Drag coefficient droplet

Due to computer storage and run time limitations, it is not yet possible to accurately model the details of flows around each individual droplet in a spray. Thus, empirical or semi-empirical correlations are typically used to model the exchange processes between droplets and gas. Correlations for drag coefficients have been suggested by many researchers.[45l[559h568Fl571l For thin sprays, the drag... 

In the droplet drag sub-modelT572 598 the effects of droplet distortion and oscillation due to droplet-gas relative motion on droplet drag coefficient are taken into account. Dynamical changes of the drag coefficient with flow conditions can be calculated with this submodel. Applications of the sub-models to diesel sprays showed that... 

Ci Substitution given in the text C2 Substitution given in the text CD Drag coefficient dimensionless d Diameter of the bubble, drop, droplet, cm... 

Treatment of liquid drops is considerably more complex than bubbles, since the internal motion must be considered and internal boundary layers are difficult to handle. Early attempts to deal with boundary layers on liquid drops were made by Conkie and Savic (C8), McDonald (M9), and Chao (C4, W7). More useful results have been obtained by Harper and Moore (HIO) and Parlange (PI). The unperturbed internal flow field is given by Hill s spherical vortex (HI3) which, coupled with irrotational flow of the external fluid, leads to a first estimate of drag for a spherical droplet for Re 1 and Rep 1. The internal flow field is then modified to account for convection of vorticity by the internal fluid to the front of the drop from the rear. The drag coefficient. 

Data predictions for droplets moving freely in turbulent gas streams are confounded by the problem of ballistics of droplets. Until the droplet is essentially accelerated or decelerated to the gas stream velocity, Reynolds number, thus Nusselt number, and thus X are changing constantly, and precise calculations require very small steps. The drag coefficient is of considerable importance. El Wakil, Uyehara, and Myers (117) em-... 

Problems pertinent to the combustion of sprays are discussed by Gerstein (5C). He places special emphasis on the distribution, dynamics, trajectories, and evaporation of droplets, and includes an additional section on drag coefficients. His list of references includes much of the latest work done in the field of spray combustion. 

Spilhaus 8P) treats the shape of falling drops and the variation of the drag coefficient. Langmuir and Blodgett 6P) present a mathematical investigation of water droplet trajectories. 

The vaporization rates and drag coefficients for 2,2,4-trimethylpentane (iso-octane) sprays in turbulent air streams were determined experimentally by Ingebo (40), who reported that the effect of relative velocity on the evaporation rate was represented by the 0.6 power of the Reynolds number and that the drag coefficient varied inversely with the relative velocity of the drops in the spray. By assuming that the evaporation rate was independent of velocity and the drag coefficient for droplets obeyed Stokes s law, the present author derived a mathematical theory for the ballistics of droplets injected into an air stream for which the velocity varied linearly with distance (57) and... 

CRE is the Boucher [3] Reynolds number calculation to derive a drag coefficient, CD. The CD factor is calculated in the program by a curve-fit equation as shown. The velocity, called the terminal droplet velocity, is calculated as the variable VT, also called the dropout velocity or the settling velocity. All three terms refer to this same variable. 

Ishii, M. and Zuber, N. (1979), Drag coefficient and relative velocity in bubbly, droplet or particulate flows, AIChE J., 15, 843-855. 

Ishii M, Zuber N (1978) Drag Coefficient and Relative Velocity in Bubbly, Droplet or Particulative Flows. AlChE J 25(5) 843-854... 

The drag force is given in terms of the droplet cross-sectional area, the vapor velocity and density, and the drag coefficient Cp. At the vapor flood velocity, the drag force is... 

Here, as usual, h and R denote the film thickness and radius, and R is the curvature radius of the spherical part of the particle surface. The dependence of the dimensionless drag coefficient, fy, on the distance h for different values of the ratio R/R is illustrated in Figure 5.49. The increase of R/R and the decrease of hlR may lead to an increase of the drag force,/j, by an order of magnitude. That is the reason the film between a deformed particle and a wall can be responsible for the major part of the energy dissipation. Moreover, the formation of doublets and flocks of droplets separated by liquid films seems to be of major importance for the rheological behavior of emulsions. 

A 6-in. thick demister pad for removing fine droplets of H2SO4 from a gas stream is made of 50-pm fibers randomly oriented in the plane perpendicular to the gas flow. The average porosity is 0.90. Calculate the pressure drop for gas velocities of 1 and 3 ft/s at 90°C and 1 atm using the drag coefficients for individual fibers. 

Keywords Drag coefficient Drag of deformed drops ing droplets Flow past a droplet Interacting drops... 

The equation of motion for a particle or droplet using the steady-state drag coefficient can be expressed as... 

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