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Model of Pressure Distribution in Vortex Flow Controls

Mielczarek S., Sawicki J. M.

Archives of Hydro-Engineering and Environmental Mechanics

2015

Vol. 62, nr 1-2

41--52

Vortex valves belong to the category of hydrodynamic flow controls. They are important and theoretically interesting devices, so complex from hydraulic point of view, that probably for this reason none rational concept of their operation has been proposed so far. In consequence, functioning of vortex valves is described by CFD-methods (computer-aided simulation of technical objects) or by means of simple empirical relations (using discharge coefficient or hydraulic loss coefficient). Such rational model of the considered device is proposed in the paper. It has a simple algebraic form, but is well grounded physically. The basic quantitative relationship, which describes the valve operation, i.e. dependence between the flow discharge and the circumferential pressure head, caused by the rotation, has been verified empirically. Conformity between calculated and measured parameters of the device allows for acceptation of the proposed concept.

Instability of the non-isothermal flow between a rotating and a stationary disks

Tuliszka-Sznitko E., Soong C. Y., Serre E., Bontoux P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

2001

Vol. 5, No 4

557-566

Both theoretical linear stability analysis and direct numerical simulation are performed to study the transition flow between rotating discs. The paper reports three-dimensional spiral and annular patterns computed with a high-order (spectral) numerical method in the Bodewadt layer of a cylindrical rotor/stator cavity. The characteristic parameters of these boundary layer instabilities are compared with the theoretical results and interpreted in terms of type I and type II generic instabilities. The absolute instability regions are theoretically identified and critical Reynolds numbers of the convective/absolute transition in both layers are given. The absolute or convective nature of the flows is determined by examining the branch-point singularities of the dispersion relation.