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.

Fluctuating Lift and Drag Acting on a Cylinder in a Flow at Supercritical Reynolds Numbers

Abstract: The fluctuating lift and drag acting on a circular cylinder in a flow of an incompressible fluid at large Reynolds numbers were measured. Data on the root-mean-square values of the lift and drag coefficients, the extreme values of these coefficients, and their power spectra at various Reynolds numbers are presented.

On the force and moment on a body in an incompressible fluid, with application to rigid bodies and bubbles at high and low reynolds numbers

Abstract: An analysis is made of the force and moment exerted on a rigid body in unsteady motion in a uniform incompressible, viscous or inviscid fluid. Integral formulae are derived which express the force and moment in terms of the velocity and vorticity of the fluid and the velocity of the body. The results extend a previous investigation of this problem (1), and permit the identification of the separate influences of added mass, normal stresses induced by free vorticity, and viscous skin friction. Illustrative applications are made to airfoil theory, to the calculation of the induced drag of a vortex street and the force on a cylinder moving in a slowly varying rotational mean flow, and to the determination of the viscous drag experienced by solid spheres and bubbles. The theory gives a direct prediction of the drag on a bubble in high-Reynolds-number motion, in contrast to the usual approach in which the drag is determined by equating the viscous dissipation to the work done by the drag force.

How flexibility induces streamlining in a two-dimensional flow

Abstract: Recent work in bio-fluid dynamics has studied the relation of fluid drag to flow speed for flexible organic structures, such as tree leaves, seaweed, and coral beds, and found a reduction in drag growth due to body reconfiguration with increasing flow speed. Our theoretical and experimental work isolates the role of elastic bending in this process. Using a flexible glass fiber wetted into a vertical soap-film flow, we identify a transition in flow speed beyond which fluid forces dominate the elastic response, and yield large deformations of the fiber that greatly reduce drag. We construct free-streamline models that couple fluid and elastic forces and solve them in an efficient numerical scheme. Shape self-similarity emerges, with a scaling set by the balance of forces in a small “tip region” about the flow’s stagnation point. The result is a transition from the classical U2 drag scaling of rigid bodies to a new U4/3 drag law. We derive an asymptotic expansion for the fiber shape and flow, based on the le...