Airflow Velocity Measurements Research Articles

Flexible curved multi-functional sensors for air flow and vibration signal measurement of train bogie

Abstract The fluid-solid coupling effects with the aerodynamic noise and structural vibration signal have great part in measurement accuracy and fault diagnosis of the train bogie. It is important to collect aerodynamic noise and structural vibration data for safety evaluation and on-line structural health monitoring (SHM) of the bogie, which brings new challenges to the integration and installation of the sensors in the limited space and complicated operation condition of the train bogie. Flexible curved multifunctional sensors (FCMFS) integrated with the hot film and structural vibration sensor units is designed to the air flow and structural vibration measurement of the train bogie. Bogie vibration and wind tunnel test platforms with FCMFS are built to the air flow velocity and vibration data measurement on the bogie surface under different operation conditions. Piezoelectric Polyvinylidene fluoride(PVDF) sensors have significant output in the wind tunnel and vibration experiments, and the hot film sensor is only sensitive to the air flow signal. The effect of vibration signal to the hot film sensor could be ignored, which is applied to decouple the aerodynamic noise and structural vibration signals for improving the measurement accuracy of the train bogie. The dynamic performance of FCMFS is verified in Rail Transmit Base of East China Jiaotong University, which is applied to SHM and rapid fault diagnosis of train bogie. The air flow distribution and vibration data are collected to safety assessment and fault diagnosis of train bogie, which would promote the intelligent maintenance level of the train bogie.

Evaluation and analysis of systematic and random error components of airflow velocity measurements by anemometers

Evaluation and analysis of systematic and random error components of airflow velocity measurements by anemometers

Design and fabrication of a simple and cost-effective optical flow meter using liquid crystals and textile grid.

The measurement of airflow velocity is crucial in various fields, and several sensing approaches have been developed for detecting airflow, including optical fiber-based flowmeters. However, these sensors often require complex fabrication processes and precise optical alignment. In this paper, a simpler and more cost-effective approach has been used to measure air flow rate by utilizing the birefringence property of liquid crystals (LCs). LCs possess distinct optical characteristics, and their reorientation due to airflow can be detected by observing the intensity of the output light between crossed polarizers. The novelty of this study is the utilization of a textile grid to hold the LC layer, which simplifies the fabrication process. This LC-based gas flowmeter offers a simple, low-cost setup and provides rapid performance. This research presents what we believe to be a new approach to calculate airflow by exploiting the optical properties of LCs, which is a new frontier in gas flow measurement. The proposed airflow meter is capable of detecting airflow rates ranging from 0 l/min to 7.5 l/min with an accuracy of 0.5 l/min. It exhibits a stable response time in 75 seconds, and the sensor maintains acceptable stability over time.

玉米籽粒收获机清选装置气流场数值模拟与试验

To better analyze the distribution law of airflow in the wind sieve type cleaning device, this study took the cleaning device of Yafeng 4YZL-6S corn seed harvester as an example and conducted numerical simulation and comparative analysis of the airflow field inside the cleaning device under the sieve plate opening scales of 12, 16 and 20 mm using CFD software. The numerical simulation showed that the distribution of airflow velocity above the sieve surface was uniform at a sieve plate opening scale of 16 mm. Airflow velocity measurements were performed on the test prototype using an anemometer to verify the accuracy of the numerical simulation results. The simulation test results were supplemented by field trials, which showed that when the speed of the cleaning fan was 1200 r/min and the sieve plate opening scale was 16 mm, the impurity rate in the field harvest of the operating machinery was 1.03% and the loss rate was 1.91%. The operating effect met the standard of mechanized corn grain harvesting. This paper can provide a reference for the design and working mechanism research of corn seed harvester cleaning devices.

