Preface to Special Topic: A Tribute to John Lumley

This Special Topic Section is dedicated to the life and memory of John Leask Lumley(1930-2015), professor and scientist extraordinaire

MRI: Acquisition of Interactive Visualization Tools for Supercomputer Models

This project, acquiring a visualization facility (vizwall with high resolution display and high volume storage system to visualize large size data generated from diverse research activities), models polar ice sheets, oceans, atmospheric turbulent boundary layers, and geodynamics. The facility, whose main components consist of a visualization wall, a PRISM visualization server, and RAID storage disks, will be integrated to the university\u27s existing supercomputer cluster

Did anomalous atmospheric circulation favor the spread of COVID-19 in Europe?

The current pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is having negative health, social and economic consequences worldwide. In Europe, the pandemic started to develop strongly at the end of February and beginning of March 2020. Subsequently, it spread over the continent, with special virulence in northern Italy and inland Spain. In this study we show that an unusual persistent anticyclonic situation prevailing in southwestern Europe during February 2020 (i.e. anomalously strong positive phase of the North Atlantic and Arctic Oscillations) could have resulted in favorable conditions, e.g., in terms of air temperature and humidity among other factors, in Italy and Spain for a quicker spread of the virus compared with the rest of the European countries. It seems plausible that the strong atmospheric stability and associated dry conditions that dominated in these regions may have favored the virus propagation, both outdoors and especially indoors, by short-range droplet and aerosol (airborne) transmission, or/and by changing social contact patterns. Later recent atmospheric circulation conditions in Europe (July 2020) and the U.S. (October 2020) seem to support our hypothesis, although further research is needed in order to evaluate other confounding variables. Interestingly, the atmospheric conditions during the Spanish flu pandemic in 1918 seem to have resembled at some stage with the current COVID-19 pandemic.A, Sanchez-Lorenzo was supported by a fellowship (RYC-2016–20784) and a project (PID2019-105901RB-I00) funded by the Ministry of Science and Innovation of Spain. Javier Vaquero-Martinez was supported by a predoctoral fellowship (PD18029) from Junta de Extremadura and European Social Fund. J.A. Lopez-Bustins was supported by Climatology Group of the University of Barcelona (2017 SGR 1362, Catalan Government) and the CLICES project (CGL2017-83866-C3-2-R, AEI/FEDER, UE). This research was supported by the Economy and Infrastructure Counselling of the Junta of Extremadura through grant GR18097 (co-financed by the European Regional Development Fund)

Sediment deposition from turbidity currents in simulated aquatic vegetation canopies

A laboratory flume experiment was carried out in which the hydrodynamic and sedimentary behaviour of a turbidity current was measured as it passed through an array of rigid obstacles. The obstacles were intended primarily to simulate aquatic vegetation canopies, but could equally be taken to represent other things, for example forests or offshore wind turbines. The turbidity currents were generated by mixing naturally-sourced, poly-dispersed sediment into a reservoir of water at concentrations from 1 to 10 gL-1, which was then released in the experimental section of the flume by removing a lock gate. For each initial sediment concentration, runs with obstacle arrays with solid plant fractions of 1% and 2.5%, and control cases with no obstacles, were carried out. The progress of the current along the flume was characterized by the array drag term, CDaxtoe (where CD is the array drag coefficient, a the frontal area of cylinders per unit volume and xtoe the current toe position along the flume). The depositional flux of sediment from the current as it proceeded was measured at thirteen traps positioned along the flume. Analysis of these deposits divided them into fine (2.2–6.2 μm) and coarse (6.2-104 m) fractions. At the beginning of the development, the gravity current proceeded in an inertia dominated regime until CDaxtoe =5. And for CDaxtoe > 5, the current transitioned into a drag-dominated regime. For both fine and coarse sediment fractions, the rate of sediment deposition tended to decrease gradually with distance from the source in the inertial regime, remained approximately constant at the early drag-dominated regime, and then rose and peaked at the end of the drag-dominated stage. This implies that, when passing through arrays of obstacles, the turbidity currents were able to retain sufficient sediment in suspension to maintain their flow until they became significantly influenced by the drag exerted by the obstacles

Effect of roughness on pressure fluctuations in a turbulent channel flow

Direct numerical simulation is used to investigate the nature of pressure fluctuations induced by surface roughness in a turbulent channel flow at Re_\tau =400 for three-dimensional periodic roughness elements, whose peaks overlap approximately 25% of the logarithmic layer. The three-dimensional roughness elements alter the pressure statistics significantly, compared to the corresponding smooth-wall flow, in both the inner and outer (core) regions of the channel. The direct consequence of roughness is an increased form drag, associated with more intense pressure fluctuations. However, it also alters the pressure fluctuations in the outer layer of the flow, and modifies the length scales defined by two-point correlations. We also find that the depth of the roughness sublayer defined by the pressure fluctuations is very different from that given by the large- and small-scale statistics from the velocity field

