The effect of shortfin mako shark skin at the reattachment of a separated turbulent boundary layer.

This smooth flat experimental study investigates the capability of mako shark scales to control flow separation when placed downstream of the onset of turbulent boundary layer separation and within the reattachment region. The objective of the study is to validate the hypothesis that the shark scales' bristling and recoiling would prevent the flow separation on the flank region (the fastest flow region) of the shark. A rotating cylinder was used to induce an adverse pressure gradient over a flat plate to produce a region of separated flow where the shark skin specimen was mounted. Two types of mako shark scales (flank (B2) and between flank and dorsal fin (B1)) were positioned in the preferred flow direction on a flat plate. The B2 scales are slender, 200 µm tall, and can bristle up to 50°. In contrast, B1 scales are wider, shorter, and can bristle at 30º. The bristling angle and shape are the main mechanisms by which the scales act to inhibit flow from moving upstream near the wall. Thus, the difference in the bristling angles and structures of the scales is attributed to the fact that the B2 scales function in a thicker boundary layer (behind the shark's gills) where they must bristle sufficiently high into the boundary layer to control the flow separation, and because the adverse pressure gradient in this region is higher where flow separation is more likely. The scales are placed in the reattachment region to elucidate their ability to control and reattach an already separated turbulent flow. The results show that B2 scales placed in the reattachment region reduce the size of the turbulent separation bubble and decrease the turbulent kinetic energy, while B1 scales have the opposite effect. .

Understanding Low-Speed Streaks and Their Function and Control through Movable Shark Scales Acting as a Passive Separation Control Mechanism.

The passive bristling mechanism of the scales on the shortfin mako shark (Isurus oxyrinchus) is hypothesized to play a crucial role in controlling flow separation. In the hypothesized mechanism, the scales are triggered in response to patches of reversed flow at the onset of separation occurring in the low-speed streaks that form in a turbulent boundary layer. The two goals of this investigation were as follows: (1) to measure the reversing flow occurring within the low-speed streaks in a separating turbulent boundary layer; (2) to understand the passive flow control mechanism of movable shark skin scales that inhibit reversing flow within the low-speed streaks. Experiments were conducted using digital particle image velocimetry (DPIV). DPIV was used to analyze the flow in a turbulent boundary layer subjected to an adverse pressure gradient formation over both a smooth flat plate and a flat plate on which shark skin specimens were affixed. The experimental analysis of the flow over the smooth flat plate corroborated the findings of previous direct numerical simulation studies, which indicated that the average spanwise spacing of the low-speed streaks increases in the presence of adverse pressure gradients upstream of the point of separation. However, the characteristics of the flow over the shark skin specimen more closely resemble that of a zero-pressure gradient turbulent boundary layer. A comparative analysis of the width and velocity of the reversed streaks between flat plate and shark skin cases reveals that the mean spanwise spacing decreases, and thus, the number of streaks increases over the shark skin. Additionally, the reversed streaks observed over shark scales are thinner and the highest negative velocity within the streaks falls within the range required to bristle the scales.

Systematic review and meta-analysis of interventions to promote medication adherence among children, adolescents, and young adults with medical conditions.

OBJECTIVE: This meta-analysis examined the efficacy of adherence-promotion interventions for children, adolescents, and young adults prescribed a medication for > 90 days as part of a treatment regimen for a medical condition. METHODS: A systematic literature review was conducted to identify randomized controlled trials of adherence-promotion interventions published between 2013 and 2023 and including children, adolescents, and/or young adults with a medical condition. A total of 38 articles representing 39 trials met inclusion criteria. A narrative synthesis was conducted to summarize included trials and a random-effects model was used to compute an overall intervention effect. Effect sizes by adherence outcome assessment methodology, participant age, and technology use were also computed. RESULTS: Pediatric adherence-promotion interventions demonstrate a medium effect with those randomized to an intervention displaying greater improvements in medication adherence than those randomized to a comparator condition (SMD = 0.46, 95% CI: 0.31, 0.60, n = 37; 95% Prediction Interval: -0.32, 1.23). CONCLUSIONS: Adherence interventions for children, adolescents, and young adults with medical conditions increase adherence.

