Publication Date:
2016-12-14
Description:
Francis turbines are increasingly required to operate from 0-100% of power output. For the design of these turbines, a sound understanding of formerly “off-design” operating points, e.g. speed-no-load, is necessary. One way to assess loads at these operating points is to apply scale resolving CFD methods in order to account for the broad-band turbulence spectrum. This results in stochastic load patterns, which are characteristic for these off-design points. In this paper, two CFD approaches for scale resolving simulations are applied to a Francis model turbine to resolve the larger anisotropic scales in turbine flow at speed-no-load operation. The first uses a hybrid RANS-LES model presented by Menter & Egorov [2]. Here the resolved scales are adapted continuously by RANS-LES blending based on the actual flow condition. The second approach is a LES with a dynamic model based on Germano et al. [3]. For both approaches, spectra of resulting pressure fluctuations at the draft t...
Print ISSN:
1755-1307
Electronic ISSN:
1755-1315
Topics:
Geography
,
Geosciences
,
Physics
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