Analysis of direct force measurements during capillary pinching of visco-elastic fluids in CaBER type experiments

The Casimir force is an effect of quantum vacuum field fluctuations, with applications in many domains of physics. The ideal expression obtained by Casimir, valid for perfect plane mirrors at zero temperature, has to be modified to take into account the effects of the optical properties of mirrors, thermal fluctuations, and geometry. After a general introduction to the Casimir force and a description of the current state of the art for Casimir force measurements and their comparison with theory, this chapter presents pedagogical treatments of the main features of the theory of Casimir forces for one-dimensional model systems and for mirrors in three-dimensional space.

Download Full-text

Friction force measurements relevant to de-inking by means of atomic force microscope

Journal of Colloid and Interface Science ◽

10.1016/j.jcis.2005.05.040 ◽

2005 ◽

Vol 291 (2) ◽

pp. 361-368 ◽

Cited By ~ 15

Author(s):

Katarina Theander ◽

Robert J. Pugh ◽

Mark W. Rutland

Keyword(s):

Atomic Force Microscope ◽

Friction Force ◽

Force Measurements ◽

Atomic Force

Download Full-text

Flow force measurements and the wake transition in purely inline vortex-induced vibration of a circular cylinder

Physical Review Fluids ◽

10.1103/physrevfluids.4.034701 ◽

2019 ◽

Vol 4 (3) ◽

Author(s):

Tyler D. Gurian ◽

Todd Currier ◽

Yahya Modarres-Sadeghi

Keyword(s):

Circular Cylinder ◽

Force Measurements ◽

Vortex Induced Vibration ◽

Wake Transition

Download Full-text

Maximizing the efficiency of a flexible propulsor using experimental optimization

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.35 ◽

2015 ◽

Vol 767 ◽

pp. 430-448 ◽

Cited By ~ 63

Author(s):

Daniel B. Quinn ◽

George V. Lauder ◽

Alexander J. Smits

Keyword(s):

Leading Edge ◽

The Body ◽

Phase Lag ◽

Force Measurements ◽

Experimental Optimization ◽

Image Velocimetry ◽

Flexible Panel ◽

Gradient Based ◽

Power Scale ◽

Effective Angle

AbstractExperimental gradient-based optimization is used to maximize the propulsive efficiency of a heaving and pitching flexible panel. Optimum and near-optimum conditions are studied via direct force measurements and particle image velocimetry (PIV). The net thrust and power scale predictably with the frequency and amplitude of the leading edge, but the efficiency shows a complex multimodal response. Optimum pitch and heave motions are found to produce nearly twice the efficiencies of optimum heave-only motions. Efficiency is globally optimized when (i) the Strouhal number is within an optimal range that varies weakly with amplitude and boundary conditions; (ii) the panel is actuated at a resonant frequency of the fluid–panel system; (iii) heave amplitude is tuned such that trailing-edge amplitude is maximized while the flow along the body remains attached; and (iv) the maximum pitch angle and phase lag are chosen so that the effective angle of attack is minimized. The multi-dimensionality and multi-modality of the efficiency response demonstrate that experimental optimization is well-suited for the design of flexible underwater propulsors.

Download Full-text