This talk will first review the importance of buffeting of the rotor blades of Horizontal Axis Wind Turbines and Tidal-Stream Turbines (HAWTs and HATTs) and discuss various associated phenomena such as dynamic stalling, 3-D stall delay and dynamic inflow. The main new work which will then be presented is an analysis of the distortion of atmospheric or tidal-stream turbulence as it passes through the inflow of a rotor, some comparisons of full-scale measured data with theory and a rapid, semi-empirical calculation method for the resulting flow field. Finally the seminar will discuss the prediction of the mean and turbulent flow fields of rotor wakes and the effects of wake impact on downstream rotors in a wind-farm or tidal array.