Coordination between Crew Members on Flying Multihulls: A Case Study on a Nacra 17.

International audienceA current trend in sailing sports is the use of boats equipped with hydrofoils, allowing the boats to "fly" over the water surface. In this situation, the handling of the boat requires fine coordination between the crew members to maintain the precarious flight. The purpose of this case study was to analyze the crew activity on a flying multihull and explore the role of the shared sport equipment in the emergence of coordination between crew members. Data were collected during a training session with a crew of expert sailors. A joint analysis of phenomenological and mechanical data was conducted. The aim of the analysis was to categorize the forms of interactions between crew members, boat and environment. Results showed that collective coordination in the studied situation involves six forms of interaction that are associated with stable, unstable or critical states of the flight. Consequently, we discussed the role played by the crew members, the behavior of the boat and the environment in the collective coordination

Coordination between Crew Members on Flying Multihulls: A Case Study on a Nacra 17.

International audienceA current trend in sailing sports is the use of boats equipped with hydrofoils, allowing the boats to "fly" over the water surface. In this situation, the handling of the boat requires fine coordination between the crew members to maintain the precarious flight. The purpose of this case study was to analyze the crew activity on a flying multihull and explore the role of the shared sport equipment in the emergence of coordination between crew members. Data were collected during a training session with a crew of expert sailors. A joint analysis of phenomenological and mechanical data was conducted. The aim of the analysis was to categorize the forms of interactions between crew members, boat and environment. Results showed that collective coordination in the studied situation involves six forms of interaction that are associated with stable, unstable or critical states of the flight. Consequently, we discussed the role played by the crew members, the behavior of the boat and the environment in the collective coordination

Benchmark Sea Trials on a 6-Meter Boat Powered by Kite

International audienceThis paper presents sea trials on a 6-m boat specifically designed for kite propulsion. The kite control was automatic or manual, dynamic or static, depending on the point of sailing. The measurement system recorded boat motion and load generated by the kite. A particular attention was paid to wind measurement with several fixed and mobile locations directly on the kiteboat or in the vicinity. A high resolution weather modelling showed that a classical power law, describing the wind gradient, was not satisfactory to get the wind at kite location. 5-min measurement phases were systematically recorded. In the end, 101 runs were carried out. Data were processed with the phase-averaging method in order to produce reliable and accurate results. © 1996-2020 MDPI (Basel, Switzerland) unless otherwise state

Boat towed by kite : methodolgy for sea trials

International audienceThis paper presents sea trials on a 6-meter boat specifically designed for kite propulsion. The kite control is automatic or manual, dynamic or static, depending on the point of sailing. The measurement system records boat motion and loads generated by the kite. A particular attention was payed for wind measurement with several fixed and mobile locations directly on the kiteboat or in the vicinity. A fine modelling shows thata classical power low is not satisfactory to describe the wind at kite location. 5-minute measurement phase were systematically recorded. At the end, 101 runs were conducted. Data are processed with the phase-averaging method in order to produce reliable results. First results are presented

Influence of shaft stiffness on the performance of a plane-like hydrofoil

International audienceHydrofoils are now widely used to reduce hydrodynamic resistance, leading to increased velocities and sailing crafts performance. However, designing hydrofoils for sailing vessels such as windfoils and kitefoils remains a complex challenge, as the ride height plays a critical part on the stability and performance of foiling vessels. Furthermore, the strut between the board and the plane-like foil (called the shaft) is highly loaded and subject to significant deformation, leading to potentially important Fluid-Structure Interaction (FSI) effects. Consequently, it is now critical to consider the ride height and the FSI effects in Velocity Prediction Programs (VPP). This work first presents the development of a novel five degree-of-freedom (DoF) Velocity Prediction Program (VPP) for foiling crafts, which includes the FSI effects on the shaft of the vessel. Hydrodynamic forces are computed using a vortex lattice model with a viscous correction, solved by the panel method implemented in the software Athena Vortex Lattice (AVL). The structural behavior of the shaft is introduced in the VPP in the form of an analytical model derived from experimental tests on real shafts. This improved VPP is then applied to a generic plane-like hydrofoil, typical of a windfoil sailing upwind at a speed of 9m/s (18kts) and approximately a 20° windward-heel. Twenty shafts of different stiffness are tested, and their respective deflections, as well as the equilibrium state computed by the VPP, are compared. Results show that for a static analysis the equilibrium state and the performance are barely affected by the stiffness of the shaft. However, the use of a flexible shaft leads to a different distribution of the lateral hydrodynamic force (anti-drift) onto the different parts of the foil

