Three-Dimensional Navier-Stokes Simulation of Space Shuttle Main Propulsion 17-inch Disconnect Valves

A steady incompressible three-dimensional viscous flow analysis has been conducted for the Space Shuttle external tank/orbiter propellant feed line disconnect flapper valves with upstream elbows. The Navier-Stokes code, INS3D, is modified to handle interior obstacles and a simple turbulence model. The flow solver is tested for stability and convergence in the presence of interior flappers. An under-relaxation scheme has been incorporated to improve the solution stability. Important flow characteristics such as secondary flows, recirculation, vortex and wake regions, and separated flows are observed. Computed values for forces, moments, and pressure drop are in satisfactory agreement with water flow test data covering a maximum tube Reynolds number of 3.5 million. The predicted hydrodynamical stability of the flappers correlates well with the measurements

Frost Growth and Densification on a Flat Surface in Laminar Flow with Variable Humidity

Experiments are performed concerning frost growth and densification in laminar flow over a flat surface under conditions of constant and variable humidity. The flat plate test specimen is made of aluminum-6031, and has dimensions of 0.3 mx0.3 mx6.35 mm. Results for the first variable humidity case are obtained for a plate temperature of 255.4 K, air velocity of 1.77 m/s, air temperature of 295.1 K, and a relative humidity continuously ranging from 81 to 54%. The second variable humidity test case corresponds to plate temperature of 255.4 K, air velocity of 2.44 m/s, air temperature of 291.8 K, and a relative humidity ranging from 66 to 59%. Results for the constant humidity case are obtained for a plate temperature of 263.7 K, air velocity of 1.7 m/s, air temperature of 295 K, and a relative humidity of 71.6 %. Comparisons of the data with the author's frost model extended to accommodate variable humidity suggest satisfactory agreement between the theory and the data for both constant and variable humidity

Spectral Attenuation of Sound in Dilute Suspensions with Nonlinear Particle Relaxation

Theoretical studies on the dissipation and dispersion of sound in two-phase suspensions have been briefly reviewed. Previous studies on the sound attenuation in particle-laden flows under Stokesian drag and conduction-controlled heat transfer have been extended to accommodate the nonlinear drag and heat transfer. It has been shown that for large particle-to-fluid density ratio, the particle Reynolds number bears a cubic relationship with Omega Tau(sub d) (where Omega is the circular frequency and Tau(sub d) the Stokesian particle relaxation time). This dependence leads to the existence of a peak value in the linear absorption coefficient occurring at a finite value Omega Tau (sub d). Comparison of the predictions with the test data for the spectral attenuation of sound with water injection in a perfectly expanded supersonic air jet shows a satisfactory trend of the theory accounting for nonlinear particle relaxation processes

Pyoderma gangrenosum: a presenting sign of myelodysplastic syndrome in undiagnosed Fanconi anemia

A 26-year-old man with a history of congenital bilateral microtia, unilateral renal agenesis, left aural atresia, and right external auditory canal occlusion admitted for right rib cartilage graft harvest and left ear re-construction. Following surgery, an ulceration with violaceous borders and a yellow fibrinous base unresponsive to broad-spectrum antibiotics developed at the harvest site. The wound was expanding and not responsive to systemic broad-spectrum antibiotics. Biopsy revealed a dense dermal infiltrate of neutrophils with negative tissue cultures consistent with pyoderma gangrenosum (PG). He was treated with systemic, intralesional, and topical steroids, as well as doxycycline. Three weeks after the diagnosis of PG, he was found to have persistent anemia and leukopenia. Bone marrow aspiration analysis was consistent with hypocellular myelodysplastic syndrome and genetic testing was consistent with Fanconi anemia. There is a well-known association of PG with hematological disorders. Fanconi anemia is a rare genetic hematologic disorder with congenital defects leading to bone marrow failure and malignancy in long-standing disease. In our patient, we consider his development of PG a paraneoplastic sign associated with the onset of his hypocellular myelodysplastic syndrome

Base Flow and Heat Transfer Characteristics of a Four-Nozzle Clustered Rocket Engine: Effect of Nozzle Pressure Ratio

