Caractérisation expérimentale du décrochage dynamique dans les hydroliennes à flux transverse par la méthode PIV (Particle Image Velocimetry). Comparaison avec les résultats issus des simulations numériques

Cette thèse de doctorat a été réalisée dans le cadre du projet HARVEST, programme de recherche initié en 2001 au LEGI et consacré au développement d'un nouveau concept d'hydrolienne à axe vertical inspiré des turbines Darrieus pour la récupération de l'énergie cinétique des courants marins et fluviaux. Ce travail s'est focalisé sur la mise en place d'un moyen de mesure par Vélocimétrie par Image de Particules deux dimensions deux composantes (2D-2C) et deux dimensions trois composantes (2D-3C). L'objectif est d'une part de constituer une base de données expérimentale pour la validation locale des simulations numériques RANS 2D et 3D menées dans le cadre de travaux précédents, et d'autre part d'améliorer la compréhension des phénomènes hydrodynamiques instationnaires rencontrés dans ces machines et en particulier du décrochage dynamique. La confrontation des mesures expérimentales et des simulations a notamment permis de mettre en évidence les points forts et les limites des modèles numériques dans les différents régimes de fonctionnement de la machine.This PhD thesis has been carried out within the framework of the HARVEST project. This research program, initiated in 2001 by the LEGI laboratory (Grenoble, France), is devoted to the development of a new marine turbine concept inspired from Darrieus turbines in order to convert kinetic energy of marine, tidal or river currents into electric energy. This work has been focused on the development of an experimental apparatus based on two dimensions two components (2D-2C) and two dimensions three components (2D-3C) Particle Image Velocimetry. The objective is to provide an experimental database for the local validation of 2D and 3D RANS computations and to improve our understanding of unsteady hydrodynamics phenomena experienced in this type of turbine and especially of dynamic stall. Comparison between measurements and computations enabled to identify strengths and limitations of numerical models for various operating conditions of this type of turbine.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Mechanism of Calcium Incorporation Inside Sol–Gel Silicate Bioactive Glass and the Advantage of Using Ca(OH)2 over Other Calcium Sources

Calcium is an essential component of osteogenesis and is often required for imparting significant bioactivity to synthetic bone substitutes and, in particular, silicate-based materials. However, the mechanism of calcium incorporation inside sol–gel silicates is poorly understood. In this work, we shed light on the determinant parameters for incorporation of calcium into acid–base-catalyzed sol–gel silicates at ambient temperature: increasing the pH above the isoelectric point of silicic acid and the nature of the calcium counterion in the calcium precursor are found to be the key. Based on our proposed reaction sequence, we were able to compare calcium precursors and select an ideal candidate compound for the synthesis of bioactive glasses (BG) and organic–inorganic hybrids at ambient temperature. Reproducible syntheses and gel times of SiO2–CaO BG were obtained using calcium hydroxide (CH), and we demonstrate its usability in the synthesis of promising BG–polycaprolactone hybrid scaffolds. BG and hybrids prepared with CH were able to form nanocrystalline nonstoichiometric apatite in simulated body fluid. The increased reliability of low-temperature syntheses associated with the use of a stable and inexpensive alkaline-earth precursor are major steps toward the translation of calcium silicate hybrids or other alkaline-earth silicates from bench to clinic

Effect of Hydrocortisone on Mortality and Organ Support in Patients With Severe COVID-19: The REMAP-CAP COVID-19 Corticosteroid Domain Randomized Clinical Trial.

