Numerical study of the entrance flow and its transition in a circular pipe (2)
Abstract
The experimental data and results of prior investigations lead to defining the problem of the transition from laminar to turbulent flow in a circular pipe. The flow field of a circular pipe is examined with particular emphasis on the entrance and transition length, using a twodimensional computational scheme. Symmetric disturbances were superimposed on points near the inlet and wall of the pipe. It was found for the first time that the transition length is predicted fairly satisfactorily by the computational simulation. A numerical, finitedifference method is shown to simulate development of the HagenPoiseuille flow and transition to turbulent flow. Conclusions are: (1) the turbulence transition occurs only within the entrance region; (2) the transition length decreases as the Reynolds number increases under the same inlet conditions; (3) a good bellmouth lessens disturbances at the inlet and the critical Reynolds number becomes larger; (4) the transition is numerically simulated on the conditions that the aspect ratios of the rectangular mesh system are 2 for Re=2,700 and 1 for Re=10,000 and that the disturbance is given at the point very near the wall of the inlet; and (5) the result of simulation satisfies two theorems of Rayleigh (dependence of the flow stability on laminar velocity profiles).
 Publication:

Symposium on Mechanics for Space Flight
 Pub Date:
 March 1987
 Bibcode:
 1987tmsf.proc...47K
 Keywords:

 Circular Tubes;
 Computational Fluid Dynamics;
 Computerized Simulation;
 Flow Stability;
 Flow Velocity;
 Laminar Flow;
 Numerical Analysis;
 Perturbation;
 Pipes (Tubes);
 Reynolds Number;
 Transition Flow;
 Turbulent Flow;
 Aspect Ratio;
 Conical Inlets;
 Wall Flow;
 Fluid Mechanics and Heat Transfer