Engineering topics

Ludwieg, H.

Publications and source records attributed to Ludwieg, H..

3 records

NASA NTRS1984

Stability of fluid flow in a cylindrical annulus

Helical flow in an annulus between two coaxial cylinders is investigated with regard to its stability against the formation of helical vortices of the type known as Taylor's annular vortices. Assuming the annulus to be small and the velocities to vary linearly with radius, it is shown that the problem can be reduced to the classical case of flow between two rotating cylinders. An appropriate stability criterion for helical flows is derived from Rayleigh's stability criterion applicable to such flows.

Ludwieg, H.↗

NASA NTRS1980

An explanation of the instability of the free vortex cores occurring over delta winds with raised edges

By rolling up the surfaces of discontinuity originating from the leading edge of delta wings, free vortex cores are formed above the wing. In case of greater angles of incidence, the flow in these vortex cores shows an instability which abruptly produces strong turbulence. In the present paper an explanation is given of this instability being a "frictionless instability" of the vortex core flow by increasing helical interference vortices. The occurring vortex core flows are calculated and investigated for stability by means of a stability criterion concerning flows with helical streamlines given by H. Ludwieg.

Ludwieg, H.↗

NASA NTRS1947

Drag Corrections in High-Speed Wind Tunnels

In the vicinity of a body in a wind tunnel the displacement effect of the wake, due to the finite dimensions of the stream, produces a pressure gradient which evokes a change of drag. In incompressible flow this change of drag is so small, in general, that one does not have to take it into account in wind-tunnel measurements; however, in compressible flow it beoomes considerably larger, so that a correction factor is necessary for measured values. Correction factors for a closed tunnel and an open jet with circular cross sections are calculated and compared with the drag - corrections already bown for high-speed tunnnels.

Ludwieg, H.↗