Effect Of Air Flow Research Articles

Surface Dielectric Barrier Discharge in a Cylindrical Configuration – Effect of Airflow Orientation to the Microdischarges

ABSTRACT This paper is devoted to studying the effect of airflow orientation on the microdischarges of the surface dielectric barrier discharge in cylindrical configuration through varying air input into the discharge chamber, the number of input nozzles, and the geometry of the active electrode. The air is supplied into the discharge chamber tangentially, radially, or axially through one or four input nozzles. Air input into the discharge chamber and the number of input nozzles determine the airflow regime. We used two active electrode geometries that are the axial strips or azimuthal rings. The change of active electrode geometry from rings to strips affects the orientation of microdischarges with respect to the airflow. For the discharge, the variation of air inputs and the number of input nozzles influences the flow regime in the discharge chamber, which, together with the active electrode geometry, affects the temperature field distribution in the chamber. These factors play an important role in plasmachemical processes leading to the discharge generation of various species, such as ozone. It is found that, for the maximum effect of airflow on discharge ozone generation, the streamlines should be uniformly distributed in the discharge chamber and predominantly oriented perpendicular to the majority of microdischarges.

Piezo2-peripheral baroreceptor channel expressed in select neurons of the mouse brain: a putative mechanism for synchronizing neural networks by transducing intracranial pressure pulses.

Here we use immunohistochemistry to examine the expression of Piezo2 in neurons of the mouse dorsal root ganglia and brain. Whereas Piezo2 is expressed in the large majority (≥ 90%) of dorsal root ganglia neurons, Piezo2 expression is restricted to select neuron types in specific brain regions, including neocortical and hippocampal pyramidal neurons, cerebellar Purkinje cells and mitral cells of the olfactory bulb. Given the well-established role of Piezo2 as a low-threshold pressure sensor (i.e., ≤5 mmHg) in peripheral mechanosensation, including the regulation of breathing and blood pressure, its expression in central neurons has interesting implications. In particular, we hypothesize that Piezo2 provides neurons with an intrinsic resonance that promotes their entrainment by the normal intracranial pressure pulses (~5 mmHg) associated with breathing and cardiac cycles. The pressure-induced change in neural activity need only be very subtle to increase, for example, the robustness of respiration-entrained oscillations reported previously in widely distributed neuronal networks in both rodent and human brains. This idea of a "global brain rhythm" first arose from the effect of nasal airflow in activating mechanosensitive olfactory sensory neurons, which then synaptically entrain mitral cells within the olfactory bulb and through their projections, neural networks in other brain regions, including the hippocampus and neocortex. Our proposed, non-synaptic, intrinsic mechanism, where Piezo2 tracks the highly predictable and "metronome-like" intracranial pressure pulses-to date generally considered epiphenomena-would have the advantage that a physical force rapidly transmitted throughout the brain also contributes to this synchronization.

A systematic review and meta-analysis of indoor bioaerosols in hospitals: The influence of heating, ventilation, and air conditioning.

To evaluate (1) the relationship between heating, ventilation, and air conditioning (HVAC) systems and bioaerosol concentrations in hospital rooms, and (2) the effectiveness of laminar air flow (LAF) and high efficiency particulate air (HEPA) according to the indoor bioaerosol concentrations. Databases of Embase, PubMed, Cochrane Library, MEDLINE, and Web of Science were searched from 1st January 2000 to 31st December 2020. Two reviewers independently extracted data and assessed the quality of the studies. The samples obtained from different areas of hospitals were grouped and described statistically. Furthermore, the meta-analysis of LAF and HEPA were performed using random-effects models. The methodological quality of the studies included in the meta-analysis was assessed using the checklist recommended by the Agency for Healthcare Research and Quality. The mean CFU/m3 of the conventional HVAC rooms and enhanced HVAC rooms was lower than that of rooms without HVAC systems. Furthermore, the use of the HEPA filter reduced bacteria by 113.13 (95% CI: -197.89, -28.38) CFU/m3 and fungi by 6.53 (95% CI: -10.50, -2.55) CFU/m3. Meanwhile, the indoor bacterial concentration of LAF systems decreased by 40.05 (95% CI: -55.52, -24.58) CFU/m3 compared to that of conventional HVAC systems. The HVAC systems in hospitals can effectively remove bioaerosols. Further, the use of HEPA filters is an effective option for areas that are under-ventilated and require additional protection. However, other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi. Although our study analysed the overall trend of indoor bioaerosols, the conclusions cannot be extrapolated to rare, hard-to-culture, and highly pathogenic species, as well as species complexes. These species require specific culture conditions or different sampling requirements. Investigating the effects of HVAC systems on these species via conventional culture counting methods is challenging and further analysis that includes combining molecular identification methods is necessary. Our study was the first meta-analysis to evaluate the effect of HVAC systems on indoor bioaerosols through microbial incubation count. Our study demonstrated that HVAC systems could effectively reduce overall bioaerosol concentrations to maintain better indoor air quality. Moreover, our study provided further evidence that other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi. Our research showed that HEPA filters are more effective at removing bioaerosols in HVAC systems than the current LAF system. Therefore, instead of opting for the more costly LAF system, a filter with a higher filtration rate would be a better choice for indoor environments that require higher air quality; this is valuable for operating room construction and maintenance budget allocation.

