Engineering topics

Presz, W. M., Jr.

Publications and source records attributed to Presz, W. M., Jr..

4 records

NASA NTRS1986

Forced mixer lobes in ejector designs

Forced mixer lobes in augmentor primary ejectors obtain a 100-percent increase in pumping over conventional design, together with nearly complete mixing in very short mixing ducts, through the generation of large scale axial vorticity in the mixing duct. The vorticity causes rapid mixing of the primary and secondary flows with low losses; since mixing length is minimized, wall friction losses are reduced, allowing more secondary flow to be pumped for a given total pressure in the primary flow. Analytical results are presented that are judged to have significant implications for future ejector test work.

Presz, W. M., Jr.↗

NASA NTRS1980

Separation region on boattail nozzles

Computer subroutine package VISCUS offers flow analyst practical engineering computational procedure to model viscous effects of separated reverse flow on afterbody pressures and drag. Program is written in FORTRAN IV.

Buteau, J. D.↗

NASA NTRS1978

An improved analytical model of the separation region on boattail nozzles at subsonic speeds

A practical engineering calculation was developed to model the viscous effects of a separated, reverse flow region on afterbody pressures and drag. This viscous calculation was iteratively coupled with an inviscid flow calculation by means of an aerodynamic interface. A standard boundary layer displacement thickness was used to modify the afterbody shape where the flow was attached. A discriminating streamline calculation was developed to account for displacement effects of the reverse flow in separated regions with and without a flowing jet. The viscous flow calculation was coupled with a potential flow calculation. The analysis accurately predicted afterbody pressures and drag with variations in Reynolds number, Mach number, and afterbody shape.

Presz, W. M., Jr.↗

NASA NTRS1978

An improved analytical model of the separated region on nozzle boattails

A viscous flow calculation is formulated for modelling the effects of separated, reverse flow regions on nozzle afterbody pressures and drags at subsonic Mach numbers. A discriminating streamline approach is used. Effects of skin friction, axial pressure gradient, and nozzle jet entrainment on the separated discriminating streamline shape are included. The viscous flow calculation is coupled to a potential flow calculation. The combined analysis is found to accurately predict both the magnitude of the measured afterbody pressures and drag, and also their variation with Reynolds number, Mach number and afterbody shape.

Presz, W. M., Jr.↗