Abstract
The effect of spatial resolution on streamwise velocity measurements with single hot-wires is targeted in the present study, where efforts have been made to distinguish between spatial resolution and Reynolds number effects. The basis for measurements to accurately determine the mean velocity and higher order moments is that the probability density distribution is measured correctly. It is well known that the turbulence intensity is increasingly attenuated with increasing wire length. Here, it is also shown (probably for the first time) that besides the probability density distribution and hence the higher order moments, even the mean velocity is affected, albeit to subtle extent, but with important consequences in studies of concurrent wall-bounded turbulence.
Similar content being viewed by others
Notes
Note, however, that their conclusions are partially biased, due to the fact that they obtained, estimated or calculated the viscous-scaled wire length an order of magnitude too small, at least for the experiments by Purtell et al. (1981), Andreopoulos et al. (1984), and Erm and Joubert (1991), on which their analysis on the rms, skewness and flatness factors in zero pressure-gradient (ZPG) turbulent boundary layer (TBL) flows are primarily based.
For further information regarding the flow quality in the MTL wind tunnel, the interested reader is refered to Lindgren and Johansson (2002).
The reason for the observed different rms values within the overlap region may be twofold, viz. a Reynolds number effect and it could be caused by the scaling with the friction velocity, which in the case of Smith (1994) and DeGraaff and Eaton (2000) was deduced from a fit to the log law with classical values. The latter is probable to give higher values of the friction velocity and hence shifts the profiles towards lower values of the normalised velocity (Karlsson 1980; Murlis et al. 1982).
Note that the log law constants are extracted from a huge number of measurement sets and present an average value. This explains the observed small offset seen in such a sensitive quantity as Ψ, which is not recognisable in the conventional U + versus y + plot.
Note that while the open circles were extracted from the original data base, the shown mean velocity profiles in the figure were re-evaluated in order to fit the data better to the shown log law in order to ease comparison. Hence, some of the open circles are extracted from the same profiles as those represented by the solid symbols.
Utilising the modified Musker profile (Musker 1979) by Chauhan et al. (2009), which incorporates the overshoot over the log law, one can employ the same procedure used to generate the upper insert in Fig. 6. Doing so, it can be found that Ψ pp increases asymptotically to a value of 0.28 at the higher end of Reynolds numbers measured by Österlund et al. (2000), giving an approximate increase of around 0.1 u τ from his lowest Reynolds number on.
References
Andreopoulos J, Durst F, Zaric Z, Jovanovic J (1984) Influence of Reynolds number on characteristics of turbulent wall boundary layers. Exp Fluids 2:7–16
Barenblatt GI (1999) Scaling laws for turbulent wall-bounded shear flows at very high Reynolds numbers. J Eng Math 36:361–384
Bernard P, Wallace J (2002) Turbulent flow: analysis, measurement, and prediction. Wiley, New York
Bruun HH (1995) Hot-wire anemometry: principles and signal analysis. Oxford University Press Inc., New York, USA
Buschmann MH, Gad-el-Hak M (2006) Recent developments in scaling of wall-bounded flows. Prog Aero Sci 42:419–467
Chauhan KA, Monkewitz PA, Nagib HM (2009) Criteria for assessing experiments in zero pressure gradient boundary layers. Fluid Dyn Res 41:021404
Coles DE (1968) The Young person’s guide to the data. Computation of turbulent boundary layers. In: 1968 AFOSR-IFP Stanford conference, vol 2. Stanford University, CA
