Abstract: The acute and chronic devices and methods described herein include a body lumen fluid flow modulator including an upstream flow accelerator and a downstream flow decelerator. The fluid flow modulator preferably includes one or more openings that define a gap/entrainment region that provides a pathway through which additional fluid from a branch lumen(s) is entrained into the fluid stream flowing from the upstream flow accelerator to the downstream flow decelerator. Delivery devices including a sheath and inner assembly also are provided for delivering the flow modulator to the body lumen. The delivery device may maintain the flow modulator in its collapsed, delivery state upon retraction of the sheath for ease of readjustment within the body lumen prior to full deployment of the flow modulator within the body lumen.