Background Flow Research Articles

The Honda Automotive Laboratories of Ohio Wind Tunnel

<div class="section abstract"><div class="htmlview paragraph">The Honda Automotive Laboratories of Ohio (HALO) includes a new aeroacoustic wind tunnel located near Marysville, Ohio that started operations in 2022. This facility provides world-class aerodynamic flow quality and acoustic testing capabilities for the development of both passenger and motorsports vehicles.</div><div class="htmlview paragraph">This closed-return ¾ open jet wind tunnel features a two-position flexible nozzle system with cross sections of 25 m<sup>2</sup> and 18 m<sup>2</sup>, providing wind speeds of up to 250 km/h and 310 km/h, respectively. There is a ±180 degree turntable with boundary layer control systems, and interchangeable single belt and 5-belt moving ground plane (MGP) modules. Extensive applications of acoustic treatment in the test section and throughout the wind tunnel circuit provide a hemi-anechoic test environment and low background noise levels. A temperature control system provides uniform and stable air temperature over an operating environment between 10 °C and 50 °C.</div><div class="htmlview paragraph">The primary instrumentation of the wind tunnel includes the wind speed, temperature, and humidity measurement systems, a 6-component force balance integrated within the turntable, and an acoustic test system (ATS). The ATS includes four planar microphone arrays for external measurements and a spherical microphone array and binaural heads for internal measurements. A flow survey traverse system equipped with a 4-D probe holder mechanism is capable of placing a probe anywhere within the test volume.</div><div class="htmlview paragraph">The HALO facility includes the wind tunnel control room, secure vehicle preparation bays and office spaces for segregated customers, and a vehicle frontal and side area measurement system.</div><div class="htmlview paragraph">This paper provides an introduction to the HALO wind tunnel testing capabilities, design features and development, and the results of the aeroacoustic commissioning program. The background noise level and flow quality characteristics are provided.</div></div>

Abstract 2527: Investigation of doxorubicin interference in flow cytometry measurements of apoptosis and necrosis

Abstract Background: Doxorubicin (DOX) is frequently used for investigations of breast cancer using flow cytometry with fluorescent stains for apoptosis and necrosis. DOX interference, however, can occur with these fluorescent measurements which is not reported in many published reports. The objectives of this study were to identify such interference and to assess its extent. Methods: MDA-MB-231 and MCF-7 cells were incubated for 24 h with 0.1, 1, and 10 µM DOX. Cells were then stained for apoptosis and necrosis using two commercial assay kits. Fluorescence was measured with FL1 (apoptosis), FL2 (primary for DOX), and FL3 (necrosis) detectors in cells with DOX alone, with DOX plus stains, and in control cells without DOX. Measurements were repeated two to five times using replicates and trials. Statistics were evaluated by t-tests. Results: Overall, DOX fluorescence interference increased with concentration in both cell lines. After DOX incubation, cells stained with caspase 3/7 and SYTOX showed fluorescence in the FL1 detector indicating caspase 3/7 activation in apoptosis. But the DOX component of fluorescence with this detector ranged from 11 to 95%. Dox fluorescence in the FL3 detector for SYTOX measurements indicating necrosis ranged from 26 to 96% of total fluorescence. Cells stained with Annexin V (with the FITC label) and propidium iodide (PI) showed fluorescence in the FL1 detector for Annexin V indicating apoptosis. However, the DOX component of fluorescence ranged from 11 to 25%. DOX fluorescence in the FL3 detector for PI indicating necrosis ranged from 87 to 106%. Conclusions: Without correction for DOX interference, and even at low concentrations, substantial errors can occur for apoptosis and necrosis measurements using flow cytometry with these stains in breast cancer cells. At high DOX concentrations, the interference can erroneously indicate an extensive presence of these cell death processes. Corrections for DOX interference include background subtraction and flow cytometer compensation. Acknowledgments: The authors gratefully acknowledge financial support from the Agnes Varis Trust for Women in Science (REN), the Milton Lev Memorial Faculty Research Fund (CMO) as well as Saint Joseph’s University support for student research. The authors also thank Bin Chen, PhD, and Richard Howley for assistance with flow cytometry. Citation Format: Rachel E. Nicoletto, Richard Wilkes, Clyde M. Ofner. Investigation of doxorubicin interference in flow cytometry measurements of apoptosis and necrosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2527.

