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Hot-wire anemometric method for flow velocity vector measurement in 2D gas flows based on artificial neural network
Abstract
For measurement of two-dimensional flow velocity vector a special multi-wire measurement probe was used. Its design allows to determine magnitude, orientation and the sense of the flow velocity vector. The conducted research were related to the analysis of the possibility of using an artificial neural network for flow velocity vector measurements. A neural network with two hidden layers was used to determine the components of velocity vector based on measurement signals. The structure of neural network was chosen experimentally. The results were compared to those obtained by the method based on King and Jorgensen formulae. Despite the increased computational cost, the method based on neural network performed ten times better in terms of mean square error.
... As a result, it reacts quickly to temperature fluctuations. Since the measurement of the flow velocity using the correlation method consists in determining the time shift between two recorded temperature signals, there is no need to determine the static characteristics of individual temperature sensors in advance, as in the case of classic hot-wire anemometry probes [13,14]. The advantage of this method is also the ability to detect the sense of the velocity vector, which is impossible in case of the conventional hot-wire anemometry probe. ...
Changes in the temperature of the medium significantly affect the static characteristics of hot-wire anemometry measuring wires, which causes errors in the results of flow velocity measurements. High temperatures of the medium make it necessary to additionally heat the sensor to even higher temperatures, which may lead to its damage due to wire burnout. The article proposes a solution to the problem of measuring the flow velocity in conditions of non-stationary temperatures with the use of the method of cross-correlation of signals from two-wire resistance thermometers. The main assumptions of the method and its experimental verification were presented.
... Many studies have been conducted based on the accurate measurement of flow velocities [3]. These include tests performed both in wind tunnels and under real measurement conditions, like studies on the wake effect from wind turbines, turbulent boundary layer research, heat loss experiments, and many others [3][4][5][6]. Ventilation measurement methods and devices are also used to determine boundary conditions and validate numerical models in computational fluid dynamics [7]. ...
The complex ventilation system development process is associated with the stages of modelling, design, execution, and testing. Each of these steps requires the use of measuring equipment that is capable of determining the basic parameters of the flow. In the process of calibrating instruments for measuring flow velocity, one of the limitations is the size of the calibrated devices positioned in the test section of the wind tunnel. This is related to the change in the flow condition within the vicinity of the calibrated anemometers, which is caused by the blockage effect. Instruments with significant dimensions in relation to the cross-sectional area of the wind tunnel test section may have an impact on the reference velocity as indicated by the standard. In such cases, the calibration results may be affected by additional systematic error. This article presents a study of this effect using a real case of a calibration laboratory and commonly used sensors. The influence of different types of air velocity sensors on velocity profiles in the measurement standard area is also investigated. Additionally, the area of the blockage effect is described. The obtained results indicate the possibility of a proper placement for the measuring standard due to minimization of the flow-blocking effect.
This book presents the select proceedings of the International Conference on Functional Material, Manufacturing and Performances (ICFMMP) 2019. The book covers broad aspects of several topics involved in the metrology and measurement of engineering surfaces and their implementation in automotive, bio-manufacturing, chemicals, electronics, energy, construction materials, and other engineering applications. The contents focus on cutting-edge instruments, methods and standards in the field of metrology and mechanical properties of advanced materials. Given the scope of the topics, this book can be useful for students, researchers and professionals interested in the measurement of surfaces, and the applications thereof.
In the present study, we use wind tunnel model as a medium to calculate and analyze the flow velocity of the air passes through any aerodynamic medium and besides automobile too. An experimental study was carried out on a wind tunnel to evaluate and optimize the performance and results of the model obtained. Experiments were carried out with four different In the present study, we use wind tunnel model as a medium to calculate and analyze the flow velocity of the air passes through any aerodynamic medium and besides automobile too. An experimental study was carried out on a wind tunnel to
evaluate and optimize the performance and results of the model obtained. Experiments were carried out with four different
In this paper, an anemometric type flow meter has been designed and developed using a transistor as a flow sensor. The heat is dissipated from the surface of the p–n diode created by short circuiting the emitter and base terminal of the transistor CL100B causing the drop in the temperature with respect to the fluid velocity and it is utilized to measure the flow rate of the fluid across the pipeline section. Two identical sets of transistor acting like p–n diodes are used, the first diode senses the fluid velocity and produces an inconstant voltage and the other is in contact with the stagnated fluid produces a constant voltage. In this paper, the temperature effect is easily compensated by taking the difference in the output of diodes. The difference between the output voltages of the identical transducer only depends on the flow rate. The transducer design and its theoretical characteristic equation and graphs have been derived and discussed in this paper. The proposed transducer has a low cost with good linearity, accuracy, and repeatability.
