Anderson Erik J.

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Anderson
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Erik J.
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  • Article
    The hydrodynamic footprint of a benthic, sedentary fish in unidirectional flow
    (Acoustical Society of America, 2007-08) Coombs, Sheryl ; Anderson, Erik J. ; Braun, Christopher B. ; Grosenbaugh, Mark A.
    Mottled sculpin (Cottus bairdi) are small, benthic fish that avoid being swept downstream by orienting their bodies upstream and extending their large pectoral fins laterally to generate negative lift. Digital particle image velocimetry was used to determine the effects of these behaviors on the spatial and temporal characteristics of the near-body flow field as a function of current velocity. Flow around the fish's head was typical for that around the leading end of a rigid body. Flow separated around the edges of pectoral fin, forming a wake similar to that observed for a flat plate perpendicular to the flow. A recirculation region formed behind the pectoral fin and extended caudally along the trunk to the approximate position of the caudal peduncle. In this region, the time-averaged velocity was approximately one order of magnitude lower than that in the freestream region and flow direction varied over time, resembling the periodic shedding of vortices from the edge of a flat plate. These results show that the mottled sculpin pectoral fin significantly alters the ambient flow noise in the vicinity of trunk lateral line sensors, while simultaneously creating a hydrodynamic footprint of the fish's presence that may be detected by the lateral line of nearby fish.
  • Article
    Ontogenetic changes in larval swimming and orientation of pre-competent sea urchin Arbacia punctulata in turbulence
    (Company of Biologists, 2016-05-04) Wheeler, Jeanette D. ; Chan, Kit Yu Karen ; Anderson, Erik J. ; Mullineaux, Lauren S.
    Many marine organisms have complex life histories, having sessile adults and relying on the planktonic larvae for dispersal. Larvae swim and disperse in a complex fluid environment and the effect of ambient flow on larval behavior could in turn impact their survival and transport. However, to date, most studies on larvae–flow interactions have focused on competent larvae near settlement. We examined the importance of flow on early larval stages by studying how local flow and ontogeny influence swimming behavior in pre-competent larval sea urchins, Arbacia punctulata. We exposed larval urchins to grid-stirred turbulence and recorded their behavior at two stages (4- and 6-armed plutei) in three turbulence regimes. Using particle image velocimetry to quantify and subtract local flow, we tested the hypothesis that larvae respond to turbulence by increasing swimming speed, and that the increase varies with ontogeny. Swimming speed increased with turbulence for both 4- and 6-armed larvae, but their responses differed in terms of vertical swimming velocity. 4-Armed larvae swam most strongly upward in the unforced flow regime, while 6-armed larvae swam most strongly upward in weakly forced flow. Increased turbulence intensity also decreased the relative time that larvae spent in their typical upright orientation. 6-Armed larvae were tilted more frequently in turbulence compared with 4-armed larvae. This observation suggests that as larvae increase in size and add pairs of arms, they are more likely to be passively re-oriented by moving water, rather than being stabilized (by mechanisms associated with increased mass), potentially leading to differential transport. The positive relationship between swimming speed and larval orientation angle suggests that there was also an active response to tilting in turbulence. Our results highlight the importance of turbulence to planktonic larvae, not just during settlement but also in earlier stages through morphology–flow interactions.