Role of Air Flow on Changing Soil Properties and Plant Nutrition in Egyptian Alluvial Soil

Study the effect of air flow on changing some soil properties and plant nutrition is highly important to increase crop quality and productivity. The pot experiment was carried out focusing on Agric faba bean C.V. Giza 2 in Egyptian alluvial soil (clay) during 2017-18 seasons. Two soil samples with three replicates were taken. The results revealed that hygroscopic water (HW), saturation percentage (SP) and real density (RD) have not affected by air flow, while organic matter (OM), hydraulic conductivity (HC) and bulk density (BD) have remarkable increase with air flow. The available macro and micronutrients concentrations in soil and plant are also discussed where different results have been obtained depending upon type of nutrient. The total count of bacteria (TCM) is found to be affected with air flow than without aeration techniques. The findings of this study reveal that aeration or air flow promotes healthy levels of soil gases and plays a critical role in plant growth.

Measuring the effective thermal resistance of ventilated air-spaces behind common wall assemblies: theoretical uncertainty analysis and recommendations for the hot box method modifications (ASHRAE 1759-RP)

A well-designed ventilated wall that incorporates air-space behind cladding can reduce energy use for conditioning buildings by adding a thermally resistive layer. The scarcity of thermal performance data and standardized test methods is a particular barrier for practitioners to implement ventilated air gaps behind the facades. The current standardized test method to evaluate the thermal performance of a wall structure, such as ASTM 1363-19, does not consider the effect of the ventilated air-space behind external claddings. Therefore, testing and design recommendations are required to account for the impact of ventilation airflow on the thermal resistance of vertical air-spaces behind common cladding materials. In this study, the theoretical uncertainty analysis of the effective thermal resistance of the ventilated cavity is performed for a steady-state condition. The results revealed that temperature sensors with an absolute uncertainty of ±0.18 (±0.1 °C) and heat flux sensors with a relative uncertainty of 3% or lower are required to capture a wide range of the effective thermal resistance of the ventilated air gap. Thereafter, based on the uncertainty of temperature and heat flux measurements, the modifications of the ASTM C1363-19 test method to account for the airflow effects on the thermal performance of the wall assembly are proposed. A detailed description of the experimental setup is provided, and protocols for collecting, analyzing, and evaluating data are suggested. An example demonstrating how the proposed method can be practically used to measure the thermal resistance of a ventilated air-space is also presented.

Decoupling mechanisms of “avalanche” phenomenon for laser ablation of C/SiC composites in hypersonic airflow environment

When C/SiC composites subjected to high-power laser irradiation under hypersonic airflow environment, “avalanche” phenomenon was found, i.e., the ablation rate was significantly higher than that under static air environment. To reveal this phenomenon, parallel experiments of laser ablation under static air, short-time and long-time hypersonic airflow environments were carried out. Ablation models including oxidation, sublimation and erosion considering coupling effects of airflow and C/SiC composites were introduced, and a coupled fluid-thermal-ablation numerical simulation procedure was proposed and carried out. The relationship between ablation rates and aerodynamic pressure was discussed, and the contributions of different ablation mechanisms were quantitively evaluated. In hypersonic airflow environments, sublimation rate was increased due to the decreased local pressure, and erosion rate was accelerated as a result of increased pressure head at downstream area. The combined effect of augmented sublimation and accelerated erosion accounted for the main reason of “avalanche” phenomenon under hypersonic airflow.

