Methods to Set Up and Investigate Low Reynolds Number, Fully Developed Turbulent Plane Channel Flows

Abstract

The tripping of fully developed turbulent plane channel flow was studied at low Reynolds number, yielding unique flow properties independent of the initial conditions. The LDA measuring technique was used to obtain reliable mean velocities, rms values of turbulent velocity fluctuations and skewness and flatness factors over the entire cross-section with emphasis on the near-wall region. The experimental results were compared with the data obtained from direct numerical simulations available in the literature. The analysis of the data indicates the important role of the upstream conditions on the flow development. It is shown that the fully developed turbulent state at low Reynolds number can be reached only by significant tripping of the flow at the inlet of the channel. Effects related to the finite size of the LDA measuring control volume and an inaccuracy in the estimation of the wall shear stress from near-wall velocity measurements are discussed in detail since these can yield systematic discrepancies between the measured and simulated results.

Effects of blowing through a porous strip in a turbulent channel flow

“…The sampling frequency was chosen to be equal to the viscous frequency ðf v ¼ u 2 s =mÞ. Table 1 summarizes the flow conditions for the present study and for the measurements of Durst et al [27], Gü nther et al [28], Antonia et al [29] and Johansson and Alfredsson [30]. These authors studied in similar conditions a fully developed two-dimensional channel flow.…”

Downstream relaxation of velocity profiles in pipe-flow with swirl disturbances

“…the standard deviation) of this histogram quantifies the turbulence intensity (18). As discussed by Durst et al [5] and generalized by Pashtrapanska [25], the turbulence intensity (18) …”

“…Senoo and Nagata [29] derive an exponential law for the decay of through differentiating (1) with respect to the pipe length and making additional assumptions on the decay of the axial momentum flux. Similarly, Ito et al [13] determine the decay associated with (5) …”

“…Different Rossby numbers Ro and Ro * (Equations (3) and (4) in Table 1) are used by Yajnik and Subbaiah [37] and Steenbergen and Voskamp [32]. Further, a dimensionless swirl intensity (Equation (5) in Table 1) is defined by Ito et al [13], where is the Table 1.…”

Numerical simulation of turbulent flow through Schiller’s wavy pipe

“…In order to avoid laminarization and ensure development of turbulence, we initialized simulations as is done experimentally by tripping the flow at the pipe inlet with tripping plates or wires, which block the flow in the near-wall region to create conditions leading to the rapid development of turbulence (Schlichting 1968). For a blockage ratio greater than 10 %, defined as the ratio of the blocked area to the pipe cross-sectional area, development towards the fully developed turbulent state (in a plane channel) is fairly rapid (Durst et al 1998;Fischer 1999).…”