Turbulent Flow Measurement with Hot-wire Anemometer

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1 Vol. 19, No Turbulent Flow Measurement with Hot-wire Anemometer Akiyoshi IIDA Abstract Recent progress of computer technology enabled that the computational fluid dynamics became useful tools of industrial developments. Breakthroughs of the image-processing technologies also realized Particle Image Velocimetry and Particle Tracking Velocimetry. Instantaneous twodimensional flow fields of the industrial application can be measured by these methods. As a result, CFD and Image-processing technology attract fluid dynamics researchers and engineers. On the other hand, there are few opportunities of studying the velocity-measurement technique with hot-wire anemometers and LDV. However, the classical hot-wire anemometers are useful tools for measurement of turbulence and unsteady flow fields. In this paper, the author introduces how to use hot-wire anemometers and know-how of the turbulence measurement. The experimental results obtained from the hot-wire measurement, energy spectra of isotropic turbulence, coherent structures of the boundary layer and the rectangular jet, aerodynamic sound source radiated from a circular cylinder, are also presented., PIV PTV,, LDV,,,, Key Words Hot-wire Anemometer, Turbulence, Flow Measurement, Wake, Jet,,,,,,,,,, Kogakuin Unibersity, Department of Mechanical Enginnering665-1 Nakano, Hachioji, Tokyo , Japan

2 Vol. 19, No. 300,,,,, PTVParticle Tracking Velocimetry, PIVParticle Image Velocimetry,,,,,, PTV PIV,,,, 1-3,,,,,,,,, SN 100 khz, SN 80 db 1,, 0 khz, SN PIV, Fig.1 1 µm 5 µm, Tp R w, I, U, T a 1-3 IR w Tw l Fig.1 x d dx Wire element Prong Heat generated Heat conduction in πdcg w ρw Tw = dh Tw Ta 4 t + π ( ) 1 d, c w, ρ w, h, l d l/d 00,, R w=r o1 βt w T o 3, T w, I I,, T w, 1 I R w πdht w T a 3 Collis Williams 4 h, π dh T + = (. +. Re ) ( w T a ) = A+ BU T f ( n) λ T T 4 Re, λ 43, E IR w U 5 a Heat accumulated Heat to cross-flow Schematic of hot-wire probe. Heat conduction out U B oe C o 1/n 5 a

3 RW Fig. R1 RL R R3 Ei Constant temperature anemometer containing a Wheatstone bridge and a feedback amplifier. n Fig.,,,,,,,,,,,,,,,,,,, LDV,,,,,, RG E Tr,,,,,,,,, 1, 10 0,, 5,,,,,,,,,, 1 m/s,,, 1 m/s 150 m/s, 1 m/s,,,,,,,,,,,,,,

4 Vol. 19, No. 300, 1,, 1,,,, Fig.3 6,, Wavelet 6,,,,,,,, FFT RMS,,,,,, 1,,, Fig.4,,, 7,,,, 6 6,,,,,,,, u/ue Fig.3 Outputm/s Fig Timems Velocity waveform in the wake of a circular cylinder 6. Velocity Error Hotwire No Velocitym/s Error Linearity and error of hot-wire anemometer.,, X,,, 8 9 Fig.5

,, Fig.6a 10 U eff cos α 1 κ sin α 1 6,, Fig.6b, 1 X,,, v,,,, 11 1 Fig.

Ueff 1 0.8 0.6 0.4 0.,,, PIV,,,,, Fig.7 13 b 0 90 45 0 45 90 αdeg Fig.

afinal resultafter calibration.bfirst and second attemptsnot calibrated.

5 ,, Fig.6a 10 U eff cos α 1 κ sin α 1 6,, Fig.6b, 1 X,,, v,,,, 11 1 Fig.5 Photograph of hot-wire support with azimuth angle adjuster. a 1. Ueff ,,, PIV,,,,, Fig.7 13 b αdeg Fig.6 Examples of the direction sensitivity of hotwire anemometer. afinal resultafter calibration.bfirst and second attemptsnot calibrated. Fig.7 One-dimensional energy spectra E 1and E in a homogenous isotropic turbulence.

6 Vol. 19, No. 300 Fig.9 16-channel rake probe for measurement of turbulent boundary layer 1. Fig.8 Energy spectra at far-dissipation region. Symbols Experiment, DNS 14, EVK 15, Pao 16, Heisenberg 17., 0.01 Hz10 khz6,,, Fig , 1 PIV,,, Fig.9, I 16 ch 3ch X Fig.10 1,, LDV 16 ch, LDV Fig.10 Contours of instantaneous velocity perturbation of single spot in turbulent boundary layer. ay/δ 0.,bY/δ 0.4,cY/δ ,,,, PIV,,,,,,,,

,,,,,,,,,,, Fig.11 4 10 4 7 60, 600,,,,, Cantwell,, I, X X I, X 3 4, 3 3,,,,, 3, 13 4 7 X, Z, X Z Y ω z ω z ω z ω z = u + v y x = Ω + Ω 1 7 u Y Y v X Fig.