Comte-Bellot G, Strohl A, Alcaraz E (1971) On aerodynamic disturbances caused by single hot-wire probes. J Appl Mech 93:767–774
DeGraaff DB, Eaton J (2000) Reynolds-number scaling of the flat-plate turbulent boundary layer. J Fluid Mech 422:319–346
Derksen R, Azad R (1983) An examination of hot-wire length corrections. Phys Fluids 26:1751–1754
Durst F, Zanoun ES (2002) Experimental investigation of near-wall effects on hot-wire measurements. Exp Fluids 33:210–218
Erm LP, Joubert P (1991) Low-Reynolds-number turbulent boundary layers. J Fluid Mech 230:1–44
Fernholz HH, Finley P (1996) The incompressible zero-pressure-gradient turbulent boundary layer: an assessment of the data. Prog Aero Sci 32:245–311
Frenkiel F, Klebanoff PS (1973) Probability distributions and correlations in a turbulent boundary layer. Phys Fluids 16:725–737
Gad-el-Hak M, Bandyopadhyay P (1994) Reynolds number effects in wall-bounded turbulent flows. Appl Mech Rev 47:307–365
George WK, Castillo L (1997) Zero-pressure-gradient turbulent boundary layer. Appl Mech Rev 50:689–730
Gibbings J (1996) On the measurement of skin friction from the turbulent velocity profile. Flow Meas Instrum 7:99–107
Hafez S, Chong MS, Marusic I, Jones MB (2004) Observations on high Reynolds number turbulent boundary layer measurements. Proceedings of the 15th Australasian Fluid Mechanics Conference, Sydney, Australia
Hoyas S, Jiménez J (2006) Scaling of the velocity fluctuations in turbulent channels up to Re τ = 2003. Phys Fluids 18:011702
Hutchins N, Choi K (2002) Accurate measurements of local skin friction coefficient using hot-wire anemometry. Prog Aero Sci 38:421–446
Hutchins N, Marusic I (2007) Large-scale influences in near-wall turbulence. Phil Trans R Soc A 365:647–664
Hutchins N, Nickels TB, Marusic I, Chong MS (2009) Hot-wire spatial resolution issues in wall-bounded turbulence. J Fluid Mech 635:103–136
Johansson AV, Alfredsson PH (1983) Effects of imperfect spatial resolution on measurements of wall-bounded turbulent shear flows. J Fluid Mech 137:409–421
Karlsson RI (1980) Studies of skin friction in turbulent boundary layers on smooth and rough walls. Ph D thesis, Chalmers University of Technology, Göteborg, Sweden
Khoo B, Chew Y, Li G (1997) Effects of imperfect spatial resolution on turbulence measurements in the very near-wall viscous sublayer region. Exp Fluids 22:327–335
Klewicki JC, Falco R (1990) On accurately measuring statistics associated with small-scale structure in turbulent boundary layers using hot-wire probes. J Fluid Mech 219:119–142
Knobloch K, Fernholz HH (2004) Statistics, correlations, and scaling in a turbulent boundary layer at \(Re_{{\delta}_2}\le 1.15\times10^5\). In: AJ Smiths (Ed) IUTAM symposium on Reynolds number scaling in turbulent flow. Kluwer Academic Publisher, Dordrecht, pp 11–16
Ligrani P, Bradshaw P (1987) Spatial resolution and measurement of turbulence in the viscous sublayer using subminiature hot-wire probes. Exp Fluids 5:407–417
Lindgren B, Johansson AV (2002) Evaluation of the flow quality in the MTL wind-tunnel. Tech Rep TRITA-MEK 2002:13. Royal Institute of Technology, Stockholm, Sweden
Marusic I, Kunkel GJ (2003) Streamwise turbulence intensity formulation for flat-plate boundary layers. Phys Fluids 15:2461–2464
Metzger M (2006) Length and time scales of the near-surface axial velocity in a high Reynolds number turbulent boundary layer. Int J Heat Fluid Flow 27:534–541
Mochizuki S, Nieuwstadt FTM (1996) Reynolds-number-dependence of the maximum in the streamwise velocity fluctuations in wall turbulence. Exp Fluids 21:218–226
Morrison JF, McKeon B, Jiang W, Smits AJ (2004) Scaling of the streamwise velocity component in turbulent pipe flow. J Fluid Mech 508:99–131
