Suction effects on turbulence statistics in a heated pipe flow

An experimental study concerning characteristic length scales of the longitudinal velocity fluctuation u′ and the temperature fluctuation θ′ is made in a turbulent pipe flow with a slightly heated porous wall. Frequencies derived, using Taylor’s hypothesis, from time microscales and integral scales, are measured for u′ and θ′ deep in the viscous sublayer. Very near the wall it appears that suction reduces the inflow number which is directly linked to the process of generation of turbulence. Moreover, the skewness and flatness factors of u′ and θ′, and of their time derivatives, are measured. The main results are the relatively high values of flatness with internal intermittency and of skewness with high production of kinetic or thermal turbulence. These values are also reduced by suction.