Drag coefficient cylinders

Calculated from drag coefficient for single cylinders using maximum velocity — Experimental... 

FIG. 6-57 Drag coefficients for spheres, disks, and cylinders =area of particle projected on a plane normal to direction of motion C = over-... 

The drag coefficients for disks (flat side perpendicular to the direction of motion) and for cylinders (infinite length with axis perpendicular to the direclion of motion) are given in Fig. 6-57 as a Function of Reynolds number. The effect of length-to-diameter ratio for cylinders in the Newton s law region is reported by Knudsen and Katz Fluid Mechanics and Heat Transfer, McGraw-Hill, New York, 1958). 

Figure 11-2 Drag coefficient for spheres, cylinders, and disks. (From Perry, 1984.) o Eq. (11-5), spheres. Eq. (11-7), cylinders.

For flow past a circular cylinder with L/d > normal to the cylinder axis, the flow is similar to over for a sphere. An equation that adequately represents the cylinder drag coefficient over the entire range of NRc (up to... 

As seen in Fig. 11-2, the drag coefficient for the sphere exhibits a sudden drop from 0.45 to about 0.15 (almost 70%) at a Reynolds number of about 2.5 x 105. For the cylinder, the drop is from about 1.1 to about 0.35. This drop is a consequence of the transition of the boundary layer from laminar to turbulent flow and can be explained as follows. 

Their curve for a long cylinder corresponds to drag coefficients 10-20% lower than those given by Pruppacher et al. (P8). The Pruppacher values are preferred, since they are based on a more extensive data compilation. 

Drag Coefficients and Terminal Velocities for Cylinders with Secondary Motion ... 

FIG. 6-57 Drag coefficients for spheres, disks, and cylinders A = area of particle projected on a plane normal to direction of motion C = overall drag coefficient, dimensionless Dp - diameter of particle Fd = drag or resistance to motion of body in fluid Re = Reynolds number, dimensionless u = relative velocity between particle and main body of fluid (I = fluid viscosity and p = fluid density. (From Lapple and Shepherd, Ind. Eng. Chem., 32, 60S [1940].)... 

Figure 5.1 Schematic showing the time history of lift and drags coefficients for flow past a circular cylinder at Re = 100.

The origin of the cyhndrical coordinate system (r, 0, z) is held fixed on the axis of one cylinder. The polar axis (6 = 0) is set parallel to the applied electric field E so that E is perpendicular to the cylinder axis. Let the electrolyte be composed of M ionic mobile species of valence zt and drag coefficient 2,- (i = 1, 2,. . . , M), and be the concentration (number density) of the /th ionic species in the... 

The average drag coefficients C j, for cross-flow over a smooth single circu lar cylinder and a sphere aie given in Fig, 7-17. The curves exhibit different behaviors in different ranges of Reynolds numbers ... 

Average drag coefficient for cross-flow over a smooth circular cylinder and a smooth sphere. From //. ScMichtift. Boyndary Layer Theory 7c. Copyright Q i979 The McGrow-Hill Companies. 

In the moderate range of 10 < Re < 1 O . Ihe drag coefficient remains relatively constant. This behavior is characteristic of blunt bodies. Tlie flow in the boundary layer is laminar in this range, but the flow in the separated region past the cylinder or sphere is highly turbulent with a wide turbulent wake. 

Once the drag coefficient is available, the drag force acting on a body in cross-flow can be determined from Fq. 7-1 where A is the frontal area (A = LD for a cylinder of length L and A for a sphere). It should be kept... 

The drag coefficient corresponding to this value is, from Fig. 7-17, Cy = 1.0. Also, the frontal area for flow past a cylinder is 4 = LD. Then the drag force acting on the pipe becomes... 

C Consider laminar flow of air across a hot circular cylinder. At what point on the cylinder will the heat liansfer be highest What would your answer be if the flow were turbulent 7-38C In flow over cylinders, why does ihe drag cocfTicient suddenly drop when the flow becomes turbulent Isn t turbulence supposed to increase the drag coefficient instead of decreasing it ... 

The literature in the field of fluid mechanics [8] provides us with an expression as the definition of the fiictional drag coefficient For spheres, disks, cylinders, and similar bodies, the diameter is... 

Some paradoxes of the turbulence in canopies, or EPRs, were pointed out by Raupach and Thom in their state-of-art review of 1981, [522], The first phenomenon is the value of the drag coefficient of elements that constitute the EPR. The highly precise measurements in aerodynamic tubes brought values that depend on the obstacle shape, the flow turbulence level, and the mutual disposition of obstacles but vary near cf 0.5 for spheres and cf 1 for cylinders in the working range of the local Reynolds number 103 < Re < 105. The same coefficient determined from the field measurements in forests turned out to be several times less (in this case, the indirect calculations were performed). A similar paradox takes place for the exchange coefficients. 

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