Impacts of Mountain Topography and Background Flow Conditions on the Predictability of Thermally Induced Thunderstorms and the Associated Error Growth

Abstract Thermally induced thunderstorm simulations were conducted with the Weather Research and Forecasting (WRF) Model in an idealized configuration to investigate the associated error growth and predictability. We conducted identical twin experiments with different topography and background winds to assess the impacts of these factors. The results showed that mountain topography restrains error growth at the early stage of convection development. This topographic effect is sensitive to mountain geometry and background winds: it was more noticeable in cases with higher and narrower mountains and difficult to see without background wind. The topographic effect and its sensitivity resulted from the different natures of convection initiation. However, the topographic effect became less apparent when moist convection continued growing and triggered rapid error growth. The predictability of thunderstorms is then limited at the timing after the convective activity reached its maximum. A smaller initial error or starting a simulation at a later time did not break this timing of predictability limit. Mountain topography also limitedly affected the timing of the maximum convective activity and the predictability limit. In contrast, background flows changed the convection evolution and the following predictability. The predictability limit assessed by rainfall suggested other aspects of the topographic effect. The domain-scale rainfall distribution and the intense accumulated rainfall can be adequately captured in the presence of mountains.

Sensible heat fluxes control cloud trail strength

AbstractConvective cloud bands known as “cloud trails” (CTs) are commonly found downwind of small islands (<(100) km2) throughout the world. They occur primarily in the afternoon, and are known to form in response to land–sea contrasts under the presence of background flow. A set of idealized numerical experiments with 100‐m horizontal grid spacing is performed to quantify the relationship between the surface forcing produced by an island and the strength of the resulting CT circulation. These experiments are based on observed environmental conditions for which a CT occurred off Bermuda, a small subtropical island. For these simulations, the CT circulation is found to be controlled by the strength of the integrated excess heating of the flow as it passes over the island. This excess heating is in turn controlled by the strength of the island heat fluxes when the wind speed and the island geometry are kept constant. Our experiments show, all else equal, a linear relationship between CT circulation strength and the island surface heat flux.

Spatially quasi-periodic water waves of finite depth

We present a numerical study of spatially quasi-periodic gravity-capillary waves of finite depth in both the initial value problem and travelling wave settings. We adopt a quasi-periodic conformal mapping formulation of the Euler equations, where one-dimensional quasi-periodic functions are represented by periodic functions on a higher-dimensional torus. We compute the time evolution of free surface waves in the presence of a background flow and a quasi-periodic bottom boundary and observe the formation of quasi-periodic patterns on the free surface. Two types of quasi-periodic travelling waves are computed: small-amplitude waves bifurcating from the zero-amplitude solution and larger-amplitude waves bifurcating from finite-amplitude periodic travelling waves. We derive weakly nonlinear approximations of the first type and investigate the associated small-divisor problem. We find that waves of the second type exhibit striking nonlinear behaviour, e.g. the peaks and troughs are shifted non-periodically from the corresponding periodic waves due to the activation of quasi-periodic modes.

Time-resolved simulation of blood flow through left anterior descending coronary artery: effect of varying extent of stenosis on hemodynamics

Background and objectivesReal-time blood flow variation is crucial for understanding the dynamic development of coronary atherosclerosis. The main objective of this study is to investigate the effect of varying extent of stenosis on the hemodynamic features in left anterior descending coronary artery.MethodsVarious Computational fluid dynamics (CFD) models were constructed with patient-specific CT image data, using actual fractional flow reserve (FFR) as boundary conditions to provide a real-time quantitative description of hemodynamic properties. The hemodynamic parameters, such as the local and instantaneous wall shear stress (WSS), oscillating shear index (OSI) and relative residence time (RRT), blood flow velocity and pressure drop during various phases of cardiac cycle were provided in detail.ResultsThere was no evident variation in hemodynamic parameters in the cases of less than 50% stenosis while there were abrupt and dramatic changes in hemodynamics when the stenosis aggravated from 60 to 70%. Furthermore, when the stenosis was beyond 70%, there existed substantial pressure difference, WSS, and blood flow velocity in the center of the stenosis. Although OSI and RRT increased along with the aggravation of stenosis, they appeared with obvious abnormalities across all cases, even in mild stenosis.ConclusionThe simulation could present a dynamic and comprehensive profile of how hemodynamic parameters vary in accordance with divergent severities of stenosis, which could serve as an effective reference for the clinicians to have a deeper insight into the pathological mechanism of coronary atherosclerosis and stenosis.

