Extracting from fluid flow dynamics...these photos reveal key features of the Aerator air injection design. The spillway water flow will "fall" in a curve from the upper lip as the flow has a given inertial velocity. This forms a lower pressure cavity region at the face of the vertical lip. Using this low pressure formation, the placement of an "air vent" at this low pressure area facilitates a volume of air to be drawn into the crease region or the face region of the vertical step.
This natural energy powered arrangement is formed as the air vent is part of a hollow box concrete column. The column is the inlet to the air. Not sure from he shadows of the concrete inlet if column has an internal taper to the "box" outline into the smaller area of the "air vent". This is important to insure a clean laminar airflow while avoiding a resonant pulsation effect. A non-tapered "bottom" design could resonate a bit like a church organ pipe and hinder the intended maximum airflow injection & pressure. Overall, a simple and elegant design. If it does resonate with "pulsations", the acoustics of this may be interesting, but not amusing to the nearby homeowners to the dam.
Another feature is observed in a special pour of "rough surface" concrete at the sidewall at the Aerator lip. This "rough surface" will induce a turbulence to the sidewall surface water flow - most likely to prevent vortices from forming at the post drop lip sidewall. This is a similar effect type of design used in aircraft wings where little metal tabs are spaced along a section of the wing to keep the airflow from separating from the wing's surface (forming oscillatory vortices and destabilizing lift/control/efficiency).
The main goal of an Aerator design is to inject as much air bubbles as efficiently as possible without creating disruptive oscillatory conditions, pulsations, or vortices. It will be interesting to see how far the air penetrates in the crease region to the center regions of the spillway.
Note: Answer on the "large crane" in the spillway - DWR revealed in a recent press update that Kiewit will disassemble the crane in the spillway and truck out the crane components through the Gates. No mention of the "trucking out timeframe" considering the curing of the fresh patchwork on the Upper Spillway. It's possible that plates may laid down to drive over any "patches" still in any sensitive curing window from any tire weight distribution. I guess DWR is not as concerned now about PR of getting the crane out quickly.
Crane lifting out Small Excavator - Nov 1. Note the custom "rough surface" concrete on the sidewall at the Aerator transition slab - plus the Aerator "Air Injection" vent at the RCC level.
Closer view of the custom "rough surface" concrete and the lighting shadows revealing the "Air Injection" vent at the sidewall lip of the Aerator lift. Air will be pulled into and underneath the "curved fall" of the spillway waterflow. Hollow "box column" allows a volume of Air to flow down into this vent via "differential pressure" formation.