A 3-D measuring method for particle movement was established by using a single-lens dual-camera system. The light through an object-space telecentric lens was split half-and-half by a beam splitter and then are received by two CCD industrial cameras, respectively. These two image sensors have different distances from the telecentric lens. As for the same imaging particle, two images with different degrees of defocus will be captured. These two images were used to solve the ambiguous problem of 3-D particle positions. Combining with the PTV technology and the single-frame and multiple-exposure imaging method, the system can determine the magnitude and direction of 3-D velocity. The feasibility was then proved by experiments.
The balance of mass or volumetric flow of air in ventilation systems may be carried out on the basis of the flow velocity field assessment. The minimization of the measurement error of such a measurement requires the application of a method allowing for determination of the magnitude, direction and sense of the velocity vector in examined points of measurement space. In the case of unsteady flows, the measurement method should additionally enable the measurements of variable signals changing in a specific spectral range. The authors of this study have performed a research aimed to elaborate such a measurement method. This paper presents a hot-wire anemometric method for two-dimensional measurement of flow velocity vector. This method takes advantage of the specialist multi-wire measurement probe. The design of the probe allows for the determination of magnitude, direction and the sense of the flow velocity vector. Presented are the results of measurement probe calibration as well as of the analysis of errors of the fit of experimentally measured data to calibration data. In order to test the measurement method under reverse flow conditions, an experimental measurement was performed at the measurement site which presented a model of mining gallery with branching.
Although the integral quantities of atmospheric turbulence are conveniently measured using sonic anemometers, obtaining relevant finescale variables such as the kinetic energy dissipation using conventional hot-film/wire techniques remains a challenge because of two main difficulties. The first difficulty is the mean wind variability, which causes violation of the requirement that mean winds have a specific alignment with the hot-film/wire probe. To circumvent this problem, a combination of collocated sonic and hot-film anemometers, with the former measuring mean winds and aligning the latter in the appropriate wind direction via an automated platform, is successfully designed and implemented. The second difficulty is the necessity of frequent and onerous calibrations akin to hot-film anemometry that lead to logistical difficulties during outdoor (field) measurements. This is addressed by employing sonic measurements to calibrate the hot films in the same combination, with the output (velocity) to input (voltage) transfer function for the hot film derived using a neural network (NN) model. The NN is trained using low-pass-filtered hot-film and sonic data taken in situ. This new hot-film calibration procedure is compared with the standard calibration method based on an external calibrator. It is inferred that the sonic-based NN method offers great potential as an alternative to laborious standard calibration techniques, particularly in the laboratory and in stable atmospheric boundary layer settings. The NN approximation technique is found to be superior to the conventionally used polynomial fitting methods when used in conjunction with unevenly spaced calibration velocity data generated by sonic anemometers.
The sensors, which use the convective heat transfer at hot wires in order to measure the flow rate of gases, are well known. Hot-Wire Anemometry (HWA), which is operated in either constant-current mode or in constant temperature mode, represents the most popular methods to measure the velocity and the flow rate of the fluid flow. Generally, the hot-wire sensors are calibrated against the flow velocity under atmospheric pressure conditions. To calibrate hot-wire sensors under different air densities; a special calibration test rig is needed. In the present paper, calibrations are shown to yield the same hot-wire response curves for density locations in the range of 1 to 7 kg/m3 and its usable mass flow rate range (rU) is 0.1 to 25 kg/m²s.
Also, a neural network has been trained with the output data for the hot-wire sensor and tested on our measurements. It was observed that the quality of the results depends on the number of hidden neurons. The predicted values are close to the real ones which indicate the neural net model gives a good approximation for the calibration curves of the hot-wire anemometer under different flow densities. The hot-wire sensor that used in the present study has 5 mm diameter and 1.25 mm length so its aspect ratio is 250.
A four-point constant-current/temperature controlled circuit is an electronic system for supplying a resistance measuring sensor in two modes of operation: either in constant-current or in constant-temperature mode. This circuit is destined for anemometric applications. It is new nonbridge, four-point constant-current/temperature anemometer circuit. Separation of current and voltage leads of the sensor makes it possible to eliminate the effects of leads’ resistance on the preset value of sensor supply parameters. In such a circuit no cable adjustment is required. The value of sensor current or its resistance is set with digital signals. This article presents the design of the original measuring circuit and its principle of operation. Design of measuring circuit based on those principles is also presented. Attention is also given to its applications. The most important advantages of the new circuit are: both constant-current or constant-temperature modes of operation are available, precise digital control of sensor current or resistance can be performed, and four-point sensor operation in both modes is possible. It enables high-precision laboratory anemometric measurements, especially under the conditions of low sensor resistance, low overheat ratio range, and long sensor supply cables. © 2000 American Institute of Physics.