Near-inertial waves generated by typhoon MITAG under the influence of anticyclonic eddy east of Taiwan

Based on subsurface mooring observations and HYCOM data, a complete investigation was conducted of the near-inertial waves (NIWs) caused by Typhoon MITAG to the east of Taiwan. HYCOM data were mainly used to reveal the role played by anticyclonic eddies in the propagation of NIWs. The results show that most typhoon-generated NIWs propagate towards negative vorticity, and NIWs near the edge gradually accumulated towards the eddy center and down to 800 m. NIWs propagating through the thermocline to the deep ocean were mainly concentrated in the eddy, and the near-inertial energy flux showed a significant enhancement from 400 to 600 m. Moreover, the downwards propagation of NIWs in the eddy enhanced the kinetic energy of background flow. NIWs outside the anticyclonic eddy dissipated quickly, while inside the eddy, there were high value areas of e-folding time. Dynamic mode decomposition illustrates that the anticyclonic eddy mainly captures higher modes of NIWs, and the state of continuous energy growth of higher modes can be maintained for more than a week. In addition, NIWs can also be carried westwards by the advection of the mean background flow at the eddy’s edge.

Determining flow stasis zones in the intracranial aneurysms and the relation between these zones and aneurysms' aspect ratios after flow diversions.

Flow diverter stents (FDSs) are widely used to treat aneurysms in the clinic. However, even the same flow diverter (FD) use on different patients' aneurysm sites can cause unexpected hemodynamics at the aneurysm region yielding low success rates for the overall treatment. Therefore, the present study aims to unfold why FDs do not work as they are supposed to for some patients and propose empirical correlation along with a contingency table analysis to estimate the flow stasis zones in the aneurysm sacs. The present work numerically evaluated the use of FRED4518 FDS on six patients' intracranial aneurysms based on patient-specific aneurysm geometries. Computational fluid dynamics (CFD) simulation results were further processed to identify the time evolution of weightless blood particles for six patients' aneurysms. Stagnation zone formation, incoming and outgoing blood flow at the aneurysm neck, and statistical analysis of six patients indicated that FRED4518 showed a large flow stasis zone for an aspect ratio larger than 0.75. However, FRED4518, used for aneurysms with an aspect ratio of less than 0.65, caused small stagnant flow zones based on the number of blood particles that stayed in the aneurysm sac. A patient-specific empirical equation is derived considering aneurysms' morphological characteristics to determine the amount of stagnated fluid flow zones and magnitude of the mean aneurysm velocity in the aneurysm sac for FRED4518 based on weightless fluid particle results for the first time in the literature. As a result, numerical simulation results and patient data-driven equation can help perceive stagnated fluid zone amount before FRED4518 placement by shedding light on neuro-interventional surgeons and radiologists.

Multitarget Reactive Magnetron Sputtering towards the Production of Strontium Molybdate Thin Films

X-ray photoelectron spectroscopy was used to study the direct synthesis of strontium and molybdenum oxide thin films deposited by multitarget reactive magnetron sputtering (MT-RMS). Sr and Mo targets with a purity of 99.9% and 99.5%, respectively, were co-sputtered in an argon-oxygen gas mixture. The chamber was provided with an oxygen background flow plus an additional controlled oxygen supply to each of the targets. We demonstrate that variation in the power applied to the Mo target during MT-RMS enables the production of strontium and molybdenum oxide films with variable concentrations of Mo atoms. Both molybdenum and strontium were found in the oxidized state, and no metallic peaks were detected. The deconvoluted high-resolution XPS spectra of molybdenum revealed the presence of several Mo 3d peaks, which indicates molybdenum bonds in a lower valence state. Contrary to the Mo spectra, the high-resolution strontium Sr 3d spectra for the same samples were very similar, and no additional peaks were detected.

