Etude experimentale de la turbulence au voisinage de la paroi d'un tube legerement chauffe

Direct numerical simulation of turbulent forced convection in a pipe

“…The skewness of the IWT temperature ÿeld agrees with the MT results for y + ¡10; beyond this distance, the quantitative agreement is lost and the IWT proÿle attains smaller 595 positive values. The experimental data by Elena [25] are in excellent quantitative agreement with the present IWT results. The large negative values of S # for the MT and IWT temperature ÿelds, for y + ¡20, are consistent with the large positive values of S ux and S ur , which denote the presence of intense sweep events.…”

“…Figure 7(b) shows the kurtosis of the velocity components and of the three temperature ÿelds. The experimental data by Elena [25] for F # are in relatively good agreement with the IWT result in the near-wall region. The kurtosis of all velocity components and of the MT and IWT temperature ÿelds increases sharply approaching the wall, due to the wall-blocking e ect; due to the low correlation between the radial velocity and the IWHF temperature uctuations, the IWHF atness does not present relevant variations approaching the wall and attains an approximately constant value of 3 in the viscous wall region, corresponding to the normal distribution.…”

“…The atness of all temperature ÿelds exceeds the value of 3 at the centreline. As already found by Elena [25], the atness of both u x and #, for the MT and IWT cases, presents a minimum value around 2.0, near the location where the corresponding skewness factor crosses the zero. Elena relates this feature to the presence of harmonic uctuations, corresponding to S = 0 and F = 1:5, related to the hydrodynamic instability evidenced by Blackwelder et al [26] in this region.…”

“…In addition, they obtain Pr t ≈ 0:87 in the central region of the channel for Pr = 1, which is larger than the present results. [25]; HHH: Su x , Fu x by Elena [25]. strongly a ected by the boundary conditions, both in the near wall and in the core regions.…”

“…a) reports the skewness of the velocity components and of the three temperature ÿelds, considered in the present study. For comparison, the experimental data for a turbulent pipe ow of air are reported[25].The skewness factors of the three temperature ÿelds are Turbulent Prandtl number. Turbulent di usivity.…”