow velocity, fish spent 1·5‐times more energy as turbulence increased, (2) that domesticated fish differed in their morphology (having deeper bodies and smaller fins) and in their net swimming costs (being up to 30·3% higher than for wild fish) and (3) that swimming cost models developed for farmed fish may be also be applied to wild fish in turbulent environments.     

流速对细鳞裂腹鱼游泳行为及能量消耗影响的研究

通过自制密封的鱼类游泳实验装置, 研究了流速对细鳞裂腹鱼游泳行为和能量消耗的影响。结果显示,细鳞裂腹鱼的摆尾频率随游泳速度的变化有明显的变化规律, 摆尾频率随着流速的增加而显著性的增加,而摆尾幅度有减小趋势, 差异性不显著。结果还表明, (26±1) ℃时, (10.60±0.54) cm 细鳞裂腹鱼的相对临界游泳速度为(11.5±0.5) BL/s, 绝对临界游泳速度为(110.28±2.02) cm/s。测定的相对临界流速较其他的鲤科鱼大,是对生存水流环境(流速0.5—1.5m/s)适应性的表现。这一结果表明鱼类的游泳能力是能够训练的。运动代谢率与相对流速的关系为, AMR = 93.08e(0.307v) + 314.33, R2= 0.994; 单位距离能耗与流速的指数关系为COT =28e (-1.03V) +6.05, R2= 0.998。流速达到8 BL/s 时, 裂腹鱼耗氧率开始下降, 从流速7 BL/s 时, (1245.57±90.97 )mg O2/(kg·h)最大, 下降到(978.78±189.38) mg O2/(kg·h)。1—7 BL/s 流速范围内, 裂腹鱼单位时间内的耗氧率随着游泳速度的增加而增加, 而且随着游泳速度的增加, 单位距离能耗(COT)逐渐减少, 最小能耗在6 倍体长流速, 0.68 m/s 时, 为(6.00±1.57) J/(kg·m), 其能量利用效率最大。