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.

An Experimental Study on Aerodynamic Drag of Rectangular Cylinders

Abstract: An experimental study is carried out on the aerodynamic drag of rectangular cylinders, where the REYNOLDS number ranges up to 6×104. It is revealed that the drag coefficient, CD, varies con-siderably with the d/h ratio of rectangles, and that the maximum value of CD is as high as 2.6 for d/h of 2/3 compared with CD of about 2.0 for the cases of flat plate and square cylinder (Fig.1). The STROUHAL number of the shedding vortices, on the contrary, remains approximately constant for d/h up to 1.0, decreases slowly for larger values of d/h, and then increases abruptly at d/h ratio of about 2.8 (Fig.2), where the flow reattaches on the lateral surfaces of the cylinder.

The fall of single liquid drops through water

Abstract: The steady motion of single drops of ten organic liquids falling through a stationary water field is discussed. A correlation is presented for nine systems with the exception of the aniline-water system, in the form of a single curve relating the drag coefficient, Weber number, Reynolds number, and a physical property group. The curve can be used directly to predict the terminal velocity, drag coefficient, Reynolds number, and Weber number for any given equivalent drop size. A break point in the curve serves to predict the peak velocity and its related quantities. The critical drop size is predicted from the pertinent physical properties alone. All these estimations were accurate within 10% for the systems used. The interfacial tensions ranged from 24 to 45 dynes/cm. and the drop densities from 1.100 to 2.947g./ml., the latter resulting in a twentyfold range of density differences. The drop viscosities had no apparent effect.

On the equation for spherical-particle motion: effect of Reynolds and acceleration numbers

Abstract: The existing model equations governing the accelerated motion of a spherical particle are examined and their predictions compared with the results of the numerical solution of the full Navier–Stokes equations for unsteady, axisymmetric flow around a freely moving sphere injected into an initially stationary or oscillating fluid. The comparison for the particle Reynolds number in the range of 2 to 150 and the particle to fluid density ratio in the range of 5 to 200 indicates that the existing equations deviate considerably from the Navier–Stokes equations. As a result, we propose a new equation for the particle motion and demonstrate its superiority to the existing equations over a range of Reynolds numbers (from 2 to 150) and particle to fluid density ratios (from 5 to 200). The history terms in the new equation account for the effects of large relative acceleration or deceleration of the particle and the initial relative velocity between the fluid and the particle. We also examine the temporal structure of the near wake of the unsteady, axisymmetric flow around a freely moving sphere injected into an initially stagnant fluid. As the sphere decelerates, the recirculation eddy size grows monotonically even though the instantaneous Reynolds number of the sphere decreases.