Magnitude Of Air Flow Research Articles

Soft Airflow Sensors With Artificial Hair Structures and Printed Ionogel Channels for Wind Gust Detection for Small Uncrewed Vehicles

This article describes the design of a soft airflow sensor capable of detecting the direction and the magnitude of airflow, taking advantage of an additive manufacturing technique for rapid prototyping. The sensor consists of an artificial hair structure and conductive ionogel channels. The artificial hair, made by 3-D printing, is designed to maximize the moments at the base caused by the airflows applied to the hair structure. The ionogel channels are directly printed on a flexible printed circuit board and then embedded in an elastomeric layer. A compact readout circuit is prepared to acquire the impedance information from the sensing channels. The sensor shows reliable and repeatable responses to unidirectional airflows ranging from 6 to 13 m/s. A clear relationship between the applied loads and the sensor outputs is observed. We also demonstrate the performance and the application of the proposed airflow sensor by installing it on a small uncrewed ground vehicle that achieves stable operation through the detection of atmospheric disturbances.

Flow separation sensing on airfoil using a 3D printed biomimetic artificial hair sensor

Small-scale unmanned air vehicles require lightweight, compact, and low-power sensors that encompass a variety of sensing modalities to enable flight control and navigation in challenging environments. Flow sensing is one such modality that has attracted much interest in recent years. In this paper, a micro-scale artificial hair sensor is developed to resolve both the direction and magnitude of airflow. The sensor structure employs a high-aspect ratio hair structure and a thin flexible membrane to facilitate the transduction of directional airflow to membrane deflection. The sensor readout is based on capacitive sensing and two pairs of electrodes orthogonal to each other are used to obtain airflow directional information. The sensor structure was fabricated using two-photon polymerization and integration onto a miniature printed circuit board to enable simple measurement. The sensor’s responses to static displacement loading from different directions were characterized. The experimental results are in good agreement with the simulation results. Furthermore, the sensor’s capability to measure the direction and magnitude of flow was demonstrated. Finally, the sensor was mounted on an airfoil and its ability to detect flow separation was verified.

Aerodynamic and Micro-Fluidic Effect in Masks with Impact in Covid-19 and Other Pandemic Propagation

US has ignored the hierarchy of pandemic control, misinformed population on virus propagation needed protection by using masks and other complementary protection measures facilitating the human disaster. The population mindset was to dismiss science, the virus and hope to dodge the pandemic with a fabric over the mouth and a free vaccine that will result in more than 600,000 deaths, and over 30 Million infected. In fact, masks are filters, and have a limited protection factor, known when used in medical practice. The masks were mainly designed and measured for stopping solid particulates, but when used against aerosolized watery droplets loaded with bio-agents nano-fluidic effects are responsible for anomalous, nonlinear and unpredictable complex behavior. Using an aerodynamic test bench, and various sizes of radioactive nano-powders, we performed measurements on the retention factor dependence for various filter materials of airflow magnitude, temperature, airflow regime, and filter's load. The results showed that a retention function of particle magnitude, measured for particulates, vary with temperature and when filter is used for aerosolized loaded watery droplets, an "atomization" effect happens transforming larger aerosols in finer ones, due to micro-nano-fluidic and aerodynamic instabilities. The measurements showed that pulsed and reciprocating airflow regimes trigger loaded filters to release some of previously retained particles, making the masks offer a reduced protection factor, and imposing special rules of safe usage. It was not told to public that is a contagious person uses correctly a mask, without any lateral leakage, through the mask passes nano-sized, airborne aerosols, containing virioli that float in air for weeks, driven by air currents, and special complementary measures to sterilize or remove the air have to be taken for safety.

