5/28/2023 0 Comments Rotor blades in forward flightIt is worth noting that these experimental results are not based on a measured induced velocity in wind tunnel or free-flight, rather the total power consumption of the rotor was measured and simple momentum theory-like relations were assumed to arrive at the corresponding uniform induced inflow velocity. When experimental measurements are laid on this figure, notwithstanding the scatter in the measurements, they largely follow the trend of the solid lines. An alternate way of presenting the same results is by plotting the total inflow velocity on the y-axis. This is because the flow is highly turbulent in these scenarios and the simple momentum theory does not capture that and incurs an error. However, if the results were simply extended (denoted using dashed lines) to regions that we now understand to be the turbulent wake state or the vortex ring state, the results would not match with that observed in reality (solid lines). The variation would then be as denoted by the solid lines. While not explicitly derived as part of the lectures, the inflow velocity during the windmill brake state can be derived using momentum theory along the lines of the derivation for the normal working state. The following show induced velocity of the rotor as a function of climb velocity (negative climb velocity denotes a descent flight state).
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