Dynamic shear stress in parallel-plate flow chambers

An in vitro model using a parallel-plate fluid flow chamber is supposed to simulate in vivo fluid shear stresses on various cell types exposed to dynamic fluid flow in their physiological environment. The metabolic response of cells in vitro is associated with the wall shear stress. However, parallel-plate flow chambers have not been characterized for dynamic fluid flow experiments. We use a dimensionless ratio h/λ_v, in determining the exact magnitude of the dynamic wall shear stress, with its oscillating components scaled by a shear factor T. It is shown that, in order to expose cells to predictable levels of dynamic fluid shear stress, two conditions have to be met: (1) h/λ_v<2, where h is the distance between the plates and λ_v is the viscous penetration depth; and (2) f₀<f_c/m, where the critical frequency f_c is the upper threshold for this flow regime, m is the highest harmonic mode of the flow, and f₀ is the fundamental frequency of fluid flow.