Predictors of objective treatment adherence in adolescents with epilepsy: The important role of motivation.

OBJECTIVE: Adolescents with epilepsy are at heightened risk for suboptimal anti-seizure medication (ASM) adherence; however, there is a paucity of adherence interventions for this age group. The current study aimed to identify a comprehensive and novel set of predictors of objective, electronically-monitored ASM adherence in adolescents with epilepsy. METHODS: Participants included 104 adolescents (13-17 years old; M = 15.36 ± 1.40), diagnosed with epilepsy and their caregivers. Cross-sectional data were collected from adolescents, caregivers, healthcare providers, and medical chart reviews, including demographics (i.e., age, race/ethnicity, sex, insurance status), the COVID-19 pandemic (i.e., participation before versus during), seizure characteristics (i.e., presence and severity), ASM side effects (Pediatric Epilepsy Side Effects Questionnaire), adherence motivation (1-item 6-point Likert scale item), and adherence barriers (Pediatric Epilepsy Medication Self-Management Questionnaire). Electronically-monitored adherence data was collected via the AdhereTechTM pill bottle or the Vaica SimpleMedTM pillbox over 30 days. RESULTS: Adolescents demonstrated suboptimal adherence at 78 ± 31.6%, despite high ASM adherence motivation (M = 4.43 ± .94) and minimal adherence barriers (M = 35.64 ± 3.78). Hierarchical multiple regression, which included non-modifiable sociodemographic and medical variables (Block 1) and behaviorally modifiable psychosocial variables (Block 2) was significant, F(12,87) = 3.69, p < .001. Specifically, having private insurance (versus Medicaid or public insurance; t = -2.11, p = .038) and higher adherence motivation (t = 2.91, p = .005) predicted higher objective ASM adherence. CONCLUSION: Routine assessment of adherence predictors is vital for the promotion of adherence among adolescents with epilepsy. Adolescent adherence motivation may be an important element of multi-component interventions focused on improving ASM adherence in adolescents with epilepsy.

Development of the Engage with Impact Toolkit: A comprehensive resource to support the evaluation of patient, family and caregiver engagement in health systems.

INTRODUCTION: Recent shifts in the patient, family and caregiver engagement field have focused greater attention on measurement and evaluation, including the impacts of engagement efforts. Current evaluation tools offer limited support to organizations seeking to reorient their efforts in this way. We addressed this gap through the development of an impact measurement framework and accompanying evaluation toolkit-the Engage with Impact Toolkit. METHODS: The measurement framework and toolkit were co-designed with the Evaluating Patient Engagement Working Group, a multidisciplinary group of patient, family and caregiver partners, engagement specialists, researchers and government personnel. Project activities occurred over four phases: (1) project scoping and literature review; (2) modified concept mapping; (3) working group deliberations and (4) toolkit web design. RESULTS: The project scope was to develop a measurement framework and an evaluation toolkit for patient engagement in health systems that were practical, accessible, menu-driven and aligned with current system priorities. Concept mapping yielded 237 impact statements that were sorted, discussed and combined into 81 unique items. A shorter list of 50 items (rated 8.0 or higher out of 10) was further consolidated to generate a final list of 35 items mapped across 8 conceptual domains of impact: (1) knowledge and skills; (2) confidence and trust; (3) equity and inclusivity; (4) priorities and decisions; (5) effectiveness and efficiency; (6) patient-centredness; (7) culture change and (8) patient outcomes and experience. Working Group members rated the final list for importance (1-5) and identified a core set of 33 items (one for each of the 8 domains and 25 supplementary items). Two domains (priorities and decisions; and culture change) yielded the highest overall importance ratings (4.8). A web-based toolkit (www.evaluateengagement.ca) hosts the measurement framework and related evaluation supports. CONCLUSION: The Engage with Impact Toolkit builds on existing engagement evaluation tools but brings a more explicit focus to supporting organizations to assess the impacts of their engagement work. PATIENT CONTRIBUTION: Patient, family and caregiver partners led the early conceptualization of this work and were involved at all stages and in all aspects of the work. As end-users of the toolkit, their perspectives, knowledge and opinions were critical.