Cellulose Nano Fibers Infused Polylactic Acid Using the Process of Twin Screw Melt Extrusion for 3D Printing Applications

In this thesis, cellulose nanofiber (CNF) reinforced polylactic acid (PLA) filaments were produced for 3D printing applications using melt extrusion. The use of CNF reinforcement has the potential to improve the mechanical properties of PLA, making it a more suitable material for various 3D printing applications. To produce the nanocomposites, a master batch with a high concentration of CNFs was premixed with PLA, and then diluted to final concentrations of 1, 3, and 5 wt% during the extrusion process. The dilution was carried out to assess the effects of varying CNF concentrations on the morphology and mechanical properties of the composites. The results showed that the addition of 3 wt.% CNF significantly enhanced the mechanical properties of the PLA composites. Specifically, the tensile strength increased by 77.7%, the compressive strength increased by 62.7%, and the flexural strength increased by 60.2%. These findings demonstrate that the melt extrusion of CNF reinforced PLA filaments is a viable approach for producing nanocomposites with improved mechanical properties for 3D printing applications. In conclusion, the study highlights the potential of CNF reinforcement in improving the mechanical properties of PLA for 3D printing applications. The results can provide valuable information for researchers and industries in the field of 3D printing and materials science, as well as support the development of more advanced and sustainable 3D printing materials

Cellulose Nano Fibers Infused Polylactic Acid Using the Process of Twin Screw Melt Extrusion for 3d Printing Applications

IndianapolisIn this thesis, cellulose nanofiber (CNF) reinforced polylactic acid (PLA) filaments were produced for 3D printing applications using melt extrusion. The use of CNF reinforcement has the potential to improve the mechanical properties of PLA, making it a more suitable material for various 3D printing applications. To produce the nanocomposites, a master batch with a high concentration of CNFs was premixed with PLA, and then diluted to final concentrations of 1, 3, and 5 wt% during the extrusion process. The dilution was carried out to assess the effects of varying CNF concentrations on the morphology and mechanical properties of the composites. The results showed that the addition of 3 wt.% CNF significantly enhanced the mechanical properties of the PLA composites. Specifically, the tensile strength increased by 77.7%, the compressive strength increased by 62.7%, and the flexural strength increased by 60.2%. These findings demonstrate that the melt extrusion of CNF reinforced PLA filaments is a viable approach for producing nanocomposites with improved mechanical properties for 3D printing applications. In conclusion, the study highlights the potential of CNF reinforcement in improving the mechanical properties of PLA for 3D printing applications. The results can provide valuable information for researchers and industries in the field of 3D printing and materials science, as well as support the development of more advanced and sustainable 3D printing materials

Implications of Stably Stratified Atmospheric Boundary Layer Turbulence on the Near-Wake Structure of Wind Turbines

Turbulence structure in the wake behind a full-scale horizontal-axis wind turbine under the influence of real-time atmospheric inflow conditions has been investigated using actuator-line-model based large-eddy-simulations. Precursor atmospheric boundary layer (ABL) simulations have been performed to obtain mean and turbulence states of the atmosphere under stable stratification subjected to two different cooling rates. Wind turbine simulations have revealed that, in addition to wind shear and ABL turbulence, height-varying wind angle and low-level jets are ABL metrics that influence the structure of the turbine wake. Increasing stability results in shallower boundary layers with stronger wind shear, steeper vertical wind angle gradients, lower turbulence, and suppressed vertical motions. A turbulent mixing layer forms downstream of the wind turbines, the strength and size of which decreases with increasing stability. Height dependent wind angle and turbulence are the ABL metrics influencing the lateral wake expansion. Further, ABL metrics strongly impact the evolution of tip and root vortices formed behind the rotor. Two factors play an important role in wake meandering: tip vortex merging due to the mutual inductance form of instability and the corresponding instability of the turbulent mixing layer

COVID19-Newyork

Data set associated with the publication "Local Atmospheric Factors that enhance Air-borne Dispersion of Coronavirus - High-fidelity Numerical Simulation of COVID19 case study in Real-Time

Modeling of Stenotic Coronary Artery and Implications of Plaque Morphology on Blood Flow

A diseased coronary artery has been modeled to study the implications of plaque morphology on the fluid dynamics. In our previous study, we have successfully classified the coronary plaques of 42 patients who underwent intravascular ultrasound (IVUS) into four-types (Type I, Type II, Type III, and Type IV) based on the plaque morphology. In this study, we demonstrate that, for the same degree of stenosis (height of the plaques), hemodynamics parameters are strongly dependent on the plaque shape. This study is the first one to clearly demonstrate that in addition to wall shear stress, presence of turbulence and location of transition from laminar to turbulence state are additional hemodynamics parameters to identify plaques vulnerable to rupture