Numerical simulation of hydraulic optimization for regulating tank in pumping station

Based on the governing equations of steady incompressible fluid, renormalization group (RNG) turbulence model and SIMPLEC algorithm are used to calculate the steady flow field of regulating tank in the pumping station with six different geometries operating under same condition. The impacts of the layout schemes of guide walls for the flow field of the regulating tank are analyzed. The numerical results are verified by physical model experiment and good agreement is found. The results show that: 1) serious flow separation of side wall will occur in the regulating tank when the interval of diversion wall is 10 L; 2) the flow velocity in the regulating tank will be too low when the diversion wall spacing is 16 L; 3) the improvement of the flow pattern of the regulating tank is not obvious; and the project cost is increased when the excavation depth of the regulating tank is increased by 1 m; 4) the bottom velocity reached the non-silting velocity and the head loss of the regulating tank reducing nearly 1.2 m by using arrangement form of wide 21 L and narrow 10L of the guide walls, which provides a certain guarantee for the safe operation of the pumping station. The regulation tank layout scheme proposed in the paper can be applied to engineering practice.

Thermally Optimum Spacing between Inner Plates in Natural Convection Flows in Cavities by Numerical Investigation

Buoyancy-driven airflow that included two isothermal inner plates established in a vented cavity is investigated numerically. The thermally optimum wall-to-wall spacing of the immersed channel, as well as its dependence with respect to the relevant governing parameters, are determined. Results are presented as a function of the aspect ratio b/H for a wide range of Rayleigh numbers RaH. A logarithmic correlation for the optimum (b/H)opt as a function of RaH is presented. In addition, since the outlined configuration might be subject to intense heating conditions, the influence of considering variable thermophysical properties is also included in the analysis. In fact, an appreciable influence of the variation of properties on (b/H)opt is also detected for a representative value of RaH = 109. Obtained results can be directly applied to the optimization of electronic equipment cooling, or even to thermal passive devices in buildings.

SEISMIC RESISTANCE INVESTIGATION OF A LARGE-PANEL BUILDING WITH SUPER-WIDE WALL SPACING

В работе рассмотрена проблема сейсмического прогноза и его эффективности. Проведен анализ ситуации при реализации среднесрочного прогноза разрушительного Тбилисского землетрясения 25 апреля 2002 года в Грузии. Рассмотрены инженерно-геологические, геоморфологические и гидрогеологические условия г. Тбилиси. Показаны изосейсты 5‑ти бального форшока и 7‑ми бального основного толчка. В данной статье рассматриваются записи ряда разрушительных землетрясений, очаг которых находился вблизи урбанизированной территории. Проведен анализ инструментальных записей. Показано, что нахождение урбанизированной территории в ближней зоне источника обуславливает наличие высокочастотной вертикальной составляющей, предваряющей основные колебания. Хорошо известно, что поглощение сейсмических волн прямо пропорционально частоте колебаний, что предполагает быстрое затухание высокочастотной составляющей сигнала. При этом, за редким исключением, большинство записей производится станциями, достаточно удаленными от места событий. Традиционное использование инерционных сейсмоприемников при этом исключает регистрацию указанных высокочастотных сигналов. Исходя из того обстоятельства, что землетрясения расположены непосредственно под территорией г. Тбилиси использование соответствующих записей должно позволить получать реакции зданий и сооружений на подобные воздействия максимально приближенными к реальным условиям. В этой связи исследована эффективность применения в жилых зданиях конструктивной схемы с супершироким шагом на примере 5‑этажного крупнопанельного дома. Был произведен динамический расчет методом конечных элементов The problem of earthquake prediction and its effectiveness is discussed. The analysis of the situation with the implementation of the medium-term forecast of devastating earthquake April 25, 2002, Tbilisi, Georgia was held. Engineering-geological, geomorphological and hydrogeological conditions of Tbilisi are reviewed. 5‑point forshock and 7‑point main shock isoseists are shown. This article discusses a number of devastating earthquakes records, which source was close to the urbanized territory. The analysis of instrumental records was held. It is shown that the near-source zone urbanized territory determines the availability of high-frequency vertical component, anticipating major fluctuations. It is well known that absorption of seismic waves is directly proportional to the frequency of the oscillations, which involves rapid attenuation of signal high-frequency component. Thus, with few exceptions, most of the records produced by stations, quite remote from the scene. Traditional use of inertial seismic detectors excludes the registration of these high frequency signals. Earthquakes are located directly beneath the territory of Tbilisi so the use of appropriate records should enable to receive buildings and structures reactions to such impact closest to real conditions. In this context, we investigated the efficacy of residential design concept with super-wide wall spacing on the example of 5‑storeyed large-panel building. Dynamic calculation using finite element was produced.

Field Emission from Nanocrystalline Diamond/Carbon Nanowall Composite Films Deposited on Scratched Substrates

ABSTRACTWe report the deposition and field emission properties of nanostructured composites consisting of carbon nanowalls (CNWs) and nanocrystalline diamond films by introducing two kinds of substrate scratching pretreatment, i.e., undulation and ultrasonic vibration. With increasing duration of scratching pretreatment, the morphology of the deposits changes from simple CNWs to a film/CNW composite and lastly to CNWs on a film, and then the space between the walls is increased. The emission turn-on field is reduced from 2.1 V/μm for simple CNWs to around 1.2 V/μm for the composite films, accompanied by an increase in field enhancement factor. The results indicate that electric field screening between the walls is successfully suppressed by widening of the wall spacing.

Effect of Jet-to-Jet Spacing in Impingement Arrays on Heat Transfer

Detailed heat transfer measurements are presented for jet impingement through arrays of jet holes. The effect of jet-to-wall spacing, hole-to-hole spacing are studied for inline arrays of holes. The axial and spanwise spacing (S/D) of holes are varied to produce square and rectangular arrays of holes. The results are presented at a jet average Reynolds numbers of 5000, 10000, and 15000. The jet-to-wall spacing is varied from 1 to 5. The arrays of 25 holes are placed to create four different configurations. The first configuration has an axial jet-to-jet spacing (SX/D) of 4 and a jet-to-jet spanwise spacing (SY/D) of 4, the second configuration has a SX/D of 8 and SY/D of 4, and the last configuration has a SX/D and SY/D of 8. Detailed heat transfer measurements are obtained using the transient liquid crystal technique. Results show that increase in jet-to-wall spacing reduces cross-flow effect. Results also show that the increase spacing between jets increases lateral spreading.