In this article a single-wire hot-wire anemometric probe enabling the detection of the sense of flow velocity vector is described. In a single probe an additional third support was introduced in the "middle" of a wire. Thanks to this it is possible to obtain a voltage U-c measured across the whole wire and the voltage U-s measured across its one half. The voltage drop across the one part of the wire equals U-s while on the other it amounts U-c - U-s. The voltage difference Delta U between the two parts of the wire thus amounts U-c - 2U(s). The sign of the voltage difference Delta U provides information on the sense of the flow velocity vector in the co-ordinate system connected with the measuring probe.
An overall directional characterisic is set up for DISA Type 55F11, 55F31, and 55F26 probes, and expressions are given for the effective cooling velocity as a function of yaw and pitch angles. The effecive cooling velocity is characterized by yaw and pitch factors kSUP1 and kSUP2 , whose magnitude and dependence on yaw and pitch angles are determined. Relative errors on U(o) are calculated for kSUP1 kSUP1 (90SUP), and kSUP1 kSUP1 (60SUP) , showing the influence of the selection of kSUP1 on the accuracy of the determination of U(o) . The importance of including the pitch correction when the velocity vector is not in the sensor-prong plane is illustrated by the relative error on U(o) with and without pitch correction. (A)
Hot wire anemometers (HWAs) are used as research tools in fluid mechanics. In HWA measurements, a hot wire probe calibration stage must be carried out before the experiments, in order to determine the relation between the probe voltage and fluid velocity at the nozzle exit, because of variation in the ambient conditions. In this study, a hot wire probe calibration system is used to calibrate a one-dimensional hot wire probe by means of an AN-1005 HWA, which operates as a constant temperature anemometer (CTA). Experimental results have been used to train an artificial neural network (ANN) in order to produce a new calibration curve for new conditions, because calibration is time consuming and difficult. The network has yielded an R2 value of 0.999, and very small root-mean-squared values, which indicate that predicted values are close to the experimental ones, and the ANN model gives a good approximation for the calibration curve under different conditions. In addition, formulations have been prepared according to a hidden number of neurons studied. Since the necessary formulae have been given, anyone could use these variables to obtain predictions from the ANN as if the hot wire probe has been operated.
Three types of hot-wire anemometric probes for the measurement of a two-dimensional flow velocity vector and its sense are presented in this paper. Such probes are a modification of type X hot-wire probes, in which additional supports are introduced in the middle of wires. The idea of the sense of a flow velocity vector assessment is based on the phenomenon of the temperature distribution asymmetry upon the wire placed askew with respect to the flow sense. The temperature distribution asymmetry is underlined by the flow direction- and sense-dependent heat energy transfer occurring within the wire. The measurement of the voltage difference between both halves of the wire is used for the detection of the flow sense. The voltages on whole wires are used for the determination of the flow velocity vector components. For such purposes, a modification of the measuring algorithm used for the type X hot-wire probes was used. The results from testing of measuring probes which were developed are presented and their metrological properties are discussed.
Thermal flow sensors with a wide dynamic range are widely applied in practical fluid flow measurements to yield local velocity information and also for volume flow-rate measurements. The importance of such flow sensors inspired the authors’ investigations into wide-velocity range thermal sensors and the outcome of this work is summarized in this paper. The present novel sensor is mechanically the same as the hot-wire anemometer, but it is excited by discrete, widely separated, square waves of electrical current rather than a continuous current. The nominal output of the new sensor is a function of the time constant of the heated wire and thus also of the velocity of flow. The time constant decreases as the flow velocity increases, while the heat transfer increases. In this paper, the results obtained suggest that our measurements for flow velocity and volume flow rate are in very good agreement with the theoretical results for the present thermal flow sensor. A neural network has been trained with the output data for the flow sensor and tested on our measurements. It was observed that the quality of the results depends on the number of hidden neurons. The predicted values are close to the real ones which indicate the neural net model gives a good approximation for the calibration curve of the single wire thermal flow sensor under different operating temperatures. The sensor described here was developed for slowly changing unidirectional flows, and uses one wire of 12.5 μm diameter. It is excited at 30 Hz frequency and its usable flow velocity range is 0.01–25 m/s. This yields an effective operating range and corresponds to a bandwidth of 1–2500.