A Dyson/Hitachi style air multiplier shroud for a small ducted BLDC fan (listed below)
https://www.aliexpress.com/item/1005006532726309.html?spm=a2g0o.order_list.order_list_main.32.3b561802ML3iPh
Glue or silicone the slip joint.
The author marked this model as their own original creation.