Commercial blown film production is often limited by the rate of cooling that can be achieved in the production line.  The flow of the cooling air (through narrow passages and around the curved bubble) is characterized by rather complex aerodynamics, including the Venturi and Coanda effects.” To see full the full text of the article “The Aerodynamics of Blown Film Bubble Cooling”  click on the attachment link below.  These papers posted with permission. The Aerodynamics of Blown Film Bubble Cooling