SLAM CHARACTERISTICS OF A HIGH-SPEED WAVE PIERCING CATAMARAN IN IRREGULAR WAVES

Slam characteristics of a 112m INCAT wave piercing catamaran in a range of realistic irregular sea conditions are presented in this paper. Towing tank testing of a 2.5 m hydroelastic segmented catamaran model was used to gather a database of slam events in irregular seas. The model was instrumented to measure motions, centrebow surface pressures and forces, encountered wave elevations and wave elevations within the bow area tunnel arches. From these measurements characteristics of the vessel slamming behaviour are examined: in particular relative vertical velocity, centrebow immersion, archway wave elevations and slam load distributions. A total of 2,098 slam events were identified over 22 different conditions, each containing about 80 to 100 slam events. The data, although inherently scattered, shows that encounter wave frequency and significant wave height are important parameters with regard to centrebow slamming. Relative vertical velocity was found to be a poor indicator of slam magnitude and slams were found to occur before the centrebow arch tunnel was completely filled, supporting the application of a two-dimensional filling height parameter as a slam indicator.

Numerical Investigation for the Resin Filling Behavior during Ultraviolet Nanoimprint Lithography of Subwavelength Moth-Eye Nanostructure

Accurate analysis of the resin filling process into the mold cavity is necessary for the high-precision fabrication of moth-eye nanostructure using the ultraviolet nanoimprint lithography (UV-NIL) technique. In this research, a computational fluid dynamics (CFD) simulation model was proposed to reveal resin filling behavior, in which the effect of boundary slip was considered. By comparison with the experimental results, a good consistency was found, indicating that the simulation model could be used to analyze the resin filling behavior. Based on the proposed model, the effects of process parameters on resin filling behavior were analyzed, including resin viscosity, inlet velocity and resin thickness. It was found that the inlet velocity showed a more significant effect on filling height than the resin viscosity and thickness. Besides, the effects of boundary conditions on resin filling behavior were investigated, and it was found the boundary slip had a significant influence on resin filling behavior, and excellent filling results were obtained with a larger slip velocity on the mold side. This research could provide guidance for a more comprehensive understanding of the resin filling behavior during UV-NIL of subwavelength moth-eye nanostructure.

A General Outflow Theory Based on Momentum Balance

One of the oldest problems in the history of hydraulics is the outflow from a vessel through an orifice. In 1644 it was described by the Torricelli principle stating that the outflow velocity is the fall velocity from the filling level. From a theoretical point of view the Torricelli principle is valid because it follows from Bernoulli's energy conservation principle. In this paper the outflowproblem will be described by Newton's momentum balance principle. Here the Torricelli formula is obtained when the rounded orifice is treated as a contraction. For the sharp edged orifice the bulk outflow velocity is the fall velocity from half the filling height. In this momentum balance theory no artificial outflow coefficients are needed to distinguish between the cases of sharp edged and rounded orifices.

Calculation of the Efficiency of Regenerative Air Heat Exchanger with Intermediate Heat Carrier

The study deals with a new regenerative air heat exchanger with an intermediate heat carrier used in the systems of room ventilation. A physical and mathematical model of the heat transfer process is proposed. The influence of design and operating parameters on the temperature efficiency of the heat exchanger is analyzed. The possibility of a significant increase in its efficiency with a decrease in the packing diameter is shown. As a result of calculations, it was found that with a decrease in the filling height, the maximum temperature efficiency shifted towards a decrease in the air flow rate from its value determined from the equality of water equivalents of liquid and air.

Shearing of granular materials in a confined split-bottom Couette cell

Formation of shear bands is one of the most remarkable phenomena in the dynamics of granular matter. Several parameters have been so far identified to influence the behavior of the shear bands. We carried out experiments to investigate the evolution of the shear bands in the split-bottom Couette cell in the presence of confining pressure. We employed the Particle Image Velocimetry (PIV) to characterize the shear band both in the absence and presence of external pressure. Our results show that the location and width of the shear band are affected by both the confining pressure and the filling height. The shear zone evolves towards the middle of the cylinder and expands to a broader region with increasing applied pressure or filling height; also the angular velocity decreases relative to the rotation rate of the bottom disk. Our findings are consistent with prior empirical observations on the formation of wide shear bands at free surfaces.

