Density-dependent drag coefficient for gas-adsorbed particles in free-molecule flows

Drag force, diffusion coefficient, and electric mobility of small particles. I. Theory applicable to the free-molecule regime.

The transport of small particles in the free-molecule regime is investigated on the basis of gas kinetic theory. Drag force formulations were derived in two limiting collision models-namely, specular and diffuse scattering-by considering the potential force of interactions between the particle and fluid molecules. A parametrized drag coefficient equation is proposed and accounts for the transit...

A New Correlation for Drag Coefficient of Extrudate Quadralobe Particles by CFD Simulation

Compressible Flows with a Density-Dependent Viscosity Coefficient

We prove the global existence of weak solutions for the 2-D compressible Navier-Stokes equations with a density-dependent viscosity coefficient (λ = λ(ρ)). Initial data and solutions are small in energy-norm with nonnegative densities having arbitrarily large sup-norm. Then, we show that if there is a vacuum domain at the initial time, then the vacuum domain will retain for all time, and vanish...

Free molecular gas drag on fluffy aggregates

Dynamical behaviors of dust particles are governed by gas drag forces in a variety of environments of astrophysical interest, such as protoplanetary disks, upper planetary atmospheres or cometary coma. Monte Carlo (MC) and Quasi Monte Carlo (QMC) simulations have been performed to estimate the drag forces on fluffy aggregates in the free molecular limit, using two different models of molecule-s...

Comparison of formulas for drag coefficient and settling velocity of spherical particles

Two formulas are proposed for explicitly evaluating drag coefficient and settling velocity of spherical particles, respectively, in the entire subcritical region. Comparisons with fourteen previously-developed formulas show that the present study gives the best representation of a complete set of historical data reported in the literature for Reynolds numbers up to 2×10.