Rotation effects on a fully-developed turbulent pipe flow (original) (raw)

THE PREDICTION OF TURBULENT TRANSPORT IN AN AXIALLY ROTATING PIPE

Two Reynolds stress transport closures are adopted for modelling flow and heat transfer in fully-developed, axially-rotating pipe flow. Modelled transport equations are solved for the turbulent stresses and heat fluxes, and the turbulence-energy dissipation rate. Numerical calculations are performed with and without rotation, and the results show that both models simulate the strong attenuation of turbulent transport due to rotation. The model solutions are in reasonable agreement with published data and large eddy simulations.

A Second Turbulent Regime When a Fully Developed Axial Turbulent Flow Enters a Rotating Pipe

Volume 2B: Turbomachinery, 2016

When a fluid enters a rotating circular pipe a swirl boundary layer with thickness ofδ S appears at the wall and interacts with the axial momentum boundary layer with thickness ofδ. We investigate a turbulent flow applying Laser-Doppler-Anemometry to measure the circumferential velocity profile at the inlet of the rotating pipe. The measured swirl boundary layer thickness follows a power law taking Reynolds number and flow number into account. A combination of high Reynolds number, high flow number and axial position causes a transition of the swirl boundary layer development in the turbulent regime. At this combination, the swirl boundary layer thickness as well as the turbulence intensity increase and the latter yields a self-similarity. The circumferential velocity profile changes to a new presented selfsimilarity as well. We define the transition inlet length, where the transition appears and a stability map for the two regimes is given for the case of a fully developed axial turbulent flow enters the rotating pipe. NOMENCLATURẼ Dimensional value. A Constant in the velocity profile u φ for regime II. B Constant in the velocity profile u φ for regime II. C Constant in the growth law for δ S .

Two turbulent flow regimes at the inlet of a rotating pipe

European Journal of Mechanics - B/Fluids, 2016

When a fluid enters a rotating circular pipe a swirl boundary layer with thickness ofδ S appears at the wall and interacts with the axial momentum boundary layer with thickness ofδ. We investigate the turbulent flow applying Laser-Doppler-Anemometry to measure the circumferential velocity profile at the inlet of a rotating pipe. The measured swirl boundary layer thickness follows a power law taking Reynolds number and flow number into account. A critical combination of Reynolds number, flow number and axial position causes a transition of the swirl boundary layer development in the turbulent regime. At this critical combination, the swirl boundary layer thickness as well as the turbulence intensity increase and the latter yields a self-similarity. The circumferential velocity profile changes to a new presented self-similarity. A method is established to define the transition inlet length, when the transition appears and a stability map for two regimes is given.

The influence of the tangential velocity of inner rotating wall on axial velocity profile of flow through vertical annular pipe with rotating inner surface

In the oil and gas industries, understanding the behaviour of a flow through an annulus gap in a vertical position, whose outer wall is stationary whilst the inner wall rotates, is a significantly important issue in drilling wells. The main emphasis is placed on experimental (using an available rig) and computational (employing CFD software) investigations into the effects of the rotation speed of the inner pipe on the axial velocity profiles. The measured axial velocity profiles, in the cases of low axial flow, show that the axial velocity is influenced by the rotation speed of the inner pipe in the region of almost 33% of the annulus near the inner pipe, and influenced inversely in the rest of the annulus. The position of the maximum axial velocity is shifted from the centre to be nearer the inner pipe, by increasing the rotation speed. However, in the case of higher flow, as the rotation speed increases, the axial velocity is reduced and the position of the maximum axial velocity is skewed towards the centre of the annulus. There is a reduction of the swirl velocity corresponding to the rise of the volumetric flow rate.

1 Experiments on rotating flows : impact of rotation on flow through tilted rectangular ducts

2007

In nature, flows can turn unstable and generate waves. Depending on circumstances, these waves may in turn retard or accelerate these flows. The importance of rotation on this process is studied. This is done by pumping fluid through a rectangular duct that is put on a rotating platform, and by measuring, for given pump and rotation rates, cross-channel pressure difference as well as through flow. As the flow passes the rigid-lid duct, instabilities develop that lead to inertial waves. Depending on a lateral tilt of the duct, these waves may or may not be focused onto a simple-shaped wave attractor, which may impact the through flow. Key-words: inertial waves; wave attractor; fluid experiments

