# Problem Specification — Lesson 1

## Problem Statement Consider a fluid flow through a sudden expansion in an axisymmetric pipe. The flow is laminar and axisymmetric. Due to symmetry, the computational domain covers only half of the pipe. BD is the axis of symmetry. The radius R1 = 1m and R2/R1 = 2.

L1/R1 = 20 and L2/R2 = 50. The inlet velocity at AB is uniform, U1 = 0.277 m/s. The fluid exhausts into the ambient atmosphere which is at a pressure of 1 atm at CD. The density ρ = 1kg/m3, and the dynamic viscosity is: µ = 0.01 kg/(ms).

The Reynolds number Re at AB = (2 R1 ρ U1) /µ = 55.4.

This Re value is selected to match one of the experimental cases in the paper by Hammad et al. (1999).

Use Fluent via Ansys Workbench to predict the flow and validate your results by comparing them with those in the following journal papers:

1. Macagno, E. and Hung, T-K.“Computational and experimental study of a captive annular eddy”, J. Fluid Mechvol. 28 (1967) pp. 43-64.
2. Hammad, KJ, Otugun, MV and Arik, EB “A PIV study of the laminar axisymmetric sudden expansion flow”, Experiments in Fluids 26 (1999) pp. 266-272.