scholarly journals Constant-Temperature Anemometer Bandwidth Shape Determination for Energy Spectrum Study of Turbulent Flows

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4495
Author(s):  
Paweł Ligęza
Keyword(s):  
Energy Spectrum ◽  
Turbulent Flows ◽  
Constant Temperature ◽  
Indirect Method ◽  
Natural Phenomena ◽  
Hot Wire ◽  
Common Occurrence ◽  
Wide Range ◽  
Shape Determination ◽  
Constant Temperature Anemometer

Due to their common occurrence and fundamental role in human-realized processes and natural phenomena, turbulent flows are subject to constant research. One of the research tools used in these studies are hot-wire anemometers. These instruments allow for measurements in turbulent flows in a wide range of both velocities and frequencies of fluctuations. This article describes a new indirect method of determining the bandwidth shape of a constant-temperature anemometer. The knowledge of this bandwidth is an important factor in the study of the energy spectrum of turbulent flows.

A method for determination and control of the frequency response of the constant-temperature hot-wire anemometer

1975 ◽  
Vol 67 (4) ◽  
pp. 769-786 ◽  
Author(s):  
N. B. Wood
Keyword(s):  
Frequency Response ◽  
Constant Temperature ◽  
Hot Wire ◽  
Flow Conditions ◽  
Mean Flow ◽  
Quantitative Results ◽  
The Mean ◽  
Constant Temperature Anemometer ◽  
And Control ◽  
Simultaneous Variation

The theory of the constant-temperature anemometer has been extended in order to obtain quantitative results for the frequency response. A simple electrical test against which to check the theory has been devised, and the validity of the anemometer equations is demonstrated. Important differences in design philo-sophies and modes of operation are indicated, and results are presented for a design in which high d.c. gain is employed in the servo amplifier. The square-wave response is briefly investigated, and it is concluded that commonly used criteria for determining the frequency response from it should be treated with caution.To measure fluctuations with a hot-wire anemometer in flows containing both velocity and temperature perturbations, the hot wire must be operated at more than one temperature. Variation of the mean wire temperature causes, in general, a variation in the frequency response, as does variation of the mean flow conditions. It is shown that, by simultaneous variation of the gain of the servo amplifier in the anemometer, the frequency response may be held nearly constant over a useful range of both overheat and flow conditions.

Response Compensation Scheme for Constant-Current Hot-Wire Anemometry Based on Frequency Response Analysis

2011 ◽  
Author(s):  
Kazuhide Kaifuku ◽  
Soe Minn Khine ◽  
Tomoya Houra ◽  
Masato Tagawa
Keyword(s):  
Turbulent Flows ◽  
Constant Temperature ◽  
Response Speed ◽  
Wake Flow ◽  
Constant Current ◽  
Response Analysis ◽  
Compensation Scheme ◽  
Hot Wire ◽  
Velocity Fluctuations ◽  
Hot Wire Anemometry

Hot-wire anemometry (HWA) is used for measuring velocity fluctuations such as turbulent flows. It is generally operated in three modes; constant-temperature (CT), constant-current (CC) and constant-voltage (CV) types. The constant-temperature anemometer (CTA) is the mainstream anemometer, while others are rarely used in measuring normal turbulent flows because of their insufficient response speed. However, since the constant-current anemometer (CCA) can be composed of simple circuits, the HWA can be realized at quite a low cost. In this study, the response characteristics of the CCA are theoretically analyzed, and a compensation scheme is proposed. The scheme is experimentally tested in a turbulent wake flow formed behind a cylinder. As a result, it has been confirmed that the root-mean-square (rms) velocities and the power-spectrum distributions compensated by the present scheme agree well with those measured with CTA. Hence, the CCA provides reliable measurement of turbulent velocity fluctuations.

scholarly journals Mathematics in the spirit of Joe Keller

2017 ◽  
Vol 28 (5) ◽  
pp. 708-715
Author(s):  
J. R. OCKENDON ◽  
B. D. SLEEMAN
Keyword(s):  
20Th Century ◽  
Natural Phenomena ◽  
Wide Range ◽  
The World ◽  
Mathematical Techniques

Over the two days 2–3 March 2017, about 80 mathematicians and friends gathered in Cambridge to celebrate the life and work of Joseph Bishop Keller (1923–2016), one of the pre-eminent applied mathematicians of the 20th century. Joe, as he was known throughout the world, made pioneering contributions to a wide range of natural phenomena and developed fundamental mathematical techniques with which to understand them. Twenty-four talks were presented at the meeting, given by mathematicians who have either worked with Joe or have been influenced by his work. Rather than summarise each presentation, we have collated all the contributions under the headings of waves, fluids, solids, chemistry and biology, and finally some history.

