54 research outputs found
Design mining interacting wind turbines
© 2016 by the Massachusetts Institute of Technology. An initial study has recently been presented of surrogate-assisted evolutionary algorithms used to design vertical-axis wind turbines wherein candidate prototypes are evaluated under fan-generated wind conditions after being physically instantiated by a 3D printer. Unlike other approaches, such as computational fluid dynamics simulations, no mathematical formulations were used and no model assumptions weremade. This paper extends that work by exploring alternative surrogate modelling and evolutionary techniques. The accuracy of various modelling algorithms used to estimate the fitness of evaluated individuals from the initial experiments is compared. The effect of temporally windowing surrogate model training samples is explored. A surrogateassisted approach based on an enhanced local search is introduced; and alternative coevolution collaboration schemes are examined
Control of Transonic Cavity Flow Instability by Streamwise Air Injection
A time-dependent numerical model of a turbulent
Mach 1.5 flow over a rectangular cavity has been developed,
to investigate suppression strategies for its
natural self-sustained instability. This instability adversely
affects the cavity form drag, it produces large-amplitude
pressure oscillations in the enclosure and it
is a source of far-field acoustic radiation.
To suppress the natural flow instability, the leading
edge of the two-dimensional cavity model is fitted with
a simulated air jet that discharges in the downstream
direction. The jet mass flow rate and nozzle depth are
adjusted to attenuate the instability while minimising
the control mass flow rate.
The numerical predictions indicate that, at the selected
inflow conditions, the configurations with the
deepest nozzle (0.75 of the cavity depth) give the most
attenuation of the modelled instability, which is dominated
by the cavity second mode. The jet affects both
the unsteady pressure field and the vorticity distribution
inside the enclosure, which are, together, key
determinants of the cavity leading instability mode
amplitude. The unsteadiness of the pressure field is reduced
by the lifting of the cavity shear layer at the rear
end above the trailing edge. This disrupts the formation
of upstream travelling feed-back pressure waves
and the generation of far-field noise. The deep nozzle
also promotes a downstream bulk flow in the enclosure,
running from the upstream vertical wall to the
downstream one. This flow attenuates the large-scale
clockwise recirculation that is present in the unsuppressed
cavity flow. The same flow alters the top shear
layer vorticity thickness and probably affects the convective
growth of the shear layer cavity second mode
POD Analysis of Cavity Flow Instability
A Mach 1.5 turbulent cavity flow develops large-amplitude
oscillations, pressure drag and noise. This
type of flow instability affects practical engineering applications,
such as aircraft store bays. A simple model
of the flow instability is sought towards developing a
real-time model-based active control system for simple
geometries, representative of open aircraft store bays.
An explicit time marching second-order accurate
finite-volume scheme has been used to generate time-dependent
benchmark cavity flow data. Then, a simpler
and leaner numerical predictor for the unsteady
cavity pressure was developed, based on a Proper Orthogonal
Decomposition of the benchmark data.
The low order predictor gives pressure oscillations
in good agreement with the benchmark CFD method.
This result highlights the importance of large-scale
phase-coherent structures in the Mach 1.5 turbulent
cavity flow. At the selected test conditions, the significant
pressure âenergyâ content of these structures
enabled an effective reduced order model of the cavity
dynamic system. Directions and methods to further
streamline and simplify the unsteady pressure predictor
have been highlighted
In vitro safety âclinical trialâ of the cardiac liability of drug polytherapy
Abstract Only a handful of US Food and Drug Administration (FDA) Emergency Use Authorizations exist for drug and biologic therapeutics that treat severe acute respiratory syndromeâcoronavirus 2 (SARSâCoVâ2) infection. Potential therapeutics include repurposed drugs, some with cardiac liabilities. We report on a chronic preclinical drug screening platform, a cardiac microphysiological system (MPS), to assess cardiotoxicity associated with repurposed hydroxychloroquine (HCQ) and azithromycin (AZM) polytherapy in a mock phase I safety clinical trial. The MPS contained human heart muscle derived from induced pluripotent stem cells. The effect of drug response was measured using outputs that correlate with clinical measurements, such as QT interval (action potential duration) and drugâbiomarker pairing. Chronic exposure (10Â days) of heart muscle to HCQ alone elicited early afterdepolarizations and increased QT interval past 5Â days. AZM alone elicited an increase in QT interval from day 7 onward, and arrhythmias were observed at days 8 and 10. Monotherapy results mimicked clinical trial outcomes. Upon chronic exposure to HCQ and AZM polytherapy, we observed an increase in QT interval on days 4â8. Interestingly, a decrease in arrhythmias and instabilities was observed in polytherapy relative to monotherapy, in concordance with published clinical trials. Biomarkers, most of them measurable in patientsâ serum, were identified for negative effects of monotherapy or polytherapy on tissue contractile function, morphology, and antioxidant protection. The cardiac MPS correctly predicted clinical arrhythmias associated with QT prolongation and rhythm instabilities. This high content system can help clinicians design their trials, rapidly project cardiac outcomes, and define new monitoring biomarkers to accelerate access of patients to safe coronavirus disease 2019 (COVIDâ19) therapeutics
Integrated Isogenic Human Induced Pluripotent Stem Cell-Based Liver and Heart Microphysiological Systems Predict Unsafe Drug-Drug Interaction.
Three-dimensional (3D) microphysiological systems (MPSs) mimicking human organ function in vitro are an emerging alternative to conventional monolayer cell culture and animal models for drug development. Human induced pluripotent stem cells (hiPSCs) have the potential to capture the diversity of human genetics and provide an unlimited supply of cells. Combining hiPSCs with microfluidics technology in MPSs offers new perspectives for drug development. Here, the integration of a newly developed liver MPS with a cardiac MPS-both created with the same hiPSC line-to study drug-drug interaction (DDI) is reported. As a prominent example of clinically relevant DDI, the interaction of the arrhythmogenic gastroprokinetic cisapride with the fungicide ketoconazole was investigated. As seen in patients, metabolic conversion of cisapride to non-arrhythmogenic norcisapride in the liver MPS by the cytochrome P450 enzyme CYP3A4 was inhibited by ketoconazole, leading to arrhythmia in the cardiac MPS. These results establish integration of hiPSC-based liver and cardiac MPSs to facilitate screening for DDI, and thus drug efficacy and toxicity, isogenic in the same genetic background
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