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.

Generalized Correlations for Inertial Impaction of Particles on a Circular Cylinder

Abstract: The trajectories of spherical particles impacting a relatively larger circular cylinder in crossflow are calculated using finite difference methods to solve the equations of motion in a Lagrangian form. Drag forces on the particles are described using an empirical correlation for the drag coefficient (as a function of Reynolds number) and the solution for steady, inviscid, incompressible flow (potential flow) around a circular cylinder. Numerical integration of the particle equations of motion is started upstream of the cylindrical target, and calculations are carried out until the particle impacts the cylinder or bypasses it completely. The effects of particle interception are neglected. Results for target efficiency and angle of impingement compare favorably with previous numerical solutions at low-particle Reynolds numbers but are found to be more accurate for free-stream velocity Reynolds numbers (Re0) > 1. In addition, results for particle velocity, angle of impact, and particle concentration are pre...

Tidal-scale hydrodynamics within mangrove swamps

Abstract: Both the drag force and the horizontal eddy viscosity play a dominant role in the tidal-scale hydrodynamics in mangrove wetlands. Using field observations and basic fluid mechanics laws, the drag coefficient and the coefficient of dynamic eddy viscosity are found to be predictable as a function of the Reynolds Number based on the characteristic length scale of the vegetation. The characteristic length scale of the vegetation varies greatly with vegetation species, vegetation density and tidal elevation. Both these coefficients decrease with increasing values of the Reynolds Number. At the low range of the Reynolds Number both these coefficients reach much higher values than those typical of vegetation-poor estuaries and rivers. Consequently, the tidal flow within mangrove areas depends to a large degree upon the submerged vegetation density that varies with the tidal stage. These findings may be applied also in other vegetated tidal wetlands, including salt marshes.

On Climatological Monthly Mean Wind Stress and Wind Stress Curl Fields over the World Ocean

Abstract: Using a version of the global surface marine observation historical data set, a new 1° spatial resolution global ocean surface wind stress climatology has been evaluated using the Large and Pond surface drag coefficient formulation. These new results are compared, after spatial smoothing, with those of Hellerman and Rosenstein, who used a different drag coefficient form. It is found that the new stresses are almost everywhere smaller than those of Hellerman and Rosenstein, often by 20%–30%, which is greater than the formal error estimates from their calculations. The stress differences show large-scale spatial structure, as would he expected given the spatial variation of the surface stability parameter and the known different wind variability regions. Basin zonally averaged Ekman transports are computed to provide perspective on the significance of the stress differences; annual mean differences can exceed 10 Sv (Sv = 106 m3 s−1) equatorward of 20° lat, but are smaller poleward. Wind stress curl...

Aerodynamic Shape Optimization of an Adaptive Morphing Trailing-Edge Wing

Abstract: Adaptive morphing trailing-edge wings have the potential to reduce the fuel burn of transport aircraft. However, to take full advantage of this technology and to quantify its benefits, design studies are required. To address this need, the aerodynamic performance benefits of a morphing trailing-edge wing are quantified using aerodynamic design optimization. The aerodynamic model solves the Reynolds-averaged Navier–Stokes equations with a Spalart–Allmaras turbulence model. A gradient-based optimization algorithm is used in conjunction with an adjoint method that computes the required derivatives. The baseline geometry is optimized using a multipoint formulation and 192 shape design variables. The average drag coefficient is minimized subject to lift, pitching moment, geometric constraints, and a 2.5g maneuver bending moment constraint. The trailing edge of the wing is optimized based on the multipoint optimized wing. The trailing-edge morphing is parameterized using 90 design variables that are optimized i...