Experiments in Fluids 8, 33-40 (1989) Experimentsin Fluids 9 Springer-Verlag 1989 Rotation effects on a fully-developed turbulent pipe flow M. Anwer and R. M. C. So Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ 85287-6106, USA Abstract. A fully-developed turbulent pipe flow is allowed to pass through a rotating pipe section, whose axis of rotation coincides w: with the pipe axis. At the exit end of the rotating section, the flow passes into a stationary pipe. As a result of the relaxation of surface X 6 rotation, the turbulent flow near the pipe wall is affected by extra turbulence production created by the large circumferential shear v strain set up by the rapid decrease of the rotational velocity to zero 0 at the wall. However, the flow in the most part of the pipe is absent tr of this extra turbulence production because the circumferential strain is zero as a result of the solid-body rotation imparted to the f2 flow by the rotating pipe section. The combined effect of these two phenomena on the flow is investigated in detail using hot-wire Subscript anemometry techniques. Both mean and turbulence fields are mea- 0 sured, together with the wall shear and the turbulent burst behavior at the wall. A number of experiments at different rotational speeds are carried out. Therefore, the effects of rotation on the behavior of wall shear, turbulent burst at the wall, turbulence production and the near-wall flow can be documented and analysed in detail. List of symbols a Cf~ C f2 D L L F k us P(T) r S t TB TB U,V,W U r, Vt , W ~ Wo radius of the pipe friction coefficient, zw/~Oa W02. friction coefficient, Zw/[ 89 Q (Wd + (a f2)2)] diameter of the pipe energy spectrum of shear stress dimensional burst frequency L normalized burst frequency, -- (L)0 (<)/(~;2)2 normalized kurtosis, D")/(U)qo threshold level (used in VITA) swirl number, a f2/Wo probability of inter-burst time, T radial coordinate normalized skewness, integration time (used in VITA) mean inter-burst time, 1If b w~ rBIv normalized scaled burst frequency, - - (w~rB/v)o mean velocity components in radial, circumferential and axial directions, respectively fluctuating components of velocity in radial, circum- ferential and axial directions, respectively axial bulk mean velocity friction velocity, ( ~ ) lj2 distance measured from the entrance of the bend thickness of the viscous layer kinematic viscosity density of fluid (T~v2~)l/2 normalized standard deviation, __ (~;2)U rotational speed of pipe in RPM condition at X/D = -- 18 1 Introduction When a turbulent wall shear flow is subjected to axial rota- tion, a destabilizing and/or a stabilizing effect would result depending on the flow condition. Here, the term destabiliz- ing is used to describe the phenomenon of extra turbulence production created by flow rotation, while the term stabiliz- ing is used to describe the rotating flow characteristics with- out the extra turbulence production present. In the case of a flow through an axially rotating pipe with uniform entrance velocity, flow regions with extra turbulence production pres- ent (destabilizing) or absent (stabilizing) could be found in different parts of the pipe. Near the entrance, the wall boundary layer is very thin. Therefore, fluid rotation has to decrease quickly from pipe rotation at the wall to zero out- side of the wall boundary layer. The flow near the wall is subjected to a very high mean circumferential shear strain and turbulence production is greatly enhanced. As a result, the near-wall flow is destabilized by rotation. Far down- stream, the flow becomes fully-developed and the fluid ro- tates as a solid body. Since the solid-body rotation curve has a constant slope, turbulence production due to the mean circumferential shear strain is zero. Consequently, rotation gives rise to a stabilizing effect on the flow. In the region spanning the entrance and the fully-developed region, the flow is subjected to both destabilizing and stabilizing effects