Self-Disclosure Patterns Among Children and Youth with Epilepsy: Impact of Perceived-Stigma.

This review aimed to synthesize the minimal existing literature on the impact of perceived stigma on self-disclosure patterns among children and youth with epilepsy (YWE). Initial literature searches were conducted in PsycInfo, Scopus, Web of Science, and PubMed using search terms focused on epilepsy, pediatrics, disclosure, and/or stigma. Articles were included if they were original human research articles published in peer-reviewed journals that were accessible in English through Cincinnati Children's Hospital Medical Center Pratt Library and fit study aims. Thirteen articles, which primarily used qualitative self-report methodologies, fit the study's inclusion criteria. YWE report greater perceived stigma and lower illness disclosure compared to youth with other chronic health conditions. Across studies, perceived stigma was consistently identified as a barrier to YWE disclosing their epilepsy diagnosis. Consequences of perceived stigma included lower self-esteem, poorer perceived competency, lack of self-confidence, social withdrawal, and lower quality of life. YWE's reluctance to disclose epilepsy was associated with worry about differential treatment, negative impact on close relationships, negative impact on others' perceptions, and negative self-perceptions. While WHO and ILAE have identified stigma as contributing to higher disease burden in people with epilepsy and have highlighted the importance of prioritizing social policy focused on decreasing epilepsy-related stigma, progress has been incremental and much work remains. Future research is needed to understand socio-cultural factors perpetuating stigma among YWE in order to further develop, evaluate, and disseminate evidence-based clinical and education programming to combat epilepsy-related stigma.

Community-recruited parent perspectives of concern dismissal by pediatric providers.

INTRODUCTION: Effective communication is a central tenet of family centered care, yet parent concerns are sometimes un- or underattended to by pediatric providers. This study aimed to explore the prevalence of, and factors related to, parental perceptions of concern dismissal by pediatric providers. METHOD: In Spring 2020, 270 community-recruited parents of children ages 6-12 years (74% White, 74% female, 69% married) responded to an online survey about perceived concern dismissal experiences with their children. Characteristics of concern dismissal, differences in concern dismissal occurrence by parent factors, and emotional and practical impacts were assessed and explored. RESULTS: Thirty-three percent reported having experienced concern dismissal, most often in pediatric primary care settings. Concern dismissal was reported more frequently among parents employed in health care settings than those without health care employment histories. Most dismissed concerns related to the child's physical health and many incidents were characterized by provider impoliteness or provision of less testing or treatment than expected or desired. Many parents expressed disappointment in the health care system after experiences of concern dismissal. DISCUSSION: Concern dismissal was found to be common and upsetting for community-recruited parents. Future research should incorporate child and provider perspectives with demographically diverse samples. Pediatric providers should continue to work toward implementation of family centered care to decrease the likelihood of perceived dismissal by thoroughly recognizing and responding to concerns presented by parents and caregivers of pediatric patients. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Effects of Weight and Pain on Physical Activity: Insights from the Lived Experiences of Youth with Co-Occurring Chronic Pain and Obesity.

