THERMAL SCIENCE

International Scientific Journal

TRANSIENT MODELING OF IMPINGING HEAT TRANSFER FROM AN ACOUSTICALLY MODULATED TURBULENT AIR JET TO A NORMALLY POSITIONED FLAT SURFACE

ABSTRACT
The subject of this study is the numerical investigation of the impingement of an axisymmetric turbulent air jet on a flat surface, the influence of acoustic modulations on the coherent structures that form around the jet, and the effects on the heat transfer from the jet to the heated surface. The study showed how controlled acoustic perturbations influence the exit velocity profile from the nozzle and the formation of vortices in the boundary-layer of the jet. Since vortices are responsible for the redistribution of thermal energy transferred from the jet to the surface in impinging jet flow configurations, it is crucial to investigate whether their formation and evolution can be controlled. The results of the numerical simulations indicated very good agreement with experimentally measured velocity field. However, a problem arises in the prediction of the heat transfer because the standard k-ε model overestimates the values of the heat transfer coefficient in the stagnation zone because they were theoretically developed to use shear stresses for the generation of the turbulent kinetic energy, while in reality normal stresses are responsible for their generation in this flow situation. Due to the unstructured mesh used for the calculations, there are discrepancies in the results at larger edge distances. The complex flow at the impingement surface, the occurrence of secondary vortices and recirculation zones and their direct effect on the heat transfer cannot be fully captured by the mathematical model, even if the numerical errors are acceptable compared to experiments.
KEYWORDS
PAPER SUBMITTED: 2024-10-30
PAPER REVISED: 2024-11-27
PAPER ACCEPTED: 2024-12-04
PUBLISHED ONLINE: 2025-03-22
DOI REFERENCE: https://doi.org/10.2298/TSCI2501767C
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2025, VOLUME 29, ISSUE Issue 1, PAGES [767 - 780]
REFERENCES
  1. Abramovich, G. N., The Theory of Turbulent Jets, English translation, M.I.T. Press, Cambridge, Mass., USA, 1963, pp. 671, doi.org/10.7551/mitpress/6781.001.0001
  2. Kataoka, K. et al, Unsteady Aspects of Large-Scale Coherent Structures and Impingement Heat Transfer in Round Air Jets With and Without Controlled Excitation, Int. J. Engng Fluid Mech, 25 (2005), 1, pp. 31-44
  3. Martin, H., Heat and Mass Transfer Between Impinging Gas Jets and Solid Surfaces, in: Advances in Heat Transfer, (eds.: Irvine Jr., T. F., Hartnett, J. P.), Academic Press, New York, USA, 1977, Vol. 13, pp. 1-60
  4. Stevanović, Ž., Numerical Aspects of Turbulent Transfer of Momentum and Heat (in Serbian), Publisher Grafika Galeb, Faculty of Mechanical Engineering, University of Niš, Nis, Serbia, 2008
  5. Ćetenović, N., Experimental and Numerical Analysis of the Influence of Acoustic Modulations of a Turbulent Air Jet on Heat Transfer from the Jet to the Surface (in Serbian), M. Sc. thesis, Faculty of Mechanical Engineering, University of Belgrade, Belgrade, 2023
  6. Cvetinović, D., Experimental and Numerical Investigation of the Influence of Turbulent Axisymmetric Jet Modification by Acoustic Oscillations on the Heat Transfer Process upon Impact on a Flat Heated Surface (in Serbian), Ph. D. thesis,, Faculty of Mechanical Engineering, University of Belgrade, Belgrade, 2014
  7. Cvetinović, D. et al, Velocity Measurements and Flow Structure Visualisations of a Self-Sustained Oscillating Jet, Thermal Science, 10 (2006), 2, pp. 113-125
  8. Popiel, C. O., Trass, O., Visualization of a Free and Impinging Round Jet, Experimental Thermal and Fluid Science, 4 (1991), 3, pp. 253-264
  9. Abid, R., Evaluation of Two-Equation Turbulence Models for Predicting Transitional Flows, International Journal of Engineering Science, 31 (1993), 6, pp. 831-840
  10. Baughn, J. W., et al., An Experimental Study of Entrainment Effect on the Heat Transfer from a Flat Surface to a Heated Circular Impinging jet, J. Heat Transfer, 113 (1991), 4, pp. 1023-1025
  11. Lam, C. K. G., Bremhost, K., A Modified Form of the k-ε Model for Prediction Wall Turbulence, Transactions of the ASME, Journal of Fluids Engineering, 103 (1981), 3, pp. 456-460
  12. Wang, S. J., Mujumdar, A. S., A Comparative Study of Five Low Reynolds Number k-ε Models for Impingement Heat Transfer, Applied Thermal Engineering, 25 (2005), 1, pp. 31-44

2025 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence