Passive vortex generators (VGs) have been widely applied on wind turbines to boost the aerodynamic performance. Although VGs can delay the onset of static stall, the effect of VGs on dynamic stall is ...still incompletely understood. Therefore, this paper aims at investigating the deep dynamic stall of NREL S809 airfoil controlled by single-row and double-row VGs. The URANS method with VGs fully resolved is used to simulate the unsteady airfoil flow. Firstly, both single-row and double-row VGs effectively suppress the flow separation and reduce the fluctuations in aerodynamic forces when the airfoil pitches up. The maximum lift coefficient is therefore increased beyond 40%, and the onset of deep dynamic stall is also delayed. This suggests that deep dynamic-stall behaviors can be properly controlled by VGs. Secondly, there is a great difference in aerodynamic performance between single-row and double-row VGs when the airfoil pitches down. Single-row VGs severely reduce the aerodynamic pitch damping by 64%, thereby undermining the torsional aeroelastic stability of airfoil. Double-row VGs quickly restore the decreased aerodynamic efficiency near the maximum angle of attack, and also significantly accelerate the flow reattachment. The second-row VGs can help the near-wall flow to withstand the adverse pressure gradient and then suppress the trailing-edge flow separation, particularly during the downstroke process. Generally, double-row VGs are better than single-row VGs concerning controlling deep dynamic stall. This work also gives a performance assessment of VGs in controlling the highly unsteady aerodynamic forces of a wind turbine airfoil.
Nine cancer patients were treated with adoptive cell therapy using autologous anti-MAGE-A3 T-cell receptors (TCR)-engineered T cells. Five patients experienced clinical regression of their cancers ...including 2 on-going responders. Beginning 1-2 days postinfusion, 3 patients (#'s 5, 7, and 8) experienced mental status changes, and 2 patients (5 and 8) lapsed into comas and subsequently died. Magnetic resonance imagining analysis of patients 5 and 8 demonstrated periventricular leukomalacia, and examination of their brains at autopsy revealed necrotizing leukoencephalopathy with extensive white matter defects associated with infiltration of CD3(+)/CD8(+) T cells. Patient 7, developed Parkinson-like symptoms, which resolved over 4 weeks and fully recovered. Immunohistochemical staining of patient and normal brain samples demonstrated rare positively staining neurons with an antibody that recognizes multiple MAGE-A family members. The TCR used in this study recognized epitopes in MAGE-A3/A9/A12. Molecular assays of human brain samples using real-time quantitative-polymerase chain reaction, Nanostring quantitation, and deep-sequencing indicated that MAGE-A12 was expressed in human brain (and possibly MAGE-A1, MAGE-A8, and MAGE-A9). This previously unrecognized expression of MAGE-A12 in human brain was possibly the initiating event of a TCR-mediated inflammatory response that resulted in neuronal cell destruction and raises caution for clinical applications targeting MAGE-A family members with highly active immunotherapies.
ABSTRACTTip loss correction is necessary for all aerodynamic computations based on the blade-element momentum theory (BEMT) that plays an essential role in wind turbine design. Glauert tip-loss ...correction, which is most widely used, assumes the rotor is lightly loaded and thus lose some accuracy for modern wind turbines that are highly loaded. In the present work, a new g-function involving the rotor’s thrust-coefficient is introduced, which connects the tip loss correction with the rotor’s load condition and reduces the error of the tip loss correction. Computational tests are performed on two rotors that are distinct in size and tip shape. The new g-function results in good consistency between the computed forces and the reference data, exhibiting excellent role in improving the accuracy of the BEMT computations. In general, the new g-function combines good effectiveness and applicability, and thus has great potential for engineering applications.
Passive vortex generators (VGs) are widely used to suppress the flow separation of wind turbine blades, and hence, to improve rotor performance. VGs have been extensively investigated on stationary ...airfoils; however, their influence on unsteady airfoil flow remains unclear. Thus, we evaluated the unsteady aerodynamic responses of the DU-97-W300 airfoil with and without VGs undergoing pitch oscillations, which is a typical motion of the turbine unsteady operating conditions. The airfoil flow is simulated by numerically solving the unsteady Reynolds-averaged Navier-Stokes equations with fully resolved VGs. Numerical modelling is validated by good agreement between the calculated and experimental data with respect to the unsteady-uncontrolled flow under pitch oscillations, and the steady-controlled flow with VGs. The dynamic stall of the airfoil was found to be effectively suppressed by VGs. The lift hysteresis intensity is greatly decreased, i.e., by 72.7%, at moderate unsteadiness, and its sensitivity to the reduced frequency is favorably reduced. The influences of vane height and chordwise installation are investigated on the unsteady aerodynamic responses as well. In a no-stall flow regime, decreasing vane height and positioning VGs further downstream can lead to relatively high effectiveness. Compared with the baseline VG geometry, the smaller VGs can decrease the decay exponent of nondimensionalized peak vorticity by almost 0.02, and installation further downstream can increase the aerodynamic pitch damping by 0.0278. The obtained results are helpful to understand the dynamic stall control by means of conventional VGs and to develop more effective VG designs for both steady and unsteady wind turbine airfoil flow.