Experimental study of temperature profile and gas-liquid heat transfer in flame spread over jet fuel under longitudinal air flow

The rectangular pools with the same length of 100 cm but different widths of 4 and 20 cm are used to conduct experiments of flame spread over jet fuel of RP-3. The direction of longitudinal air flow is same and opposite to direction of flame spread respectively. Six air flow velocities 0.45, 0.88, 1.3, 1.73, 2.15 and 2.57 m/s are employed. The spatial temperature distributions and convective heat dissipation at pool bottom are examined using thermocouples. The heat loss is negligible for 10 mm-thick fuel layer, but it is evident for 3 mm-thick fuel layer. The integral method is proposed to calculate the flame radiation imposed to subsurface flow region. The gas-liquid heat transfer model including liquid-phase convection, flame radiation and convective heat dissipation is established for calculating energy balance involving flame spread over RP-3. The calculated heat fluxes follow well with experimental measurements, regardless of direction and magnitude of air flow. The current findings possess potential application and practical guidelines for fire prevention of liquid fires under longitudinal air flows. In order to restrict flame spread, it is a feasible method to cut off liquid convection or shield flame radiation.

The “breathing spots” in karst areas—the sites of advective exchange of gases between soils and adjacent underground cavities

Microclimatic processes were studied in the soil of the well-defined “breathing spot” named Půlhodina (BSP) in the Hranice Karst (Czech Republic). The results have indicated that air is exchanged between the external atmosphere and a supposed underground cavity under air-buoyancy control. Upward airflow ventilation mode (UAF mode) and downward airflow ventilation mode (DAF mode) were distinguished. The virtual temperature of switching between both modes was about 16.5 °C. At the UAF mode, the underground air is rising from the cavity through the BSP, warms soil, and carries out the underground CO2. At the DAF mode, the external air is sucked into the cavity through the BSP soil, promoting the advective flux of the soil-respired CO2 deeper into the cavity. Whereas the warming of the soil is a dominant process in the UAF mode, the CO2 advective flux into the cavity is the main process in the DAF mode. The simplified mathematical model was derived as a function of the external air temperature and the soil air temperature to simulate the time evolution of CO2 concentration in the BSP. Despite simplifying assumptions, this model showed a good agreement with the collected data. The advective CO2 flux from a breathing spot soil may significantly contribute to the total CO2 flux into the adjacent underground cavity. Its total values may reach 4 × 10−3 mol s−1 or even more, based on the actual CO2 concentration, the exchanged airflow magnitude (both controlled by external temperature), and the breathing spot area. This conclusion is important for karsologists studying the cave CO2 budget, CO2 sources, and the mechanisms of CO2 transport into caves.

Development of Performance System With Musical Dynamics Expression on Humanoid Saxophonist Robot

Talented musicians can deliver a powerful emotional experience to the audience by skillfully modifying several musical parameters, such as dynamics, articulation, and tempo. Musical robots are expected to control those musical parameters in the same way to give the audience an experience comparable to listening to a professional human musician. But practical control of those parameters depends on the type of musical instrument being played. In this study, we describe our newly developed music dynamics control system for the Waseda Anthropomorphic Saxophonist robot. We first built a physical model for the saxophone reed motion and verified the dynamics-related parameters of the overall robot-saxophone system. We found that the magnitude of air flow is related to the sound pressure level, as expected, but also that the lower lip is critical to the sound stability. Accordingly, we then implemented a music dynamics control system for the robot and succeeded in enabling the robot to perform a music piece with different sound pressure levels.

