Effect of the von Karman Shedding Frequency on the Hydrodynamics of a Francis Turbine Operating at Nominal Load

Abstract

This paper presents a numerical analysis of the influence of the von Karman vortex shedding at the blade trailing edge on the hydrodynamics of a recently installed small hydro Francis turbine manifesting very loud and high-frequency acoustic pulsations when operating close to the nominal load. A reduced single-passage numerical model is developed to reduce the computational effort of the simulation while ensuring high accuracy in the assessment of fluid flow. The accuracy of the proposed numerical approach is investigated by comparing the frequency spectrum of the experimentally acquired acoustic frequency and the numerical pressure signals, confirming the nature of the machine’s vibrations. The validated numerical model represents a useful tool for an in-depth analysis of the machine’s hydrodynamics in the preliminary design phases. The proposed approach represents a valid alternative to the traditional correlation-based approach for the evaluation of the von Karman shedding frequency with less computational effort compared with a transient simulation of the entire machine.

Analysis of Stress Characteristics of a Vertical Centrifugal Pump Based on Fluid-Structure Interaction

“…The bearer of the hydro-mechanical runner, water, produces a complex hydraulic excitation on its action, and people have been actively seeking methodologies to determine the stress properties of runner blades resulting from hydraulic excitation. Nowadays, ANSYS software is one of the more commonly used software for calculating fluid structure [24][25][26]. Kan [27] used the flow field and structure to compute and examine the flow field of the axial pump impeller, as well as the strength characteristics of the runner body, and the distribution of stresses was obtained.…”