Numerical and experimental study on the effects of elbows upon the flow downstream

Abstract

The seeds of elbows upon the flow downstream were graphics. studied experimentally and numerically. The flow field was calculated for five cases: through one elbow, through two elbows arranged to make an S bend in a single plane: for 1 and 11 pipe diameters of straight pipe between the two elbows, two elbows arranged to make an 90 degree bend: for 1 and 11 pipe diameters of straight pipe between the two elbows. For each case, the simulation of the flow field was performed using the Fluent computational fluid dynamics (CFD) software and the velocity profiles were generated by computer and compared to the velocity profiles obtained by experiment for verification. For the experiments, a five-hole Pitot probe was used at dearest diameters along the pipe for different positions across the pipe and for four azimuthal ogles around the pipe at each position in order to obtain velocity profiles. As the flow progressed downstream, the flow field disturbances decreased in value and the flow began to be centered in the pipe and approach an axisymmetric condition. The elects of increasing the separation between the two elbows (in plane and out of plane) to 11D were observable: for the 11D separation, the swirl was nearer the wall at 10D (compared to the 1D separation) and was still not centered at 19D. However the values of the velocity for a 1D separation are approximately twice as large as for the 11D separation. A double structure vortex was observable for one elbow and two elbows in plane while a single vortex was observable for two elbows out of plane.