An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we...An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997;Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).展开更多
A method of data processing to determine the coefficients of linearization equations for 1050 anemometer (produced by Thermo-Systems Inc. -TSI, USA) with the sensors made of domestic hot wire using the program preferr...A method of data processing to determine the coefficients of linearization equations for 1050 anemometer (produced by Thermo-Systems Inc. -TSI, USA) with the sensors made of domestic hot wire using the program preferred in this Paper is described. By calculation and test, it is indicated that the error resulting from this method is about 0. 5% of the full scale and less than TSl's. By using this method we can set up the calibration curve according to the measurement range and the diameter of the hot wire at a certain accuracy.展开更多
A sensitivity-enhanced hot-wire anemometer based on a cladding-etched optical fiber Bragg grating(FBG)coated with a layer of silver film and optically heated by using a 1480nm laser diode is demonstrated.The silver fi...A sensitivity-enhanced hot-wire anemometer based on a cladding-etched optical fiber Bragg grating(FBG)coated with a layer of silver film and optically heated by using a 1480nm laser diode is demonstrated.The silver film absorbs the laser power to heat the FBG to a certain high temperature and the airflow cools down the FBG hot-wire with the cooling effect and hence the Bragg wavelength of the FBG is determined by the airflow velocity.Experimental measurement results show that the heating efficiency of the FBG hot wire is improved by 3.8times in magnitude by etching the fiber cladding from 125μm down to 73.4μm,and the achieved airflow velocity sensitivities,under a laser power of 200mW,are–3180pm/(m/s),–889pm/(m/s),–268pm/(m/s),and–8.7pm/(m/s)at different airflow velocities of 0.1m/s,0.5m/s,1.5m/s,and 17m/s,respectively.In comparison,the sensitivities are only–2193 pm/(m/s),–567 pm/(m/s),–161 pm/(m/s),and–4.9pm/(m/s)for the reference anemometer without cladding etching even at a much higher heating laser power of 530mW.These results prove that the method by using a cladding-etched FBG to improve sensitivity of FBG-based hot-wire anemometers works and the sensitivity is improved significantly.展开更多
In this paper, we investigate the stator wake variability along the axial direction under different rotating speeds and mass flow conditions, in the terms of wake-core position, wake depth, wake width and wake velocit...In this paper, we investigate the stator wake variability along the axial direction under different rotating speeds and mass flow conditions, in the terms of wake-core position, wake depth, wake width and wake velocity gradient. Experimental study is carried out in a single stage axial compressor by using Hot-wire Anemometer (HWA). Simultaneously, the numerical calculation is brought out in the same experiment rig. Firstly, we analyze the time-averaged velocity and radial vorticity at different axial positions, and explore the wake variability along the axial direction. Then, we present the effects of operation conditions on the wake-core position, and find out the inlet Mach number and incident angle are both the key influence factors of the wake-core position. Finally, we summarize four preliminary conclusions of the wake variability.展开更多
The purpose of this study is to investigate experimentally the effects of orbital motion on the velocity field of boundary layer flow over a rotating disk. The characteristics of velocity field at a fixed orbital angu...The purpose of this study is to investigate experimentally the effects of orbital motion on the velocity field of boundary layer flow over a rotating disk. The characteristics of velocity field at a fixed orbital angular section measured by a hot-wire anemometer show that the structure of the 3-dimensional boundary layer flow is deformed elliptically and displaced in a certain direction that is not in the orbital radial direction, but the direction of deformation depends on the combination of orbital and rotational directions. For coincide orbital and rotational directions, there are regions where the intensity of low-frequency disturbances increases rapidly in a certain central region (laminar region under pure rotation). The transient vortices, which form streaks on the coating film, are considered to be destroyed by low-frequency disturbances. However, for opposite orbital and rotational directions, the low-frequency disturbances are not observed in any section. As the adding orbital speed increases, the intensity of velocity fluctuations in the turbulence region becomes larger in the expected except in a certain region. This location of the region also depends on the direction of deformation or the combination of orbital and rotational directions.展开更多
