Machinbird & Plumb Bob,
Good posts!
To add some information, when the outer shroud translates aft, blocker doors close off downstream flow path and cascade boxes (we called them egg crates) are exposed through which the fan flow exits in a forward direction. The smooth annular surface over which the flow turns outward into the cascades is called the Dagmar. Therefore, the fan flow first turned radially outward where it approaches the cascades. The cascade boxes are comprised of turbine-stator turning vanes which accelerate the flow to the minimum section at the exit. Most of the cascade boxes have radial outward exhaust in a direction 40 to 50 degrees axial. Some boxes provide other than radial outflow by skewing of the turning vanes or by virtue of axial vanes in an arrangement that resembles an egg crate.
Each cascade is special as to location, whether it is to be used on a lefthand or righthand engine, or a center engine as on a DC-10 or MD-11. It requires close teamwork with the aircraft manufacturer to establish the proper parameters of the cascade design in relation to the surrounding features.
Reverse thrust of the engine system alone results from three sources. The unaffected core engine thrust is more than overcome by the fan flow exhausting forward and by the fan and core flow ram drag. The ram drag is the largest of of the forces.
Reversers deployed after touchdown are generally used to speeds just above the speed at which reverse flow is re-ingested or cross ingested so as to affect engine operation. The range of speed is generally 120 knots down to 60 knots. In this speed regime, the aircraft drag is a large retarding force. However the reverse flow shrouds a part of the aircraft and changes the aircraft drag. This is why close coupling between the aircraft manufacturer and the thrust reversal system manufacturer is very important to gain the most efficient overall reversal system.
TD