Laser-Doppler velocimeter measurements of mean velocities, turbulence intensities, and Reynolds stresses are presented for periodic fully developed flows in a channel with square rib-disturbed walls on two opposite sides. Quantities such as the vorticity thickness and turbulent kinetic energy are used to characterize the flow. The investigated flow was periodic in space. The Reynolds number based on the channel hydraulic diameter was 3.3×104. The ratios of pitch to rib-height and rib-height to chamber-height were 10 and 0.133, respectively. Regions where maximum and minimum Reynolds stress and turbulent kinetic energy occurred were identified from the results. The growth rate of the shear layers of the present study was compared with that of a backward-facing step. The measured turbulence anisotropy and structure parameter distribution were used to examine the basic assumptions embedded in the k–ε and k–ε–A models. For a given axial station, the peak axial mean-velocity was found not to occur at the center point. The secondary flow was determined to be Prandtl’s secondary flow of the second kind according to the measured streamwise mean vorticity and its production term.

The effects of clearance ratio (C/H) and Reynolds number (Re) on the turbulent heat transfer and friction in a rectangular duct with ribs detached from one wall were characterized quantitatively using laser holographic interferometry and pressure measurements. The investigated flow was periodic in space both hydrodynamically and thermally. C/H and Re were varied from 0.25 to 1.5 and 5 × 103 to 5 × 104, respectively. The obtained interferograms, local (Nu) and average (Nu) Nusselt number, and thermal performance (Nup/Nus*) allowed the critical C/H characterizing different mechanisms of heat transfer augmentation to be identified and allowed a comparison of Nu, Nu, and Nup/Nus* among the detached ribbed duct, the attached ribbed duct, and the smooth duct to be made. It was found that the detached ribbed geometry has the advantage of eliminating the hot spots behind the attached ribs. Optimal clearance ratios for heat transfer enhancement between the present periodic detached ribs and previous single detached cylinder were also compared. Furthermore, compact heat transfer and friction correlations were developed for a detached ribbed duct for the first time.

Measurements and computations are presented of mean velocity and turbulence intensity for an arrangement of two pairs of turbulence promoters mounted in tandem in developing channel flow. The Reynolds number (ReD) and the pitch ratio (PR) were varied in the range of 1.2 × 104 to 1.2 × 105 and 1 to 100, respectively. The three pitch ratios 5, 10, 15 were found to provide three characteristic flows which are a useful test of the computational models. The effects of PR on the reattachment lengths and the pressure loss as well as the influence of ReD on the reattachment length were documented in detail. It was found that PR=10 was preferable to PR = 5 and PR = 15 from the standpoint of heat transfer enhancement.

Cultivation of Monascus purpureus (CCRC 31615) for the production of natural pigments was investigated. Traditionally, Monascus species were grown on rice by solid-state culture. For large-scale cultivation, solid-state cultures were associated with some problems such as contamination and scale-up. By using submerged cultures with rice particles, a stirred-tank fermentor was not suitable for submerged cultures as the impeller tended to break the particles into small pieces. A conventional bubble column was also unsuitable as its mixing capability was poor. In the present study, a modified bubble column with wire-mesh draft tubes was employed for the cultivation of M. purpureus. The proposed column had a shorter mixing time and a higher oxygen transfer rate relative to the conventional bubble column. The production of pigments using the proposed column was up to 80% higher than that achieved using the conventional bubble column.

We report a high-efficiency hard-X-ray resonator with inclined-incidence geometry. A beam incident at 36.87° with respect to [3 1 0] excites Bragg back diffraction along (12 4 0) at 14.4388 keV for resonance in a Si-based resonator to produce intense resonance fringes. The experimental results showed the visibility enhanced by nearly 30 times compared with normal incidence. Also numerical calculations of the inclined-incidence resonator demonstrate ultrahigh efficiency and extremely narrow resolving power (sub-meV) with low background. This geometry surpasses the intrinsic limits of normal-incidence crystal-based resonators and enables ultrahigh-resolution X-ray optics for X-ray diffraction, spectroscopy, and imaging applications.