Тhe error of a standard air flow velocity measurement procedure in wind tunnels of low subsonic speeds

The standard air flow velocity measurement procedure has been developed in order to unify and standardize the measuring instruments used and data processing algorithms, reduce the development time and certify such standard methods. Sources of error in indirect measurements of air flow velocity in the range 3–105 m/s are investigated. The sources of instrumental error of indirect measurements are analyzed – pressure sensors with digital and analog output signals, pitot tube, temperature and relative air humidity sensors, atmospheric pressure sensors. It is shown that the greatest contribution to the instrumental error is made by measuring the pressure difference and atmospheric pressure. The errors of method, which depends on the measurement model, is considered. A new mathematical model of measurements is proposed, which includes optimal expressions for determining the density of moist air and corrections for compressibility and allows to reduce the methodological error, and requirements for the metrological characteristics of the measuring instruments used are developed, ensuring that the total error of indirect measurements of the flow velocity complies with the allowable limits of ±0,2 m/s. Recommendations are given on the use of measuring instruments and algorithms for processing measurement results, which make it possible to reduce the measurement error by 39 % and develop a standard air flow velocity measurement procedure. The standard procedure is relevant for aviation industry enterprises, where the air flow rate is measured by the pneumometric method.

Materials analysis and image-based modelling of transmissibility and strain behaviour in approved face mask microstructures

Comparisons are made between six different approved face masks concerning their particle transmissibility allied to mechanical properties. The latter involves material testing and stretch or strain behaviour under load. SEM and X-ray elemental analyses showed contrasting structures between random and ordered fibre orientations. These constitute the mask designs where transmissibility is to be minimised. Airflow velocity measurement enabled filtration to be measured between the different mask designs, from two to six layers of different fabrics in combination. SEM provided the fibre diameter and pore size of each mask layer, up to a maximum of six. Stretching each complete mask showed its elasticity and recovery behaviour on an energy basis. The energy conversion involved in mask straining involves areas enclosed within steady and cyclic load-extension plots. Thus, the work done in extending a mask and the energy recovered from its release identified a hysteresis associated with an irrecoverable permanent stretch to the mask fabric. Failure of individual layers, which occurred successively in extended stretch tests, appeared as a drop in a load-extension response. That change is associated with permanent damage to each mask and friction contact within the rearrangement of loose fibre weaves. Masks with the greatest number of layers reduced particle transmissibility. However, woven or ordered mask fabrics in two layers with different orientations provided comparable performance. Simulation of each mechanical response, velocity streamlining and fibre distribution within the mask layers are also presented.

Intensity-interrogated hot-wire anemometer based on chirp effect of a fiber Bragg grating.

An intensity-interrogated optical fiber hot-wire anemometer based on the chirp effect of fiber Bragg grating (FBG) is presented. The FBG is coated with a silver film and heated optically by a 1480 nm laser beam, which is coupled into the fiber cladding by a long-period grating (LPG) and absorbed by the silver film to convert to thermal heat. Due to the gradual decrease of laser power along the length of the FBG, a temperature gradient is formed that induces a chirp effect to the FBG. Bandwidth of the FBG's reflection spectrum is therefore broadened that increases its reflected light power. The chirp rate of the FBG reduces with airflow velocity since the temperature gradient is weakened under the cooling effect of the airflow, resulting in a certain relationship between the reflected power of the FBG and airflow velocity. In the experiment, by detecting the reflected power of the FBG, airflow velocity measurement is achieved successfully with a high sensitivity up to -28.60 µW/(m·s-1) at airflow velocity of 0.1 m/s and a dynamic response time of under one second. The measurement range is up to 0 to 11 m/s. The intensity interrogation scheme of the FBG hot-wire anemometer reduces its cost greatly and makes it a promising solution for airflow velocity measurement in practical applications.

Improving Nasal Airflow with a Novel Nasal Breathing Stent.

