An engineering method for modeling the interaction of circular bodies and very low aspect ratio cruciform wings at supersonic speeds

An engineering method using a 2D unsteady potential formulation (called the free vortex model or FVM) has been developed to predict the normal force, centre-of-pressure and vortex position for cruciform wing-body combinations in the “plus” orientation, at supersonic speeds and cross flow Mach numbers less than or equal to 0.55 up to angles of attack 20◦. The wings are of very low aspect ratio ( ≤ 0.1), have taper ratios greater than 0.85 (or significant side edges) and have low span to body diameter ratios ( ≤ 1.5). The method predicts the position and subsequent loads imposed by the vortex along the length on the wing-body combination by determining the shed vorticity using Jorgensen’s modified Newtonian impact method. The vortex position is well predicted for angles of attack from 4◦ until symmetric vortex shedding occurs, whilst the normal force is well predicted from 0◦. The centre-of-pressure is predicted further aft at the low angles and further forward at the high angles of attack. If this method is used in combination with the single concentrated vortex of Bryson applied to cruciform wing-body combinations the vortex positions prediction limitations at angles of attack less than 4◦ can be overcome. An investigation of the lee side flow field of cruciform wing-body configurations was also performed, and revealed that the vortex position is dependent upon the lee side secondary vortex separation characteristics. Other features revealed that symmetric vortex shedding occurs when both the region of flow outside the shed vortex sheet and reverse flow region are supersonic and a termination shock exists. The thesis also investigated the applica- tion of the discrete vortex model (DVM) method to cruciform wing-body combinations and found that the potential only formulation overpredicts the normal force, whilst the inclusion of boundary layer separation (and therefore modeling the secondary separation vortex) predicted the normal force very well. The application of the concentrated vortex method of Bryson was also investigated and found to be only applicable at low angles of attack (< 4◦).EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Comparison of “IN-REC-SUR-E” and LISA in preterm neonates with respiratory distress syndrome: a randomized controlled trial (IN-REC-LISA trial)

Background: Surfactant is a well-established therapy for preterm neonates affected by respiratory distress syndrome (RDS). The goals of different methods of surfactant administration are to reduce the duration of mechanical ventilation and the severity of bronchopulmonary dysplasia (BPD); however, the optimal administration method remains unknown. This study compares the effectiveness of the INtubate-RECruit-SURfactant-Extubate (IN-REC-SUR-E) technique with the less-invasive surfactant administration (LISA) technique, in increasing BPD-free survival of preterm infants. This is an international unblinded multicenter randomized controlled study in which preterm infants will be randomized into two groups to receive IN-REC-SUR-E or LISA surfactant administration. Methods: In this study, 382 infants born at 24+0–27+6&nbsp;weeks’ gestation, not intubated in the delivery room and failing nasal continuous positive airway pressure (nCPAP) or nasal intermittent positive pressure ventilation (NIPPV) during the first 24&nbsp;h of life, will be randomized 1:1 to receive IN-REC-SUR-E or LISA surfactant administration. The primary outcome is a composite outcome of death or BPD at 36&nbsp;weeks’ postmenstrual age. The secondary outcomes are BPD at 36&nbsp;weeks’ postmenstrual age; death; pulse oximetry/fraction of inspired oxygen; severe intraventricular hemorrhage; pneumothorax; duration of respiratory support and oxygen therapy; pulmonary hemorrhage; patent ductus arteriosus undergoing treatment; percentage of infants receiving more doses of surfactant; periventricular leukomalacia, severe retinopathy of prematurity, necrotizing enterocolitis, sepsis; total in-hospital stay; systemic postnatal steroids; neurodevelopmental outcomes; and respiratory function testing at 24&nbsp;months of age. Randomization will be centrally provided using both stratification and permuted blocks with random block sizes and block order. Stratification factors will include center and gestational age (24+0 to 25+6&nbsp;weeks or 26+0 to 27+6&nbsp;weeks). Analyses will be conducted in both intention-to-treat and per-protocol populations, utilizing a log-binomial regression model that corrects for stratification factors to estimate the adjusted relative risk (RR). Discussion: This trial is designed to provide robust data on the best method of surfactant administration in spontaneously breathing preterm infants born at 24+0–27+6&nbsp;weeks’ gestation affected by RDS and failing nCPAP or NIPPV during the first 24&nbsp;h of life, comparing IN-REC-SUR-E to LISA technique, in increasing BPD-free survival at 36&nbsp;weeks’ postmenstrual age of life. Trial registration: ClinicalTrials.gov NCT05711966. Registered on February 3, 2023

Some compressibility effects on the lee side flow structures of cruciform wing–body configurations with very low aspect ratio wings

A series of validated numerical simulations of a tangent ogive circular body in combination with very low aspect ratio cruciform wings at supersonic Mach numbers and angles of attack up 25° have been performed. Inspection of the flow in the cross flow planes revealed that symmetric vortex shedding occurs when the cross flow velocity is supersonic not only in the accelerated flow region outside the vortices, but in particular, the reverse flow in the recirculation region. Symmetric vortex shedding occurs for tangent ogive bodies at cross flow Mach numbers greater than 0.65, and for circular bodies with cruciform wings in the ‘+’ orientation and span to body diameter ratios of 1.25 at cross flow Mach numbers greater than 0.55