  • Article
    From the track to the ocean : using flow control to improve marine bio-logging tags for cetaceans
    (Public Library of Science, 2017-02-14) Fiore, Giovani ; Anderson, Erik J. ; Garborg, C. Spencer ; Murray, Mark M. ; Johnson, Mark P. ; Moore, Michael J. ; Howle, Laurens ; Shorter, K. Alex
    Bio-logging tags are an important tool for the study of cetaceans, but superficial tags inevitably increase hydrodynamic loading. Substantial forces can be generated by tags on fast-swimming animals, potentially affecting behavior and energetics or promoting early tag removal. Streamlined forms have been used to reduce loading, but these designs can accelerate flow over the top of the tag. This non-axisymmetric flow results in large lift forces (normal to the animal) that become the dominant force component at high speeds. In order to reduce lift and minimize total hydrodynamic loading this work presents a new tag design (Model A) that incorporates a hydrodynamic body, a channel to reduce fluid speed differences above and below the housing and wing to redirect flow to counter lift. Additionally, three derivatives of the Model A design were used to examine the contribution of individual flow control features to overall performance. Hydrodynamic loadings of four models were compared using computational fluid dynamics (CFD). The Model A design eliminated all lift force and generated up to ~30 N of downward force in simulated 6 m/s aligned flow. The simulations were validated using particle image velocimetry (PIV) to experimentally characterize the flow around the tag design. The results of these experiments confirm the trends predicted by the simulations and demonstrate the potential benefit of flow control elements for the reduction of tag induced forces on the animal.
  • Article
    Isolating the hydrodynamic triggers of the dive response in eastern oyster larvae
    (John Wiley & Sons, 2015-05-06) Wheeler, Jeanette D. ; Helfrich, Karl R. ; Anderson, Erik J. ; Mullineaux, Lauren S.
    Understanding the behavior of larval invertebrates during planktonic and settlement phases remains an open and intriguing problem in larval ecology. Larvae modify their vertical swimming behavior in response to water column cues to feed, avoid predators, and search for settlement sites. The larval eastern oyster (Crassostrea virginica) can descend in the water column via active downward swimming, sinking, or “diving,” which is a flick and retraction of the ciliated velum to propel a transient downward acceleration. Diving may play an important role in active settlement, as diving larvae move rapidly downward in the water column and may regulate their proximity to suitable settlement sites. Alternatively, it may function as a predator-avoidance escape mechanism. We examined potential hydrodynamic triggers to this behavior by observing larval oysters in a grid-stirred turbulence tank. Larval swimming was recorded for two turbulence intensities and flow properties around each larva were measured using particle image velocimetry. The statistics of flow properties likely to be sensed by larvae (fluid acceleration, deformation, vorticity, and angular acceleration) were compared between diving and non-diving larvae. Our analyses showed that diving larvae experienced high average flow accelerations in short time intervals (approximately 1–2 s) prior to dive onset, while accelerations experienced by non-diving larvae were significantly lower. Further, the probability that larvae dove increased with the fluid acceleration they experienced. These results indicate that oyster larvae actively respond to hydrodynamic signals in the local flow field, which has ecological implications for settlement and predator avoidance.
  • Thesis
    Advances in the visualization and analysis of boundary layer flow in swimming fish
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2005-02) Anderson, Erik J.
    In biology, the importance of fluid drag, diffusion, and heat transfer both internally and externally, suggest the boundary layer as an important subject of investigation, however, the complexities of biological systems present significant and unique challenges to analysis by experimental fluid dynamics. In this investigation, a system for automatically profiling the boundary layer over free-swimming, deforming bodies was developed and the boundary layer over rigid and live mackerel, bluefish, scup and eel was profiled. The profiling system combined robotics, particle imaging velocimetry, a custom particle tracking code, and an automatic boundary layer analysis code. Over 100,000 image pairs of flow in the boundary layer were acquired in swimming fish alone, making spatial and temporal ensemble averaging possible. A flat plate boundary layer was profiled and compared to known laminar and turbulent boundary layer theory. In general, profiles resembled those of Blasius for sub-critical length Reynolds numbers, Reχ. Transition to a turbulent boundary layer was observed near the expected critical Reχ and subsequent profiles agreed well with the law of the wall. The flat plate analysis demonstrated that the particle tracking and boundary layer analysis algorithms were highly accurate. In rigid fish, separation of flow was clearly evident and the boundary layer transitioned to turbulent at lower Reχ than in swimming fish and the flat plate. Wall shear stress, τo forward of separation was slightly higher than flat plate values. Friction drag in rigid and swimming fish was determined by integrating τo over the surface of the fish. The analysis was facilitated by the definition of the relative local coefficient of friction. In general, there was no significant difference in friction drag between the rigid-body and swimming cases. In swimming, separation was, on average, delayed. Therefore, pressure drag was estimated on the basis of thickness ratio and used to calculate an upper-bound total drag on a swimming fish. Total drag was used to determine the required muscle power output during swimming and compare that with existing muscle power data. τo and boundary layer thickness oscillated with undulatory phase. The magnitude of oscillation appears to be linked to body wave amplitude.
