Fine Structure of Reynolds Shear Stress in an Unsteady Turbulent Channel Flow
The modulation characteristics of the Reynolds shear stresses in an unsteady channel flow are presented. The imposed frequency covers a large range going from the quasi-steady limit to 2 times the ejection frequency at y + = 15. The time mean contributions of the quadrants to the Reynolds shear stress are unaffected by the imposed unsteadiness. The contributions of the second and fourth quadrants are strongly modulated near the imposed frequency in wall units f + ≈ 0.002, where the modulation of the ejection frequency is weak and the phase shift with respect to the centerline velocity is maximum. In the low frequency regime the ejection frequency is modulated as the wall shear stress according to the quasi-steady behaviour, and the decline in its response in the high imposed frequency regime stretches from the near-wall to the outer layer.
KeywordsWall Shear Stress Relative Amplitude Modulation Characteristic Reynolds Shear Stress Centerline Velocity
Unable to display preview. Download preview PDF.
- Bogard, D.G. (1982):”Investigation of burst structures in turbulent channel flows through simultaneous visualization and velocity measurements”, Ph.D. Thesis, Purdue UniversityGoogle Scholar
- Feng, M.Q., Tardu, S., Binder, G. (1993): “Inner region of unsteady channel flow”, in Near Wall Turbulent Flows ( R.M.C. So, C.G. Speziale and B.E. Launder eds) ( Elsevier Science Publishers, Amsterdam, London, New-York, Tokyo ), p. 457Google Scholar
- Finnicum, D.S., Hanratty, T.J. (1987): Pressure gradient effects in the viscous wall region of a turbulent flow. Rep. No 7, Dept. of Chemical Engineering, University of IllinoisGoogle Scholar
- Finnicum, D.S., Hanratty, T.J. (1988): Influence of imposed flow oscillations on turbulence. PCH PhysicoChem. Hydrodyn. 10, 585Google Scholar
- Hon, T.L., Walker, J.D.A (1987): An analysis of the motion and effects of hairpin vortices. AFOSR Rep. FM-11, Dept. Mechanical Engineering, Lehigh UniversityGoogle Scholar
- Tardu S., Binder, G., Blackwelder, R. (1987): “Modulation of bursting by periodic oscillations imposed on channel flow” in Proc. of 6th International Symposium on Turbulent Shear Flows, Toulouse, France, p. 4. 5. 1Google Scholar
- Tardu, S., Binder, G. (1992): Response of bursting to imposed oscilations of high frequencies. J. Fluid Mech. In RevisionGoogle Scholar
- Tardu, S., Binder, G., Blackwelder, R.F. (1994): Turbulent channel flow subjected to large imposed velocity oscillations. J. Fluid Mech. In PressGoogle Scholar
- Wallace, J.M., Eckelmann, H., Brodkey, R.S. (1972): The wall region in turbulent shear flow. J. Fluid Mech. 204, 57Google Scholar