7 ,,,,,,,,,,, Fig , 600,,,,, Cantwell,, I, X X I, X 3 4, 3 3,,,,, 3, X, Z, X Z Y ω z ω z ω z ω z = u + v y x = Ω + Ω 1 7 u Y Y v X Fig.1a I Y, u 1, u, Ω 1 ai-probe uu1/ bx-probe vv1/ucdt Fig.11 Flow pattern around a circular cylinder at Re Velocity vectors measured by a conditional sampling method. Vorticity distribution calculated by the advanced vortex method. Fig.1 ci-x-i Probe Principle of vorticity measurement by using multi hot-wire probes.

8 Vol. 19, No Ω1= u = u u y 8 Y,, X,,, X,, 1,,,, 3, = Uc t x 9 U c, Fig.1b X v, 89, I X 4 Fig.1cI- X-I, Z ω z ω z 1 v v1 u u1 = U dt c 10 Fig.13 5 µm, I 1 mm, X 1.4 mm, 00, 80, Prong φ 0. Ceramic Tube φ φ 4, Fig.14 Fig.14 Y/h 3 1 Schematic of two-dimensional wind tunnel for rectangular jet ωzh/u X/h Fig.15 Y/h Contour of ensemble-averaged vorticity in two-dimensional rectangular jetvorticity probe ωzh/u X/h Fig.13 Vorticity probe 7. Fig.16 Contour of ensemble-averaged vorticity in two-dimensional rectangular jetx-probe 3.

9 ,, 3 Fig.15, Fig.16 X X 150 mm, Y 60 mm, , U c, 0.8U, U c 0.8U, Foss 4 U c U c,, U c, 10, 5 y/h1, x/h 6.5,,,,, Y, X,, 10,,,,,, Lighthill-Curle 5,,,, Howe 6 ρ 0 xi Pa ( x, t) ( u) ( y, t x / a) Yi dy 4πax t ω V 11, P a, a, ω, u, ρ a, Y i, d Yi= yi 1+ i= 1, ; Y= y 1 4 y1 + y Fig.17 7 X/D 1.5, Y/D0.4,,,,,,,,, 80, 7,,, Fig.17 Distribution of dipole sound source radiated from a circular cylinder.

Vol. 19, No. 300 7,,,,,,, 1,,, 1, 5, 1997. J. O. Hinze, Turbulence, McGraw-Hill1975. 3H. H. Bruun, Hot wire anemometry, Oxford Univ. Press 1995. 4D. C. Collis and M. J. Williams, J. Fluid Mech, 6 p.

10 Vol. 19, No ,,,,,,, 1,,, 1, 5, J. O. Hinze, Turbulence, McGraw-Hill H. H. Bruun, Hot wire anemometry, Oxford Univ. Press D. C. Collis and M. J. Williams, J. Fluid Mech, 6 p L. V. King, Phil. Trans. Roy. Soc. London, 14A, p SP37. 7A. Iida, T. Otaguro, C. Kato and S. Shimode, JSME International Journal B, Vol.4. No.4, pp A. Mizuno and T. Ito, Proc. Fourth Asian Congress of Fluid Mechanics, VI-G ,, , pp H. H. Bruun, DISA Information p , B , p ,, B , p ,, B 56-5, p S. Kida and Y. Murakami, Phys. Fluids, 30-7 p R. J. Driscoll and L. A. Kennedy, Phys. Fluids, 6-5, p Y. H. Pao, Phys. Fluids, 8 p W. Z. Heisenberg, Phsik, 14 p ,, B 64-67, p ,, B , p ,, B 65-63, p H. Makita and K. Nishizawa, J. Turbulence p B. Cantwell and D. Coles, J. Fluid Mech. 136 pp ,,, B pp J. F. Foss and J. M. Wallace, Advance in Fluid Mechanics Measurements,. Springer pp A. Iida, T. Otaguro, C. Kato and H. Fujita, Proc. FLU- COME'97 Vol.1, pp M. S. Howe, "Acoustics of fluid-structure interactions," Cambridge University Press A. Iida, A. Mizuno and C. Kato, 8 th AIAA/CEAS Aeroacoustic Conference, AIAA Akiyoshi IIDA ,, , 1998

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