Turbulent in pipes

Patterson, R.W. and Abernathy, F.H., Transition to turbulence in pipe flow for water and dilute solutions of polyethylene oxide, Journal of Fluid Mechanics, 51, pp. 177-85(1972). 

If Reynolds number is useful, it is because flow velocity and Reynolds number are related to the intensity and scale of turbulence in pipe flow. All the measurements... 

If the above intuitive picture is correct, then no turbulence can be formed except by large-scale mechanical stirring or by some kind of shearing, analogous to that shown in Fig. 16.1(a). This is indeed observed. The turbulence in pipes, ducts, and channels is produced by the shear layers at the walls of the duct. Turbulence is steadily fed into the main flow in the duct and ultimately is consumed in viscous heating in the main flow. The turbulence in the wake of ships and airplanes is caused by the shear layer adjacent to the surface of the airplane or ship, and the turbulence decays with time, due to viscosity, after the airplane or ship passes. 

Willis AP, Kerswell RR (2007) Critical behavior in the relaminaiization of localized turbulence in pipe flow. Phys Rev Lett 98 014501-1-014501-4... 

The degree of turbulence In pipes and channels is characterised by the value of the Reynolds number. For a pipe ... 

Reynolds dye experiment on transition to turbulence in pipe flow and G. I. Taylor s experiments on axial dispersion in laminar flow represent the early use of tracers in flow visualization and transport parameters evaluation in chemical engineering. A more widespread use in chemical reactors dates to the work of Danckwerts (1). He realized that the performance of process equipment depends on the residence time distribution of process fluid, and that this information can be obtained by tracer methods. Residence time distributions are now discussed in standard chemical reaction engineering texts (2,3) and are well summarized in a recent excellent monograph by Nauman and Buffham (4). Tracer methods. 

Another concept sometimes used as a basis for comparison and correlation of mass transfer data in columns is the Clulton-Colbum analogy (35). This semi-empirical relationship was developed for correlating mass- and heat-transfer data in pipes and is based on the turbulent boundary layer model... 

Reynolds dumber. One important fluid consideration in meter selection is whether the flow is laminar or turbulent in nature. This can be deterrnined by calculating the pipe Reynolds number, Ke, a dimensionless number which represents the ratio of inertial to viscous forces within the flow. Because... 

The phenomena are quite complex even for pipe flow. Efforts to predict the onset of instabiHty have been made using linear stabiHty theory. The analysis predicts that laminar flow in pipes is stable at all values of the Reynolds number. In practice, the laminar—turbulent transition is found to occur at a Reynolds number of about 2000, although by careful design of the pipe inlet it can be postponed to as high as 40,000. It appears that linear stabiHty analysis is not appHcable in this situation. 

The universal turbulent velocity profile near the pipe wall presented in the preceding subsection Tncompressible Flow in Pipes and Channels may be developed using the Prandtl mixing length approximation for the eddy viscosity,... 

Uneven wear in parts is often due to turbulence. Bad piping designs or poorly sized valves can cause turbulence and uneven wear in pumps. Whenever possible, use straight pipe sections before and after the pump. Uneven flow creates turbulent flow and excessive wear occurs. 

Figure 2-43. Evaluation curves for friction losses of air and steam flowing turbulently in commercial pipe at low pressures. By permission, Standards for Steam Jet Ejectors, 4th Ed., Heat Exchange Institute, 1988.

Turbulent flow pressure loss in pipe (Equation 4-187) is... 

Particles of fluid flowing in pipes act in the same manner. The flow is streamlined if the fluid flows slowly enough, and remains streamlined at greater velocities if the diameter of the pipe is small. If the velocity of flow or size of pipe is increased sufficiently, the flow becomes turbulent. 

While a high velocity of flow will produce turbulence in any pipe, other factors contribute to turbulence. Among these are the roughness of the inside of the pipe. 

Seawater systems should be designed to avoid excessive water velocities, turbulence, aeration, particulates in suspension, rapid changes in piping section and direction. Likewise, extended periods of shutdown should also be avoided since stagnation of contained seawater, will result in bacterial activity and HjS production with consequential and perhaps serious corrosion and health and safety problems. 

Recommended methods for assessing the corrosivity of waters, including flowing potable waters, are described in ASTM 02688 1983. Three procedures are described in which test specimens in the form of wires, sheets or tubes are placed in pipes, tanks or other equipment. The test assembly for the first of these consists of three helical wire coils mounted in series on, and electrically insulated from, a supporting frame. The assembly must be installed so that flow is not disturbed and turbulence and high velocities, e.g. of more than 1 -53 ms , are avoided. A minimum test period of 30 days is recommended. Procedures for the other specimen forms are given in the standard. 

Abrupt changes in direction of flow such as elbows, tees, return bends and changes in pipe size which create turbulence or changes in velocity. 

A typical combination of these numbers is that for turbulent flow in pipes ... 

Turbulence is known to occur in pipe flow at a Reynolds number (Re) above 2300. Beyond this stability limit, any disturbance will grow exponentially in time and the flow becomes fully chaotic at Re 4000, where Re is defined by ... 

In order to predict Lhe transition point from stable streamline to stable turbulent flow, it is necessary to define a modified Reynolds number, though it is not clear that the same sharp transition in flow regime always occurs. Particular attention will be paid to flow in pipes of circular cross-section, but the methods are applicable to other geometries (annuli, between flat plates, and so on) as in the case of Newtonian fluids, and the methods described earlier for flow between plates, through an annulus or down a surface can be adapted to take account of non-Newtonian characteristics of the fluid. 

HARTNETT and KOSTIC 26 have recently examined the published correlations for turbulent flow of shear-thinning power-law fluids in pipes and in non-circular ducts, and have concluded that, for smooth pipes, Dodge and Metzner S(27) modification of equation 3.11 (to which it reduces for Newtonian fluids) is the most satisfactory. 

Laufer. J. United States National Advisory Committee for Aeronautics. Report No. 1174 (1955). The structure of turbulence in fully developed pipe flow,... 

---