An experimental study was carried out on wall shear stress and turbulent behavior in accelerating pipe flows.A modified ensemble averaging mean method was used for the experimental data. Results showed that the transient mean wall shear stress is significantly different from that of steady flow,where a maximum of twice is observed in case 1.The decrease of acceleration and the improvement of initial flowrate would alleviate the turbulence delay and reduce the difference of wall shear stress.The mean wall shear stress and turbulent behovior are shown to respond to an imposed acceleration in four stages.Turbulence delay is seen in the first two stages and flow inertia plays a dominant role during this period.Then the effect of the development of turbulence is in the last two stages.
