Figure 12 Total-total isentropic efficiency vs. axial inter-distance
UNSTEADY FLOW ANALYSIS
The transient relative motion on each side of GGI connection was simulated and the interface position updated at each time step. The high-resolution advection scheme and second order backward Euler transient scheme were used. For every time step ten internal coefficient loops were selected and the pressure was monitored at the same spatial locations. In this section the expected dominant modes and frequencies and the sequence of interactions were determined analytically, followed by a characterization of the pressure fluctuations computed and recorded at several monitor points. The development of instabilities negatively affects the overall operating performance of axial fan stage which could be alleviated by understanding the unsteady flow interactions. Also it is useful to know the modal frequencies to ensure that any applied periodic loading frequency does not induce resonance leading to large oscillations. This section addresses the unsteadiness arising from both periodic (correlated with speed of rotation) and non-periodic fluctuations induced by RSI.