Turbulence models are developed by supplementing the renormalization group (RNG) approach of Yakhot and Orszag [J. Sci. Comput. 1, 3 (1986)] with scale expansions for the Reynolds stress and production of dissipation terms. The additional expansion parameter (η≡SK̄/■̄) is the ratio of the turbulent to mean strain time scale. While low-order expansions appear to provide an adequate description for the Reynolds stress, no finite truncation of the expansion for the production of dissipation term in powers of η suffices−terms of all orders must be retained. Based on these ideas, a new two-equation model and Reynolds stress transport model are developed for turbulent shear flows. The models are tested for homogeneous shear flow and flow over a backward facing step. Comparisons between the model predictions and experimental data are excellent.

Basal metabolic rate (BMR), thermic effect of a meal (TEM), anthropometry, and dietary intakes were measured in 18 control subjects; 18 pregnant women at 12, 24, and 34 wk gestation; and in 17 of these women at 12 and 24 wk postpartum, to uncover any metabolic economy associated with either pregnancy or lactation. Results indicated that the BMR and TEM were not associated with any energy saving either during pregnancy or lactation. Mean weight gain from 12 wk gestation to term was 11.4 +/- 3.7 kg; mean birth weight of the infants was 3.06 +/- 0.41 kg. Estimated gain in adipose tissue and fat mass were 3.1 +/- 3.6 and 2.5 +/- 2.9 kg, respectively. Energy cost of pregnancy was estimated to be 303 +/- 171 MJ. The cumulative increase in energy intake over the last two trimesters of pregnancy was 290 +/- 280 MJ, meeting a large part of the total estimated cost of pregnancy. Weight gained by infants who were exclusively breast-fed from birth to 12 wk of age was used as a proxy indicator of adequate lactational performance. The extra energy required during lactation appeared to have been met largely by increases in energy intake, rather than by any metabolic economy or increase in fat mobilization.

Maximal voluntary contraction (MVC) using a handgrip dynamometer was assessed in seventy-two young adult males. The subjects were divided into two groups on the basis of a BMI of 18.5 kg/m2. The subjects with a BMI < 18.5 kg/m2 (n 38) were further divided into an underweight (UW; n 20) group and a chronically energy-deficient (CED; n 18) group. The CED subjects had significantly lower MVC (30.1, SD 5.9 kg) than either the well-nourished controls (BMI > 18.5 kg/m2: 39.8, SD 5.8 kg) or the underweight group (37.6, SD 4.9 kg). The differences between the CED and UW groups persisted even after the MVC were corrected for forearm muscle area and stature. The results suggest that MVC may be a useful functional indicator of nutritional status particularly in differentiating subjects with chronic undernutrition from individuals who are underweight and not undernourished but have similar BMI.

A two-equation turbulence model of the K -e type was recently derived by Yakhot & Orszag based on Renormalization Group (RNG) methods. It was later reported that this RNG based model yields substantially better predictions than the standard K -6 model for turbulent flow over a backward facing step -a standard test case used to benchmark the performance of turbulence models in separated flows. The apparent improvements obtained from the RNG K -e model were attributed to the better treatment of near wall turbulence effects. In contrast to these earlier claims, it is shown in this paper that the original version of the RNG K -E model substantially underpredicts the reattachment point in the backstep problem -a deficiency that is traced to the modeling of the production of dissipation term. However, with the most recent improvements in the RNG K -E model proposed by Yakhot and co-workers, excellent results for the backstep problem are now obtained. Interestingly enough, these results are not that sensitive to the details of the near wall treatment.

A numerical study is conducted on the pressure-driven laminar flow of an incompressible viscous fluid through a rectangular channel subjected to a spanwise rotation. The full nonlinear time-dependent Navier–Stokes equations are solved by a finite-difference technique for various rotation rates and Reynolds numbers in the laminar regime. At weak rotation rates, a double-vortex secondary flow appears in the transverse planes of the channel. For more rapid rotation rates, an instability occurs in the form of longitudinal roll cells in the interior of the channel. Further increases in the rotation rate leads to a restabilization of the flow to a Taylor–Proudman regime. It is found that the roll-cell and Taylor–Proudman regimes lead to a substantial distortion of the axial-velocity profiles. The specific numerical results obtained are shown to be in excellent agreement with previously obtained experimental measurements and theoretical predictions.