This paper presents a mathematical algorithm that determines the fluid flow velocity vector （direction, intensity and orientation）, based on measured voltages on multi-channel hot-wire anemometer. As the voltage on ...This paper presents a mathematical algorithm that determines the fluid flow velocity vector （direction, intensity and orientation）, based on measured voltages on multi-channel hot-wire anemometer. As the voltage on Constant Temperature hot-wire Anemometer （CTA） is non-linear function of velocity and angle of the fluid, inverse function is also non-linear and has several mathematically correct solutions. In the Laboratory of Non-linear Mechanics at the Faculty of Mechanical Engineering in Ljubljana, the authors have decided to try developing multi-charmel hot-wire anemometer with constant temperature at which it is possible to select physically correct solutions from several mathematically correct solutions. The mathematical algorithm works correctly if the range of instrument operation is limited for the value of spherical angles ｜φ｜≤ 60°and ｜ψ｜＇1 ≤ 58°.展开更多
The paper presents the experimental results and the results of direct numerical simulation of the development and interaction of two wave trains from two point sources of controlled disturbances in a supersonic bounda...The paper presents the experimental results and the results of direct numerical simulation of the development and interaction of two wave trains from two point sources of controlled disturbances in a supersonic boundary layer on a flat plate with an incident flow Mach number of 2.5.Sources were located parallel to the leading edge of the model.For the introduction of controlled disturbances into the boundary layer,the normal component of the mass flow rate was varied in the calculations.In the experiment,periodic glow discharges at a frequency of 20 kHz were used.In both cases,the disturbances sources worked synchronously.Mass flow rate pulsations were measured and recorded in sections,parallel to the leading edge of the model,near the maximum of disturbances along the boundary layer.In the experiment,a constanttemperature hot-wire anemometer was used.After performing a discrete Fourier transform,the spatial distributions of disturbances,the beta-spectra were determined,and the wave characteristics of the development of disturbances downstream were estimated.In addition,direct numerical simulation of the downstream development of disturbances from a single source was performed.The work presents a comparison of experimental and theoretical calculated data.The paper discusses the effects inherent in the interaction of unstable traveling controlled disturbances from two sources operating synchronously.展开更多
文摘An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997;Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).
文摘A method of data processing to determine the coefficients of linearization equations for 1050 anemometer (produced by Thermo-Systems Inc. -TSI, USA) with the sensors made of domestic hot wire using the program preferred in this Paper is described. By calculation and test, it is indicated that the error resulting from this method is about 0. 5% of the full scale and less than TSl's. By using this method we can set up the calibration curve according to the measurement range and the diameter of the hot wire at a certain accuracy.
基金Sponsor and financial support acknowledgments are placed here.This work was supported by National Key Research and Development Program of China(Grant No.2020YFB1805804),National Natural Science Foundation of China(Grant No.11974083),Open Projects Foundation(Grant No.SKLD1905)of State Key Laboratory of Optical Fiber and Cable Manufacture Technology(YOFC),and the Program for Guangdong Introducing Innovative and Entrepreneurial Teams(Grant No.2019ZT08X340).
文摘A sensitivity-enhanced hot-wire anemometer based on a cladding-etched optical fiber Bragg grating(FBG)coated with a layer of silver film and optically heated by using a 1480nm laser diode is demonstrated.The silver film absorbs the laser power to heat the FBG to a certain high temperature and the airflow cools down the FBG hot-wire with the cooling effect and hence the Bragg wavelength of the FBG is determined by the airflow velocity.Experimental measurement results show that the heating efficiency of the FBG hot wire is improved by 3.8times in magnitude by etching the fiber cladding from 125μm down to 73.4μm,and the achieved airflow velocity sensitivities,under a laser power of 200mW,are–3180pm/(m/s),–889pm/(m/s),–268pm/(m/s),and–8.7pm/(m/s)at different airflow velocities of 0.1m/s,0.5m/s,1.5m/s,and 17m/s,respectively.In comparison,the sensitivities are only–2193 pm/(m/s),–567 pm/(m/s),–161 pm/(m/s),and–4.9pm/(m/s)for the reference anemometer without cladding etching even at a much higher heating laser power of 530mW.These results prove that the method by using a cladding-etched FBG to improve sensitivity of FBG-based hot-wire anemometers works and the sensitivity is improved significantly.
