周期的に拡大, 縮小を繰返す管内乱流の流動と熱伝達

抄録

Experimental study was carried out to examine the effects of pressure gradient for the fluid flow and heat transfer in the duct flow. Air flow in a fully developed turbulent state was decelerated through a linearly diverging section, and then accelerated through a linearly converging section. Experiments were performed with two different ducts, whose acceleration parameter K in the accelerating section was 2.2×10^-6 and 4.5×10^-6. The wall static pressure, the heat transfer coefficient and fluctuations of streamwise velocity as well as the time-averaged velocity profiles were measured. The heat transfer coefficient and turbulence intensity in the converging section were considerably lower than these in the diverging section and the viscous sublayer expanded in the converging section. The behavior of the increase or decrease of the heat transfer coefficient was similar to that of the turbulence intensity in the near-wall region.