  • Preprint
    Light stimulates swimming behavior of larval eastern oysters Crassostrea virginica in turbulent flow
    ( 2017-05) Wheeler, Jeanette D. ; Luo, Elaine ; Helfrich, Karl R. ; Anderson, Erik J. ; Starczak, Victoria R. ; Mullineaux, Lauren S.
    Planktonic larvae of the eastern oyster Crassostrea virginica are able to regulate their vertical position in the water, but the environmental cues responsible for this regulation, particularly in turbulent settings, remain unclear. We quantified swimming responses of late-stage oyster larvae in a grid-stirred turbulence tank to determine how light affects the swimming behavior of larvae over a range of hydrodynamic conditions similar to their natural coastal environments. We used particle image velocimetry and larval tracking to isolate larval swimming from local flow and to quantify 3 behavioral metrics: vertical swimming direction, proportion of larvae diving, and proportion of larvae swimming helically. We compared these metrics across turbulence levels ranging from still water (ε = 0 cm2 s-3) to estuarine-like conditions (ε = 0.4 cm2 s-3) in light and dark. At all turbulence levels, light had no effect on the proportion of upward swimming larvae, but elicited detectable increases in the proportion of helical swimming and diving behaviors. We further examined the effect of light and turbulence on specific characteristics of helical trajectories, and found that these environmental cues induce changes to both vertical and horizontal velocities of helically swimming larvae, changing the helix geometry. The increased prevalence of these behaviors in light likely plays an ecological role: increased diving in light (in conjunction with turbulence) is a potential mechanism to enhance settlement success, while changes to helical swimming in light may serve an anti-predatory function. Together, these behaviors provide insight into potentially complex larval responses to multiple simultaneous environmental cues.
  • Article
    Upward swimming of competent oyster larvae Crassostrea virginica persists in highly turbulent flow as detected by PIV flow subtraction
    (Inter-Research, 2013-08-15) Wheeler, Jeanette D. ; Helfrich, Karl R. ; Anderson, Erik J. ; McGann, B. ; Staats, P. ; Wargula, Anna E. ; Wilt, K. ; Mullineaux, Lauren S.
    Investigating settlement responses in the transitory period between planktonic and benthic stages of invertebrates helps shape our understanding of larval dispersal and supply, as well as early adult survival. Turbulence is a physical cue that has been shown to induce sinking and potentially settlement responses in mollusc larvae. In this study, we determined the effect of turbulence on vertical swimming velocity and diving responses in competent eastern oyster larvae Crassostrea virginica. We quantified the behavioural responses of larvae in a moving flow field by measuring and analyzing larval velocities in a relative framework (where local flow is subtracted away, isolating the behavioural component) in contrast to the more common absolute framework (in which behaviour and advection by the flow are conflated). We achieved this separation by simultaneously and separately tracking individuals and measuring the flow field around them using particle image velocimetry in a grid-stirred turbulence tank. Contrary to our expectations, larvae swam upward even in highly turbulent flow, and the dive response became less frequent. These observations suggest that oyster larvae are stronger swimmers than previously expected and provide evidence that turbulence alone may not always be a sufficient cue for settlement out of the water column. Furthermore, at a population level, absolute velocity distributions differed significantly from isolated larval swimming velocities, a result that held over increasing turbulence levels. The absolute velocity distributions indicated a strong downward swimming or sinking response at high turbulence levels, but this observation was in fact due to downwelling mean flows in the tank within the imaging area. Our results suggest that reliable characterization of larval behaviour in turbulent conditions requires the subtraction of local flow at an individual level, imposing the technical constraint of simultaneous flow and behavioural observations.