文摘In this paper, we investigate the stator wake variability along the axial direction under different rotating speeds and mass flow conditions, in the terms of wake-core position, wake depth, wake width and wake velocity gradient. Experimental study is carried out in a single stage axial compressor by using Hot-wire Anemometer (HWA). Simultaneously, the numerical calculation is brought out in the same experiment rig. Firstly, we analyze the time-averaged velocity and radial vorticity at different axial positions, and explore the wake variability along the axial direction. Then, we present the effects of operation conditions on the wake-core position, and find out the inlet Mach number and incident angle are both the key influence factors of the wake-core position. Finally, we summarize four preliminary conclusions of the wake variability.
文摘The purpose of this study is to investigate experimentally the effects of orbital motion on the velocity field of boundary layer flow over a rotating disk. The characteristics of velocity field at a fixed orbital angular section measured by a hot-wire anemometer show that the structure of the 3-dimensional boundary layer flow is deformed elliptically and displaced in a certain direction that is not in the orbital radial direction, but the direction of deformation depends on the combination of orbital and rotational directions. For coincide orbital and rotational directions, there are regions where the intensity of low-frequency disturbances increases rapidly in a certain central region (laminar region under pure rotation). The transient vortices, which form streaks on the coating film, are considered to be destroyed by low-frequency disturbances. However, for opposite orbital and rotational directions, the low-frequency disturbances are not observed in any section. As the adding orbital speed increases, the intensity of velocity fluctuations in the turbulence region becomes larger in the expected except in a certain region. This location of the region also depends on the direction of deformation or the combination of orbital and rotational directions.
文摘This paper presents a mathematical algorithm that determines the fluid flow velocity vector （direction, intensity and orientation）, based on measured voltages on multi-channel hot-wire anemometer. As the voltage on Constant Temperature hot-wire Anemometer （CTA） is non-linear function of velocity and angle of the fluid, inverse function is also non-linear and has several mathematically correct solutions. In the Laboratory of Non-linear Mechanics at the Faculty of Mechanical Engineering in Ljubljana, the authors have decided to try developing multi-charmel hot-wire anemometer with constant temperature at which it is possible to select physically correct solutions from several mathematically correct solutions. The mathematical algorithm works correctly if the range of instrument operation is limited for the value of spherical angles ｜φ｜≤ 60°and ｜ψ｜＇1 ≤ 58°.
基金The research was supported by RFBR(Grant No.18-31-00171 mol_a)The research was partly carried out within the framework of the Program of Fundamental Scientific Research of the state academies of sciences in 2013-2020(project No.АААА-А17-117030610125-7)The work was performed using the equipment of the CCU“Mechanics”.
文摘The paper presents the experimental results and the results of direct numerical simulation of the development and interaction of two wave trains from two point sources of controlled disturbances in a supersonic boundary layer on a flat plate with an incident flow Mach number of 2.5.Sources were located parallel to the leading edge of the model.For the introduction of controlled disturbances into the boundary layer,the normal component of the mass flow rate was varied in the calculations.In the experiment,periodic glow discharges at a frequency of 20 kHz were used.In both cases,the disturbances sources worked synchronously.Mass flow rate pulsations were measured and recorded in sections,parallel to the leading edge of the model,near the maximum of disturbances along the boundary layer.In the experiment,a constanttemperature hot-wire anemometer was used.After performing a discrete Fourier transform,the spatial distributions of disturbances,the beta-spectra were determined,and the wave characteristics of the development of disturbances downstream were estimated.In addition,direct numerical simulation of the downstream development of disturbances from a single source was performed.The work presents a comparison of experimental and theoretical calculated data.The paper discusses the effects inherent in the interaction of unstable traveling controlled disturbances from two sources operating synchronously.
