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.

Fluid Flow Around and Heat Transfer From an Infinite Circular Cylinder

Abstract: In this study, an integral approach of the boundary layer analysis is employed to investigate fluid flow around and heat transfer from an infinite circular cylinder. The Von Karman‐Pohlhausen method is used to solve momentum integral equation and the energy integral equation is solved for both isothermal and isoflux boundary conditions. A fourth-order velocity profile in the hydrodynamic boundary layer and a third-order temperature profile in the thermal boundary layer are used to solve both integral equations. Closed form expressions are obtained for the drag and the average heat transfer coefficients which can be used for a wide range of Reynolds and Prandtl numbers. The results for both drag and heat transfer coefficients are in good agreement with experimental/numerical data for a circular cylinder. DOI: 10.1115/1.1924629

Axisymmetric Spindown Dynamics of Hurricane-like Vortices

Abstract: This work examines the spindown problem of hurricane-like vortices subject to a quadratic drag law in the surface layer. Since intense hurricanes over the open ocean are approximately axisymmetric due in part to Rossby elasticity and axisymmetrization processes that tend to keep the vortex erect and circular, the axisymmetric spindown problem serves as a useful benchmark. As a basis for the numerical experiments presented, the essential results of Eliassen and Lystad’s balanced spindown‐spinup theory are reviewed first. The theory is then tested with an axisymmetric Navier‐Stokes numerical model. The numerical experiments broadly confirm the theoretical predictions for a range of vortex heights, maximum tangential wind speeds, constant and variable drag coefficients, and vortex sizes considered relevant for tropical storm and hurricane strength vortices. But unlike the monotonic decay of the swirling flow predicted by theory, the numerical simulations reveal a temporary spinup of the tangential winds in the boundary layer before the demise of the vortex. The theory is shown to furnish a consistent description of the weakening phase of two hurricanes observed by research aircraft. Despite the idealizations employed to yield a tractable model, the theory appears useful in elucidating weakening episodes of hurricanes not associated with strong asymmetries.

The effect of observed ice conditions on the drag coefficient in the summer East Greenland Sea Marginal Ice Zone

Abstract: The summer East Greenland Sea marginal ice zone is a region characterized by extreme horizontal variations of surface roughness characteristics. The surface drag coefficient is found to be correlated with these roughness characteristics, in particular, ice concentration and ice floe roughness and size. The estimates of wind stress and wind speed yield neutral drag coefficients CDN with standard deviations of 2.3 ± 0.8 × 10−3 for areas with less than 40% ice concentration and 4.0 ± 1.1 × 10−3 for ice concentrations greater than 70%. Much of the variation in CDN for a given ice concentration is explained by differences in ice floe size and roughness. Very small, concentrated, rough floes that have been affected by wave action produce twice as much wind stress (CDN = 4.2 ± 0.7 × 10−3) as relatively large, flat floes (CDN = 2.1 ± 0.6 × 10−3) and 4 times as much as typical open ocean for a given wind speed and stability. The drag coefficients in this region are higher than other marginal ice zones, probably a result of the presence of large amounts of multiyear ice floes that extend higher above the ocean surface and create more drag than first-year floes.

Steady-State Numerical Solution of the Navier-Stokes and Energy Equations around a Horizontal Cylinder at Moderate Reynolds Numbers from 100 to 500

Abstract: A numerical analysis of forced-convection heat transfer from a horizontal stationary circular cylinder dissipating a uniform heat flux in a crossflow of air is conducted by solving the full two-dimensional steady-state Navier-Stokes and energy equations in the range of the Reynolds numbers from 100 to 500 (based on diameter). A numerical study by this author for Reynolds numbers less than 100 was previously conducted and therefore is not repeated here. Dependence on the Reynolds number of the flow and thermal fields, vorticity and pressure distributions, separation angle, drag coefficient, and local and average Nusselt number around the cylinder are shown. Correlations for the separation angle and drag coefficient as functions of Reynolds number are suggested. Quantities such as vorticity, pressure, and Nusselt number at the forward and rear (base) stagnation points are also calculated and correlated as functions of Reynolds number. The local and average values of the Nusselt numbers are shown to be in go...

In-flight particle velocity measurements with DPV-2000 in cold spray

Abstract: The measurements of in-flight particle velocities and deposition efficiency at cold spraying of two stainless 316L powders having different morphology and almost the same size distributions were carried out. It was found that the angular particle had faster velocity than spherical one and resulted in greater deposition efficiency. The critical velocity of both powders was almost the same and did not depend on their micro-hardness. Therefore, the deposition efficiency was not affected by the particle micro-hardness. The critical velocity significantly depended on He gas temperature and decreased as the temperature increases, but little depended on N2 gas temperature. The critical velocity little depended on operating gas pressure. The cause why the angular particle morphology gives faster velocity in supersonic gas flow compared with the spherical one has to be investigated and clarified. The drag coefficient appears to depend on particle morphology. An angular particle seems to have a larger drag coefficient than a spherical particle.