Objective: Pediatric obesity and chronic pain are each associated with an increased risk for numerous poor physical and mental health outcomes. Co-occurring chronic pain and obesity (CPO) result in greater functional disability compared with either condition alone. The aim of the present study was to use qualitative methods to better understand the challenges experienced by adolescents with CPO, with a specific focus on physical activity. Methods: Semistructured interviews were conducted with 13 youth with CPO. Participants were questioned about pain, physical activity, coping strategies, and the perceived relationship between weight and pain. Interviews were audiorecorded, transcribed, and analyzed according to Interpretative Phenomenological Analysis. Results: Superordinate themes expressed by youth included: Impact of Chronic Pain on Relationships, Impact of Pain on Self-Perception, Using Food to Cope with Pain, Perceived Relationship between Pain and Weight after Onset of Pain, Attitudes toward Physical Activity, Barriers to Physical Activity, and Supports to Physical Activity. Conclusions: Participants identified challenges associated with CPO. Notably, participants identified pain as a greater barrier to exercise than weight, implicating the salience of chronic pain in the lives of youth with CPO. Furthermore, participants identified a desire to be more physically active, yet discussed struggles and concerns about attempts to increase their physical activity and indicated a desire for guidance about being more active. This study highlights the complexities of the relationship between CPO and underscores the importance of providers collaboratively working with patients to develop a practical plan to resume movement and physical activity.

Adolescent Experiences with Self-Asphyxial Behaviors and Problematic Drinking in Emerging Adulthood.

Self-asphyxial behavior to achieve a euphoric high (The Choking Game; TCG), occurs most often during early adolescence. Participants in TCG often engage in other risky behaviors. This study investigated the relationship between prior experience with TCG and problematic drinking behaviors in emerging adulthood. Emerging adults, 18 to 25 years old (N = 1248), 56% female, and 78% Caucasian completed an online survey regarding knowledge of and prior engagement in TCG and current drinking behaviors. Participants who personally engaged in TCG during childhood/adolescence or were familiar with TCG reported significantly more problematic drinking behaviors during emerging adulthood. Those present when others engaged in TCG but resisted participation themselves reported significantly less current problematic drinking behaviors than those who participated, but significantly more current problematic drinking behaviors than those never present. Emerging adults with increased social familiarity with TCG during adolescence endorsed greater problematic drinking behaviors. Results suggest resistance skills may generalize across time/activities.

Parent Ethical Concerns About Patient Feedback Measures to Improve Pediatric Clinical Care.

There are limited studies evaluating parental willingness to complete patient feedback measures to improve pediatric clinical care. Parents were randomly assigned to read a vignette that varied by parent satisfaction and type of feedback measure. Parents were generally willing to participate in the hypothetical research study aimed to improve their child's clinical care. Parents in the dissatisfied condition invited to participate in a potentially identifiable interview, compared to an anonymous survey, reported they would be less likely to respond honestly and more likely to feel obligated to participate. Researchers aiming to improve pediatric clinical care should be encouraged to use patient feedback measures that collect potentially identifiable information; however, researchers must consider the potential impact of parent satisfaction on feedback.

Development and utility of the Family-Centered Autism Navigation interview.

LAY ABSTRACT: When a parent learns of their child's autism diagnosis, they may be overwhelmed, confused, and frustrated. Family navigation services are designed to improve access to care. While these services are a promising intervention to enhance well-being and developmental outcomes, there are limited tools that can systematically facilitate the development of a shared navigation plan that prioritizes the concerns of the family. The Family-Centered Autism Navigation semi-structured interview guide is designed for family navigators to triage and prioritize caregiver's needs to coordinate and navigate systems of care after learning of their child's autism spectrum disorder diagnosis. The goals of the Family-Centered Autism Navigation interview are to (1) identify family and child strengths; (2) identify family/caregiver concerns regarding navigation of services and systems following their child's diagnosis of autism; (3) measure change in caregiver knowledge, ability and skill as it relates to understanding, remembering, and evaluating information they receive; and (4) assist with the development of a shared navigation plan. When using the Family-Centered Autism Navigation guide, family navigators and caregivers co-create a family-centered, prioritized action plan that supports and prepares caregivers as they navigate systems of care. This short report describes the development process of the Family-Centered Autism Navigation semi-structured interview guide. We utilized brief interviews (n = 42), expert feedback (n = 13), and quality improvement strategies (n = 2 family navigators) to develop the questions and determine the usability of the Family-Centered Autism Navigation interview in practice.

