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Numerical simulation of steady and unsteady cavitating flows inside water-jetsChang, Shu-Hao 03 October 2012 (has links)
A numerical panel method based on the potential flow theory has been refined and
applied to the simulations of steady and unsteady cavitating flows inside water-jet pumps.
The potential flow inside the water-jet is solved simultaneously in order to take the
interaction of all geometries (blades, hub and casing) into account. The integral equation
and boundary conditions for the water-jet problem are formulated and solved by
distributing constant dipoles and sources on blades, hub and shroud surfaces, and
constant dipoles in the trailing wake sheets behind the rotor (or stator) blades. The
interaction between the rotor and stator is carried out based on an iterative procedure by
considering the circumferentially averaged velocities induced on each one by the other.
The present numerical scheme is coupled with a 2-D axisymmetric version of the
Reynolds Averaged Navier-Stokes (RANS) solver to evaluate the pressure rise on the
shroud and simulate viscous flow fields inside the pump.
A tip gap model based on a 2-D orifice equation derived from Bernoulli’s obstruction
theory is implemented in the present method to analyze the clearance effect between the
blade tip and the shroud inner wall in a global sense. The reduction of the flow from
losses in the orifice can be defined in terms of an empirically determined discharge
coefficient (CQ) representing the relationship between the flow rate and the pressure
difference across the gap because of the viscous effect in the tip gap region.
The simulations of the rotor/stator interaction, the prediction of partial and super
cavitation on the rotor blade and their effects on the hydrodynamic performance
including the thrust/torque breakdown of a water-jet pump are presented. The predicted
results, including the power coefficient (P*), head coefficient (H*), pump efficiency (η),
thrust and torque coefficients (KT and KQ), as well as the cavity patterns are compared
and validated against the experimental data from a series of on the ONR AxWJ-2 pump
at NSWCCD. / text
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CALCUL DE L'ECOULEMENT AUTOUR DES STRUCTURES MINCES PAR LA METHODE DES SINGULARITES. DEVELOPPEMENT DU PRINCIPE DE MINIMISATION ET APPLICATION A DIFFERENTES CONFIGURATIONS SUB- ET PARTIELLEMENT CAVITANTES.Pellone, Christian 26 April 1985 (has links) (PDF)
Une méthode de calcul non-linéaire d'écoulement autour de structures minces par la méthode des singularités est présentée. Le concept de minimisation est développé et appliqué à des configurations sub-cavitantes, partiellement cavitantes et super-cavitantes. Ce concept est relatif aux erreurs numériques commises sur les débits de fuite. Le calcul non-linéaire de la géométrie de la poche de cavitation est obtenu par une procédure itérative. La méthode est validée par différentes comparaisons des résultats avec les résultats de référence issus de la littérature. Le cas de la grille d'aubes a été traité, les résultats comparés à ceux obtenus avec une méthode d'éléments finis. La comparaison est excellente. Le code de calcul a été étendu au calcul 3D de l'écoulement autour d'une aile partiellement cavitante et super-cavitante en présence d'une surface libre ainsi qu'au calcul 3D d'une hélice sub-cavitante, suivie de son sillage, en écoulement tournant. Les résultats sont confrontés aux résultats expérimentaux.
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