**5. Conclusions**

In this work we investigated the wake from a full-scale turbine (T80) and a subscale turbine (T27) using the VFS-Wind code to carry out large-eddy simulation with actuator surface models for turbine blades and nacelle. The T80 turbine is 2.96 times larger than the T27 turbine in terms of both rotor diameter and hub height. In both cases, the same turbulent inflow is employed. The same lift and drag coefficients are also employed for the two turbines. The key differences between the inflows for the two cases are the different distributions of wind shear and turbulence intensity across the rotor caused by different rotor diameters and different hub heights. The computed results show differences between the two cases for both velocity deficits and turbine-added turbulence kinetic energy. It is observed that the wake center of the T27 turbine shifts upwards in the far wake of the turbine (e.g., more than 0.5*D* above the hub height at 10*D* downwind the rotor), which remains at hub height for the T80 turbine. The maximum turbulence kinetic energy in the wake of the T27 turbine is higher than that from the T80 case in the near wake region (e.g., more than 20% higher at 2*D* downwind the rotor), but decreases rapidly and becomes lower than that from the T80 turbine at further downwind locations (e.g., about 50% lower at 8*D* downwind the rotor). We explore the reason for these differences by examining the budgets for the mean kinetic energy. Compared with the T80 case, we found that the MKE entrainment for the T27 case is higher for the lateral component of the turbulence convection term, while lower for the vertical component of the turbulence convection term. This explains the upward shift of wake center for the T27 case. We also examined the turbulence production term. It is observed that the magnitude of the turbulence production term from the T27 case is significantly higher than that from the T80 case in the near wake region, which explains the higher turbulence kinetic energy in the near wake for the T27 case. Both the inflow turbulence and the size of the turbine relative to the incoming eddies may cause these observed differences in the wake characteristics. Further study (e.g., space-time correlation study [35]) is needed to probe in more depth the underlying cause for the differences between the two turbines of different scales. A systematic study on the wakes from turbines of different scales for different turbulent inflows is also needed to further investigate the phenomenon observed in this work.

**Author Contributions:** Conceptualization, D.M., X.Y. and F.S.; methodology, X.Y. and D.F.; software, X.Y. and D.F.; validation, X.Y. and D.F.; resources, D.M.; writing—original draft preparation, X.Y.; writing—review and editing, X.Y., D.F., C.K., D.M. and F.S.; visualization, X.Y.; supervision, F.S.; project administration, F.S. and D.M.; funding acquisition, F.S. and D.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by Department of Energy DOE (DE-EE0002980, DE-EE0005482 and DE-AC04- 94AL85000). Computational resources were provided by Sandia National Laboratories and the University of Minnesota Supercomputing Institute.

**Conflicts of Interest:** The authors declare no conflict of interest.