Nasal obstruction requires close attention, as it is a risk factor for obstructive sleep apnea (OSA). This study evaluated airflow rates of our newly designed nasal breathing stent (NBS) compared with those of existing nasal dilators in 10 adult men. We hypothesized that the NBS would expand the nasal passage more than the other nasal dilators by means of airflow measurements. We compared airflow measurements between the NBS and three existing appliances and no appliance. Velocity measurements were recorded by analyzing 499 videographic images when each appliance was placed next to a steam generator at 0, 5, and 10 mm from the outlet port for airflow visualization. The peak nasal inspiratory flow (PNIF) rate was measured using an inspiratory flow meter. The NBS resulted in significantly higher airflow velocity measurements at all distances from the outlet port and a higher PNIF rate than the other appliances. Thus, the NBS offers a significantly decreased resistance to air movement compared with other appliances. Future in-depth investigations are required to demonstrate the use of NBS as a nasal dilator in conjunction with continuous positive airway pressure/oral appliance treatments in patients with OSA.

Design and Fabrication of Piezoelectric Artificial Cilia for Airflow Sensing in Mobile Robot with Surface Mount

In order to realize the measurement of airflow velocity in narrow spaces, we fabricate, package and characterize a flexible and surface mount piezoelectric artificial cilia (PAC) for airflow sensing in a piezoelectric mobile robot (PMR). The diameter and height of the cilia are 0.3 mm and 5 mm, respectively, whose sensitivity is 30 (mV)/(m/s). Meanwhile, the PMR is 32.8 g in mass and 55 mm × 50 mm × 20 mm in size and it is capable of achieving a velocity of 200 mm/s. This sensing robot has advantages of light weight, miniature size, and low cost, which has potential to effectively evaluate air leakage in the pipeline.

Airflow and Air Velocity Measurements While Playing Wind Instruments, with Respect to Risk Assessment of a SARS-CoV-2 Infection.

Due to airborne transmission of the coronavirus, the question arose as to how high the risk of spreading infectious particles can be while playing a wind instrument. To examine this question and to help clarify the possible risk, we analyzed 14 wind instruments, first qualitatively by making airflows visible while playing, and second quantitatively by measuring air velocity at three distances (1, 1.5, 2 m) in the direction of the instruments’ bells. Measurements took place with wind instrumentalists of the Bamberg Symphony in their concert hall. Our findings highlight that while playing, no airflows escaping from any of the wind instruments—from the bell with brass instruments or from the mouthpiece, keyholes or bell with woodwinds—were measurable beyond a distance of 1.5 m, regardless of volume, pitch or what was played. With that, air velocity while playing corresponded to the usual value of 1 m/s in hall-like rooms. For air-jet woodwinds, alto flute and piccolo, significant air movements were seen close to the mouthpiece, which escaped directly into the room.

Reduction of electromagnetic interferences in measurements of fast-changing air velocity fluctuations by means of hot-wire anemometer

Air flow velocity measurements are the key issues in examining the condition and progress of mine ventilation process. In addition to standard measurements carried out in the stock exploitation process, it is necessary to conduct cognitive scientific research in this area. One of the important issues here is the measurement of fast-changing fluctuations of air velocity, enabling the knowledge of the spectral structure of the tested flow. Hot-wire anemometers are used for such measurements both in laboratories and in industrial conditions. A frequent metrological problem is the presence in the measuring area of a high level electromagnetic interference (EMI) from electrical networks and devices. Due to the metrological properties of hot-wire anemometers, such as high gain and wide frequency bandwidth, measuring signal in the presence of electromagnetic interferences may be subject to strong disturbances. Therefore, it is necessary to develop methods for reducing or eliminating these disturbances. The article presents such a new method based on the use of an additional induction loop in the anemometric sensor for compensation or reduction of interferences.

Optoelectronic sensor applied to airflow velocity measurements on flare systems

Optoelectronic sensor applied to airflow velocity measurements on flare systems

Airflow velocity measurement of the electrostatic spray gun

The results of an experimental study of the airflow velocity measurement of the electrostatic spray gun are presented. It has been shown experimentally that airflow velocity rate varies in the range from 1 to 25 m/s depending on the distance from the nozzle of the spray gun and air pressure.

