Topic
Drag coefficient
About: Drag coefficient is a research topic. Over the lifetime, 14471 publications have been published within this topic receiving 303196 citations. The topic is also known as: drag factor.
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TL;DR: In this paper, a new method for predicting aluminum oxide particle size was developed for use in the Air Force Improved Solid Performance Program (SPP), which was compared with available particle size data.
Abstract: A new method for predicting aluminum oxide particle size was developed for use in the Air Force Improved Solid Performance Program (SPP). Theoretical models of particle growth and breakup in rocket nozzles were compared with available particle size data. It was found that no adequate theoretical model existed to relate particle size to propellant composition and motor parameters; therefore, an empirical approach was adopted using linear and nonlinear least-squares methods. Correlations were attempted with parameters, groupings, and functional forms suggested by the theoretical models. A relatively simple model employing only three free parameters was recommended for use in SPP. Nomenclature a = speed of sound CD = drag coefficient Dc = critical diameter for breakup £>, = diameter of particles in ith class D0 = diameter before breakup Dt = nozzle throat diameter D43 = mass-weighted average diameter dp = particle diameter Isp = specific impulse ni = number of particles in /th class n, m = generalized exponents m = motor mass flow rate P = pressure Rec = particle Reynolds number based on ac Ret = Reynolds number at nozzle throat Rc = nozzle throat radius of curvature R t = nozzle throat radius S = pcDt /ppdp = dimensionless scale parameter for two-phase flow s = estimate of standard deviation T = temperature Aw = magnitude of particle-gas velocity difference Vc = chamber volume a, j8 = generalized coefficients £ = aluminum oxide concentration, g-mole/lOOg fjig = gas viscosity pg = gas density PL = liquid density a = standard deviation of \ogloD\ surface tension T =pcyc/m = chamber residence time Subscripts
90 citations
TL;DR: In this paper, the hydrodynamic drag force exerted on an individual floc moving steadily through an quiescent Newtonian fluid over a wide range of Reynolds numbers was numerically evaluated.
90 citations
TL;DR: In this article, the effects of the wall temperature and Prandtl number on the predicted results have been analyzed, as well as the grid independency analysis, and the influence of cavity location, the length-to-depth ratio of the cavity and the molecular weight of the injectant on the flow field properties have been investigated.
90 citations
TL;DR: A two-dimensional two-phase fluiddynamic model with included k-ϵdiss turbulence model was used to calculate local values of velocity, holdup and effective viscosity of both phases as mentioned in this paper.
90 citations
TL;DR: In this paper, afterbody rounding of the roof/backlight intersection was shown to reduce drag up to 16% and additional rear curvature associated with side pillar rounding did not further modify the drag.
Abstract: Experimental analyzes were performed to understand the drag evolution and the flow field modifications resulting from afterbody rounding on the Ahmed body, a simplified vehicle model with 25 degrees rear slant. Curvature effects were investigated using balance measurements, flow visualizations, wall pressure, and particle image velocimetry measurements. The rear end of the original well-known Ahmed body has sharp connections between the roof and the rear window as well as squared rear pillars. Similarly to previous studies, rounding the roof/backlight intersection was shown to reduce drag up to 16 %. Surprisingly, additional rear curvature associated with side pillar rounding did not further modify the drag. However, the zero net effect was found to result from opposite drag effects on the slanted and vertical surfaces and to hide strong local modifications on the flow field. The tridimensional organization and vorticity transport in the near wake were analyzed and connected to the observed local increase in the pressure drag on the base. Finally, these results were shown to be generic for a realistic rounded-end car shape.
90 citations