Importance: Evidence regarding corticosteroid use for severe coronavirus disease 2019 (COVID-19) is limited. Objective: To determine whether hydrocortisone improves outcome for patients with severe COVID-19. Design, Setting, and Participants: An ongoing adaptive platform trial testing multiple interventions within multiple therapeutic domains, for example, antiviral agents, corticosteroids, or immunoglobulin. Between March 9 and June 17, 2020, 614 adult patients with suspected or confirmed COVID-19 were enrolled and randomized within at least 1 domain following admission to an intensive care unit (ICU) for respiratory or cardiovascular organ support at 121 sites in 8 countries. Of these, 403 were randomized to open-label interventions within the corticosteroid domain. The domain was halted after results from another trial were released. Follow-up ended August 12, 2020. Interventions: The corticosteroid domain randomized participants to a fixed 7-day course of intravenous hydrocortisone (50 mg or 100 mg every 6 hours) (n = 143), a shock-dependent course (50 mg every 6 hours when shock was clinically evident) (n = 152), or no hydrocortisone (n = 108). Main Outcomes and Measures: The primary end point was organ support-free days (days alive and free of ICU-based respiratory or cardiovascular support) within 21 days, where patients who died were assigned -1 day. The primary analysis was a bayesian cumulative logistic model that included all patients enrolled with severe COVID-19, adjusting for age, sex, site, region, time, assignment to interventions within other domains, and domain and intervention eligibility. Superiority was defined as the posterior probability of an odds ratio greater than 1 (threshold for trial conclusion of superiority >99%). Results: After excluding 19 participants who withdrew consent, there were 384 patients (mean age, 60 years; 29% female) randomized to the fixed-dose (n = 137), shock-dependent (n = 146), and no (n = 101) hydrocortisone groups; 379 (99%) completed the study and were included in the analysis. The mean age for the 3 groups ranged between 59.5 and 60.4 years; most patients were male (range, 70.6%-71.5%); mean body mass index ranged between 29.7 and 30.9; and patients receiving mechanical ventilation ranged between 50.0% and 63.5%. For the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively, the median organ support-free days were 0 (IQR, -1 to 15), 0 (IQR, -1 to 13), and 0 (-1 to 11) days (composed of 30%, 26%, and 33% mortality rates and 11.5, 9.5, and 6 median organ support-free days among survivors). The median adjusted odds ratio and bayesian probability of superiority were 1.43 (95% credible interval, 0.91-2.27) and 93% for fixed-dose hydrocortisone, respectively, and were 1.22 (95% credible interval, 0.76-1.94) and 80% for shock-dependent hydrocortisone compared with no hydrocortisone. Serious adverse events were reported in 4 (3%), 5 (3%), and 1 (1%) patients in the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively. Conclusions and Relevance: Among patients with severe COVID-19, treatment with a 7-day fixed-dose course of hydrocortisone or shock-dependent dosing of hydrocortisone, compared with no hydrocortisone, resulted in 93% and 80% probabilities of superiority with regard to the odds of improvement in organ support-free days within 21 days. However, the trial was stopped early and no treatment strategy met prespecified criteria for statistical superiority, precluding definitive conclusions. Trial Registration: ClinicalTrials.gov Identifier: NCT02735707

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Experimental Caracteristics of dynamic stall in HARVEST Turbines with Particles Image Velocimetry method (PIV). Comparing with modeling results

Cette thèse de doctorat a été réalisée dans le cadre du projet HARVEST, programme de recherche initié en 2001 au LEGI et consacré au développement d'un nouveau concept d'hydrolienne à axe vertical inspiré des turbines Darrieus pour la récupération de l'énergie cinétique des courants marins et fluviaux. Ce travail s'est focalisé sur la mise en place d'un moyen de mesure par Vélocimétrie par Image de Particules deux dimensions – deux composantes (2D-2C) et deux dimensions – trois composantes (2D-3C). L'objectif est d'une part de constituer une base de données expérimentale pour la validation locale des simulations numériques RANS 2D et 3D menées dans le cadre de travaux précédents, et d'autre part d'améliorer la compréhension des phénomènes hydrodynamiques instationnaires rencontrés dans ces machines et en particulier du décrochage dynamique. La confrontation des mesures expérimentales et des simulations a notamment permis de mettre en évidence les points forts et les limites des modèles numériques dans les différents régimes de fonctionnement de la machine.This PhD thesis has been carried out within the framework of the HARVEST project. This research program, initiated in 2001 by the LEGI laboratory (Grenoble, France), is devoted to the development of a new marine turbine concept inspired from Darrieus turbines in order to convert kinetic energy of marine, tidal or river currents into electric energy. This work has been focused on the development of an experimental apparatus based on two dimensions – two components (2D-2C) and two dimensions – three components (2D-3C) Particle Image Velocimetry. The objective is to provide an experimental database for the local validation of 2D and 3D RANS computations and to improve our understanding of unsteady hydrodynamics phenomena experienced in this type of turbine and especially of dynamic stall. Comparison between measurements and computations enabled to identify strengths and limitations of numerical models for various operating conditions of this type of turbine

Caractérisation expérimentale du décrochage dynamique dans les hydroliennes à flux transverse par la méthode PIV (Particle Image Velocimetry). Comparaison avec les résultats issus des simulations numériques

