LES-based evaluation of a microjet noise reduction concept in static and flight conditions

AbstractThe Large-Eddy Simulation (LES) numerical system established since 2002 for jet-noise computation is first evaluated in terms of recent gains in accuracy with increased computer resources, and is then used to explore the relatively new “microjet” noisereduction concept (injection of high-pressure microjets in the vicinity of the main jet nozzle exit), which currently attracts significant attention in the aeroacoustic community. The simulations are found to capture the essential features of the flow/turbulence and the far-field noise alteration by the microjets observed in experiments, and to reveal the subtle flow features responsible for the effect of injection on noise. They also confirm the experimental observation that in static conditions microjets provide a noise reduction comparable with that from chevrons in the low-frequency range, and probably have a less pronounced high-frequency penalty. This positive evaluation of the microjets concept is, however, mitigated by results of simulations in flight conditions, which were never studied experimentally. The latter results, which are awaiting an experimental verification, make a practical use of the concept in its current form rather unlikely

Simulation of a Shear Coaxial GO2/GH2 Rocket Injector with DES and LES Using Flamelet Models

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97098/1/AIAA2012-3744.pd

Biallelic variants in WARS1 cause a highly variable neurodevelopmental syndrome and implicate a critical exon for normal auditory function

Aminoacyl-tRNA synthetases (ARSs) are essential enzymes for faithful assignment of amino acids to their cognate tRNA. Variants in ARS genes are frequently associated with clinically heterogeneous phenotypes in humans and follow both autosomal dominant or recessive inheritance patterns in many instances. Variants in tryptophanyl-tRNA synthetase 1 (WARS1) cause autosomal dominantly inherited distal hereditary motor neuropathy and Charcot-Marie-Tooth disease. Presently, only one family with biallelic WARS1 variants has been described. We present three affected individuals from two families with biallelic variants (p.Met1? and p.(Asp419Asn)) in WARS1, showing varying severities of developmental delay and intellectual disability. Hearing impairment and microcephaly, as well as abnormalities of the brain, skeletal system, movement/gait, and behavior were variable features. Phenotyping of knocked down wars-1 in a C. elegans model showed depletion is associated with defects in germ cell development. A wars1 knockout vertebrate model recapitulates the human clinical phenotypes, confirms variant pathogenicity and uncovers evidence implicating the p.Met1? variant as potentially impacting an exon critical for normal hearing. Together, our findings provide consolidating evidence for biallelic disruption of WARS1 as causal for an autosomal recessive neurodevelopmental syndrome and present a vertebrate model that recapitulates key phenotypes observed in patients. This article is protected by copyright. All rights reserved

Improvement of delayed detached-eddy simulation for LES with wall modelling

Adjustments are proposed of the Delayed Detached Eddy Simulation (DDES) approach to turbulence. They preserve the DDES capabilities particularly for natural DES uses, and resolve the mismatch of the logarithmic layers discovered earlier for the basic DES technique when used for Wall-Modelled Large-Eddy Simulation (WMLES) of attached flows. The adjustments are defined both for the Spalart-Allmaras and the Menter SST models. The first one concerns the definition of the LES length scale in general for anisotropic grids near a wall, and makes use of the wall distance along with the grid spacing; it clearly benefits even the Smagorinsky model. The second one manages the blending of RANS and LES behaviour within a WMLES to advantage, greatly increasing the resolved turbulence activity near the wall, and finely adjusting the resolved logarithmic layer. This is seen in channel flow over a wide Reynolds-number range, and through some grid variations. Tests show that the new method, although somewhat more complex, returns the desired behaviour not only in channel-flow LES, but also in channel-flow RANS, in a backward-facing-step case with side-by-side LES and RANS regions, and over an airfoil in deep stall