Patient and caregiver experience in the transition from hospital to home - brainstorming results from group concept mapping: a patient-oriented study.

BACKGROUND: Improving the quality of care for patients who return home after a hospital stay is an international priority; however, few jurisdictions have engaged broadly with patients and caregivers to understand what most affects their experience transitioning home. We performed Ontario-wide group concept mapping, beginning with a brainstorming phase, to understand patient and caregiver priorities in the transition. METHODS: We used group concept mapping to engage patients and caregivers who had lived experience transitioning from hospital to home in Ontario in the previous 3 years. We report on the first phase, brainstorming, conducted over 10 weeks beginning Jan. 11, 2018 via an online survey or facilitated group discussion. Participants responded to a single focal prompt: "When leaving the hospital for home, some thing(s) that affected the experience were: ____." The study team identified recurrent concepts and overarching themes. Patients and caregivers informed the study design, recruitment and data interpretation. RESULTS: In all, 665 people (263 patients [39.5%], 352 caregivers [52.9%] and 50 people who were both patient and caregiver [7.5%]) participated in brainstorming online, and 71 people participated in 1 of 8 group discussions. Participants identified 6 key areas affecting their experience of transition from hospital to home: home and community care, the discharge process, medical follow-up after discharge, medications, patient and caregiver education, and the kindness and caring of the health care team in hospital. Most notable were challenges with the timeliness, sufficiency, reliability and consistency of publicly funded home care services. INTERPRETATION: Patients and caregivers from across Ontario noted a range of issues affecting their experience transitioning from hospital to home, particularly the quality and sufficiency of publicly funded home care. Our findings will be used to inform a provincial quality standard on the transition from hospital to home.

Patient and caregiver priorities in the transition from hospital to home: results from province-wide group concept mapping.

BACKGROUND: Patients and caregivers often face significant challenges when they are discharged home from hospital. We sought to understand what influenced patient and caregiver experience in the transition from hospital to home and which of these aspects they prioritised for health system improvement. METHODS: We conducted group concept mapping over 11 months with patients-and their caregivers-who were admitted to a hospital overnight in the last 3 years in Ontario, Canada and discharged home. Home included supportive housing, shelters and long-term care. Participants responded to a single focal prompt about what affected their experience during the transition. We summarised responses in unique statements. We then recruited participants to rate each statement on a five-point scale on whether addressing this gap should be a priority for the health system. The provincial quality agency recruited participants in partnership with patient, community and healthcare organisations. Participation was online, in-person or virtual. RESULTS: 736 participants provided 2704 responses to the focal prompt. Unique concepts were summarised in 52 statements that were then rated by 271 participants. Participants rated the following three statements most highly as a gap that should be a priority for the health system to address (in rank order): 'Not enough publicly funded home care services to meet the need', 'Home care support is not in place when arriving home from hospital' and 'Having to advocate to get enough home care'. The top priority was consistent across multiple subgroups. CONCLUSIONS: In a country with universal health insurance, patients and caregivers from diverse backgrounds consistently prioritised insufficient public coverage for home care services as a gap the health system should address to improve the transition from hospital to home.

Parents Reliably Identify Pain Dismissal by Pediatric Providers.

