Extreme Pressure Values Research Articles

Enhancing tsunami resilience for coastal bridge piers through seawall-integrated breakwaters: An experimental study

In ocean engineering, breakwater plays a crucial role in protecting coastal structures such as bridge pier from the impact of extreme sea waves. However, enhancing the existing breakwaters' ability to withstand extreme wave remains an urgent issue to address. This study explores the reinforcement strategy of breakwater against extreme sea waves by installing seawalls on the breakwater. Utilizing dam-break wave generation techniques to simulate tsunamis, the study experimentally evaluates the effectiveness of seawalls in reducing the tsunami forces exerted on bridge pier model and numerically investigates the tsunami forces on the seawalls. The focus of this research is to analyze the pressure distribution on seawalls and the impact of different seawall configurations on the reduction of tsunami forces on bridge pier model. Results show that: Under the tested wave condition (a) The height of the seawall on the breakwater is a critical parameter, as increasing wall height reduces the tsunami forces exerted on the bridge pier behind it. The taller seawalls are subjected to greater tsunami forces in tested cases; (b) The trend of extreme pressure values for different seawalls starts increasing at the bottom and then decreases; (c) There is a critical distance that the breakwater being most effective at reducing tsunami impact forces between the bridge pier model and the breakwater. This study not only deepens the understanding of the interaction between tsunami waves and seawalls but also offers practical guidance for designing structures with disaster resilience, significantly influencing the future design and construction of tsunami-resistant coastal infrastructure.

Investigating the Impact of Operating Conditions on Relief Pressure Valve Flow through CFD and Statistical Analysis

This paper presents a comprehensive computational fluid dynamics (CFD) analysis of air/water flow through a discharge valve, focusing on four different seat–valve distances and three adjustment nozzle positions. The study investigates the velocity distribution, pressure profiles, tangential stresses, and turbulent kinetic energy within the valve and analyzes its performance under various operating conditions. Notably, peak velocities of 3210 m/s were observed between the valve seat and valve, with significant variations for different nozzle positions. Extreme pressure values centered on the valve plate, reaching 4.3 MPa. Tangential stresses were highest on the chamfered plate surface and varied on the seat, turbulent kinetic energy (TKE) exhibited randomness. This study provides valuable information for enhancing the valve’s efficiency in a wide range of industrial applications.

Ashless and non-corrosive disulfide compounds as excellent extreme pressure additives in naphthenic oil

Medium chain chlorinated paraffin (MCCP) and zinc dialkyl dithiophosphate (ZDDP) are widely used as extreme pressure (EP) additives in metalworking fluids (MWFs). Currently, sulfur-based EP additives are found to be more environmentally friendly and biodegradable. Although naphthenic base oil (NBO) is suitable to be used in MWFs due to its low pour point and better emulsified ability, there is a lack of study on the sulfur additives in this type of oil. In this study, two organo disulfides compounds namely dibenzyl disulfide (DBDS) and dioctyl disulfide (DODS) have been synthesized as EP additives. These DBDS and DODS demonstrate an excellent EP performance, non-corrosive, ashless, and good anti-wear (AW) properties in NBO. The DBDS shows 1961 N (EP value) and 6 mm2 (AW scar area) in NBO, which is superior to DODS, MCCP and ZDDP. This is due to the formation of sulfur-based tribofilm on the interface that acts as a protective sulfur layer thus, enhancing the property of EP.

Bimodal distribution of wind pressure on windward facades of high-rise buildings induced by interference effects

Understanding the characteristics of wind pressures on structural façades is of great importance for wind-resistant design of claddings and glass curtains of buildings. This article presents some interesting findings about the behavior of wind pressure on the façades of a high-rise building influenced by an interference building via wind tunnel tests. The bimodal probability distribution (BPD) of wind pressure acting on the windward side of the principal building is highlighted, which has been rarely reported and investigated in previous studies. This BPD featured wind pressure consists of both positive and negative components that alternate along time in a consistent way to the vortex shedding downwind of the interference building. By changing the relative position between the principal building and interference building, it is observed that the bimodal distribution can be transformed to a unimodal form, mostly with a long tailed on the left-hand-side of the probability-density-function (PDF). Based on the above findings, this study proposes a mixture PDF model which is actually a combination of the Gaussian model and the generalized-extreme-value (GEV) model. While the Gaussian PDF accounts for the component dominated by the background approaching flows, the GEV one is associated with the aerodynamic interference effects. Parametric analysis is then conducted for the BPD feature based on the proposed mixture model, and detailed process for the transformation of different PDF patterns (from varied bimodal patterns to both Gaussian and tailed unimodal statuses) is reproduced. The findings can provide useful insights for the wind-resistant design of claddings and curtain walls of high-rise buildings, and for further analyzing non-Gaussian characteristics of wind pressure, such as for estimating extreme pressure values.