Computation of turbulent flow in a rotating pipe using the structure-based model

Mean rotation induces dynamical effects on turbulence that enter the transport equations through the non-local pressure-strain-rate correlation. It was shown in and that, to describe this effect accurately using one-point turbulence statistics, a turbulence model should include the transport equations not only for Reynolds stresses, but also for additional tensors providing information on turbulence structure missing from the Reynolds stresses. Two second-rank tensors, dimensionality D ij and circulicity F ij , as well as the third-rank stropholysis tensor Q * ijk along with the Reynolds stresses R ij , form a minimal set of independent tensors necessary for a one-point closure in the case of inhomogeneous turbulence. Relying on these ideas, the structure-based model has been developed in and tested successfully for a wide range of deformations of homogeneous turbulence as well as for some simple wall-bounded flows .

The effects of system rotation with three orthogonal rotating axes on turbulent channel flow

The effect of Coriolis force on turbulent channel flow has been sought in a more general manner by taking into account the alignment between the rotation axis and the direction of mean pressure gradient and the rotation rate as well. Three different, but orthogonal rotation vectors coincident with the Cartesian coordinates have been imposed on a plane channel, in which homogeneity is presumed in the planes parallel to the wall. A series of DNS has been performed for each case starting from the non-rotating plane channel, while increasing the rotation number and keeping the Reynolds number based on the friction velocity at 150. Detailed statistics are obtained including mean quantities, turbulent intensities, vorticities, and higher-order moments. The budgets of transport equations of the quantities relevant to turbulence modeling are prepared for the three orthogonal cases in order to help assessing turbulence models. An attempt to investigate the near-wall structures has been tried.

Nonparallel stability of the flow in an axially rotating pipe

Fluid Dynamics Research, 2003

The linear stability of the developing ow in an axially rotating pipe is analyzed using parabolized stability equations (PSE). The results are compared with those obtained from a near-parallel stability approximation that only takes into account the axial variation of the basic ow. Though the PSE results obviously coincide with the near-parallel ones far downstream, when the ow has reached a Hagen-Poiseuille axial velocity proÿle with superimposed solid-body rotation, they di er signiÿcantly in the developing region. Therefore, the onset of instability strongly depends on the axial evolution of the perturbations. The PSE results are also compared with experimental data from Imao et al. [Exp. Fluids 12 (1992) 277], showing a good agreement in the frequencies and wavelengths of the unstable disturbances, that take the form of spiral waves. Finally, a simple method for detecting one of the conditions to characterize the onset of absolute instability using PSE is given.

Observations on the predictions of fully developed rotating pipe flow using differential and explicit algebraic Reynolds stress models

European Journal of Mechanics - B/Fluids, 2006

The differences between two differential Reynolds stress models (DRSM) and their corresponding explicit algebraic Reynolds stress models (EARSM) are investigated by studying fully developed axially rotating turbulent pipe flow. The mean flow and the turbulence quantities are strongly influenced by the imposed rotation, and is well captured by the differential models as well as their algebraic truncations. All the tested models give mean velocity profiles that are in good qualitative agreement with the experimental data. It is demonstrated that the predicted turbulence kinetic energy levels vary dramatically depending on the diffusion model used, and that this is closely related to the model for the evolution of the length-scale determining quantity. Furthermore, the effect of the weak equilibrium assumption, underlying the EARSMs, and the approximation imposed for 3D mean flows on the turbulence levels are investigated. In general the predictions obtained with the EARSMs rather closely follow those of the corresponding DRSMs.  2005 Elsevier SAS. All rights reserved.

Velocity measurements of the laminar flow through a rotating straight pipe

Physics of Fluids, 1994

Some measurements have been obtained for the axial velocity of the fully developed laminar flow in a circular straight pipe with radius a, which is rotating with constant angular speed fi about an axis perpendicular to its own axis. A diode laser LDA system was mounted together with a circulating pipe flow system on a rotating table for the experiment. According to previous analyses and calculations, there exist four types of axial velocity distributions that result from the various effects of the secondary fiow on the main stream via the convection and Coriolis effect for different values of R( = w&/v) and R,(=&"/v), where W; is the mean axial velocity and v is the kinematic viscosity of the fluid. The present study provides experimental validation for the previous theoretical and numerical analyses. Experiments have also been carried out for studying the asymptotic nature of the slow flow in a rapidly rotating pipe (R@l and RnSR) and the rapid flow in a slowly rotating pipe (RR,&1 and R%R,).