OBJECTIVES: Approximately 40% of children and adolescents with chronic pain report at least 1 dismissal experience, citing medical providers and parents as the primary and most distressing dismissers. Previous research indicates sex differences in pain dismissal experience and observer pain perception. This study examined parental reactions to dismissive provider-child scenarios and the influence of provider and patient sex on perceptions. METHODS: Community parents (N=326) completed an online survey. Parents were randomized to listen to 1 of 8 vignettes of a provider-child chronic pain scenario. Vignettes varied by type of scenario (appropriate vs. dismissive)×provider sex×patient sex. RESULTS: Overall, parents rated the dismissive scenario more negatively. There was a significant interaction between provider sex and scenario regarding likelihood to bring their own child to this provider and a significant 3-way interaction regarding provider belief of the pain complaint. When asked how they would feel if this was their own child, parents who heard the dismissive scenario reported more negative reactions. When asked what they would say to the provider, parents in the dismissive condition were more likely to defend their child and request a second opinion. DISCUSSION: Parents consistently identified the dismissive language in a child and provider scenario. Female providers and sex-matched dyads seem to be more polarizing in terms of likelihood to bring their child to the provider and belief of pain, respectively. Providers within these groups may need to be especially cautious with their language when responding to pediatric chronic pain complaints.

Passive bristling of mako shark scales in reversing flows.

Shark skin has been shown to reduce drag in turbulent boundary layer flows, but the flow control mechanisms by which it does so are not well understood. Drag reduction has generally been attributed to static effects of scale surface morphology, but possible drag reduction effects of passive or active scale actuation, or 'bristling', have been recognized more recently. Here, we provide the first direct documentation of passive scale bristling due to reversing, turbulent boundary layer flows. We recorded and analysed high-speed videos of flow over the skin of a shortfin mako shark, Isurus oxyrinchus These videos revealed rapid scale bristling events with mean durations of approximately 2 ms. Passive bristling occurred under flow conditions representative of cruise swimming speeds and was associated with two flow features. The first was a downward backflow that pushed a scale-up from below. The second was a vortex just upstream of the scale that created a negative pressure region, which pulled up a scale without requiring backflow. Both flow conditions initiated bristling at lower velocities than those required for a straight backflow. These results provide further support for the role of shark scale bristling in drag reduction.

Evaluating Differential Effects of Specific Pain Dismissal Interactions With Physicians.

OBJECTIVES: Over 40% of adolescents with chronic pain report experiencing pain dismissal, which is a response from another individual that is perceived as diminishing, denying, or disbelieving an individual's report of pain. Pain dismissal by physicians often leaves patients feeling discredited, which may discourage them from seeking and receiving proper treatment for their pain. The purpose of this study was to investigate how the 4 most commonly reported types of physician pain dismissal differentially affect individuals' reactions. MATERIALS AND METHODS: Emerging adults, age 18- to 25-years old (N=352, 60% female), were randomly assigned to read 1 of 4 vignettes describing patient-provider interactions that included the most commonly reported types of pain dismissal identified by previous research: denial/disbelief, minimizing, faking for secondary gain, and psychogenic. Participants answered questions regarding their reactions to the pain dismissal vignettes. RESULTS: All 4 vignettes were perceived as dismissive and problematic by the majority of participants, but participants who read the psychogenic pain dismissal vignette were less dissatisfied overall with the hypothetical medical appointment than participants who read the other 3 vignettes. DISCUSSION: All 4 types of physician pain dismissal were broadly perceived negatively, suggesting that the experience of pain dismissal is likely not due to patient hypersensitivity but to physician behavior. Discussion of the psychological factors associated with pain was less likely to be perceived as dismissive. Psychologists and physicians should collaborate to develop recommended language that validates patients' experiences of pain, communicates appropriate levels of empathy, and reduces the frequency of perceived physician pain dismissal.

Gender differences in the experience of pain dismissal in adolescence.

This study examined physician-generated pain dismissal experiences in adolescence between males and females. Young adults (ages 18-24, N = 178) with chronic or recurrent pain reported at least one pain dismissal experience in adolescence and answered a series of questions regarding the experience during this time period. Females were significantly more likely to report pain dismissal and a physician as the dismisser. Males were more likely to report that the dismisser expressed hostility toward them, feeling ambivalent regarding the dismissal experience, and a desire to avoid the dismisser. Females were more likely to report a desire to plead for understanding with the dismisser. Results suggest that female adolescents are more likely to report a pain dismissal experience with physicians, raising concerns that adolescent females may receive, or at least perceive, differential treatment for their chronic pain.

