Mapping of the turbulent round jet developing region using a constant temperature anemometer (CTA)

Authors

  • Mohd Rusdy Yaacob Universiti Teknikal Malaysia Melaka
  • Rasmus Korslund Schlander Technical University of Denmark
  • Preben Buchhave Intarsia Optics
  • Clara Marika Velte Technical University of Denmark

DOI:

https://doi.org/10.11113/mjfas.v14n0.1298

Keywords:

hot wire, turbulent round jet, turbulence

Abstract

The fully developed round turbulent jet has been extensively studied, whereas the developing region is much less understood. The high shear and turbulence intensities in the most interesting parts of the developing region make them inaccessible to common measurement techniques such as Constant Temperature Anemometry (CTA) due to the high demands on the measurement techniques for accuracy of the measurements. Turbulence measurements are therefore planned using our in-house laser Doppler anemometer (LDA) system based on its capability to provide accurate measurements and with its inherent ability to properly distinguish velocity components.   A rigorous measurement with the intended LDA system however demands impractical processing time, so knowing the critical points at which measurement are to be taken will save valuable time. This information is herein acquired significantly faster and more practically, however less accurately, with single-wire CTA. A high-resolution measurement was done using a computer-controlled single-wire CTA with the wire probe mounted perpendicular to the incoming flow from the jet orifice. The measurements covered several points in the radial (r-direction) along x/D=10, x/D=15, x/D=20 and x/D=30 downstream (where D is the jet exit diameter), with spatial resolutions ranging from 1 to 3 mm between the points, depending on how far the measurement was from the jet centerline. A proper alignment was also conducted prior to measurement so that the same points can be reached again for LDA measurement on the same jet afterwards. The radial profiles of mean velocity and turbulence intensity at each downstream position are presented to show the statistics of the air flow inside and outside the jet. As expected from theory, the mean profiles display a nearly Gaussian shape, spread out and tapered with the downstream direction. The highest velocities are located at the centerline.

Author Biographies

Mohd Rusdy Yaacob, Universiti Teknikal Malaysia Melaka

Faculty of Electrical Engineering

Rasmus Korslund Schlander, Technical University of Denmark

Department of Mechanical Engineering

Preben Buchhave, Intarsia Optics

Intarsia Optics

Clara Marika Velte, Technical University of Denmark

Department of Mechanical Engineering

References

Ball, C. G., Fellouah, H. & Pollard, A., 2012. The flow field in turbulent round free jets. Progress in Aerospace Sciences, 50, pp. 1–26.

Buchhave, P., 1984. Three-component LDA measurements. Disa Information, (29), pp. 3–9.

Buchhave, P., George, W. K. & Lumley, J. L., 1979. The measurement of turbulence with the laser-Doppler anemometer. Annual Review of Fluid Mechanics, 11, pp. 443–503.

Buchhave, P. & Velte, C. M., 2017. Measurement of turbulent spatial structure and kinetic energy spectrum by exact temporal-to-spatial mapping. Physics of Fluids, 29(8), 085109.

F. Gökhan Ergin, 2016. Constant Temperature Anemometry - A Theoretical Introduction. Dantec Dynamics.

Fellouah, H., Ball, C. G. & Pollard, A., 2009. Reynolds number effects within the development region of a turbulent round free jet. International Journal of Heat and Mass Transfer, 52(17–18), pp. 3943–3954.

Hinze, J. O., 1975. Turbulence 2nd ed., Michigan: McGraw-Hill.

Hussein, H. J., Capp, S. P. & George, W. K., 1994. Velocity measurements in a high-Reynolds-number, momentum-conserving, axisymmetric, turbulent jet. Journal of Fluid Mechanics, 258, pp. 31–75.

Jørgensen, F. E., 2002. How to measure turbulence with hot-wire anemometers - A practical guide. Dantec Dynamics.

Jørgensen, F. E., 1996. The computer-controlled Aspects of set-up, probe calibration, data acquisition and data conversion. Measurement Science and Technology, 7(10), pp.1378–1387.

Kaushik, M., Kumar, R. & Humrutha, G., 2015. Review of computational fluid dynamics studies on jets. American Journal of Fluid Dynamics, 5(3A), pp.1–11.

Mossa, M. & Serio, F. De, 2016. Rethinking the process of detrainment : Jets in obstructed natural flows. Bari: Nature Publishing Group.

Vassilicos, J. C., 2015. Dissipation in turbulent flows. Annual Review of Fluid Mechanics, 47, pp. 95–114.

Velte, C. M., Buchhave, P. & Hodzic, A., 2017. Measurement of turbulent kinetic energy spectrum - Part 2 : Convection record measurements. In iTi Conference on Turbulence VII. Springer, pp. 171–176.

Velte, C. M., George, W. K. & Buchhave, P., 2014. Estimation of burst-mode LDA power spectra. Experiments in Fluids, 55(1674), p. 1-20.

Yaacob, M. R., Schlander, R. K., Velte, C. M., & Buchhave, P., 2018. Validation of improved laser Doppler anemometer (LDA) based on the fully developed turbulent round jet. Symposium of Electrical, Mechatronics and Applied Science. November 2018. Melaka. [Manuscript accepted for publication].

Yaacob, M. R., Schlander, R. K., Velte, C. M., & Buchhave, P., 2018. Experimental evaluation of kolmogorov’s -5/3 and 2/3 power laws in the developing turbulent round jet. Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 45(2), pp. 14–21.

Downloads

Published

25-10-2018