Wedge flow

Wedg e Meters. The wedge flow meter consists of a flanged or wafer-style body having a triangular cross section dam across the top of the fluid conduit. Pressure taps are on either side of this restriction. Overall meter sizes range from 10 to 600 mm. Within each size several restrictions are available to provide the range of differential pressure desired for the appHcation. 

I. Transport Phenomena in Wedge Flows with Suction at the Surface... 

Figure 5.7 illustrates a spherical variation of the Jeffery-Hamel flow. Here the flow either originates or terminates in a point source or sink. As in the wedge flow (Section 5.2) the analysis here considers steady, incompressible, constant-property flow. 

Recall that there is a fundamental scaling difference between the cylindrical wedge flow and the spherical inclined-disk flow. In the wedge flow, the Reynolds number is independent of r, whereas in the spherical case, the Reynolds number scales as /r. Thus, in the spherical case, there is a different Reynolds number at every radial position in the channel. In practice, a quantitative determination of the velocity profile is more complex in the spherical case. The nondimensional velocity profile must be determined at each radial position where the actual velocity profile is desired. 

For the given geometry and flow conditions, develop a nondimensional representation of the velocity field based on the Jeffery-Hamel wedge flow. Remember that the flow is radially inward, so the Reynolds number is negative. Use the properties of the helium carrier gas. 

So far, we have been talking about the stability of zero pressure gradient flows. It is possible to extend the studies to include flows with pressure gradient using quasi-parallel flow assumption. To study the effects in a systematic manner, one can also use the equilibrium solution provided by the self-similar velocity profiles of the Falkner-Skan family. These similarity profiles are for wedge flows, whose external velocity distribution is of the form, 11 = k x . This family of similarity flow is characterized by the Hartree parameter jSh = 2 1 the shape factor, H =. Some typical non-dimensional flow profiles of this family are plotted against non-dimensional wall-normal co-ordinate in Fig. 2.7. The wall-normal distance is normalized by the boundary layer thickness of the shear layer. 

Abers, G.A., van Kelcen, P.E., Kneller, E.A., Ferris, A., and Stachnik, J.C., 2006. The thermal structure of subduction zones constrained by seismic imaging implications for slab dehydration and wedge flow. Earth Planet. Sci. Lett., 241, 387-97. 

Different two phase flow characteristics in a channel, (a) Bubbly flow, (b) Wedging flow, (c) Slug flow. 

Looking specifically at a DMFC, several authors used cells with a transparent cover in order to observe carbon monoxide evolution and two-phase flow behavior visually. Bubbly flow, wedging flow or slug flow could be observed on the anode side. Fmthermore some preferred points could be identified on top of the GDL where the gas evolved. This transition process can be compared to liquid... 

To understand the processing and dispensing behavior of adhesives we often need to construct flow models of the process. While all models are approximations, they still have to satisfy continuity of mass and the balance of momentum and thermal energy. The constitutive equation, plus the appropriate initial and/or boundary conditions of the problem at hand, provide closure to these balance laws. While any realistic solution to a particular processing problem will generally involve numerical computations, several generic problems of interest may be amenable to analytical development. For instance, when a pressure-sensitive adhesive is pressed down unto a surface, we have an example of squeeze flow. Similarly, if a paste is spread onto a surface via a knife, we have an example of wedge flow. These two flows will be discussed for the PLF. 

In this section we illustrate two rheology problems that have direct relevance to adhesion. When pressure is applied on a pressure-sensitive adhesive, the material will flow between the backing and the substrate. This is an example of so-called squeeze flow . Likewise, if we have two plates that are placed at an angle to each other, with adhesive in between them at the joint, and proceed to press the plates together, then we have an example of wedge flow . This case could also approximate the flow one gets when a clump of material, such as caulk, is spread on a surface with a spatula. We now examine these two flows. 

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