Engineering topics

Moser, Robert D.

Publications and source records attributed to Moser, Robert D..

21 records · Page 2

NASA NTRS1989

On the secondary instability in plane Poiseuille flow

Numerical experiments were performed to clarify apparent differences between experimental observations and a theoretical prediction of the secondary instability in plane Poiseuille flow. It is shown that subharmonic breakdown is unlikely in natural transition as a result of the initial growth of what we call the 'minus' modes and consequent forcing of Orr-Sommerfeld modes present in the background noise. Subharmonic breakdown was achieved only when these minus modes were continuously suppressed.

Kim, John↗

NASA NTRS1989

Characteristic-eddy decomposition of turbulence in a channel

Lumley's proper orthogonal decomposition technique is applied to the turbulent flow in a channel. Coherent structures are extracted by decomposing the velocity field into characteristic eddies with random coefficients. A generalization of the shot-noise expansion is used to determine the characteristic eddies in homogeneous spatial directions. Three different techniques are used to determine the phases of the Fourier coefficients in the expansion: (1) one based on the bispectrum, (2) a spatial compactness requirement, and (3) a functional continuity argument. Similar results are found from each of these techniques.

Moin, Parviz↗

NASA NTRS1989

The development of three-dimensional temporally-evolving mixing layers

The temporal development of three-dimensional mixing layers subjected to a broad range of low-wavenumber three-dimensional initial disturbances is examined. Particular attention is paid to the development of the coherent structures in the flow during rollup and pairing. New vortex structures, including cup-like and hoop-like structures, are observed. Despite the sensitivity of the flow to initial conditions a 'typical' development is observed.

Rogers, Michael M.↗