We created a very basic wind_plugin which just applies a force to some body, you can take a look at https://github.com/ethz-asl/rotors_simulator/blob/master/rotors_gazebo_plugins/src/gazebo_wind_plugin.cpp, maybe this is sufficient for your application, otherwise you could modify this and make it a world plugin such that it acts on multiple bodies.
We created a very basic wind_plugin which just applies a force to some body, you can take a look at https://github.com/ethz-asl/rotors_simulator/blob/master/rotors_gazebo_plugins/src/gazebo_wind_plugin.cpp, https://github.com/ethz-asl/rotors_simulator/blob/master/rotors_gazebo_plugins/src/gazebo_wind_plugin.cpp maybe this is sufficient for your application, otherwise you could modify this and make it a world plugin such that it acts on multiple bodies.