Effect of transverse airflow on the deflection of negative corona discharge on the Trichel pulse mode at atmospheric pressure

Negative corona discharge can deflect in transverse airflow in pin-to-plane electrodes at atmospheric pressure. In this paper, we investigate the mechanism of Trichel pulse discharge deflection in transverse airflow and give a further understanding of the dynamic process of the deflection through experiments and simulations. In experiments, we quantitatively record the deflection angle by processing the discharge images, and they show that a larger airflow speed will lead to a larger deflection angle. In simulations, the discharge deflection angle is calculated through a 2D fluid model. Besides, the periodic fluctuation of the deflection angle with Trichel pulses is revealed, and this phenomenon can be explained by the alternative dominant effect of airflow or ionization on the net production of positive ions in the vicinity of the tip. When the effect of airflow is dominant, more positive ions will generate away from the center of the tip, which will lead to an increase in the deflection angle. On the other hand, when the effect of ionization prevails, more positive ions will generate near the center because the electric field here is stronger, and the deflection angle will decrease. In addition, if these two effects balance, the deflection angle will reach its maximum or minimum value.

The effect of a lateral airflow created on nozzle tip on the spray droplets deposition

The effect of a lateral airflow created on nozzle tip on the spray droplets deposition

Воздействие воздушного потока на аэродинамическое устройство для пантографа

Objective: To evaluate the infl uence of the parameters of current collectors of high-speed and very high-speed trains on the value of aerodynamic resistance. To study the effect of airfl ow on a pantograph aerodynamic device using SolidWorks software. Methods: A comparison of the obtained values of aerodynamic air resistance with those that were produced earlier is carried out. Results: By means of aerodynamic device, it is possible to reduce the speed of the air fl ow effecting the pantograph, to reduce the values of aerodynamic resistance and energy consumption, to extend the service life of current collectors. Practical importance: The proposed design can improve the current collection, which will reduce the load on the overhead line and the pantograph slide, and reduce the energy consumption of electric rolling stock.

On the Benefits of Whole-building IAQ, Ventilation, Infiltration, and Energy Analysis Using Co-simulation between CONTAM and EnergyPlus

Publicly available tools to perform whole-building simulation of indoor air quality, ventilation, and energy have been available for several decades. Until recently, these tools were developed in isolation, such as the whole-building contaminant transport and airflow analysis tool, CONTAM, developed by the National Institute of Standards and Technology (NIST) and the whole-building energy analysis tool, EnergyPlus, developed by the U.S. Department of Energy (DOE). The ability to couple these tools during runtime has been implemented through co-simulation, enabling improved analysis of the interdependent effects of temperature and airflow on contaminant transport and energy use on a whole-building scale.This presentation will include the development of a set of coupled reference building models for the purposes of evaluating the potential benefits of using co-simulation between CONTAM and EnergyPlus. A set of Residential Prototype Building Models available from DOE has been modified by NIST and utilized to demonstrate the coupling process and the benefits of this coupling with respect to IAQ and energy analysis, and to evaluate multiple whole-building simulation methods related to infiltration, ventilation, and occupant exposure. These methods include an original EnergyPlus prototype model, the original model with NIST-based infiltration correlations, co-simulation between EnergyPlus and CONTAM, and stand-alone CONTAM simulations. Potential benefits will be explored related to the ability of co-simulation to address the effects of variations in building typology and ventilation system performance on contaminant transport results while leveraging the capabilities of whole-building energy analysis.

Influence of asymmetric airflow on the cooling performance of brake disc of railway vehicle

The main objective of this article is to discuss the influence of asymmetric airflow on the cooling performance of the brake disc. This asymmetry might be caused by the air inlet pipe curvature of the UIC test bench for frictional components, whereas in reality this asymmetry might be caused by various factors. In the first part of the paper, a brief summary of effects of heat and temperature changes on the brake disc is presented. Additional information about UIC test bench is given with the focus on cooling effects of airflow on the disc. In the second part, a CFD simulation was made, and its settings and results are presented in detail. In the last part, temperature differences in various time points and positions on the brake disc are compared graphically in order to assess the influence of airflow from the inlet pipe and its curvature on the cooling performance of the brake disc.

