Numerical and Experimental Study to Predict the Entrance Length in Pipe Flows

Here, a steady, incompressible and isothermal flow in the inlet region of a circular pipe were numerically and experimentally studied to predict the entrance length. The region in the upstream of fully developed pipe flow is referred to as the developing flow region, the effects of which on flow parameters are referred to as entrance effects. Entrance length shows the length of the developing flow region. The analysis of entrance flow is difficult and complicated as there are many parameters such as different pipe inserts affecting it. Earlier empirical results on the entrance region are inconclusive and inconsistent. Initially, an experimental study was performed with pipes of different roughness to validate the numerical results. Reynolds numbers used in the experiment ranged from 3000 to 25000. The entrance flow was numerically simulated in parallel to experimental pipe flows. Numerical results obtained were compared with those of the experimental study and of previous ones. Numerical and empirical data showed good agreement. Based on the numerical results, a well-defined numerical correlation was developed and proposed for the prediction of entrance lengths.