A variable nozzle apparatus may include a radially inward structure and a radially outward structure circumscribing the radially inward structure. An annular flow channel is defined between the radially inward structure and the radially outward structure. One of the radially inward structure and the radially outward structure includes a static portion and a moveable portion. The moveable portion may be to the static portion via helical threads and may thus configured to rotate circumferentially and translate axially relative to the static portion. Movement of the moveable portion relative to the static portion may change a radial dimension of the annular flow channel.