PIV measurement and CFD simulations of an air terminal device with a dynamically adapting geometry

Air quality is an important factor for human well-being, and it is crucial that when using mechanical ventilation system, air is properly distributed so it reaches every user of a ventilated zone. To improve ventilation systems, and in consequence the air quality, this paper focuses on studying the impact of an air terminal device (ATD) with a dynamically changing geometry on the effectiveness of a variable air volume (VAV) ventilation system. VAV system characterizes a change in the airflow magnitude through the system when the heat gains lower, which may be a risk for human health as air may not reach the furthest parts of a zone. To combat this threat, an ATD with a dynamically changing geometry was installed. As a ventilation quality indicator, the air throw was taken under consideration. Thanks to the new ATD, the steady air throw should be maintained despite the changes in flow in the ventilation system. To achieve this, the research was divided into two stages. The first stage included a series of computational fluid dynamics simulations that considered the alteration of the airflow and the air terminal device diameter. Afterwards, verifying laboratory measurements were conducted on a laboratory stand using a particle image velocimetry (PIV) system that included an air terminal device with a changing geometry. The results of the simulations and the PIV measurements showed that the changes in the geometry of the air terminal device improve the ventilation effectiveness of a VAV system, allowing the system to maintain a constant air throw despite the changing airflow magnitude through the system.

Design Parameters for the Housing of Two-Dimensional Air Flow Sensors

Micro machined sensors for the 2-D measurement of air flow magnitude and direction achieve very high sensitivity. The housing required for the protection of the sensor membrane greatly reduces the sensitivity for low velocities and induces deformation of the angle response. The first critical design factor is the gap height between the sensor surface and the protecting cover plate. The second is the layout of the necessary mounting bars to hold the cover. Several laboratory tests were conducted to evaluate and compare the influence of these factors. Best results were achieved by replacing the initial four needles holding the cover with a high number of wedge-shaped fins. The final sensor with improved housing was able to measure air flow in cooled fruit warehouses between 0.1 and 2 m/s with a 2% deviation from an ideal sinusoid angle dependency.

Effect of airflow speed and direction on convective heat transfer of standing and reclining cows

An effective ventilation system can mitigate the heat stress suffered by dairy cows by increasing the rate at which heat is transferred convectively from a cow into the air flowing around the animal. To achieve a better understanding of the main factors involved in the heat-transfer process (i.e., the cow's posture and the airflow magnitude and direction), numerical investigations were conducted during the course of this study. By applying a computational fluid dynamics (CFD) modelling method, a virtual wind tunnel, and simplified geometric models representing a standing cow and a reclining cow, the heat transfer associated with a typical cow was simulated and analysed. The shear stress transport (SST) k–ω turbulence model was adopted, and it was shown that using a CFD method to analyse the heat-transfer data generated by this setup could produce results that are accurate and support the following conclusions: 1) airflow speed has a positive effect on the convective heat-transfer coefficient associated with both postures; 2) airflow direction affects the convective heat transfer coefficient, with the largest coefficient occurring in the cross flow case and the lowest in the downward airflow case; 3) the effect of posture on the convective heat transfer coefficient in a horizontal airflow is limited, whereas the effect in a downward airflow is relatively significant. However, the rate at which heat dissipates from a standing cow is greater than that of reclining cow, since a standing cow has more surface area in contact with the air. Based on these conclusions, it is recommend that, to cool cows under hot conditions, the airflow in the animal-occupied zone should be increased and that using a horizontal airflow to target the animal occupied zone should be encouraged whenever it is feasible to create.

Experimental Investigation and FE Simulation of the Effect of Variable Control on Temperature Distribution in Orthogonal Metal Cutting Process

