摘要:

The unsteady (oscillatory) Stokes resistance is numerically computed for finite‐length, circular cylinders using a first‐kind, boundary integral formulation for low and moderate dimensionless frequencies. Translational oscillations parallel and perpendicular to the cylinder axis (axial and transverse oscillations) are considered. For arbitrarily oriented cylinders with length‐to‐width ratios in the range: 1/10≤a/b≤10, a simple, previously proposed, expression accurately (±5%) describes the oscillatory Stokes resistance at all frequencies in terms of steady Stokes and inviscid flow resistance parameters. Numerical calculations for spheroids agree with previous results; the results for cylinders and transverse oscillations of oblate spheroids are new.

ISSN:0899-8213    

DOI:10.1063/1.858707

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A comparison between the inner regions of self‐preserving turbulent boundary layers over an impervious wall and a porous surface with a uniform moderate suction rate indicates that, in each case, the relevant velocity and length scales are those of the ‘‘active’’ motion. There is close agreement between the two flows for velocity and temperature variances and longitudinal heat fluxes when the measurements are conditioned on only the negative part of the Reynolds shear stress and are normalized by the scales of the active motion

ISSN:0899-8213    

DOI:10.1063/1.858708

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Nuclear magnetic resonance (NMR) imaging is a noninvasive technique that allows velocity measurement in systems where classical techniques are not suitable due either to opacity or the presence of a solid phase. NMR velocity phase encode measurements for the flow of fiber suspensions yield quantitative data for the average flow field in the suspensions and qualitative information on the microscopic nature of the flow. Bulk translational motion causes modulation of the phase of the sample magnetization which provides information on the average velocity field within the sample. Motions on spatial and time scales that are small relative to the measurement scales cause damping of the magnetization, as reflected by signal attenuation.

ISSN:0899-8213    

DOI:10.1063/1.858709

出版商:AIP    

年代:1993

数据来源: AIP

ISSN:0899-8213    

DOI:10.1063/1.858710

出版商:AIP    

年代:1993

数据来源: AIP