The fundamentals of fully developed laminar flow in a pipe were investigated; in particular the velocity profile was visualized using radioactive isotope m99TC as a tracer at different flow velocities within the laminar region. The current work is to run and simulate these flow conditions using a computational fluid dynamics (CFD) model of fully-developed laminar flow in pipe where the flow was fully laminar before the sudden pipe enlargement was introduced; laminar flow was then re-established before the sudden contraction. A comparison using CFD simulation results and radioactive isotope m99TC tracer experimental work was validated and were in good agreement with the predicted laminar flow.