Density-Driven Convection for CO2 Solubility Trapping in Saline Aquifers: Modeling and Influencing Factors

Industrial development has significantly increased the concentration of CO2 in the atmosphere, resulting in the greenhouse effect that harms the global climate and human health. CO2 sequestration in saline aquifers is considered to be one of the efficient ways to eliminate atmospheric CO2 levels. As an important mechanism, the solubility trapping greatly determines the efficiency of CO2 sequestration in saline aquifers, and this depends, in turn, on the density-driven convection that occurs during the sequestration. Density-driven convection is influenced by multiple factors. However, existing discussions on some of these influential factors are still ambiguous or even reach contradictory conclusions. This review summarizes the common modeling approaches and the influence of factors on density-driven convection. We suggest that saline aquifers with high values of depth, permeability, pH, and SO2 impurity concentration are the ideal CO2 sequestration sites. A certain degree of porosity, fractures, stratification, slope, hydrodynamic dispersion, background flow, and formation pressure are also considered advantageous. Meanwhile, the geological formation of the Permian White Rim Sandstone or carbonate is important, but it should not contain brine with excessive viscosity and salinity. Finally, we discuss the contents in need of further research.

Modeling virus transport and dynamics in viscous flow medium

ABSTRACT In this paper, we developed a mathematical model to simulate virus transport through a viscous background flow driven by the natural pumping mechanism. Two types of respiratory pathogens viruses (SARS-Cov-2 and Influenza-A) are considered in this model. The Eulerian–Lagrangian approach is adopted to examine the virus spread in axial and transverse directions. The Basset–Boussinesq–Oseen equation is considered to study the effects of gravity, virtual mass, Basset force, and drag forces on the viruses transport velocity. The results indicate that forces acting on the spherical and non-spherical particles during the motion play a significant role in the transmission process of the viruses. It is observed that high viscosity is responsible for slowing the virus transport dynamics. Small sizes of viruses are found to be highly dangerous and propagate rapidly through the blood vessels. Furthermore, the present mathematical model can help to better understand the viruses spread dynamics in a blood flow.

Application to the World Ocean of the Theory of Transformation of a Mesoscale Vortex into a Submesoscale Vortex Thread When the Vortex Elongates by an Inhomogeneous Barotropic Flow

This paper is a continuation of the authors’ research [5]. We apply some aspects of the theory about strong horizontal stretching of large-scale mesoscale eddies in the World ocean based on ‘the ellipsoidal eddies’ theory to the ocean conditions. Two areas are considered, characterized by increased eddy manifestation. They are the Lofoten Basin in the Norwegian Sea and the Agulhas Current area. We also discuss the condition of the Atlantic Ocean and the World Ocean. The main purpose of this paper is to check the feasibility of the physical conditions for unbounded eddy elongation in the real ocean and estimate the fraction of mesoscale ocean eddies that are elongating into filaments and redistributing energy from the mesoscale to the submesoscale. We estimate the share of eddies in the World Ocean that are strongly elongated. We propose the maps of the geographical location of unlimited eddy elongation zones and give the interpretation of the obtained results. We also describe the effect of a decrease in the vortices’ self-energy due to the tensile action of the background flow. We suppose that it is a possible mechanism for energy transfer from the vortex to the flow and a manifestation of the negative viscosity effect.

Enhancing Simulations of Superparamagnetic Magnetic Drug Delivery to Predict Efficacy of Treatment

Globally, leukemia and skin cancers are the most common types of cancers. However, current measures (radiation, chemotherapy, etc.) cannot exercise high accuracy when targeting such tumors and cancers, causing extensive damage to surrounding tissue and leading to the adverse effects commonly associated with treatments such as chemotherapy. Magnetic drug delivery applies anticancer nanoparticles as a component vehicle for charged, targeted treatment. Building upon prior research, a stochastic numerical model was enhanced to simulate the motion of a superparamagnetic cluster suspended in different types of flow while being guided by an external magnet to travel to a target. The model supplanted the assumed Carreau blood flow to a realistic Hagen-Poiseuille flow under the influence of a magnetic field. The specific application of such clusters is magnetic drug targeting, with clusters in the range of 10–200 nm radii. Using a magnetic dipole model for the external magnet close to the surface of the skin, the time of arrival at the target was calculated through a physics-informed neural network by defining the pathway for the clusters. Variations in the release position, background flow, magnetic field strength, number of clusters, and stochastic effects are assessed to see how they affect the capture rate. The capture rate is found to depend weakly on variations in the velocity profile, and strongly on the cluster size, the magnetic moment, and the distance between the magnet and the blood vessel wall. The model is validated with existing data and good agreement with experimental results is shown