3E Analysis of the Effect of Different Type of Fans on Cooling Performance Applied to an Industrial Deep Freezer

In this study, two different industrial refrigerators were designed, manufactured and tested to analyze the impact of different types of fans (Type 1 and Type 2) used in industrial cooling systems on the performance of the cooling system. In order to test the fan performance and airflow effects, two axial fan configurations with different structures and different motor technology (EC and shaded-pole induction) were tested in two separate industrial refrigerator test rooms in accordance with TS EN ISO 23953-2 standards. R290 (Propane) was used as a refrigerant in the systems. The average temperature and relative humidity values of the environment where the experiment was conducted were measured as 25 °C and 60 % (Class 3), respectively. During the experiments, the total of 51.71 kWh energy was consumed in system 1, while the total of 54.22 kWh energy was consumed in system 2 and the difference between the energy consumption of the two systems was calculated as 4.85%. The average temperatures of the inlet and outlet of the evaporator of the system 1 and 2 were -21.57 °C, -18.97 °C and -23.43 °C, -20.94 °C, respectively. The average refrigerant temperatures for the system 1 and 2 were calculated as -24.65 °C, -26.44 °C, respectively. While the average coefficient of performance value of the type 1 system was 1.74, it was calculated as 1.54 for the type 2 cooling system. The average second-law efficiencies for the two cooling systems were calculated as 30.85 % and 29.81 %, respectively. In addition, the environmental economy analysis was carried out using the amount of CO2 that was prevented from emitting and the CO2 emission price calculated accordingly.

Decontamination of multispecies oral biofilm from rough implant surface by airflow with glycine.

ObjectivesDecontamination of biofilm‐colonized rough implant surfaces remains challenging. We investigated the effect of airflow with glycine powder (AFG) on decontamination of mature oral multispecies biofilm from a sandblasted and acid etched (SLA) titanium surface.Materials and MethodsSubgingival dental plaque was cultured on SLA disks anaerobically for 21 days. AFG with various settings and distances was applied directly on the disks with or without previous rinse of 0.9% NaCl. The specimens were then analyzed through scanning electron microscope and remaining bacteria on the implant surface were quantified and statistically compared.ResultsMature oral biofilm with cocci and rods as major morphotypes, as well as spiral‐ and filamentous‐shaped organisms, was formed on the untreated disks. Saline rinsing removed the thick biofilm layer but left numerous of coccoid bacteria in rough surface pits. AFG effectively removed most of the bacteria from the pits. Both 25% and 50% power settings were equally effective at 3‐mm distance. With 50% power, AFG successfully removed bacteria at both 3‐ and 6‐mm distance. When AFG was applied on native biofilm without prior rinsing with saline, it effectively removed the biofilm including bacteria in the pits.ConclusionApplication of AFG appears effective in removing bacteria from rough implant surfaces.

Influence of airflow movement on methane migration in coal mine goafs with spontaneous coal combustion

Spontaneous coal combustion was proved to cause methane accumulation and methane explosions in coal mine goafs. To avoid possible methane explosions, the empirical engineering measure, ventilation dilution, is proposed in coal mines though its disaster prevention mechanism has not been well understood. Through experimental and numerical simulations, the superposition effect of the air leakage and coal combustion-induced chimney effect was studied to reveal disaster prevention effect of ventilation dilution. Research results show that the high temperature area of coal combustion is steady and can provide continuous buoyancy force to form upward airflow even under ventilation dilution; the drifting methane accumulation is observed under the superposition effect of air leakage and upward airflow; ventilation dilution can weaken and even eliminate methane accumulation by overcoming chimney effect, but an increase in coal combustion temperature will enhance the upward airflow of chimney effect to cause methane accumulation again. The competitive relationship between the coal combustion-induced chimney effect and air leakage provides a new insight to study methane migration for the disaster formation and prevention mechanism.

The effect of external airflows on ventilation with a rooftop windcatcher

This study aims to investigate how a modern style windcatcher, which is much shorter than the traditional ones, is more sensitive to the exterior flows interacting with the associated building itself. This interaction between the onset flows and building façades can influence the ventilation behaviour inside the building. Therefore, full simultaneous exterior and interior measurements are conducted in the wind tunnel around the envelope of a 1:12 generic building model with a two-sided rooftop windcatcher and a wall window. Wind tunnel flow visualisations are carried out to gain insights into the effect of the exterior building topology on ventilation. It was found that rooftop windcatchers performance is strongly influenced by the flows surrounding the building's façades, especially at the building roof with dominating flow separation, and near the room window. Hence, the windcatcher was most effective at oblique wind directions and with an opened room window. On the other hand, the performance response of two Reynolds-averaged Navier-Stokes (RANS) based turbulence models was presented throughout the results.

