Wave flow

Droplets appeared on the surface of the pipe (Fig. 5.33b) after increasing the water flow rate up to I/ls = 0.007 m/s. Spedding et al. (1998) referred to this regime as film plus droplet pattern. When the water flow rate increased and superficial liquid velocity was Gls = 0.03 m/s (Fig. 5.33c) droplets began to roll back into the liquid film. Kokal and Stanislav (1989) identified such a regime as annular plus roll wave flow pattern. The experimental facility used in the present study allowed us to achieve values of superficial gas velocities up to 20 m/s in the 49.2 mm pipe. 

Blast wind (Air mass movement) Drag loading—forces on a structure resulting from the high velocity of the air particles in the blast wave flowing around the structure... 

Kapitza, P. L., 1964, Wave Flow of Thin Layers of a Viscous Fluid, in Collected Papers of P. L. Kapitsa, vol. II, Macmillan, New York. (3)... 

Tube diameter is clearly an important factor, as one can easily appreciate by considering wave flow in a small-diameter pipe where this pattern can hardly exist, and the same situation in a large-diameter pipe where conditions must approach those of a free liquid surface. Since the... 

Up to the present time, work has been done which allows prediction of the onset of large waves (H2), and of formation of other types of waves (VI, HI), but only on flat uniform liquid surfaces. The extent to which these results can be applied to pipe line flow is uncertain. Apparently, Gazley s papers are still the only basic reports of stratified and wave flow in horizontal pipe incidentally they also show a parallel between liquid instability in pipe flow as evidenced by wave formation, and that evidenced in packed towers by flooding. 

Accdg to Ref 66, p 137, actually occurring oneadimensional flows often contain uniform and simple wave flow regions, shocks and contact discontinuities which move toward or thru one another. The interference of one type of flow with another leads to complex patterns re quiring the general solutions of the conservation equations... 

Other examples of idealized solutions are one-dimensional flow of an ideal gas through a normal shock wave flow of an ideal gas without viscosity through a pipe of slowly changing cross section (wind tunnel) and one-dimensional finite waves in an ideal gas. Numerous other solutions involve making whatever approximations and assumptions necessary to obtain descriptions of observed flows. 

Baker presented five flow regimes the three additions to the preceding were annular flow, plug flow, and wave flow [11]. A quick review of these add-ons reveals that all three resemble each other, each being variations of flow regime in low-Reynolds-number areas. 

Second, a peak-intensity ultrasound echo can be used to detect the gas-liquid interface, but in this case the aim is the development of a flow meter capable of estimating the ratio of component phases accurately and in real time. Our results are promising for the estimation of the liquid flow rate of gas-liquid two-phase flow further research will produce valuable data that will allow the estimation of flow rates for the two phases simultaneously. The results presented here show the liquid flow rate estimated by the peak echo intensity method can provide an accurate estimate of the actual liquid flow rate. This method can be applied to pure liquid as well as to a two-phase flow where the void fraction is as high as 50%. The flows tested are of the stratified, elongated bubble, and slug flow types. Other types of flow such as wave flow and dispersive flow were not tested the present experimental setup does not provide the gas and liquid flow rates needed to achieve such flows. 

Figure 9. The triangular grid early in a calculation of wave flow over a halfcylinder. The first wave of a wave train has passed over the cylinder from the left.

Think of a still pond. Drop in a pebble and the waves flow smoothly away from the point of disturbance, spreading over the pond, as do conducting electron waves in a pure metal. Now, add a few tree stumps to the pond and drop another pebble. As before, the wave starts to flow smoothly away from the point of disturbance. But when it strikes a stump, it is scattered in many directions. The scattered flow of water caused by the addition of stumps to a pond is analogous to the scattering of electron waves when an alloying agent is added to a pure metal. 

This model predicted 65% of the intermittent and discrete wave flow data points within 20%. This somewhat lower prediction accuracy is due to the inclusion of the discrete-wave flow points into the data set. The above model predicted 75% of the intermittent flow points within 20%, which is comparable with the results obtained with the original intermittent flow models of Garimella et al. [24, 25]. 

The average of tiiese two pressiwe drops resulting from die interpolation based on G and x represents die two-phase pressiwe drop for the d ansition region data point. This model predicts 87% of die data widiin 20%. It should be noted diat diese predictions include not only die annular flow region, but also die mist and disperse-wave flow data, whereas die preliminary model of Garimella et al. 