The study aimed at building a 3-Dimensional finite element simulation to monitor orthogonal machining process under a dry machining environment. The study was conducted in two stages of experimentation and finite element modelling and simulation (FEMS). The purpose of the experimentation was to obtain data which will be used to validate the FEMS result. The FEMS was carried out with a commercially available solver. The workpiece material employed for the study was mild steel in the form of round bar of solid shaft having 45mm diameter and length of 500mm. Mild steel was selected due to its wide range of applications in the fields of manufacturing tools and mould industry. The tool material used was tungsten carbide of DIN4980R 20 mm x 20 mm, with cutting angle of 80-degree tool steel, which was modelled in the FEMS as a rigid body. Various cutting conditions such as speed, feed rate and depth of cut were considered to obtain the tool chip temperature. Different values of temperature were recorded at interval of 10 seconds and ranged from 10 to 100 seconds. The FEMS was carried out by making one of the conditions vary while the others were constant. The temperature values measured with a digital thermocouple were used to validate the FEMS data obtained. The result show that the cutting temperature predicted by the FEMS is within 20% of the real experimental value and followed the same trend. It was discovered that the values of temperature obtained from simulation were also much higher than that of experimentation. Therefore, the experimental value might not be accurate, due to some experimental errors and environmental effects like partial contact between the measuring device and the cutting tools, fluctuation in the magnitude of air flow around the surrounding which may affect the cutting temperature, room temperature and pressure effect. Generally, with an increase in the cutting speed, feed rate and depth of cut, the tool temperature also increased and the cutting speed was found to be the most effective parameter when consideration is given to temperature effects, especially in high range of cutting conditions.

New Approach for Airflow Measurement Using Thermal Resistance Simulation

<p>This paper presents a new model-based approach to detect and compensate errors of positive temperature coefficient (PTC) sensors used for airflow measurement. From modeling and simulation, it can be shown that the thermal resistance of the sensor at self-heating mode was influenced by air flow magnitude. The sensor of type EPCOS-AG B59010 in a steel case, length 20 mm, diameter 2 mm was characterised over the flow rate range between 0 and 6 m/s and modeled to determine coupling thermal resistance interaction R<sub>th</sub> between the medium surrounding and sensor’s structure. Soiling caused by dust transported with the air on the sensor surface changing in the thermal resistance has observed and simulated in an experiment using a cylindrical sheath of PTFE – <em>Polytetrafluorethylen</em> with known heat conductivity λ<sub>S</sub> = 0.24 W/Km and diameter D. Parameters of model were then calibrated by evaluating current-voltage I(U)-characteristic at air velocity of v = 0m/s, and recalibration is then also used to correct the model parameters for v ¹ 0m/s. Result shows the soiling has exceeded critical thickness at D/d = 9 wherein the thermal resistance tends to be constant meaning cleaning sensor surface or replacing are needed.</p>

New Approach for Airflow Measurement Using Thermal Resistance Simulation

<p>This paper presents a new model-based approach to detect and compensate errors of positive temperature coefficient (PTC) sensors used for airflow measurement. From modeling and simulation, it can be shown that the thermal resistance of the sensor at self-heating mode was influenced by air flow magnitude. The sensor of type EPCOS-AG B59010 in a steel case, length 20 mm, diameter 2 mm was characterised over the flow rate range between 0 and 6 m/s and modeled to determine coupling thermal resistance interaction R<sub>th</sub> between the medium surrounding and sensor’s structure. Soiling caused by dust transported with the air on the sensor surface changing in the thermal resistance has observed and simulated in an experiment using a cylindrical sheath of PTFE – <em>Polytetrafluorethylen</em> with known heat conductivity λ<sub>S</sub> = 0.24 W/Km and diameter D. Parameters of model were then calibrated by evaluating current-voltage I(U)-characteristic at air velocity of v = 0m/s, and recalibration is then also used to correct the model parameters for v ¹ 0m/s. Result shows the soiling has exceeded critical thickness at D/d = 9 wherein the thermal resistance tends to be constant meaning cleaning sensor surface or replacing are needed.</p>

Full scale measurements and CFD simulations of diffuse ceiling inlet for ventilation and cooling of densely occupied rooms

Spaces with high occupant densities result in high heat gains and need for relatively high air change rate. By means of traditional mechanical ventilation diffusers it becomes a challenge to supply large amounts of fresh air into the space without creating a local discomfort for occupants. One solution to this problem is use of a diffuse ceiling inlet supplying a fresh air into the room through a large area of perforated ceiling.The aim of this paper was to report the research conducted on diffuse ceiling inlet installed in the full scale test outdoor facility. The diffuse ceiling inlet based on gypsum boards with airtight connections was created utilizing the full potential of diffuse layer without undesirable crack flow reported by other authors. The measured values were used to validate the detailed Large Eddy Simulation model of test room created in CFD software with aim to evaluate an indoor comfort numerically.Results of our investigations have shown that diffuse ceiling inlet is a suitable solution for the spaces with high density occupancy. The results have shown that transient calculations using Large Eddy Simulation models can predict well temperatures and velocity magnitude of air flow in the room.

