Hydroelastic Modeling of Wet Deck Slamming on Multihull Vessels

Slamming against the wet deck of a multihull vessel in head sea waves is studied analytically and numerically. The theoretical slamming model is a two-dimensional, asymptotic method valid for small local angles between the undisturbed water surface and the wet deck in the impact region. The disturbance of the water surface as well as the local hydroelastic effects in the slamming area are accounted for. The elastic deflections of the wet deck are expressed in terms of "dry" normal modes. The structural formu­lation accounts for the shear deformations and the rotatory inertia effects in the wet deck. The findings show that the slamming loads on the wet deck and the resulting elastic stresses in the wet deck are strongly influenced by the elasticity of the wet deck structure.

RISK ASSESSMENT FOR HAZARDOUS SUBSTANCES STORAGE

The goal of this article is to demonstrate the general principles of environmental risk assessment for hazardous substance storage. Matrixes, HAZOP, FTA, and Monte Carlo are examples of methodologies that can be used in conjunction with one another. Environmental assessment, which anticipates the physical, biological, and social repercussions of a project, is used in conjunction with risk assessment. A computer system can be utilized to determine the spill's impact region. When evaluating the probability of an event, and hence the risk, it is vital to have correct statistical data in order to generate more precise conclusions. Following international guidelines is the greatest method to reduce danger.

Optical spectra of FO Aquarii during low and high accretion rates

ABSTRACT Between 2016 May and 2018 September, the intermediate polar (IP) FO Aquarii exhibited two distinct low states and one failed low state. We present optical spectroscopy of FO Aquarii throughout this period, making this the first detailed study of an accretion disc during a low state in any IP. Analysis of these data confirm that the low states are the result of a drop in the mass transfer rate between the secondary star and the magnetic white dwarf primary, and are characterized by a decrease in the system’s brightness coupled with a change of the system’s accretion structures from an accretion disc-fed geometry to a combination of disc-fed and ballistic stream-fed accretion, and that effects from accretion on to both magnetic poles become detectable. The failed low state only displays a decrease in brightness, with the accretion geometry remaining primarily disc-fed. We also find that the WD appears to be exclusively accretion disc-fed during the high state. There is evidence for an outflow close to the impact region between the ballistic stream and the disc which is detectable in all of the states. Finally, there is marginal evidence for narrow high-velocity features in the H α emission line during the low states which may arise due to an outflow from the WD. These features may be evidence of a collimated jet, a long predicted yet elusive feature of cataclysmic variables.

Experimental Investigation of Solid Particle Erosion in Successive Elbows in Gas Dominated Flows

When a fluid containing erosive particles flows through two or more elbows mounted in series with short distances between them, the downstream elbows which are installed after the first elbow are exposed to erosion from a flow that is not fully developed, and therefore, the characteristics of erosive wear in the second elbow can be different than the first. In this work, the erosion magnitude and pattern in two standard successive vertical–horizontal and horizontal–vertical elbows are examined experimentally. Utilizing an ultrasonic technique (UT), erosion measurements are performed in gas–sand and gas–liquid–sand annular flows to investigate the effects of particle size and flowrates. A paint removal study is also performed to capture the erosion patterns in two elbows for different flow conditions. Using two clear elbows, a flow visualization is performed which shows the quality of phase distribution in the two elbows in series in annular and stratified flows. Measurements show the erosion in the second elbow for this geometry and these flow conditions are less than or in a few cases nearly equal to the first elbow. The location of maximum erosion for all the cases considered is around 45 and 65 deg from the inlet of the elbow in the first and second elbows, respectively. Two areas of high impact frequencies are identified in both elbows. One high-intensity particle impact region which is affected primarily by first impact of particles, and another pattern is formed due to rebounded particles from the first impact.

End to Philippine-US military pact would impact region

Headline PHILIPPINES/US: End to pact would impact region

Evaluation of Jet Impact Region and Fluid Force Generated From Ruptured Pipes: Part 4 — Numerical Evaluation of Affected Region by Flashing Jet Flow

Nuclear power plants are designed to prevent the damage of safety installations and human safety due to the jet impingement when a pipe is ruptured. We have investigated evaluation methods for the design basis of protection of plants against effects of postulated pipe rupture using computational fluid dynamics analysis (CFD). The flashing steam jet was evaluated in this study. Shapes of flashing jet were obtained by CFD calculations, and we have found that the affected region was wider than usual steam jet flow and strongly depends on the nozzle exit flow conditions. This is thought as the different tendency from established standards.

Experimental Investigation of Solid Particle Erosion in Successive Elbows in Gas Dominated Flows

When a fluid containing erosive particles flows through two or more elbows mounted in series with short distances between them, the downstream elbows which are installed after the first elbow are exposed to erosion from a flow that is not fully developed. Particle velocities and concentration distributions change due to change of flow direction within the first elbow which may cause the characteristics of erosive wear in the second elbow to be different than the first. In the present study, the erosion magnitude and pattern in two 4-inch standard successive elbows installed with 13D distance from each other are examined experimentally. Utilizing a state-of-the-art ultrasonic technique, erosion measurements are performed in gas-sand and gas-liquid-sand annular flows to investigate the effects of particle size and flow rates. A paint removal study is also performed to capture the erosion patterns in two elbows for different flow conditions. Using two clear elbows, a flow visualization is performed which shows the quality of phase distribution in the two elbows in series in annular and stratified flows. Erosion measurements show the results in the second elbow for this geometry and these flow conditions are less than or in a few cases nearly equal to the first elbow. The location of maximum erosion for all the cases considered is around 45 and 65 degrees from the inlet of the elbow in the first and second elbows, respectively. Two areas are identified in erosion patterns of both elbows. One high intensity particle impact region which is affected primarily by first impact of particles, and another pattern is formed due to impacting particles that have rebounded from the first impact.

Simplified Transient Numerical Model of a Supersonic Jet Impacting a Substrate

The transient flow field near the surface of a substrate impacted by a pulsating supersonic jet emerging from a long tube is investigated using a simplified axially symmetric numerical approach. In the system being modeled, the pulses are created using a rotary valve located at the tube entrance. This flow situation approximates the conditions existing in the Shock-Induced Cold Spray process for coating surfaces with metallic particles. Previous numerical studies of transient supersonic jets either focused on jets emerging from orifices or did not give details of the complex supersonic flow field in the jet impact region. The current approximate numerical method considers the flow within the long tube and in the jet impact region. The procedure involves two stages. The upstream pressure variation with time is first determined using a one-dimensional compressible flow approximation of the entire tube and rotary valve arrangement. The resulting pressure versus time curve serves as the transient inlet boundary condition for an axially symmetric computational fluid dynamic solution of the flow through the tube and region of jet impact on the substrate. The numerical solutions of substrate pressure on the jet centerline versus time are compared with available experimental results and predict certain general features of the substrate pressure traces. Although the simplified model is only in fair agreement with some aspects of the experimental curves, it is shown to be useful in explaining certain peculiar flow features. With the aid of the numerical solution, an explanation for the movement and instability of the bow shock wave which forms ahead of the substrate is described.