Dynamic Inflow in BEM

Hi All,

I have a Matlab script which I have written myself to try to incorporate variable velocity accross a 3-bladed horizontal axis turbine. Generally it seems to work well with all the usual additions such as tip-loss, stall delay, CT correction etc. I have also included skewed axial inflow factor as per AeroDyn.

I have attempted to include the simplified Dynamic Inflow correction found in Burton et al. which is based on Pitt and Peters. I’m not convinced I have done this correctly? Does anyone have any suggestions as to how I can check this?

As a side note, would one expect Dynamic Inflow or Dynamic Stall to be the largest loading contributor (I would assume dynamic inflow since it affects the turbine as a whole)? To clarify, I mean the greatest range in loading for a blade. For the moment I am only interested in establishing mean loads and their range rather than looking at resonance and fatigue effects.



Dear Pascal,

I’m also attempting to implement a dynamic inflow model and to incorporate this within my BEM model.

In terms of validation, I think in literature there are some graphs showing the induced flow variation with time, for an assigned variation of pitch angle.
You could try to reproduce these results with your code. (for example in the NREL report on Inflow models, by Tangler and Bir, some results of this kind are shown).
Or, if you like, we can do some comparisons between our results (once that I complete the implementation of my dynamic inflow model).

About the “largest loading contributor”, I do not understand your question; could you try to clarify?
From my understanding there is not a general rule, it should really depend on the different operating conditions. Furthermore, I would be tempted to consider the dynamic
stall contribution as higher. Indeed, with the dynamic inflow you model the unsteady phases between two stable conditions; therefore you improve the accuracy when
modelling the transition between one condition and the other, because you consider that the wake does not instantly adapts to the new load condition upon the rotor.
On the contrary, with the dynamic stall you can really model an higher load contribution, that would be neglected by a static stall model. So, I think that in general a
dynamic inflow model improves the accuracy of your angles of attack during unsteady phases, but does not forcedly predict higher loads than a static inflow; whereas,
a dynamic stall model allows capturing loads values that are underestimated by a static stall model when a sudden increase of angle of attack takes place.

I hope this helps a bit.