Optimization of flexible printed circuit board’s cooling with air flow and thermal effects using response surface methodology

Purpose This study aims to investigate the interaction of independent variables [Reynolds number (Re), thermal power and the number of ball grid array (BGA) packages] and the relation of the variables with the responses [Nusselt number ((Nu) ¯ ), deflection/FPCB’s length (d/L) and von Mises stress]. The airflow and thermal effects were considered for optimizing the Re of various numbers of BGA packages with thermal power attached on flexible printed circuit board (FPCB) for optimum cooling performance with least deflection and stress by using the response surface method (RSM). Design/methodology/approach Flow and thermal effects on FPCB with heat source generated in the BGA packages have been examined in the simulation. The interactive relationship between factors (i.e. Re, thermal power and number of BGA packages) and responses (i.e. deflection over FPCB length ratio, stress and average Nusselt number) were analysed using analysis of variance. RSM was used to optimize the Re for the different number of BGA packages attached to the FPCB. Findings It is important to understand the behaviour of FPCB when exposed to both flow and thermal effects simultaneously under the operating conditions. Maximum d/L and von Misses stress were significantly affected by all parametric factors whilst (Nu)¯ is significantly affected by Re and thermal power. Optimized Re for 1–3 BGA packages with maximum thermal power applied has been identified as 21,364, 23,858 and 29,367, respectively. Practical implications This analysis offers a better interpretation of the parameter control in FPCB with optimized Re for the use of force convection electronic cooling. Optimal Re could be used as a reference in the thermal management aspect in designing the BGA package. Originality/value This research presents the parameters’ effects on the reliability and heat transfer in FPCB design. It also presents a method to optimize Re for the different number of BGA packages attached to increase the reliability in FPCB’s design.

Purifying air over the operating field with a new mobile laminar airflow device to reduce the possibility of airborne contamination.

To investigate the effectiveness of a mobile laminar airflow (LAF) device designed to reduce both airborne particles and lint fibers within the sterile field during cataract surgery. Cincinnati Eye Institute, Cincinnati, Ohio. Prospective case series. The number of airborne particles sized 0.5 μm, 1.0 μm, and 1.5 μm were measured at different locations and times during 116 routine phacoemulsification procedures with and without the use of a mobile LAF device. In a companion study, the presence of lint fibers in 99 eyes undergoing cataract surgery with a mobile LAF device was compared with 50 eyes in the control group. Lint fibers were differentiated as either falling onto the ocular surface or being carried into the sterile field by an instrument. A statistically significant reduction (P < .0005) occurred in all 3 particle sizes measurements when the LAF device was used: 79.0% (93.6 ± 16.1 vs 445.3 ± 30.9), 81.7% (11.30 ± 1.98 vs 61.85 ± 5.34), and 90.8% (0.241 ± 0.056 vs 2.624 ± 0.362) in the 0.5 μm, 1.0 μm and 5.0 μm particles, respectively. Lint fibers were identified in 18% (9/50) of eyes in the control group and 16.16% (16/99) of eyes in the LAF group. Although the number of lint fibers carried into the sterile field was similar in each group, the incidence of lint fibers falling onto the sterile field was reduced from 6% (3/50) to 0% (0/99) when the LAF was used (P = .014). The mobile LAF device was highly effective in reducing the number of particulate matter and lint fibers within the sterile surgical field when used during cataract surgery.

Dynamics of negative coronas in airflow

Recent numerical studies captured the effects of airflow on positive streamers, when subjected to a lateral wind. The positive streamers initiate from the trailing side of the anode and propagate with a clear tilting in the direction of the airflow. In this paper, we present the results of a simulation of two successive negative corona pulses and investigate their behaviour when exposed to a lateral wind. We use a three-dimensional numerical model that couples the electrical discharge dynamics with the airflow and allows the study of the discharge on electrons and ions timescales. The results show that negative coronas are not easily influenced by the airflow and tilt just slightly in the flow direction. Our simulation explains the physical mechanism that governs the formation and termination of negative corona pulses (Trichel pulses) and describes for the first time the proposed cathode-directed streamer mechanism for negative corona current pulses.

The effect of airflow on (visually induced) motion sickness during a simulated driving task

The effect of airflow on (visually induced) motion sickness during a simulated driving task

Investigation into the Effects of Turbulent Air Flow on Stall of a NACA 2412 Airfoil Using Spalart-Allmaras Turbulence Model in STARCCM+

The simulation results of the air flow around NACA 2412 airfoil in STARCCM+ are submitted. The 9 groups of comparative experiments were simulated at 9 angles of attack: 0, 10, 13, 14, 15, 16, 18, 20, 30 degrees. By analyzing the air flow near the upper surface airfoil, the relationship between the generation condition of separation vortex and the angle of attack and the law of change of angle of attack and lift force were obtained. Finding the range of angle of attack for the stall, the angle of attack with maximum lift effectiveness was determined.