This PhD thesis has been carried out within the framework of the HARVEST project. This research program, initiated in 2001 by the LEGI laboratory (Grenoble, France), is devoted to the development of a new marine turbine concept inspired from Darrieus turbines in order to convert kinetic energy of marine, tidal or river currents into electric energy. This work has been focused on the development of an experimental apparatus based on two dimensions – two components (2D-2C) and two dimensions – three components (2D-3C) Particle Image Velocimetry. The objective is to provide an experimental database for the local validation of 2D and 3D RANS computations and to improve our understanding of unsteady hydrodynamics phenomena experienced in this type of turbine and especially of dynamic stall. Comparison between measurements and computations enabled to identify strengths and limitations of numerical models for various operating conditions of this type of turbine.Cette thèse de doctorat a été réalisée dans le cadre du projet HARVEST, programme de recherche initié en 2001 au LEGI et consacré au développement d'un nouveau concept d'hydrolienne à axe vertical inspiré des turbines Darrieus pour la récupération de l'énergie cinétique des courants marins et fluviaux. Ce travail s'est focalisé sur la mise en place d'un moyen de mesure par Vélocimétrie par Image de Particules deux dimensions – deux composantes (2D-2C) et deux dimensions – trois composantes (2D-3C). L'objectif est d'une part de constituer une base de données expérimentale pour la validation locale des simulations numériques RANS 2D et 3D menées dans le cadre de travaux précédents, et d'autre part d'améliorer la compréhension des phénomènes hydrodynamiques instationnaires rencontrés dans ces machines et en particulier du décrochage dynamique. La confrontation des mesures expérimentales et des simulations a notamment permis de mettre en évidence les points forts et les limites des modèles numériques dans les différents régimes de fonctionnement de la machine

Polycaprolactone / bioactive glass hybrid scaffolds with controlled porosity

International audienc

Polycaprolactone / bioactive glass hybrid scaffolds with controlled porosity

International audienc

Darrieus turbine modellings - Comparisons with performance measurements and PIV fields

International audienceDarrieus marine turbines are subjected to large variations of relative velocity on the blades both in amplitude and direction during rotation. As a result, the incidence of the relative speed of the incoming flow on the blade can exceed by far the static stall angle, in which case a major unsteady phenomenon, known as "dynamic stall", may occur. It is characterized by the shedding of large vortical structures impacting the mean and dynamic load as well as the turbine efficiency. In this paper, the ability of a RANS modelling to address the complex flow field of a Darrieus turbine is examined. The considered turbine is the A-12 small scale marine turbine model developed at LEGI. It is a three bladed model inspired by the Darrieus turbine (Fig. 1). The specificity of the turbine is a special design of the arms linking the blades to the rotor which limits the induced drag and the hydrodynamic interactions with the blade. The turbine diameter and height are 175 mm. The chord of the blades defined as the length of the curved midline is c = 32.08 mm, leading to a solidity σ = 1.1 which corresponds to the best efficiency according to Shiono et al. [1]. The blade profile is a NACA0018 foil section projected on the rotation circle. The corresponding blade camber is 4.6%. The incident flow velocity U∞ is 2.8 m.s-1 resulting in a Reynolds number based on the diameter of the turbine ReD = 4.9 x 105. The blade Reynolds number ReC, based on the chord length, depends on the operating condition investigated in this paper and is on the order of 2 x 105. The LEGI water tunnel [2] used for testing the turbine model. It is a closed loop with a water capacity of 36 m3. A motor pump of 165 kW with variable speed allows a flow rate up to 500 L.s-1. The flow rate is measured by a turbine flow meter with an accuracy of ± 0.5%. The test section used for marine turbine experiments is shown in Fig. 2. It has a cross section of 0.70 x 0.25 m with a length of 1 m. Maximum speed in the test section is 2.8 m.s-1. A force balance mounted on the top of the test section allows measuring the instantaneous torque and the forces exerting on the turbine. Three transparent PMMA (Polymethyl Methacrylate) windows on the bottom and on the two sides allow ample optical access for visualization and PIV measurements [3]. The turbulence level has been measured in the water tunnel equipped with another test section by Franc and Michel [4] and is very low (typically smaller than 2‰) thanks to honeycombs and elbows equipped with guiding blades. A fully turbulent model and a transitioning model are used to study the possible occurrence of a partially laminar boundary layer developing along the blades at moderate Reynolds number aforementioned. The wall grid refinement sensitivity (y+) has been precisely studied in a previous study [5]. The performances obtained with the 2 models are compared to those obtained experimentally with the balance. In addition the ability of computations to capture the dynamic stall is investigated using two dimensions-two components (2D-2C) and two dimensions-three components (2D-3C) Particle Image Velocimetry (PIV) (fig.3). The vortex shedding mechanism is described in detail on the basis of measured velocity and vorticity fields for different values of the tip speed ratio which strongly influences dynamic stall