Murlis J, Tsai H, Bradshaw P (1982) The structure of turbulent boundary layers at low Reynolds numbers. J Fluid Mech 122:13–56
Musker AJ (1979) Explicit expression for the smooth wall velocity distribution in a turbulent boundary layer. AIAA J 17:655–657
Nagib HM, Chauhan KA (2008) Variations of von Kármán coefficient in canonical flows. Phys Fluids 20:101518
Nagib HM, Christophorou C, Monkewitz PA (2004) High Reynolds number turbulent boundary layers subjected to various pressure-gradient conditions. In: GEA Meier, KR Sreenivasan (Eds) IUTAM symposium on one hundred years of boundary layer research. Göttingen, Germany, pp 383–394
Nickels TB, Marusic I, Hafez S, Hutchins N (2007) Some predictions of the attached eddy model for a high Reynolds number boundary layer. Phil Trans R Soc A 365:807–822
Oberlack M (2001) A unified approach for symmetries in plane parallel turbulent shear flows. J Fluid Mech 427:299–328
Örlü R (2009) Experimental studies in jet flows and zero pressure-gradient turbulent boundary layers. Ph D thesis, Royal Institute of Technology, Stockholm, Sweden http://www.mech.kth.se/thesis/2009/phd/phd_2009_ramis_orlu.pdf
Österlund JM (1999) Experimental studies of zero pressure-gradient turbulent boundary layer flow. Ph D thesis, Royal Institute of Technology, Stockholm, Sweden
Österlund JM, Johansson AV, Nagib HM, Hites MH (2000) A note on the overlap region in turbulent boundary layers. Phys Fluids 12:1–4
Park JY, Chung MK (2004) Revisit of viscous sublayer scaling law. Phys Fluids 16:478–481
Pope S (2000) Turbulent flows. Cambridge University Press, Cambridge, MA
Purtell L, Klebanoff PS, Buckley F (1981) Turbulent boundary layer at low Reynolds number. Phys Fluids 25:802–811
Schlatter P (2009) Personal communication
Schlatter P, Örlü R, Li Q, Brethouwer G, Fransson JHM, Johansson AV, Alfredsson PH, Henningson DS (2009) Turbulent boundary layers up to Re θ = 2500 studied through simulation and experiment. Phys Fluids 21:051702
Spalart P, Coleman G, Johnstone R (2008) Direct numerical simulation of the Ekman layer: a step in Reynolds number, and cautious support for a log law with a shifted origin. Phys Fluids 20:101507
Smith R (1994) Effect of Reynolds number on the structure of turbulent boundary layers. Ph D thesis Princeton University, USA
Smits AJ, Dussauge J (2006) Turbulent shear layers in supersonic flow, 2nd edn. Springer, Berlin
Talamelli A, Persiani F, Fransson JHM, Alfredsson PH, Johansson AV, Nagib HM, Rüedi JD, Sreenivasan KR, Monkewitz PA (2009) CICLoPE - a response to the need for high Reynolds number experiments. Fluid Dyn Res 41:021407
Tennekes H, Lumley JL (1972) A first course in turbulence. MIT Press, Cambridge, MA
Wu X, Moin P (2008) A direct numerical simulation study on the mean velocity characteristics in turbulent pipe flow. J Fluid Mech 608:81–112
Zagarola MV, Smits AJ (1998) Mean-flow scaling of turbulent pipe flow. J Fluid Mech 373:33–79
Zhao R, Smits AJ (2007) Scaling of the wall-normal turbulence component in high-Reynolds-number pipe flow. J Fluid Mech 576:457–473
Acknowledgements
Dr. Jens H. M. Fransson and Mr. Thomas Kurian are acknowledged for their help in setting up the experiment. The authors made use of experimental data of Drs. D. B. DeGraaf, J. Österlund and R. W. Smith and express their thanks for making these data sets available. Dr. P. Schlatter is acknowledged for providing his numerical ZPG TBL data that were used to calculate the Kolmogorov scale in Section 3. The support of the Swedish Research Council (VR) is also acknowledged.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Örlü, R., Alfredsson, P.H. On spatial resolution issues related to time-averaged quantities using hot-wire anemometry. Exp Fluids 49, 101–110 (2010). https://doi.org/10.1007/s00348-009-0808-1
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00348-009-0808-1