Theoretical study of thermophoretic impulsive force exerted on a particle in fluid

Thermophoresis has important applications in microparticle separation, colloidal crystal growth processes and other fields. Considering the unsteady variation of the temperature gradient in the fluid, the viewpoint that particles in fluids will experience thermophoretic impulsive force is proposed. The force is related to the particle motion in thermophoresis but different from the traditional thermophoretic force. The basic approach to obtain the expression of thermophoretic impulsive force has been introduced. In analogy with the additional mass force and Basset force on a particle in unsteady flows, the expression for thermophoretic impulsive force exerted on the particles has been given resulting from the unsteady temperature gradient. It is suggested that the thermophoretic impulsive force is related to the time rate of the averaged temperature gradient and its history effect.