科研之友
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摘要
The fluid-structure interactions between a flexible web and an externally pressurized air cushion are modeled allowing for the possibility of contact. The web is wrapped around a porous, cylindrical turn-bar at an oblique angle (helically). The turn-bar supplies pressurized air into the web/turn-bar clearance to float the web. The shell model, developed to represent the mechanics of the web, allows it to be wrapped around the cylinder in a helical fashion. The fluid mechanics of the air in the web/turn-bar clearance is a two-dimensional form of the incompressible Navier-Stokes equations averaged in the clearance direction and augmented by nonlinear source terms. Contact between the web and the reverser, which is undesirable in a turn-bar application, is included in the model in order to enable the analysis of the limiting cases. The coupled equilibrium between fluid mechanics, shell deflections and contact is found numerically. This paper describes the theory. Case studies are conducted in order to understand the mechanics of the coupled system, and to make design recommendations. It is shown that the helix angle has a strong influence on the equilibrium configurations: increasing helix-angle results in increased web-reverser separation, while the air pressure settles to a lower value. This behavior is due to the reduced shell stiffness and belt-wrap pressure for the helically wrapped webs. Conditions that render a nearly uniform web/turn-bar clearance in the circumferential direction are identified. The supply pressure and airflow rates necessary to prevent web-scratches are calculated.
- 出版日期2007-7
- 单位东北大学