The dynamics of biofouled particles in vortical flows

When using mathematical models to predict the pathways of biofouled microplastic in the ocean, it is necessary to parametrise the impact of turbulence on their motions. In this paper, statistics on particle motion have been computed from simulations of small, spherical particles with time-dependent mass in cellular flow fields. The cellular flows are a prototype for Langmuir circulation and flows dominated by vortical motion. Upwelling regions lead to particle suspension and particles fall out at different times. The uncertainty of fallout time and a particle's vertical position is quantified across a range of parameters. A slight increase in settling velocities, for short times, is observed for particles with inertia due to clustering in fast downwelling regions for steady, background flow. For particles in time-dependent, chaotic flows, uncertainty is significantly reduced and we observe no significant increase in the average settling rates due to inertial effects.

Hydrostatic and Non‐Hydrostatic Baroclinic Instability in the Dynamical Core of the DOE Global Climate Model

AbstractThe dynamical core of the Department of Energy global climate model is used to understand the role of non‐hydrostatic dynamics in the simulation of dry and moist baroclinic waves. To reduce computational cost, the Diabatic Acceleration and REscaling approach is adopted. Scale analysis and numerical simulations suggest that the model solution is not distorted by the change of spherical metric terms due to the change of Earth radius, neither are the inter‐scale interactions strongly altered as indicated by the analysis of spectral flux. Compared with hydrostatic simulations, the onset of baroclinic instability is delayed under non‐hydrostatic dynamics as the associated weaker vertical motions tend to increase the critical wavelength and narrow the range of waves that can be baroclinically unstable. During the development of baroclinic waves, non‐hydrostatic dynamics tends to induce vertical motions in the upper troposphere, accelerating the eastward propagation of upper‐level ridges through their impact on local vorticity tendency. These processes reduce the westward tilt of the vertical ridge axes and suppress the conversion of mean flow available potential energy to eddy kinetic energy, leading to weaker baroclinic eddies than in hydrostatic simulations. The contrasts between hydrostatic and non‐hydrostatic settings hold in supplemental experiments that vary the background flow Rossby number, the amount of water vapor content and vertical resolution. We also find that mesoscale and smaller‐scale activities can be considerably under‐represented when the vertical resolution is limited to that typically used in global climate models.

Inertial focusing of spherical particles in curved microfluidic ducts at moderate Dean numbers

We examine the effect of Dean number on the inertial focusing of spherical particles suspended in flow through curved microfluidic ducts. Previous modelling of particle migration in curved ducts assumed the flow rate was small enough that a leading-order approximation of the background flow with respect to the Dean number produces a reasonable model. Herein, we extend our model to situations involving a moderate Dean number (in the microfluidics context) while the particle Reynolds number remains small. Variations in the Dean number cause a change in the axial velocity profile of the background flow which influences the inertial lift force on a particle. Simultaneously, changes in the cross-sectional velocity components of the background flow directly affect the secondary flow induced drag. In keeping the particle Reynolds number small, we continue to approximate the inertial lift force using a regular perturbation while capturing the subtle effects from the modified background flow. This approach pushes the limits at which a regular perturbation is applicable to provide some insights into how variations in the Dean number influence particle focusing. Our results illustrate that, as the extrema in the background flow move towards the outside of edge of the cross-section with increasing Dean number, we observe a similar shift in the stable equilibria of some, but not all, particle sizes. This might be exploited to enhance the lateral separation of particles by size in a number of practical scenarios.

