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In a body submerged in a fluid, unsteady forces due to acceleration of that body with respect to the fluid, can be divided into two parts: the virtual mass effect and the Basset force. The Basset force term describes the force due to the lagging boundary layer development with changing relative velocity (acceleration) of bodies moving through a fluid.〔C. Crowe et al., Multiphase flows with droplets and particles, CRC Press, 1998, ISBN 0-8493-9469-4, p. 81〕 The Basset term accounts for viscous effects and addresses the temporal delay in boundary layer development as the relative velocity changes with time. It is also known as the "history" term. The Basset force is difficult to implement and is commonly neglected for practical reasons; however, it can be substantially large when the body is accelerated at a high rate.〔R.W. Johnson, The handbook of fluid dynamics, CRC Press, 1998, ISBN 0-8493-2509-9, pp. 18–3〕 This force in an accelerating Stokes flow has been proposed by Joseph Valentin Boussinesq in 1885 and Alfred Barnard Basset in 1888. Consequently, it is also referred to as the Boussinesq–Basset force. ==Acceleration of a flat plate== Consider an infinitely large plate started impulsively with a step change in velocity—from 0 to ''u0''—in the direction of the plate–fluid interface plane. The equation of motion for the fluid—Stokes flow at low Reynolds number—is : where ''u''(''y'',''t'') is the velocity of the fluid, at some time ''t'', parallel to the plate, at a distance ''y'' from the plate, and ''νc'' is the kinematic viscosity of the fluid (c~continuous phase). The solution to this equation is, : where ''up(t)'' is the velocity of the plate, ''ρc'' is the mass density of the fluid, and ''μc'' is the viscosity of the fluid. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Basset force」の詳細全文を読む スポンサード リンク
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