Numerical Investigation of the Transition Length at the Entrance Region of Pipe Flows

Yıl 2018, Sayı: 2, 101 - 110, 19.08.2018

Hasan Duz Ahmet Beyzade Demırpolat

Öz

In
this study, the steady, incompressible and axis symmetric flows in the pipe
entrance region has been simulated numerically for the Reynolds numbers between
1000 and 25000 and for the square edged pipe inlets. The developing boundary
layer at the pipe entrance region first grows as laminer then disturbed to a
turbulent state at downstream away of the inlet. From pipe inlet to a
downstream distance where laminer to turbulent transition begins is called the
transition length. Determination of the transition length has been significiant
for hydro and aeromechanics and yet it seems not to be defined clearly. The
effects of wall surface roughness, pipe diameter and Reynolds numbers on
transition length has been investigated numerically by covering transition and
turbulent flow regimes too. On the purpose, water flows were simulated
numerically including five different relative roughness. The numerical results
obtained has shown that the transiton length is the power function of the
Reynolds number inverse proportionally. Likewise the numerical study has also
shown that changing the pipe diameter but keeping the relative roughness the
same has left no effect on the transition length. As an outcome, a numerical
correlation which define the dimensionless transition length and well fitting
the numerical values was derived as a function of Reynolds number.

Anahtar Kelimeler

Entrance length, Pipe flow, Developing flow, Numerical

Kaynakça

• Anselmet, F., Ternat, F., Amielh, M., Boiron, O., Boyer, P., & Pietri, L. (2009). Axial development of the mean flow in the entrance region of turbulent pipe and duct flows. Comptes Rendus Mécanique, 337(8), 573-584. Augustine, J. R. (1988). Pressure Drop Measurements in the Transition Region for a Circular Tube with a Square-Edged Entrance (Master’s Thesis). Bachelor of Science in Mechanical Engineering. The University of Southwestern Louisiana Lafayette, Louisiana. Barbin, A. R., & Jones, J. B. (1963). Turbulent flow in the inlet region of a smooth pipe. Journal of Basic Engineering, 85(1), 29-33. Doherty, J., Ngan, P., Monty, J., & Chong, M. (2007, January). The development of turbulent pipe flow. In 16th Australasian Fluid Mechanics Conference (AFMC) (pp. 266-270). School of Engineering, The University of Queensland. Minkowycz, W. J., Abraham, J. P., & Sparrow, E. M. (2009). Numerical simulation of laminar breakdown and subsequent intermittent and turbulent flow in parallel-plate channels: Effects of inlet velocity profile and turbulence intensity. International Journal of Heat and Mass Transfer, 52(17-18), 4040-4046. Nikuradse J (1966). Gestzmassigkeiten der turbuleten stromung in glatten rohren. Forschung auf dem Gebiet des. Ingenieurwesens. Translated in NASA TT F-10, 359(3), 1932, 1-36. Laufer, J. (1954). The structure of turbulence in fully developed pipe flow. NACA Report, Washington, National Bureau of Standards. Ozisik, M. N. (1985). Heat transfer: a basic approach. New York: McGraw-Hill Patel, V. C., & Head, M. R. (1969). Some observations on skin friction and velocity profiles in fully developed pipe and channel flows. Journal of Fluid Mechanics, 38(1), 181-201. Perry, A. E., & Abell, C. J. (1975). Scaling laws for pipe-flow turbulence. Journal of Fluid Mechanics, 67(2), 257-271. Salami, L. A. (1986). An investigation of turbulent developing flow at the entrance to a smooth pipe. International journal of heat and fluid flow, 7(4), 247-257. Tam, H. K., Tam, L. M., & Ghajar, A. J. (2013). Effect of inlet geometries and heating on the entrance and fully-developed friction factors in the laminar and transition regions of a horizontal tube. Experimental thermal and fluid science, 44, 680-696. White, F. M. (2003). Fluid Mechanics. 5th edition, McGraw–Hill Book Co, New York. Zanoun, E. S., Kito, M., & Egbers, C. (2009). A study on flow transition and development in circular and rectangular ducts. Journal of Fluids Engineering, 131(6), 061204. Zimmer, F., Zanoun, E. S., & Egbers, C. (2011). A study on the influence of triggering pipe flow regarding mean and higher order statistics. In Journal of Physics: Conference Series (Vol. 318, No. 3, p. 032039). IOP Publishing.