Effect of Fluid Viscosity and Inertia

Effect of Fluid Viscosity and Inertia The dynamic effect of viscosity on a rotating liquid slurry as found in a sedimenting centrifuge is confined in veiy thin fluid layers, known as Ekman layers. These layers are adjacent to rotating surfaces which are perpendicular to the axis of rotation, such as bowl heads, flanges, and conveyor blades, etc. The thickness of the Ekman layer 6 is of the order... 

The effect of fluid properties and wetting properties of the channel wall on the flow regime and flow pattern transition was studied [72]. For lower hydrophilidty of the channel surface, the transition boundaries of the slug flow to the slug-annular flow and the slug-annular flow to the annular flow shift to lower Red Rei Figure 9.16). The effect of wettability on micro-fluidics in the surface tension-dominated zone was more apparent than that in the inertia-dominated zone. Both surface tension and viscosity of the liquid are influencing the flow pattern transitions. 

The combination of low viscosity and high density creates a risk situation, which might be described as Tanker effect . Assuming a tanker without separators and with a 50% filling of the tank accelerates, the inertia of the fluid mass creates pressure on the inner back side of the tank. If the driver pushes the break firmly, all liquid will move to the front and will create pressure on the inner front side of the tank. 

Taylor bubbles (gas plugs) in a vertical tube move under the influence of surface tension, inertia, gravitation, and viscous effects. For a Newtonian fluid with constant viscosity and density these phenomena can be described by the Navier-Stokes equations for circular geometry using cylindrical coordinates ... 

Problem 9-6. Inertial Effects on the Motion of a Gas Bubble for Re bubble rises through an infinite body of fluid under the action of buoyancy. The Reynolds number associated with this motion is very small but nonzero. Assume that the bubble remains spherical, and use the method of matched asymptotic expansions to calculate the drag on the bubble, including the first correction that is due to inertia at 0(Re). You may assume that the viscosity and density of the gas are negligible compared with those of the liquid so that you can apply the boundary conditions... 

Microfluidics handles and analyzes fluids in structures of micrometer scale. At the microscale, different forces become dominant over those experienced in everyday life [161], Inertia means nothing on these small sizes the viscosity rears its head and becomes a very important player. The random and chaotic behavior of flows is reduced to much more smooth (laminar) flow in the smaller device. Typically, a fluid can be defined as a material that deforms continuously under shear stress. In other words, a fluid flows without three-dimensional structure. Three important parameters characterizing a fluid are its density, p, the pressure, P, and its viscosity, r. Since the pressure in a fluid is dependent only on the depth, pressure difference of a few pm to a few hundred pm in a microsystem can be neglected. However, any pressure difference induced externally at the openings of a microsystem is transmitted to every point in the fluid. Generally, the effects that become dominant in microfluidics include laminar flow, diffusion, fluidic resistance, surface area to volume ratio, and surface tension [162]. 

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