Separation control over a grooved surface inspired by dolphin skin.

Over many decades the biological surfaces of aquatic swimmers have been studied for their potential as drag reducing surfaces. The hydrodynamic benefit of riblets, or grooves embedded parallel to the flow which appear on surfaces such as shark skin, have been well documented. However the skin of dolphins is embedded with sinusoidal grooves that run perpendicular or transverse to the flow over their bodies. It is theorized that the transverse grooves present on dolphin skin trap vortices between them, creating a partial slip condition over the surface and inducing turbulence augmentation in the boundary layer, thus acting as a potential mechanism to reduce flow separation and thus pressure drag. In an attempt to test this hypothesis and study these effects, an adverse pressure gradient was induced above a flat plate resulting in a controlled region of flow separation occurring within a tripped, turbulent boundary layer. Small transverse grooves of both rectangular and sinusoidal shape were 3D printed and mounted to the plate to measure their effect on the boundary layer flow. The results were compared to a flat plate without grooves using digital particle image velocimetry (DPIV). The strength of the adverse pressure gradient was varied, and the observed control in flow separation and other effects upon the boundary layer are discussed.

Beneficial aerodynamic effect of wing scales on the climbing flight of butterflies.

It is hypothesized that butterfly wing scale geometry and surface patterning may function to improve aerodynamic efficiency. In order to investigate this hypothesis, a method to measure butterfly flapping kinematics optically over long uninhibited flapping sequences was developed. Statistical results for the climbing flight flapping kinematics of 11 butterflies, based on a total of 236 individual flights, both with and without their wing scales, are presented. Results show, that for each of the 11 butterflies, the mean climbing efficiency decreased after scales were removed. Data was reduced to a single set of differences of climbing efficiency using are paired t-test. Results show a mean decrease in climbing efficiency of 32.2% occurred with a 95% confidence interval of 45.6%-18.8%. Similar analysis showed that the flapping amplitude decreased by 7% while the flapping frequency did not show a significant difference. Results provide strong evidence that butterfly wing scale geometry and surface patterning improve butterfly climbing efficiency. The authors hypothesize that the wing scale's effect in measured climbing efficiency may be due to an improved aerodynamic efficiency of the butterfly and could similarly be used on flapping wing micro air vehicles to potentially achieve similar gains in efficiency.

Experimental study of laminar and turbulent boundary layer separation control of shark skin.

The Shortfin Mako shark (Isurus oxyrinchus) is a fast swimmer and has incredible turning agility, and has flexible scales known to bristle up to 50° in the flank regions. It is purported that this bristling capability of the scales may result in a unique pass flow control method to control flow separation and reduce drag. It appears that the scales have evolved to be only actuated when the flow over the body is reversed; thereby inducing a method of inhibiting flow reversal close to the surface. In addition, bristled scales form cavities which could induce boundary layer mixing and further assist in delaying flow separation. To substantiate the hypothesis, samples of skin from the flank region of the mako have been tested in a water tunnel facility under various strengths of adverse pressure gradient (APG). Laminar and turbulent separation over the skin was studied experimentally using time-resolved digital particle image velocimetry, where the APG was generated and varied using a rotating cylinder. Shark skin results were compared with that of a smooth plate data for a given amount of APG. Both the instantaneous and time-averaged results reveal that shark skin is capable of controlling laminar as well as turbulent separation. Under laminar conditions, the shark skin also induces an early transition to turbulence and reduces the degree of laminar separation. For turbulent separation, the presence of the shark skin reduces the amount of backflow and size of the separation region. Under both flow conditions, the shark skin also delayed the point of separation as compared to a smooth wall.