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Experimental Investigation of Pulsating Flows in Tubes of Periodically Variable Cross-section at Small Values of Womersley Number

Cieślicki K., Lasowska A.

Bulletin of the Polish Academy of Sciences. Earth Sciences

2001

Vol. 49, nr 2

109-121

The effects of flow pulsation in tubes of periodically variable boundaries were determined in an experimental programme where square and sinusoidal disturbances were applied. Instantaneous velocity field patterns were compared to field patterns in steady-state flow conditions at the corresponding values of Re.

The dynamics of a square cavity vortex in the light of experiments

Cieślicki K., Lasowska A.

Bulletin of the Polish Academy of Sciences. Earth Sciences

2000

Vol. 48, nr 2

151-159

The problem of an axisymmetrical cavity vortex development after rapid pressure drop increase was treated experimentally. The cavity flow patterns obtained in flow visualisation were of a special interest. The conducted experiments show explicitly that for the small Re numbers the nature of the cavity flow evolution in models with different inlet velocity profiles is different, even though they tend towards the same final state. In the case of the parabolic profile, the flow separation can be observed already at the initial phases of the process. In the case of the flattened profile, the separation occurs much later and undergoes complicated transient phases. It was also demonstrated that linearisation of the Navier-Stokes equation for Re<1 acceptable in the steady state proves to be incorrect in the non-stationary states.

Discretization schemes of advection term in the finite element method for incompressible Navier-Stokes equation

Uchiyama T.

Applied Mechanics and Engineering

1998

Vol. 3, no 1

39-53

In a finite element method for an incompressible Navier-Stokes equation, the divergent, gradient, simplified, and mixed schemes are applicable to discretize the advection term. The simplified scheme substitutes the average velocity in each element for the advection velocity, and the mixed scheme is a combination of the divergent and gradient schemes. This paper investigates the effects of these schemes on the computational accuracy and CPU time of a finite element method based on the SMAC method. The investigations are accomplished by solving the flow in a square cavity for the cases in which the velocity field is calculated by the mass-lumping and multi-pass algorithms. The computational accuracy is higher in the order of divergent, mixed, gradient, and simplified schemes, irrespective of the solution algorithms for the velocity. The divergent scheme, allowing calculation with the shortest CPU time, is the most useful among the four schemes. The improvement in computational accuracy produced by the multi-pass algorithm is independent of the discretization scheme of the advection term.