The base pressure and heating characteristics of a four-nozzle clustered rocket configuration is studied numerically with the aid of OVERFLOW Navier-Stokes code. A pressure ratio (chamber pressure to freestream static pressure) range of 990 to 5,920 and a freestream Mach number range of 2.5 to 3.5 are studied. The qualitative trends of decreasing base pressure with increasing pressure ratio and increasing base heat flux with increasing pressure ratio are correctly predicted. However, the predictions for base pressure and base heat flux show deviations from the wind tunnel data. The differences in absolute values between the computation and the data are attributed to factors such as perfect gas (thermally and calorically perfect) assumption, turbulence model inaccuracies in the simulation, and lack of grid adaptation

A national policy for malaria elimination in Swaziland: a first for sub-Saharan Africa

Swaziland is working to be the first country in mainland sub-Saharan Africa to eliminate malaria. The highest level of Swaziland's government recently approved a national elimination policy, which endorses Swaziland's robust national elimination strategic plan. This commentary outlines Swaziland's progress towards elimination as well as the challenges that remain, primarily around securing long-term financial resources and managing imported cases from neighbouring countries

Fungistatic activity mediated by volatile organic compounds is isolate-dependent in Trichoderma sp. “atroviride B”

Trichoderma spp. produce multiple bioactive volatile organic compounds (VOCs). While the bioactivity of VOCs from different Trichoderma species is well documented, information on intraspecific variation is limited. The fungistatic activity of VOCs emitted by 59 Trichoderma sp. “atroviride B” isolates against the pathogen Rhizoctonia solani was investigated. Eight isolates representing the two extremes of bioactivity against R. solani were also assessed against Alternaria radicina, Fusarium oxysporum f. sp. lycopersici and Sclerotinia sclerotiorum. VOCs profiles of these eight isolates were analyzed using gas chromatography–mass spectrometry (GC-MS) to identify a correlation between specific VOCs and bioactivity, and 11 VOCs were evaluated for bioactivity against the pathogens. Bioactivity against R. solani varied among the fifty-nine isolates, with five being strongly antagonistic. All eight selected isolates inhibited the growth of all four pathogens, with bioactivity being lowest against F. oxysporum f. sp. lycopersici. In total, 32 VOCs were detected, with individual isolates producing between 19 and 28 VOCs. There was a significant direct correlation between VOC number/quantity and bioactivity against R. solani. 6-pentyl-α-pyrone was the most abundant VOC produced, but 15 other VOCs were also correlated with bioactivity. All 11 VOCs tested inhibited R. solani growth, some by >50%. Some of the VOCs also inhibited the growth of the other pathogens by >50%. This study demonstrates significant intraspecific differences in VOC profiles and fungistatic activity supporting the existence of biological diversity within Trichoderma isolates from the same species, a factor in many cases ignored during the development of biological control agents

Charakterisierung hybrider Komposit-Metall-Strukturen: Ermittlung einer Prüfmethode

Politische Anforderungen an striktere Abgasemissionen und der Elektrifizierungswille im Mobilitätssektor treiben das Bestreben nach Leichtbaustrukturen weiter an. Eine Möglichkeit, Leichtbau zu betreiben, ist das Anbringen von sogenannten Patches aus faserverstärktem Kunststoff (FVK) zur lokalen Verstärkung des Metalls. Dabei wird ein FVK-Tape aus thermoplastischer Matrix und kontinuierlichen, unidirektionalen Fasern mit entsprechender Faserorientierung durch das wärmeunterstützte Pressfügen mit dem Metall vereint. Potenzielle Einsatzgebiete derartiger Hybridstrukturen sind die B-Säule als Strukturelement oder Beplankungselemente (Motorhaube etc.) als semi-strukturelle Bauteile, für welche die Biegung auslegungskritisch ist. Allerdings existieren keine genormten Prüfmethoden für die neu geschaffene Material-klasse, womit sich die Vergleichbarkeit verschiedener Materialien und die Vorausle-gung schwierig gestaltet. Ferner liegen keine charakteristischen Kennwerte vor, die den hybriden Verbund beschreiben. Das Anwenden von bekannten Prüfmethoden zur Kenn-wertermittlung ist aufgrund der Anisotropie und der Asymmetrie des Probenaufbaus möglich, schränkt aber die Interpretation der Ergebnisse ein. Um das Verständnis der hybriden Strukturen zu erweitern und einen ersten Schritt in Richtung eines standardi-sierten Prüfprozesses zu veranlassen, wird die Dreipunkt-Biegeprüfung als Referenz-versuch herangezogen. Zunächst werden sowohl unterschiedliche Probendicken als auch verschiedene Probenpositionen untersucht und deren Auswirkungen auf die Bie-gesteifigkeit und -festigkeit beurteilt