Study on the Mechanical Relationship among the Backfilling Mining Support, Roof Rock Beam, and Gangue Filling Body in Comprehensive Mechanized Filling Mining Process

Based on the theory of elastic foundation beam, the mechanical model of the backfilling mining support-roof rock beam-gangue filling body under the condition of comprehensive mechanized filling mining is established. The foundation coefficient of each part is determined, and the subsidence of each part of roof rock beam is calculated. It is found that the initial filling height is the decisive factor to control the subsidence and migration stability of each part of the roof rock beam. Properly increasing the pushing force of backfilling-coal mining hydraulic support on the filling body can also effectively control the roof subsidence. The comprehensive mechanized filling mining process was studied by similar simulation experiments, it is found that the influence law of initial filling height on roof rock beam subsidence is the same as that of theoretical analysis, and the experimental measurement values and fitting function relationships are consistent with the theoretical calculation results.

Experimental study on deformation characteristics of collapsible loess under isotropic stress

In order to study the deformation characteristics of collapsible loess and to construct different vertical stresses, different isotropic stresses are used to represent the vertical stresses, and their corresponding stresses are set to be The hidden stresses in different positions of collapsible loess foundation are analyzed by using 0 kPa, 50 kPa, 100 kPa, 220 kPa, 330 kPa and 400 kPa. In this study, various kinds of deformation analysis of collapsible loess are needed. Ground settlement tester, GJY K0 tester produced by Suzhou Longstan Automation Factory and ADINA software are used. Experiments show that under the action of different filling heights, different isotropic stresses are applied to the foundation, and the hidden stresses of the loess are gradually decreasing. At the same time, the higher the height of the fill, the faster the decline of the underlying stress of the foundation loess; with the increase of time at the bottom of the cushion, the corresponding underlying stress at the midline decreases, while with the increase of the height of the fill, the corresponding underlying stress at the midline rises; the study of the underlying stress at the bottom of the pile is set up differently. Under certain time and position of the pile bottom, increasing the isotropic stress can increase the hidden stress at the corresponding pile bottom, and change the filling height at the pile bottom has little effect on the hidden stress at the pile bottom. Under the combined action of water content and isotropic stress, they are positively correlated with the change of lateral stress. With the increase of isotropic stress, the K0 coefficient rises as a whole. This study can provide a strong reference for the deformation characteristics of collapsible loess itself, and help construction workers to improve the safety of the project in the field of engineering construction.

Improvement of quality of work of seed treater bunker-dispenser

The issues of improving the design of the seed treater hopper are considered. As a result of the research carried out, it was proposed to improve the productivity of the hopper due to the proposed shape and determined the necessary parameters to improve the productivity of the hopper in seed treaters. The proposed improvement makes it possible to increase the productivity of the bunker-metering seeds of agricultural crops, regardless of the filling height of the bunker and granular materials in other industries, reducing the metal consumption and dimensions of the corresponding machines in which such bins are used.

Influence of background characteristics on the optimal sample filling height in gamma-ray spectrometry

The minimum detectable activity (MDA) for gamma spectrometric measurements was studied as a function of filling height for two detectors having different background characteristics and for two sample matrices: a water sample with a low content of natural radionuclides, and zircon sand, with high activities of uranium and thorium. The zircon sand is also a material in which the self-attenuation of low-energy gamma photons will be high. The results show that for the water sample it is always favourable to completely fill the sample container. However, due to the inherent content of naturally occurring radionuclides in the zircon sand the MDA may not necessarily improve with the filling height, since an increased amount of sample will increase the background in the spectrum as well.

Experimental study of the evolution of soil arching effect under cyclic loading based on trapdoor test and particle image velocimetry

Arching effect, which is a common phenomenon in any system involving soil–structure interaction, has been found to be inevitably affected by various factors, including loading conditions. This study investigated the evolution of arching effect induced by cyclic loading by conducting a series of tests using a trapdoor apparatus. The test box was instrumented to control the displacement of the moving gate and to record the variation of vertical stress distribution by using a set of dynamic load cells. Digital images were captured during tests and processed using particle image velocimetry (PIV) to determine the displacement field and hence to examine the variation of geometric features of arch and particle movements. The evolution process of arching effect, from the initial formation to the finial collapse, was identified. Depending on the analysis for the geometry appearance, displacement region, and variation of cyclic stresses, both stable and collapsed arches were observed. By increasing the amplitude of cyclic loading step by step, critical loading amplitude corresponding to the threshold of collapse of the arching effect was determined. Based on the results, the effects of trapdoor displacement, cyclic loading frequency, and filling height on arching effect are discussed.