A second-order dynamic subgrid-scale stress model

A second-order dynamic model based on the general relation between the subgrid-scale stress and the velocity gradient tensors was proposed. A priori test of the second-order model was made using moderate resolution direct numerical simulation date at high Reynolds number ( Taylor microscale Reynolds number R-lambda = 102 similar to 216) for homogeneous, isotropic forced flow, decaying flow, and homogeneous rotating flow. Numerical testing shows that the second-order dynamic model significantly improves the correlation coefficient when compared to the first-order dynamic models.

Effect of surface tension on the mode selection of vertically excited surface waves in a circular cylindrical vessel

Singular perturbation theory of two-time-scale expansions was developed in inviscid fluids to investigate patternforming, structure of the single surface standing wave, and its evolution with time in a circular cylindrical vessel subject to a vertical oscillation. A nonlinear slowly varying complex amplitude equation, which involves a cubic nonlinear term, an external excitation and the influence of surface tension, was derived from the potential flow equation. Surface tension was introduced by the boundary condition of the free surface in an ideal and incompressible fluid. The results show that when forced frequency is low, the effect of surface tension on the mode selection of surface waves is not important. However, when the forced frequency is high, the surface tension cannot be neglected. This manifests that the function of surface tension is to cause the free surface to return to its equilibrium configuration. In addition, the effect of surface tension seems to make the theoretical results much closer to experimental results.

Surface waves in a vertically excited circular cylindrical container

The nonlinear free surface amplitude equation, which has been derived from the inviscid fluid by solving the potential equation of water waves with a singular perturbation theory in a vertically oscillating rigid circular cylinder, is investigated successively in the fourth-order Runge-Kutta approach with an equivalent time-step. Computational results include the evolution of the amplitude with time, the characteristics of phase plane determined by the real and imaginary parts of the amplitude, the single-mode selection rules of the surface waves in different forced frequencies, contours of free surface displacement and corresponding three-dimensional evolution of surface waves, etc. In addition, the comparison of the surface wave modes is made between theoretical calculations and experimental measurements, and the results are reasonable although there are some differences in the forced frequency.

Effects of g-jitter on the critical marangoni number

A half floating zone is fixed on a vibrational deck, which supports a periodical applied acceleration to simulate the effect of g-jitter. This paper deals with the effects of g-jitter on the fluid fields and the critical Marangoni number, which describes the transition from a forced oscillation of thermocapillary convection into an instability oscillatory convection in a liquid bridge of half floating zone with top rod heated. The responses of g-jitter field on the temperature profiles and flow pattern in the liquid bridge were obtained experimentally. The results indicated that the critical Marangoni number decreases with the increasing of g-jitter effect and is slightly smaller for higher frequency of g-jitter with fixed strength of applied gravity.

Numerical experiments on one-dimensional model of turbulence

The initial-value problem of a forced Burgers equation is numerically solved by the Fourier expansion method. It is found that its solutions finally reach a steady state of 'laminar flow' which has no randomness and is stable to disturbances. Hence, strictly speaking, the so-called Burgers turbulence is not a turbulence. A new one-dimensional model is proposed to simulate the Navier-Stokes turbulence. A series of numerical experiments on this one-dimensional turbulence is made and is successful in obtaining Kolmogorov's (1941) k exp(-5/3) inertial-range spectrum. The (one-dimensional) Kolmogorov constant ranges from 0.5 to 0.65.

Capacidades tecnológicas y certificaciones de calidad: Aplicación empírica a las pymes familiares de La Rioja

Ponencia presentada y defendida en las XIV Jornadas Hispano-Lusas de Gestión Científica celebradas en las Azores en febrero de 2004.

Air Flow Land-Sea-Air Interface: Monterey Bay, California - 1971. Annual Report, Part 1, July 1972

Air flow at the land-sea-air interface influences to a large extent the atmospheric conditions that determine the transport, di lution, and trapping of natural and man-made air pollutants in the coastal areas of Monterey Bay and the Salinas Valley. Analysis of the hourly air flow on a daily and monthly basis indicates patterns of stagnation from midnight to noon of the fol lowing day with moderate to strong air flow during period 1300 to 2200. Throughout the year 1971 whenever flow is greater than 5 mph, the prevailing wind direction is onshore and from a westerly direction. Suggestions for urbanization and industrialization are made on the basis of an understanding of the atmospheric conditions which lead to trapping and dispersal of atmospheric waste. (27 page document)

Tidal oscillations at the head of Monterey Submarine Canyon and their relation to oceanographic sampling and the circulation of water in Monterey Bay. Annual report, Part 6, September 1972

During a 25-hour hydrographic times series at two stations near the head of Monterey Submarine Canyon, an internal tide was observed with an amplitude of 80 to 115 m in water depths of 120 and 220 m respectively. These large oscillations produced daily variations in hydrographic and chemical parameters that were of the same magnitude as seasonal variations in Monterey Bay. Computed velocities associated with the internal tide were on the order of 10 em/sec, and this tidally induced circulation may have a significant role in the exchange of deep water between Monterey Submarine Canyon and the open ocean. (PDF contains 49 pages)

A short survey of the environment at the dumping site for Santa Cruz Harbor dredging and A study of seaward dipping internal structures in marine ripple marks at Whaler's Cove, California. Annual report, Part 4, August 1972

(PDF contains 76 pages)

Biological Studies. Annual Report, Part 5, September 1972

(54 page document)

三角翼受迫俯仰滚转耦合运动的气动特性研究

基于刚性动网格的技术,选用B-L湍流模型,利用有限控制体积法对N-S方程进行数值离散,对76°大后掠三角翼的受迫俯仰滚转耦合运动进行了数值模拟,在此基础上,对俯仰滚转耦合运动的气动力特性和流场结构进行了分析.计算结果表明:俯仰滚转耦合运动时,三角翼上表面的涡分布的非对称性将产生横侧方向的偏航力矩和滚转力矩,滚转力矩和偏航力矩随着滚转振幅角和滚转缩减频率的增大而增大,但对法向力影响不大.

Results of the Sea Grant fishes sampling program for the 1971-1972 Season. Annual Report, Part 6, 1973

(PDF contains 48 pages)

Sand Transport Studies in Monterey Bay, California: Annual Report, Part 5, 1973

(PDF contains 71 pages)

A quantitative survey of the benthic infauna of northern Monterey Bay, California: Annual report, Part 8, 1973

(PDF contains 241 pages)