Topic

# Drag coefficient

About: Drag coefficient is a(n) research topic. Over the lifetime, 14471 publication(s) have been published within this topic receiving 303196 citation(s). The topic is also known as: drag factor.

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TL;DR: In this paper, an isothermal, one-dimensional, steady-state model for a complete polymer electrolyte fuel cell (PEFC) with a 117 Nation | membrane is presented, which predicts an increase in membrane resistance with increased current density and demonstrates the great advantage of a thinner membrane in alleviating this resistance problem.

Abstract: We present here an isothermal, one-dimensional, steady-state model for a complete polymer electrolyte fuel cell (PEFC) with a 117 Nation | membrane. In this model we employ water diffusion coefficients electro-osmotic drag coefficients, water sorption isotherms, and membrane conductivities, all measured in our laboratory as functions of membrane water content. The model pre.dicts a net-water-per-proton flux ratio of 0.2 H20/H § under typical operating conditions, which is much less than the measured electro-osmotic drag coefficient for a fully hydrated membrane. It also predicts an increase in membrane resistance with increased current density and demonstrates the great advantage of a thinner membrane in alleviating this resistance problem. Both of these predictions were verified experimentally under certain conditions.

2,765 citations

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TL;DR: In this article, a comparison of the dissipation and Reynolds flux results shows excellent agreement on average, for wind speeds from 4 to 20 m s−1, for a modified Gill propeller-vane anemometer was used to measure the velocity.

Abstract: Measurements of the momentum flux were made by the Reynolds flux and dissipation methods on a deep water stable tower operated by the Bedford Institute of Oceanography, A modified Gill propeller-vane anemometer was used to measure the velocity. Drag coefficients from 196 Reynolds flux measurements agree well with those reported in Smith (1980) based on independent observations at the same site. Based on 192 runs, a comparison of the dissipation and Reynolds flux results shows excellent agreement on average, for wind speeds from 4 to 20 m s−1. The much more extensive dissipation data set (1086 h from the tower and 505 h from the weathership PAPA, CCGS Quadra) was used to investigate the dependence of the drag coefficient on wind speed, fetch and stability. The drag coefficient reduced to 10 m height and neutral conditions (CDN), is independent of stability and fetch (for fetch/height ≳800) but increases with wind speed above 10 m s−1. Some time series of the momentum flux and drag coefficient are ...

2,480 citations

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TL;DR: The experiments of McDonald and his co-workers have shown that in the larger arteries of the rabbit and the dog there is a reversal of the flow, and the simple mathematical treatment has strong similarities with the theory of the distribution of alternating current in a conductor of finite size.

Abstract: The experiments of McDonald and his co-workers (McDonald, 1952, 1955; Helps & McDonald, 1953) have shown that in the larger arteries of the rabbit and the dog there is a reversal of the flow. Measurements of the pressure gradient (Helps & McDonald, 1953) showed a phase-lag between pressure gradient and flow somewhat analogous with the phase-lag between voltage and current in a conductor carrying alternating current, and the simple mathematical treatment given below has strong similarities with the theory of the distribution of alternating current in a conductor of finite size.

1,542 citations

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TL;DR: In this article, the relative motion correlations for dispersed two-phase flows of bubbles, drops, and particles were developed from simple similarity criteria and a mixture viscosity model, and satisfactory agreements were obtained at wide ranges of the particle concentration and Reynolds number.

Abstract: Drag coefficient and relative motion correlations for dispersed two-phase flows of bubbles, drops, and particles were developed from simple similarity criteria and a mixture viscosity model. The results are compared with a number of experimental data, and satisfactory agreements are obtained at wide ranges of the particle concentration and Reynolds number. Characteristics differences between fluid particle systems and solid particle systems at higher Reynolds numbers or at higher concentration regimes were successfully predicted by the model. Results showed that the drag law in various dispersed two-phase flows could be put on a general and unified base by the present method.

1,472 citations

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TL;DR: In this paper, explicit equations for the drag coefficient and for the terminal velocity of falling spherical and nonspherical particles are developed for the CD and ut. The goodness of fit of these equations to the reported experimental data is evaluated and compared with that of other recently proposed equations.

Abstract: Explicit equations are developed for the drag coefficient and for the terminal velocity of falling spherical and nonspherical particles. The goodness of fit of these equations to the reported experimental data is evaluated and is compared with that of other recently proposed equations.
Accurate design charts for CD and ut are prepared and displayed for all particle sphericities.

1,382 citations