Figure 10 presents the interface shape of the rivulet for wall superheat as 0.5 K and Re = 2.5. Here also presented the data on pressure in liquid and heat flux density in rivulet cross-section. The intensive liquid evaporation in near contact line region causes the interface deformation. As a result the transversal pressure gradient creates the capillarity induced liquid cross flow in direction to contact line. Finally the balance of evaporated liquid and been bring by capillarity is established. This balance defines the interface shape and apparent contact angle value.For the inertia flow model, the solution is obtained from a non-stationary system of equations, i.e., it is time-dependable. In this case the disturbances in flow interface can create the wave flow patterns. The solutions of unsteady state liquid spreading on heat transfer surface without and with evaporation are presented on Fig. 11. When the evaporation is not included (for zero wall superheat) the wave pattern appears on the interface. When the evaporation includes, the apparent contact angle increase immediately and deform the interface. It causes the wave suppression due to increasing of the film curvature.

B. Jiang, D. Ingram, D. Causon and R. Saunders, A Global Simulation Method for Obtaining Reduced Reaction Mechanisms for Use in Reactive Blast Wave Flows, Shock Waves 5 (1995) 81-88. 

The mechanics and applications of multiphase flow has been an area of continuing interest to chemical, environmental, and civil engineers (23,77). The multiphase flow patterns may be classified as bubble flow, plug flow, stratified flow, wave flow, slug flow, annular flow, spray flow, and froth flow. Typical sketches of these various flow patterns are shown in Fig. 3. They are self-explanatory. In the field of absorptive bubble separation processes, only multiphase bubble flow and froth flow are of interest to the process engineer. 

Wave Flow. Wave flow is similar to stratified flow except that the gas is moving at a higher velocity and the gas-liquid interface is distributed by waves moving in the direction of flow. It occurs for liquid velocities less than 1 ft/sec (0.3 m/sec) and gas velocities from about 15 ft/sec. (4.5 m/sec). 

For wave flow, the Huntington friction factor [20] is used to determine the two-phase pressure loss ... 

C USING THE REGIME FOR WAVE FLOW, DETERMINE THE TWO-PHASE MODULUS... 

THIS PROGRAM CALCULATES THE TWO PHASE FLOW MODULUS AND PRESSURE DROPS FOR WAVE FLOW REGIME. 

The heat transfer in the lower part of the sphere is highly nonlinear, and no correlation was reported for this region. Karapantsios and Karabelas [184] experimentally examined the influence of flow intermittency on direct contact condensation of a quasistagnant vapor-gas mixture on falling liquid waves. Flow intermittency was found to increase the heat transfer rate by as much as an order of magnitude. Mikielewicz et al. [218] recently included turbulent diffusion effects in studying direct-contact condensation of steam on a horizontal water film. 

PL. Kapitza, Wave Flow of Thin Layers of Viscous Fluids," Collected Papers ofKapitza, Pergamon Press Ltd., New York, 2, pp. 662-689,1948. 

Iron(IlI) in some solutions produces a well formed cathodic (reduction) wave, in which the iron(III) undergoes a thermodynamically reversible reduction to iron(II). Since the potential of this wave is determined by the energy difference between iron(ll) and (III), it could be expected that a solution of iron(II) in the same media would produce a well formed anodic (oxidation) wave at exactly the same potential. In both cases the potential of the wave would be determined by the same energy difference. In practice the two waves are separated by a very small difference in potential, (59/n mV where n is the number of electrons transferred, in this case 1). The current in one wave flows in the opposite direction to the other. If both iron(ll) and (III) are present in the same solution a single wave should develop with part cathodic and part anodic. The current direction will reverse part way up the wave. If the reversibility of the reaction is lost, through some addition to the solution, the cathodic and anodic waves will separate and move apart. 

In a planar cross-sectional slice of the tube volume subjected to examination for chemical change, as by in situ instrumental observation, one thus has continuously presented differential samples of the recently perturbed gas at successive distances behind the shock wave front. The thickness of the slice and the time inhomogeneity of the sample are mutually proportional, and these can be made typically 1 mm and a few sec, respectively. In the shock wave reflected at the tube end, the same gas sample may be viewed by stationary apparatus throughout an experiment in the incident wave flow, gas with a substantially common history flows through the observation region. 

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