Euphotic Zone Depth Anomaly in Global Mesoscale Eddies by Multi-Mission Fusion Data

As the waters of marine primary production, the euphotic zone is the primary living environment for aquatic organisms. Eddies account for 90% of the ocean’s kinetic energy and they affect marine organisms’ habitats by the excitation of vertical velocities and the horizontal advection of nutrients and ecosystems. Satellite observations indicate that anticyclones mainly deepen the euphotic zone depth, while cyclones do the opposite. The anomalies reach 5 m on average in the region of high eddy amplitude and frequent eddy occurrence. In addition, we found that the anomalies have an extreme value in each of the 5°–23° and 23°–55° and reach a maximum at around 38 degrees with the increase in latitude. In the eddy-center coordinate system, the minus gradient direction of the negative anomaly is consistent with the background flow field and the direction of the eddy movement. Meanwhile, the anomaly increases along the radial direction to about 0.2r and then decreases. Finally, there is a significant linear correlation between the anomaly magnitude and the eddy amplitude. The conclusion of this research and related mechanism explanation contributes to marine biology research and conservation, the estimates of marine primary productivity, and the understanding of the biogeochemical properties of eddy modulation in the upper water column.

On the open sea propagation of two-dimensional rotational water waves generated by a moving bed

We study the propagation of two-dimensional tsunami waves triggered by a seaquake in the open sea in the presence of underlying wind-generated currents, corresponding to background flows of constant vorticity. A suitable scaling of the governing equations introduces dimensionless parameters, of particular interest being the setting of linear waves that only depend on the vertical movement of the sea bed. We use Fourier analysis methods to extract formulae for the function f which describes the vertical displacement of the water's free surface. We show that the results are particularly useful in the physically relevant shallow-water regime: in the irrotational case the predictions fit well with the observed behaviour of some historical tsunamis. In other situations, the stationary-phase principle gives insight into the asymptotic behaviour of f.

Effects of the Kuroshio on internal tides in the Luzon Strait: A model study

Internal tides have a great impact on the meridional overturning circulation and climate variability through contributing to diapycnal mixing. The Luzon Strait (LS) is one of the most important sites of internal tide generation in the global ocean. In this study, we evaluate the effect of the Kuroshio on the M2 and K1 internal tides in both summer and winter seasons in the South China Sea (SCS), particularly within the LS. High-resolution ocean numerical simulations with the Kuroshio Current were compared with those without. We found that the Kuroshio has negligible impact on the generation site of internal tides. Compared to seasonal variability in the total barotropic to baroclinic conversion rate over the LS, the Kuroshio has relatively little influence. However, the Kuroshio flow strongly guides the propagating direction of the internal tides from the LS into the SCS. The Kuroshio also substantially decreases the southward energy fluxes going out of the LS. For both M2 and K1 tides, turning off the Kuroshio leads to a weaker energy exchange between the background shear and internal tides. Turning off the Kuroshio also weakens the divergence of internal tide energy due to the advection of background flow. Thus, our results reveal a non-negligible effect of the Kuroshio on the internal tides in the LS. If one aims to realistically simulate, or better understand, internal tides, these results indicate that one should include realistic oceanic circulation fields.

Retrieval of Peak Thunderstorm Wind Velocities Using WSR-88D Weather Radars

Abstract The current study develops a variant of the VAD method to retrieve thunderstorm peak event velocities using low-elevation WSR-88D radar scans. The main challenge pertains to the localized nature of thunderstorm winds, which complicates single-Doppler retrievals as it dictates the use of a limited spatial scale. Since VAD methods assume constant velocity in the fitted section, it is important that retrieved sections do not contain background flow. Accordingly, the current study proposes an image processing method to partition scans into regions, representing events and the background flows, that can be retrieved independently. The study compares the retrieved peak velocities to retrievals using another VAD method. The proposed technique is found to estimate peak event velocities that are closer to measured ASOS readings, making it more suitable for historical analysis. The study also compares the results of retrievals from over 2600 thunderstorm events from 19 radar–ASOS station combinations that are less than 10 km away from the radar. Comparisons of probability distributions of peak event velocities for ASOS readings and radar retrievals showed good agreement for stations within 4 km from the radar while more distant stations had a higher bias toward retrieved velocities compared to ASOS velocities. The mean absolute error for velocity magnitude increases with height ranging between 1.5 and 4.5 m s−1. A proposed correction based on the exponential trend of mean errors was shown to improve the probability distribution comparisons, especially for higher velocity magnitudes.