Momentum flux measurements in the airflow over wind-generated surface waves

The air–sea momentum exchanges in the presence of surface waves play an integral role in coupling the atmosphere and the ocean. In the current study, we present a detailed laboratory investigation of the momentum fluxes over wind-generated waves. Experiments were performed in the large wind-wave facility at the Air–Sea Interaction Laboratory of the University of Delaware. Airflow velocity measurements were acquired above wind waves using a combination of particle image velocimetry and laser-induced fluorescence techniques. The momentum budget is examined using a wave-following orthogonal curvilinear coordinate system. In the wave boundary layer, the phase-averaged turbulent stress is intense (weak) and positive downwind (upwind) of the crests. The wave-induced stress is also positive on the windward and leeward sides of wave crests but with asymmetric intensities. These regions of positive wave stress are intertwined with regions of negative wave stress just above wave crests and downwind of wave troughs. Likewise, at the interface, the viscous stress exhibits along-wave phase-locked variations with maxima upwind of the wave crests. As a general trend, the mean profiles of the wave-induced stress decrease to a negative minimum from a near-zero value far from the surface and then increase rapidly to a positive value near the interface where the turbulent stress is reduced. Far away from the surface, however, the turbulent stress is nearly equal to the total stress. Very close to the surface, in the viscous sublayer, the wave and turbulent stresses vanish, and therefore the stress is supported by the viscosity.

Research on an Artificial Lateral Line System Based on a Bionic Hair Sensor with Resonant Readout.

Inspired by the lateral line system of fish, an artificial lateral line system based on bionic hair sensor with resonant readout is presented in this paper. An artificial lateral line system, which possesses great application potential in the field of gas flow visualization, includes two different sensors: a superficial neuromast and a canal neuromast flow velocity sensor, which are used to measure the constant and oscillatory air flow velocity, respectively. The sensitive mechanism of two artificial lateral line sensors is analyzed, and a finite element simulation is implemented to verify the structural design. Then the control circuit of the artificial lateral line system is designed, employing a demodulation algorithm of oscillatory signal based on the least mean square error algorithm, which is used to calculate the oscillatory air flow velocity. Finally, the experiments are implemented to assess the performance of the two artificial lateral line systems. The experimental results show that the artificial lateral line system, which can be used to measure the constant and oscillatory air flow velocity, has a minimum threshold of 0.785 mm/s in the measurement of oscillatory air flow velocity. Moreover, the artificial canal neuromast lateral line system can filter out low-frequency disturbance and has good sensitivity for high-frequency flow velocity.

Evaluation of the effect of oral appliance treatment on upper-airway ventilation conditions in obstructive sleep apnea using computational fluid dynamics

ABSTRACT Objective: To evaluate the effect of oral appliance (OA) treatment on upper-airway ventilation conditions in patients with obstructive sleep apnea (OSA) using computational fluid dynamics (CFD). Methods: Fifteen patients received OA treatment and underwent polysomnography (PSG) and computed tomography (CT). CT data were used to reconstruct three-dimensional models of nasal and pharyngeal airways. Airflow velocity and airway pressure measurements at inspiration were simulated using CFD. Results: The apnea–hypopnea index (AHI) improved from 23.1 to 10.1 events/h after OA treatment. On CFD analysis, airflow velocity decreased at the retropalatal and epiglottis-tip levels, while airway pressure decreased at the retropalatal, uvular- and epiglottis-tip levels. The AHI of patients with OSA before OA treatment was correlated with airway pressure at the epiglottis-tip level. Discussion: Treatment with OA improved the ventilation conditions of the pharyngeal airway and AHI. Results of CFD analysis of airway pressure and airflow velocity helped determine the severity and ventilatory impairment site of OSA, respectively.