Effects of feedstock, airflow rate, and recirculation ratio on performance of composting systems with air recirculation

The thermodynamics, kinetics, and energy use of composting systems with air recirculation were determined for feedstocks comprising paper mill sludge and biosolids. Results were developed by simulating the composting system using a two-dimensional finite difference numerical model. Incorporated into the simulation model was independent regulation of temperature and oxygen using a closed loop feedback control system with a two-stage fan setting. Results showed that at low airflows and high recirculation ratios, heat removal by the exhaust gas was insufficient to maintain set point temperatures with the result that process temperatures increased and eventually limited the reaction rate. Types of feedstock, magnitude of airflow and recirculation ratio all affected the energy use of the system. Although recirculation leads to high energy use, it can produce high quality compost by having a temperature gradient of less than 2 °C across the bed.

Air flow characteristics of a room with square cone diffusers

A computational fluid dynamics model with radiant exchange between surfaces is developed to examine the air flow characteristics of a room with square cone diffusers. As an input to the full-scale 3-D room model, a 2-D diffuser model that supplies direction and magnitude of air flow into the room is developed and evaluated using infrared visualization. The room air flow model is assessed using several previously documented problems with various geometries and boundary conditions. Simulations are conducted for heating and cooling of the room with one or two supply air diffusers. The results show that the offset and lips of the diffuser work together to determine the discharge air angles, which play an important role in determining the room air flow patterns. For a certain discharge angle in the heating case, the air flows along the ceiling. The results indicate that, for the same supply air flow, operating only a single diffuser initiates more mixing of the room air flow, which results in enhanced temperature uniformity compared to that for two diffusers. Radiant exchange between the exterior window and interior surfaces causes a significant change in the window temperature.

Experimental Studies of the Effect of Rough Surfaces and Air Speed on Aerosol Deposition in a Test Chamber

Understanding the fate of particles indoors is important for human health assessment because deposited particles, unless resuspended, cannot be inhaled. To complement studies in real buildings, where control of variables is often difficult, an experimental test chamber facility (8 m 3 ) was designed to study particle deposition under well-stirred conditions using monodisperse tracer aerosol particles in the range of 0.7 to 5.4 w m. The use of neutron-activatable tracers facilitated simultaneous surface sampling and aerosol concentration decay measurements. Aerosol deposition on both smooth surfaces and regular arrays of three-dimensional roughness elements under 3 different airflow speeds was investigated in the test chamber.It was expected that the texture of the chamber surface would significantly influence particle deposition, but some counterintuitive results were observed: under the lowest airflow condition and for the smallest particle size, particle deposition onto rough samples was found to be less than on the corresponding smooth surfaces. The ratio of particle deposition on rough surfaces relative to smooth surfaces increased with particle size and magnitude of airflow. For the largest particle size and airflow speed, particle deposition on the rough surfaces exceeded that on the smooth surfaces by a factor of 3.

Effects of combined treatment with rhDNase and airflow oscillations on spinnability of cystic fibrosis sputum in vitro.

