WATER-FLOW THROUGH VESSEL PERFORATION PLATES - THE EFFECTS OF PLATE ANGLE AND THICKNESS FOR LIRIODENDRON-TULIPIFERA

The effects of scalariform perforation plate thickness and angle within vessel elements of Liriodendron tulipifera were studied with a computational fluid dynamical model. The pressure gradient and hence resistance to flow through the plate increased as the perforation plate increased in thickness. Increasing the angle of the plate relative to the axis of the vessel (same number of pores) also increased the pressure gradient along the modelled cell. For the model matching the actual vessel element, the plate contributed 8% to the flow resistance of the vessel element. This contribution increased only to 11% for doubled plate thickness, and to 14% for a plate at an angle of 60-degrees to the vessel axis. The perforation plate altered the velocity profile across the vessel element, but to a different extent depending on the angle of the plate. A plate at an acute angle to the vessel axis has little effect on the paraboloid profile as found upstream from the plate, while obtuse angle plates change the flow profile such that fluid through pores near the wall is accelerated to a greater velocity than found in the centre of the cell.