Autism spectrum disorder (ASD) is more prevalent in males; however, the etiology for this sex bias is not well understood. Many mutations on X-linked cell adhesion molecule NLGN4X result in ASD or ...intellectual disability. NLGN4X is part of an X-Y pair, with NLGN4Y sharing ∼97% sequence homology. Using biochemistry, electrophysiology, and imaging, we show that NLGN4Y displays severe deficits in maturation, surface expression, and synaptogenesis regulated by one amino acid difference with NLGN4X. Furthermore, we identify a cluster of ASD-associated mutations surrounding the critical amino acid in NLGN4X, and these mutations phenocopy NLGN4Y. We show that NLGN4Y cannot compensate for the functional deficits observed in ASD-associated NLGN4X mutations. Altogether, our data reveal a potential pathogenic mechanism for male bias in NLGN4X-associated ASD.
•Despite sharing ∼97% amino acid identity, NLGN4X and NLGN4Y are differentially regulated•NLGN4Y cannot traffic to the surface due to one amino difference from NLGN4X•A cluster of autism-associated variants in NLGN4X surrounds the critical amino acid•NLGN4X autism-associated variants display a deficit in trafficking similar to NLGN4Y
NLGN4X and NLGN4Y are thought to have similar functions due to their ∼97% shared amino acid identity. Nguyen et al. demonstrate NLGN4Y has a deficit in trafficking due to one amino acid difference. The trafficking deficit phenotype is also found in a cluster of autism-associated variants in NLGN4X near the critical amino acid.
This study aims to assess the dynamic stall of the wind turbine blade undergoing pitch oscillation (PO) and oscillating freestream (OF), respectively. Firstly, a thin-airfoil theoretical analysis was ...performed to differentiate between these two dynamic effects. During upstroke, PO results in a positive effective airfoil camber, while OF has an additional negative effective airfoil camber, and yet in contrast during downstroke, PO decreases the effective camber, while OF increases the effective camber. Secondly, the equivalence relation between PO and OF is investigated by numerically solving the unsteady Reynolds-averaged Navier-Stokes equations. The difference between PO and OF mainly exists in the linear part of the aerodynamic loads. Because the difference is great at high reduced frequencies or angle of attack (AOA) amplitudes, PO and OF should be treated separately for dynamic stall from different aerodynamic sources. Thirdly, the Beddoes-Leishman dynamic model coupled with Bak’s rotational stall delay model was used to predict the yawed responses of the blade section. The obtained results show different aerodynamic responses between PO and OF, although consideration of rotational augmentation can greatly improve the accuracy of the lift and drag coefficients. To improve the understanding and coupling modeling of rotational augmentation and dynamic stall, an extended analysis of the coupled effect was performed as well.
Rotational augmentation and dynamic stall have been extensively investigated on horizontal axis wind turbines (HAWTs), but usually as separate topics. Although these two aerodynamic phenomena mainly ...determine the unsteady loads and rotor performance, the combined effect of rotational augmentation and dynamic stall is still poorly understood and is challenging to model. We perform a comprehensive comparative analysis between the two-dimensional (2D) airfoil flow and three-dimensional (3D) blade flow to provide a deep understanding of the combined effect under yawed inflow conditions. The associated 2D aerodynamic characteristics are examined by the unsteady Reynolds-averaged Navier-Stokes Simulations, and are compared with the experimental data of NREL Phase VI rotor in three aspects: aerodynamic hysteresis, flow field development, and dynamic stall regimes. We find that the combined effect can dramatically reduce the sectional lift and drag hysteresis by almost 60% and 80% from the supposed definitions of hysteresis intensity, and further delay the onset of stall compared with either of rotational augmentation and dynamic stall. The flow field development analysis indicates that the 3D separated flow is greatly suppressed in the manner of changing the massive trailing-edge separation into the moderate leading-edge separation. Furthermore, the 3D dynamic stall regime indicates a different stall type and an opposite trend of the separated zone development, compared with the 2D dynamic stall regime. These findings suggest that the modelling of 3D unsteady aerodynamics should be based on the deep understanding of 3D unsteady blade flow rather than correcting the existing 2D dynamic stall models. This work is helpful to develop analytical models for unsteady load predictions of HAWTs.
The influence of yaw misalignment on the aerodynamic performance of the New MEXICO rotor is investigated using blade-resolved Computational Fluid Dynamics (CFD) approaches with three wind speeds ...considered at a fixed yaw angle of 30 degrees. The air-load predictions and near wake characteristics from the numerical results are compared and discussed against the most recent wind tunnel test data. The nacelle impact, dynamic stall phenomenon and wake characteristics are analyzed, demonstrating the yaw effects and numerical issues raised from Reynolds-Averaged Navier Stokes (RANS) and Detached Eddy Simulation (DES) computations.
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