Treatment with either rhDNase or high-frequency oscillation has been shown to be effective in improving the physical and transport properties of airway secretions in cystic fibrosis (CF). The objects of this in vitro study was to examine whether combined treatment with oscillation and rhDNase results in greater change of CF sputum spinnability than either treatment by itself. Aliquots of sputum (0.4 g) from eight CF patients were subjected to the following protocols for 15 minutes and then followed for a total of 30 minutes: 1) incubation with 0.04 ml DNase 50 micrograms rhDNase/normal saline (10% dilution) at 37 degrees C to achieve 5 micrograms DNase/g of sputum final concentration; 2) airflow oscillation at 27 Hz similar to the airflow magnitude produced by a commercial high-frequency chest compression (HFCC) device; 3) negative control with no treatment; 4) positive (dilution) control, incubating with 10% saline by volume; 5) combination of DNase and oscillation, and 6) combination of saline and oscillation. For each protocol, sputum spinnability (in mm, mean +/- SD) was measured by means of a filancemeter at baseline, 15, and 30 minutes. Treatment with DNase decreased spinnability significantly more than either saline or oscillation at 15 and 30 minutes (P < 0.02 and P < 0.04, respectively). Incubation with saline or oscillation of CF sputum for 15 and 30 minutes decreased spinnability significantly compared with control. The combination of DNase and oscillation decreased spinnability significantly more than treatment with DNase alone (3.74 +/- 0.45 vs. 6.54 +/- 0.73 at 15 minutes, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Ventilation rate as a determinant of symptoms and perceived odors among workers in daycare centers

The objective of this study was to assess symptoms related to the sick building syndrome (SBS) and perceived odors among daycare workers, relative to ventilation rates in Finnish daycare centers. A random sample of 30 daycare centers in the city of Espoo was selected for the study. The study population consisted of 268 female nursing workers, who filled in a questionnaire inquiring about symptoms, perceived air quality, and their possible personal and environmental determinants. The response rate was 96%. The ventilation system in most of the daycare centers (63%) was mechanical supply and exhaust; the rest of the centers (37%) had mechanical exhaust only. The exhaust airflows in the children's rooms varied remakably, ranging from 0 to 11 L/s per person (average 4.0 L/s per person). The air change rate varied from 0 to 5 m 3/hm 3 (average 1.61/h). Though potential personal and environmental confounders were controlled, no consistent associations were observed between the magnitude of airflows or air change rate and the occurence of symptoms or unpleasant odors experienced by the workers. The results indicate that relatively low mehanical ventilation rates are not associated with SBS symptoms and unpleasant odors in conditions where the potential sources of odor are strong and air change is not totally dependent on mechanical ventilation (windows are openable).

Influence of air flow on skin temperature.

The skin temperature is fundamental to heat exchange between the human body and the environment. The convective and evaporative heat exchanges depend on the temperature gradient and the extent of air flow over the skin surface. An attempt was made to study the topographical differences in skin temperature (Tsk) under varied levels of air flow and to examine the possible body temperature regulatory mechanism. Five volunteers were examined in a climatic chamber at 30 and 36 degrees C DB at 55-60% RH (ambient vapour pressure of 2.58 and 3.53 kPa and air flow of 0.6, 1.4, 1.9, 2.1 m/s). The deep body temperature (Tc) and local Tsk were recorded at 5-min intervals during 10 min pre-exposure, 30 min exposure to heat and 15 min recovery period after air flow was withdrawn. The time taken to attain at the lowest Tsk in different air speeds varied from 30 to 45 min. The highest drop in Tsk (2.4 degrees C) was recorded for forehead at 30 degrees C DB and significant skin cooling was achieved at an air flow of 0.6 m/s for most body regions. The overall drop in local Tsk was more greater at a higher ambient temperature (36 degrees C) and the changes were significantly different (p < 0.05) to those recorded at the preexposure level. There was a consistent drop in Tsk with time, while no definite pattern of drop was noted with the magnitude of air flow. The Tc increased significantly with the continued air flow and following withdrawal of air flow the Tc tended to drop, suggesting heat gain by the body with a consequent increase in Tc.

Dependence of the magnitude of air flow through lumpy material on its granulometric composition

Dependence of the magnitude of air flow through lumpy material on its granulometric composition