Print Email Facebook Twitter Experimental analysis on the dynamic wake of an actuator disc undergoing transient loads Title Experimental analysis on the dynamic wake of an actuator disc undergoing transient loads Author Yu, W. (TU Delft Wind Energy) Hong, V.W. Ferreira, Carlos (TU Delft Wind Energy) van Kuik, G.A.M. (TU Delft Wind Energy) Date 2017-10-01 Abstract The Blade Element Momentum model, which is based on the actuator disc theory, is still the model most used for the design of open rotors. Although derived from steady cases with a fully developed wake, this approach is also applied to unsteady cases, with additional engineering corrections. This work aims to study the impact of an unsteady loading on the wake of an actuator disc. The load and flow of an actuator disc are measured in the Open Jet Facility wind tunnel of Delft University of Technology, for steady and unsteady cases. The velocity and turbulence profiles are characterized in three regions: the inner wake region, the shear layer region and the region outside the wake. For unsteady load cases, the measured velocity field shows a hysteresis effect in relation to the loading, showing differences between the cases when loading is increased and loading is decreased. The flow field also shows a transient response to the step change in loading, with either an overshoot or undershoot of the velocity in relation to the steady-state velocity. In general, a smaller reduced ramp time results in a faster velocity transient, and in turn a larger amplitude of overshoot or undershoot. Time constants analysis shows that the flow reaches the new steady-state slower for load increase than for load decrease; the time constants outside the wake are generally larger than at other radial locations for a given downstream plane; the time constants of measured velocity in the wake show radial dependence.The data are relevant for the validation of numerical models for unsteady actuator discs and wind turbines, and are made available in an open source database (see Appendix). To reference this document use: http://resolver.tudelft.nl/uuid:6d3166f0-ec3f-413d-9ce5-b2111e15be74 DOI https://doi.org/10.1007/s00348-017-2432-9 ISSN 0723-4864 Source Experiments in Fluids: experimental methods and their applications to fluid flow, 58 (10) Part of collection Institutional Repository Document type journal article Rights © 2017 W. Yu, V.W. Hong, Carlos Ferreira, G.A.M. van Kuik Files PDF 10.1007_s00348_017_2432_9.pdf 3.05 MB Close viewer /islandora/object/uuid:6d3166f0-ec3f-413d-9ce5-b2111e15be74/datastream/OBJ/view