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Experimental data are provided for physical understanding and computational fluid dynamics (CFD) validation for the surface combatant David--Taylor model basin Model 5415 bow and shoulder wave breaking. A photographic study was conducted using 5.72 m replica and 3.05 m geosim models of Model 5415 over a range of Froude numbers (Fr) to identify Fr and scale effects on wave breaking and choose the best Fr for the local flow measurements, which include near- and far-field means and rms wave elevation and mean velocity under the breaking waves. The larger model and Fr=0.35 were selected due to the large extents of quasisteady plunging bow and spilling shoulder wave breaking. A direct correlation is shown between regions of wave slope larger than 17 deg and regions of large rms in wave height variation. Scars characterized by sudden changes in the mean wave height and vortices induced by wave breaking were identified. Complementary CFD solutions fill the gaps in the relatively sparse measurements enabling a more complete description of the bow and shoulder wave breaking and induced vortices and scars. The combined results have important implications regarding the modeling of the bubbly flow around surface ships, especially for bubble sources and entrainment. [DOI: 10.1115/1.2786490]

Phase-averaged organized oscillation velocities (U,V,W) and random fluctuation Reynolds stresses ([bar.uu],[bar.vv],[bar.ww],[bar.uv],[bar.uw] are presented for the nominal wake of a surface ship advancing in regular head (incident) waves, but restrained from body motions, i.e., the forward-speed diffraction problem. A 3.048 x 3.048 x 100 m towing tank, plunger wave maker, and towed, 2D particle-image velocimetry (PIV) and servo mechanism waveprobe measurement systems are used. The geometry is DTMB model 5415 (L=3.048 m, 1/46.6 scale), which is an international benchmark for ship hvdrodynamics. The conditions are Froude number Fr=0.28. wave steepness Ak=0.025, wavelength [lambda]/L= 1.5, wave frequency f=0.584 Hz, and encounter frequency [f.sub.e]=0.922 Hz. Innovative data acquisition, reduction, and uncertainty analysis procedures are developed for the phase-averaged PIV. The unsteady nominal wake is explained by interactions between the hull boundary layer and axial vortices and incident wave. There are three primary wave-induced effects: pressure gradients 4% [U.sub.c], orbital velocity transport 15% [U.sub.c], and unsteady sonar dome lifting wake. In the outer region, the uniform flow, incident wave velocities are recovered within the experimental uncertainties. In the inner, viscous-flow region, the boundary layer undergoes significant time-varying upward contraction and downward expansion in phase with the incident wave crests and troughs, respectively. The zeroth harmonic exceeds the steady-flow amplitudes by 5-20% and 70% for the velocities and Reynolds stresses, respectively. The first-harmonic amplitudes are large and in phase with the incident wave in the bulge region (axial velocity), damped by the hull and boundary layer and mostly in phase with the incident wave (vertical velocity), and small except near the free surface-hull shoulder (transverse velocity). Reynolds stress amplitudes are an order-of-magnitude smaller than for the velocity components showing large values in the thin boundary layer and bulge regions and mostly in phase with the incident wave. [DOI: 10.1115/1.2717618]

A statistical approach for estimating intervals of certification or biases of facilities or measurement systems including uncertainties is set forth based on M x N-order level testing, which is defined as M repetitions of the same N-order level experiment in M different facilities or in the same facility with M different measurement systems. In the absence of reference values, the mean facility or measurement system is used for assessing intervals of certification or biases. Certification or biases of facilities or measurement systems are defined as processes for assessing probabilistic confidence intervals for facilities or measurement systems for specific tests, data reduction equations, conditions, procedures, and uncertainty analysis. Similarly, subgroup analysis is performed for isolating and assessing levels of differences due to use of different model sizes (scale effects) or measurement systems. An example is provided for towing tank facilities for resistance tests using standard uncertainty analysis procedures based on an international collaboration between three facilities. Although the number of facilities are at a minimum, the results demonstrate the usefulness of an approach and support recommendation of future collaborations between more facilities. Knowledge of intervals of certification or biases is important for design, accrediting facilities or measurement systems, and CFD validation.

A new approach to computational fluid dynamics code validation is developed that gives proper consideration to experimental and simulation uncertainties. The comparison error is defined as the difference between the data and simulation values and represents the combination of all errors. The validation uncertainty is defined as the combination of the uncertainties in the experimental data and the portion of the uncertainties in the CFD prediction that can be estimated. This validation uncertainty sets the level at which validation can be achieved. The criterion for validation is that the magnitude of the comparison error must be less than the validation uncertainty. If validation is not accomplished, the magnitude and sign of the comparison error can be used to improve the mathematical modeling. Consideration is given to validation procedures for a single code, multiple codes and/or models, and predictions of trends. Example results of verification/validation are presented for a single computational fluid dynamics code and for a comparison of multiple turbulence models. The results demonstrate the usefulness of the proposed validation strategy. This new approach for validation should be useful in guiding future developments in computational fluid dynamics through validation studies and in the transition of computational fluid dynamics codes to design.

In this two-part paper, time-accurate solutions of the Reynolds-averaged Navier-Stokes equations are presented, which address through model problems, the response of turbulent propeller-blade boundary layers, and wakes to external-flow traveling waves. In Part 1, the Massachusetts Institute of Technology flapping-foil experiment is simulated and the results validated through comparisons with data. The physics of unsteady blade flows are shown to be complex with analogy to Stokes layers and are explicated through visualization and Fourier analysis. It is shown that convection induced steady/unsteady interaction causes deformation of the external-flow waves and is responsible for the upstream- and downstream-traveling pressure-gradient waves over the foil and in the wake, respectively. The nature of the unsteady displacement thickness suggests viscous-inviscid interaction as the mechanism for the response. In Part 2, a parametric study is undertaken to quantify the effects of frequency, foil geometry, and waveform.

The design of a Si/SiGe heterojunction complementary metal-oxide-semiconductor (HCMOS) transistor has a high hole and electron mobility, and nearly symmetric threshold voltage and current drive capacity of the n- and p-MOSFETs. It also evades parasitic channels within the operating bias range. Analytical models and numerical simulations help to predict the channel charge distribution and transport mechanism. The advantages of the HCMOS over bulk Si CMOS is demonstrated by simulated ring oscillators that exhibit a 4- to 6-times reduced power-delay product.