Within a wind plant exists a complex aerodynamic situation in which we find shear and buoyancy-driven turbulence of the atmospheric boundary layer, wind turbine wakes, and terrain induced flow structures. All of these components interact with one another, affect wind plant performance, and impose mechanical loads on the individual turbines. Because of the large scale and unsteady nature of wind plant aerodynamics, it is difficult to gain understanding through comprehensive field measurements, so simulation is playing an increasingly important role. This talk will give background on the wide range of wind-plant-aerodynamics simulation strategies, and then focus on the large-eddy simulation/actuator line approach being used at the National Renewable Energy Laboratory.