Basset coefficient

In the creeping flow range, C is equal to the ratio of the terminal velocity to the terminal velocity in continuum flow. The value of C is sensitive to the nature of molecular reflections from the surface of the particle (E5). The accommodation coefficient, o-r, may be interpreted as the fraction of molecules undergoing diffuse reflection, the balance being specularly reflected. Typical values for lie between 0.8 and unity. For near-continuum flow. Basset (B9) showed that... 

A is the friction force coefficient B is the inertia correction coefficient and C is the resistance coefficient due to the Basset force. Equation (6.65) gives... 

Basset force coefficient Transversal lift coefficient Eulerian quantity at node n ... 

A portion of this supersonic velocity will be transferred to the injected powder particles, that is the powder particles will gain acceleration from the plasma jet by momentum transfer. The particle acceleration dUp/df is proportional to the drag coefficient CD and the velocity gradient between the gas velocity and the particle velocity, Vg — Vp and inversely proportional to the particle diameter dp and the particle density pp as expressed by the Basset-Boussinesq-Oseen equation of... 

The second term is the added mass term where is the added mass coefficient. The last term in Eq. (46) is the Basset history term where C is the history coefficient, Qj is the density of the fluid, Pf the viscosity of the fluid and

dummy parameter. In most cases the added mass and the history terms are orders of magnitude less than the drag term and, consequently, may be neglected leading to the equation ... 

There is no analytic nor numerical model available, which provides the particle drag coefficient for particles over all the regimes of rarefied flows. The earlier methods to correct for rarefied flow effects were based on a correction to Stokes drag, derived by Basset to account for velocity slip at the surface. In that case, the drag coefficient can be expressed as... 

Example 3-1 Consider the motion of a 1000-/xm-diameter coal particle with specific gravity = 1.2 being accelerated with air from an initial velocity of 0.305 m/sec to a steady state in an airstream having a temperature of 21°C and 2027 kN/m pressure. Assume at all times that Up— Uf, Find the time necessary to accelerate this particle to a condition where Uf = 15.24 m/sec. Use Newton s range drag coefficients over the acceleration period and assume that terms C and D in Eq. 3-1 are significant. Ignore the Basset contribution. 

The influence of the Basset term on dispersion coefficients and phenomena (Picart et al 1982 Picart, 1984). 

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