A Parallel HOFD Scheme for Direct Numerical Simulation of Turbulent Magnetically Driven Flows

2001 ◽  
Author(s):  
X. Ai ◽  
B. Q. Li
Keyword(s):  
Numerical Simulation ◽  
Finite Difference ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Parallel Machines ◽  
Higher Order ◽  
Electrically Conducting ◽  
Wide Range ◽  
Order Scheme ◽  
Higher Order Scheme

Abstract Turbulent magnetically flows occur in a wide range of material processing systems involving electrically conducting melts. This paper presents a parallel higher order scheme for the direct numerical simulation of turbulent magnetically driven flows in induction channels. The numerical method is based on the higher order finite difference algorithm, which enjoys the spectral accuracy while minimizing the computational intensity. This, coupled with the parallel computing strategy, provides a very useful means to simulate turbulent flows. The higher order finite difference formulation of magnetically driven flow problems is described in this paper. The details of the parallel algorithm and its implementation for the simulations on parallel machines are discussed. The accuracy and numerical performance of the higher order finite difference scheme are assessed in comparison with the spectral method. The examples of turbulent magnetically driven flows in induction channels and pressure gradient driven flows in regular channels are given, and the computed results are compared with experimental measurements wherever possible.

scholarly journals Study on the Improvement of Frequency Response of the Constant Temperature Anemometer

2012 ◽  
Vol 78 (788) ◽  
pp. 862-866
Author(s):  
Osamu TERASHIMA ◽  
Kazuhiro ONISHI ◽  
Yasuhiko SAKAI ◽  
Kouji NAGATA ◽  
Shohei TAKAGI
Keyword(s):  
Frequency Response ◽  
Constant Temperature ◽  
Constant Temperature Anemometer

Combined Simultaneous Flow Visualization/Hot-Wire Anemometry for the Study of Turbulent Flows

1980 ◽  
Vol 102 (2) ◽  
pp. 174-182 ◽  
Author(s):  
R. E. Falco
Keyword(s):  
Pressure Gradient ◽  
Flow Visualization ◽  
Turbulent Flows ◽  
Unsteady Flows ◽  
Gradient Flows ◽  
Hot Wire ◽  
Visual Patterns ◽  
Favorable Pressure Gradient ◽  
Hot Wire Anemometry ◽  
Scattering Light

The measurement of coherent motions in turbulent and unsteady flows is discussed. A technique which discriminates these motions based upon the patterns they create by scattering light from a fog of tiny oil drops is described. It is shown that hot-wire anemometry can be used in this oil fog so that hot-wire data can be conditionally sampled to the visual patterns, giving directly interpretable measures of the importance of the selected features. The three-dimensionality of the coherent motions can also be directly accounted for, using mutually orthogonal sheets of light. Results of step flows, and zero and favorable pressure gradient flows are described.

Assessment of Certainty of Ventilation Processes Mathematical Modeling

2015 ◽  
Vol 725-726 ◽  
pp. 1255-1260
Author(s):  
Tamara Daciuk ◽  
Vera Ulyasheva
Keyword(s):  
Mathematical Modeling ◽  
Turbulent Flows ◽  
Turbulence Models ◽  
Field Measurements ◽  
Heat Emission ◽  
Emission Sources ◽  
Wide Range ◽  
Calculation Results ◽  
Definition Of ◽  
Semiempirical Models

Numerical experiment has been successfully used during recent 10-15 years to solve a wide range of thermal and hydrogasodynamic tasks. Application of mathematical modeling used to design the ventilation systems for production premises characterized by heat emission may be considered to be an effective method to obtain reasonable solutions. Results of calculation performed with numerical solution of ventilation tasks depend on turbulence model selection. Currently a large number of different turbulence models used to calculate turbulent flows are known. Testing and definition of applicability limits for semiempirical models of turbulence should be considered to be a preliminary stage of calculation. This article presents results of test calculations pertaining to thermal air process modeling in premises characterized by presence of heat emission sources performed with employment of different models of turbulence. Besides, analysis of calculation results and comparison with field measurements data are presented.

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