Development and validation of a multivariable prediction model of central venous catheter-tip colonization in a cohort of five randomized trials

International audienceAbstract Background The majority of central venous catheters (CVC) removed in the ICU are not colonized, including when a catheter-related infection (CRI) is suspected. We developed and validated a predictive score to reduce unnecessary CVC removal. Methods We conducted a retrospective cohort study from five multicenter randomized controlled trials with systematic catheter-tip culture of consecutive CVCs. Colonization was defined as growth of ≥10 3 colony-forming units per mL. Risk factors for colonization were identified in the training cohort (CATHEDIA and 3SITES trials; 3899 CVCs of which 575 (15%) were colonized) through multivariable analyses. After internal validation in 500 bootstrapped samples, the CVC-OUT score was computed by attaching points to the robust (> 50% of the bootstraps) risk factors. External validation was performed in the testing cohort (CLEAN, DRESSING2 and ELVIS trials; 6848 CVCs, of which 588 (9%) were colonized). Results In the training cohort, obesity (1 point), diabetes (1 point), type of CVC (dialysis catheter, 1 point), anatomical insertion site (jugular, 4 points; femoral 5 points), rank of the catheter (second or subsequent, 1 point) and catheterization duration (≥ 5 days, 2 points) were significantly and independently associated with colonization . Area under the ROC curve (AUC) for the CVC-OUT score was 0.69, 95% confidence interval (CI) [0.67–0.72]. In the testing cohort, AUC for the CVC-OUT score was 0.60, 95% CI [0.58–0.62]. Among 1,469 CVCs removed for suspected CRI in the overall population, 1200 (82%) were not colonized. The negative predictive value (NPV) of a CVC-OUT score < 6 points was 94%, 95% CI [93%–95%]. Conclusion The CVC-OUT score had a moderate ability to discriminate catheter-tip colonization, but the high NPV may contribute to reduce unnecessary CVCs removal. Preference of the subclavian site is the strongest and only modifiable risk factor that reduces the likelihood of catheter-tip colonization and consequently the risk of CRI. Clinical Trials Registration : NCT00277888, NCT01479153, NCT01629550, NCT01189682, NCT00875069

Development and validation of a multivariable model predicting the required catheter dwell time among mechanically ventilated critically ill patients in three randomized trials

Abstract Background The anatomic site for central venous catheter insertion influences the risk of central venous catheter-related intravascular complications. We developed and validated a predictive score of required catheter dwell time to identify critically ill patients at higher risk of intravascular complications. Methods We retrospectively conducted a cohort study from three multicenter randomized controlled trials enrolling consecutive patients requiring central venous catheterization. The primary outcome was the required catheter dwell time, defined as the period between the first catheter insertion and removal of the last catheter for absence of utility. Predictors were identified in the training cohort (3SITES trial; 2336 patients) through multivariable analyses based on the subdistribution hazard function accounting for death as a competing event. Internal validation was performed in the training cohort by 500 bootstraps to derive the CVC-IN score from robust risk factors. External validation of the CVC-IN score were performed in the testing cohort (CLEAN, and DRESSING2; 2371 patients). Results The analysis was restricted to patients requiring mechanical ventilation to comply with model assumptions. Immunosuppression (2 points), high creatinine > 100 micromol/L (2 points), use of vasopressor (1 point), obesity (1 point) and older age (40–59, 1 point; ≥ 60, 2 points) were independently associated with the required catheter dwell time. At day 28, area under the ROC curve for the CVC-IN score was 0.69, 95% confidence interval (CI) [0.66–0.72] in the training cohort and 0.64, 95% CI [0.61–0.66] in the testing cohort. Patients with a CVC-IN score ≥ 4 in the overall cohort had a median required catheter dwell time of 24 days (versus 11 days for CVC-IN score  7 days required catheter dwell time in the testing cohort. Conclusion The CVC-IN score, which can be used for the first catheter, had a modest ability to discriminate required catheter dwell time. Nevertheless, preference of the subclavian site may contribute to limit the risk of intravascular complications, in particular among ventilated patients with high CVC-IN score. Trials Registration NCT01479153, NCT01629550, NCT0118968