To examine numerically and experimentally the laminar-turbulance transition properties in entrance and fully developed flow region

Although there are experimental relations to calculate the pressure drop in the fully developed pipe flow region, in the developing pipe flow region there are no any experimental or analytical relations. In long pipe flows, whereas the entrance effects is not important, in short pipe flows the entrance effect becomes very important. For that reason an experimental and numerical study has been established for the analysis of flow properties in the developing pipe flow region. The aim of the experimental study is to assess different pipe sorts on roughness effects and to create a comparison ground for the numerical study. The experimental study is carried out with five different pipes manufactured from aluminium, copper, iron, galvanized and PPRC materials. Except for PPRC pipe, the others have the same diameters. This study is done for the Reynolds numbers in the range of 2000-55000. From the experimental results, the Darcy friction factor has been calculated from the fully developed pipe flow region and the roughness values of pipes has been found from the Moody diagram. When the pipe roughnesses ordered in the decreased direction; galvanised, iron, aluminium, PPRC and copper pipe values comes in sequence. A numerical study has been established for the Reynolds numbers in the range of 2000-25000. in the experimental study. The aim of the numerical study is to analyse the wall shear stress, the critical and the transition distances for the developing pipe flow region and is to derive numerical formulas for defining them. For the solution of turbulence flows, three different numerical solution methods are used. These are DNS, LES and RANS methods. In the solution with DNS, all turbulence scales are solved temporarily and spatially, whereas in the solution with LES, large turbulence scales are solved directly, but the small scales are modeled. In the solution with RANS, all turbulence scales are modeled. Due to high computation cost required in DNS and LES, the RANS has been prefered mostly. From the RANS turbulance models, the SST k-omega model which supplies laminar-turbulance transition has been chosen for the solution of pipe flows. The obtained numerical results are compared with the experimental datas and is seen very well agreement. The numerical wall shear stress has been analysed and a numerical relation is derived for its changes along the flow. The critical and transition distances has been analysed and two numerical formulas defining their changes with the Reynolds number are derived. The distance where the centerline velocity becomes maximum has been analysed and a numerical formula is derived for the changes with Reynolds numbers. The fully developed velocity profiles are compared with wall functions and other experimental datas and has been seen very well agreement. In addition to RANS solution, a numerical smooth pipe flow is carried out also with LES solution . Finally it has been seen that the flow visualisation with LES is better than RANS. Comparison of LES solution with experimental results has shown high deviation according to RANS solution. The reason is that a sufficient mesh resolution is not achieved due to high computation cost in LES. It is seen that the solution of developing pipe flow with LES require the usage of super computer or parallel computation.