Turbulent duct flow

There is also a standardized method based on the estimation of the flow rate on one measurement point only, In this method the velocity probe is placed in the duct so that the measured local velocity is equal to the mean axial velocity. In fully developed turbulent duct flow, this distance from the wall... 

Kostic M (1994) On turbulent drag and heat transfer reduction phenomena and laminar heat transfer enhancement in non-circular duct flow of certain non-Newtonian fluid. Int J Heat Mass Transfer 37 133-147... 

In both building locations, the velocity profile indicated duct floe turbulence. The drilling operation of building 1619 had flow velocities and negative static pressures that were significantly higher than the operations in building 1611. These differences can be attributed to the duct diameters, sizes, and number of dust cleanouts found in the two removal systems. 

Very large values of ST may be observed in ducted burners at high approach flow velocities. Under these conditions,. S T increases in proportion to the approach flow velocities, but is insensitive to approach flow turbulence and composition. It is believed that these effects result from the dominant influence of turbulence generated within the stabilized flame by the large velocity gradients. 

All pressure-driven, rectilinear duct flows, whether Newtonian or non-Newtonian, undergo transition to turbulence when the transition parameter of Hanks, defined by... 

Internal flows of the type here being considered occur in heat exchangers, for example, where the fluid may flow through pipes or between closely spaced plates that effectively form a duct Although laminar duct flows do not occur as extensively as turbulent duct flows, they do occur in a number of important situations in which the size of the duct involved is small or in which the fluid involved has a relatively high viscosity. For example, in an oil cooler the flow is usually laminar. Conventionally, it is usual to assume that a higher heat transfer rate is achieved with turbulent flow than with laminar flow. However, when the restraints on possible solutions to a particular problem are carefully considered, it often turns out that a design that involves laminar flow is the most efficient from a heat transfer viewpoint. 

In the present chapter and in the following two chapters, which are concerned with turbulent boundary layer flows and with turbulent duct flows, respectively, consideration will be restricted to forced flows, i.e., the effect of buoyancy forces on the mean flow and on the turbulence structure will be assumed to be negligible. Some discussion of the effect of buoyancy forces on turbulent flows will be given in Chapter 9. 

The application of the analogy approach to turbulent boundary flow and to turbulent duct flow will be discussed in Chapters 6 and 7, respectively. 

This chapter is concerned with the prediction of the heat transfer rate from the wall of a duct to a fluid flowing through the duct, the flow in the duct being turbulent. The majority of the attention will be given to axi-symmetnc flow through pipes and two-dimensional flow through plane ducts, i.e , essentially to flow between parallel plates. These two types of flow are shown in Fig. 7.1. 

As discussed in the previous chapter, most early efforts at trying to theoretically predict heat transfer rates in turbulent flow concentrated on trying to relate the wall heat transfer rate to the wall shearing stress. In the present section an attempt will be made to outline some of the simpler such analogy solutions for duct flows [13], [14],[15],[16],[17]. 

Bradshaw, P., Dean, R.B., and McEligot, N.P. (1973) Calculation of interacting turbulent shear layers duct flow, Trans. ASME I J. Fluids Engng. 95, 214-219. 

Lee SL (1987) A unified theory on particle transport in turbulent dilute two-phase suspension flow-11. Int J Multiphase Flow 13(1) 137-144 Lee SL, Borner T (1987) Fluid flow structure in a dilute turbulent two-phase suspension flow in a vertical pipe. Int J Multiphase Flow 13(2) 233-246 Lee SL, Durst F (1982) On the motion of particles in turbulent duct flows. Int J Multiphase Flow 8(2) 125-146... 

The pipe head loss may be calculated by the well known Darcy- Weisbach equation [94], valid for duct flows of any cross section and for laminar and turbulent flow ... 

For rectangular and other noncircular ducts in turbulent flow, the standard procedure is to replace R with the hydraulic radius... 

The heat transfer rate in the laminar duct flow is very sensitive to the thermal boundary condition. Hence, it is essential to carefully identify the thermal boundary condition in laminar flow. The heat transfer rate in turbulent duct flow is insensitive to the thermal boundary condition for most common fluids (Pr > 0.7) the exception is liquid metals (Pr < 0.03). Hence, there is generally no need to identify the thermal boundary condition in turbulent flow for all fluids except liquid metals. 

Velocity Fluctuations and Reynolds Stresses Li and Olsen [9, 10] were the first researchers to measure profiles of velocity fluctuations in turbulent microchannel flow. They measured streamwise and transverse velocity fluctuations and Reynolds shear stresses for a range of Reynolds numbers spanning the laminar through fully turbulent regime. They found good agreement between their measured fluctuations and Reynolds shear stresses and values reported for macroscale turbulent duct flow. 

Turbulence structure of a developing duct flow with near-wall injection of drag reducing polymers. 

Turbulence Structure of a Developing Duct Flow with Near-Wall Injection of Drag Reducing Polymers... 

For open channels and partly filled ducts in turbulent flow, the equivalent diameter and Eq. (2.10-6) are also used (PI). For a rectangle with depth of liquid y and width b. 

Liu and Agarwal performed an experimental study on deposition of aerosol particles in turbulent pipe flows. McCoy and Hanratty, Wood, and Papaver-gos and Hedley reported several collections of available data on wall deposition rates. Kvasnak et al. reported their experimental data for the deposition rate of glass beads, various dust components, and glass fibers in a horizontal duct flow. Wood, Hidy, and Papavergos and Hedley reviewed the available methods for evaluating the deposition velocity in turbulent duct flows and discussed different deposition mechanisms. 

He, C. and Ahmadi, G. (1998). Particle Deposition with Themophoresis in Laminar and Turbulent Duct Flows. Aerosol Sd. Technol., Vol. 29, pp. 525-546. 

Tian, L. and Ahmadi, G. (2007). Particle Deposition in Turbulent Duct Flows - Comparisons of Different Model Predictions, J. Aerosol Science, Vol. 38, pp. 377-397. 

Zhang, H. and Ahmadi, G. (2000). Aerosol Particle Transport and Deposition in Vertical and Horizontal Turbulent Duct Flows. J. Fluid Mech., Vol. 406, pp. 55-80. 

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