عنوان مقاله [English]
نویسندگان [English]چکیده [English]
In this paper using one, two and three dimensional simulations, the accelerating flows in developing inlet pipe region are considered numerically. The developing length calculated based on different turbulence parameters is studied thoroughly. The SST turbulence model in comparison with recent reported experimental data have been used to achieve reliable predictions. The predictions obtained using all 1, 2, and 3 dimensional cases are generally the same and follow the experiments well. Thus, it seems that one dimensional simulation in fully developed region is sufficient. However, for the inlet region in developing state a two dimensional axisymmetric analysis is required. This research shows that calculating the developing length based on only mean averaged velocity is not adequate, but also turbulence kinetic energy and viscosity must be paid enough attention. Further, the comparison between steady and unsteady flows for the developing length shows that they are very different. This length also depends on both the value of flow acceleration and turbulence delay time in addition to Reynolds number and pipe diameter.