Waterproof airflow sensor for seabird bio-logging using a highly sensitive differential pressure sensor and nano-hole array

This paper presents an airflow sensor for seabird bio-logging. Although bio-logging methods have attracted attention in the evaluation of seabird flight performance, the airflow velocity has not been directly measured. Here, an airflow sensor is added to the bio-logging system, and a direct airflow velocity measurement is applied, thus enabling more accurate evaluation of the flight performance. To attach the sensor to the bio-logging system, the sensor must be waterproof because seabirds dive into the sea to prey on fish. In addition, the sensor must also be compact and have high sensitivity. Here, we propose a Pitot tube-type airflow sensor that satisfies these requirements. The proposed sensor is composed of microelectromechanical systems (MEMS) piezoresistive cantilevers as sensing elements with high sensitivity and anodic alumina membranes with a nano-hole array as the waterproof elements with airflow penetration. The developed sensor responded sufficiently to airflow velocities from 2 m/s to 20 m/s. In addition, the sensor maintained its sensitivity after plunging into the water and returning to the air. Therefore, the proposed sensor can be utilized for practical seabird bio-logging.

Effects of throughput and operating parameters on cleaning performance in air-and-screen cleaning unit: A computational and experimental study

The influences of throughput and operating parameters on internal airflow and cleaning performance for the air-and-screen cleaning unit were investigated. The throughput experiment showed that, the airflow velocities above the vibrating screen decreased by 1.3–15.5% for every 1.0 kg s−1 increase of throughput and which below the vibrating screen decreased by 2.7–8.1%. As a result, the cleaning performance has declined. Then, the airflow velocity measurement and cleaning performance tests were taken under 4.0 kg s−1 throughput with single factor experiment in which fan speed, airflow deflector angle and sieve opening were as factors. And, the Computed Fluid Dynamic (CFD) numerical simulations were carried out to analyze the movement trend of internal airflow as an auxiliary analysis method. The following viewpoints were obtained, the fan speed has a large effect on cleaning performance by affecting the overall airflow velocities in the cleaning unit. And, the airflow velocities above the vibrating screen increased from 0.2 m s−1 to 0.4 m s−1 for every 150 r min−1 increase of fan speed, which below the vibrating screen increased from 0.4 m s−1 to 1.1 m s−1; The highest airflow velocities area above the vibrating screen moved forward to the central position in the longitudinal direction as the airflow deflector angle increased; With the reduction for each 4 mm of chaffer opening, the airflow velocities above the vibrating screen increased by 0.2–0.4 m s−1. At last, making mathematical relations between each operating parameter and the cleaning performance, and proposing the method of adjusting the single operating parameter under rated condition according to the throughput. They provide a basis for real-time automatic adjustment of the operating parameters in the air-and-screen cleaning unit.

Use and Calibration of 5-Hole Pressure Probes to Measurement of Airflow Velocity

Use and Calibration of 5-Hole Pressure Probes to Measurement of Airflow Velocity

Harvesting wind energy with pyroelectric nanogenerator PNG using the vortex generator mechanism

This paper describes an experimental study of wind energy harvesting by pyroelectric nanogenerator PNG composed by PVDF film and vortex generator called turbulator. We have used wind tunnel equipped with DAkkS calibrated flow calculation system for the air flow velocity measurements and has velocity interval from 1 m/s to 25 m/s. The characteristic of the air flow are well controlled and presents an uncertainty budget below 1.4% in the open test section of the wind tunnel. A study of the response of the PNG as a function of air flow velocity was carried out. We have demonstrated the capability of the mechanism “PVDF film + vortex generator” PNG for producing uninterrupted current when subjecting to wind flow and its signal increases with the increase of the wind velocity without saturation. Thus, our PNG based on commercial 9 μm-PVDF film was able to output a current of 0.109 μA/cm2 for 25 m/s of wind velocity. The peak power density was 2.82 μW/cm2, which is comparable to previous developed PNGs. We have presented the output power of our device stored in 1 μF capacitor with demonstration examples of loading charges. These results offer opportunities for self-powered devices on a very large scale of wind energy.