Oscillatory-vortex

Figure 4. Diagram of a cell with domains in cross-section (1) Ultrasound, (2) system of oscillatory vortex flow with the velocity v =-cosqz, (3) stationary flows, (4) profile of distortion of the nematic orientation, (5) nematics molecule, (6) acoustically rigid boundary, (7) acoustically soft boundary.

Instead of using a furrowed or dimpled membrane support plate, Sobey [41] observed that a single flow deflector in a flat membrane channel could produce many vortices under oscillatory flow conditions, an effect named the vortex wave. An important feature of the vortex wave is that it could occur under low crossflow velocity conditions or with laminar flow so that it can be used for shear-sensitive fluids. Millward et al. [42] tested the effect of vortex waves on plasma filtration with waves produced by flow deflectors with cross-sectional area of 1 x 1 mm in a 2.25 mm high channel as shown in Figure 8.22. The aim was to improve membrane applications for the separation of plasma from cellular blood components for both donor... 

Non-decaying patterns in a similar stirred oscillatory system were also found numerically by Perez-Munuzuri (2006) in the weakly chaotic flow regime of the blinking vortex flow, i.e. for small /x. When the distance between the vortices is large, the flow has little effect on the spatial structure and a pattern of spiral waves forms as in the... 

Figure 8.2 Patterns generated in numerical simulations of an oscillatory reaction-advection-diffusion system (from Perez-Munuzuri (2006)). The flow is composed of two point vortices that are switched-on alternatingly. The figures are snapshots of the concentration field for different values of the distance between the two vortex centers (decreasing from left to right).

In this study, the relationship between oscillatory heat release and large vortex structure was systematically examined as a function of flow and chemistry scaling. Figure 16.3 shows the experimental setup used for producing vortex flames. A premixed propane-air jet was ignited, and the flame was stabilized at the exit downstream of a sudden-expansion flameholder. A 75-watt compression driver was used to apply controlled disturbance and to produce periodic vortices into a jet flame. The frequency response of actuation was evaluated separately to maintain a similar amplitude of acoustic disturbance at the exit plane. The objectives were to identify the location for active fuel injection in the general case and to establish a scaling criterion. 

Tube vibrations in a tube bundle are caused by oscillatory phenomena induced by fluid (gas or liquid) flow. The dominant mechanism involved in tube vibrations is the fluidelastic instability or fluidelastic whirling when the structure elements (i.e., tubes) are shifted elastically from their equilibrium positions due to the interaction with the fluid flow. The less dominant mechanisms are vortex shedding and turbulent buffeting. 

Vortex meters are intrusive because they rely on disturbing the flow regime by placing an object in the fluid stream to produce an oscillatory motion downstream. The object can take many shapes but often a thin wire is used, as shown in Figme 6.11, which minimizes the pressure drop. The oscillatory motion is referred to as a vortex and may be detected by piezoelectric transducers, or magnetic or optical sensors. The number of vortices present is proportional to the volumetric flow rate. 

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