A comparison between the gas density in two simulations of a superwind, 7.5 Myr after the start of the starburst event (box height = 11.7 kpc; color scale is log particle number density: -3.5 (purple) to 1 (red) ). The only substantive difference between the model parameters in the two simulations is the different distribution of the disk ISM. In the left hand image (model tbn_1 of Strickland & Stevens 2000) the disk has a large vertical scale height, which tends to confine the wind more initially, and leads to more entrainment of dense disk ISM into the wind, as compared to the model shown on the right (model mod_3).
Gas density in a higher resolution (cell size 7.3 pc) simulation of a superwind. Compared to the images on the equivalent lower resolution model tbn_1 above there is a clear increase in spatial structure associated with entrained dense ambient gas (this is the material seen as warm ionized and warm neutral gas in superwinds). Theoretical models of winds must strive for high resolution in order to follow gas entrainment accurately.
Both images taken from the website of Dave Strickland.