Considerations on transients in a water supply distribution network

Lipnița is a village situated in a hilly region, in Constanta County. The water supply system has its own groundwater water source, placed in the middle of the village at a low elevation. Water is conveyed, by a long transmission duct to a storage tank from which it flows by gravity to the consumers. The distribution network has two long mains that intersect in a manifold with isolation valves, situated in the middle of the village. This topology of the system shows high static head for the transmission duct and high elevation differences between the end consumers and those in the centre of the village.The paper presents an analysis, by numerical simulation, on the transients that occur in two different segments of the system.The simulation was performed either for the original old steel made network, aiming at identifying the vulnerable cross sections and extreme pressure values. The results showed that maximal pressure values are not dangerous, but cavitation occurs along the pipeline. The same simulation was carried out for the new PEHD pipelines. The change of material and the increase in diameter of the new pipes showed better results regarding pressure variation during transients. Cavitation is avoided.

Tribological property study of mercaptobenzothiazole‐containing borate derivatives and its synergistic antioxidative effects with N‐phenyl‐α‐naphthylamine

AbstractThe synthesised mercaptobenzothiazole‐containing borate ester (MTEB) and mercaptobenzothiazole‐containing borate (MTES) have good tribological performances in rapeseed oil (RSO). At 0.5 wt% concentration, MTEB and MTES can increase the extreme pressure value of RSO by 60.7% and 67.6%, respectively. The wear scar diameters (WSDs) of oil samples decrease with increase of MTEB (MTES) contents, and the antiwear effect of MTES is better than MTEB at the same condition, because of their polarity is different. There are similar results in the friction reduction performance. The X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis results have shown that MTEB and MTES can form protective films on the metal surfaces that contain boron oxide, iron oxide, ferrous sulfate, iron sulfide (MTEB additive), and other organic nitrogen compounds. The different reaction films formed in the complex boundary possess extreme pressure and antiwear capability. MTES possessed good synergistic antioxidation effect with N‐phenyl‐α‐ naphthylamine (T531), because it increased the oxidation activation energy than RSO by 97.13% when 0.025 wt% MTES is mixed with 0.25% T531.

The Biomechanics of Lesion Formation in Endolymphatic Hydrops: Single and Double Hit Mechanisms.

The vestibular membranes of the cochlea and saccule are subject to two simultaneous constraints as they deform in endolymphatic hydrops. Boundary tethers impose a bulge-type constraint during pressure-induced transverse membrane displacement, while inherent elasticity imposes a stretch-type constraint during stress-induced longitudinal membrane distention. The aim of this study is to reconcile the effect of these dual constraints on membrane deformation. It is hypothesized that it is the interaction of these constraints that determines whether a stable membrane configuration can be achieved or progression to endolymphatic hydrops will occur. Reissner's membrane was modeled as a flat elastic ribbon that was bound along its lateral edges and subject to trans-mural pressure. The bulge and stretch constraints on membrane deformation were formulated mathematically. A graphic solution of the constraint functions was used to examine the nature of the interaction and determine how pressure and elasticity influence the hydropic process. The graphic analysis shows how bulge and stretch phenomena interact to achieve an equilibrium point that satisfies both physical requirements. Nominal values of pressure and elasticity are projected to result in a stable membrane equilibrium in the precritical zone with the modest isolated increases in either parameter alone compatible with stability. However, a sufficiently large increase in either pressure or elasticity alone can constitute a single hit mechanism to exceed the critical point and destabilize the membrane. Moreover, simultaneous modest increases in both pressure and elasticity, neither of which would be sufficient in its own right, can be additive and constitute a double hit mechanism to destabilize the membranes as well. Finally, extreme values of pressure and elasticity that fail to intersect imply that no solution is feasible and that the affected membranes will fail immediately. Sufficiently large increases in either endolymphatic pressure or membrane elasticity alone can destabilize the membranes and constitute single hit mechanisms for inducing hydrops. Combined moderate increases in both trans-mural pressure and membrane elasticity can also destabilize the membranes and constitute a double hit mechanism for hydrops induction.

Golpe de ariete en una red de tuberías debido al cierre rápido de una válvula

Water hammer in pipe networks is a subject little discussed in the technical literature. This may be due to the belief that the network shape helps to reduce its impact, since the pressure waves would tend to subdivide as they propagate through the system pipes. In this article the water hammer is analysed in a pipe network due to the closure of a valve modelled how if it were of type butterfly, gate circular, gate square, ball, needle and globe. It is concluded that the extreme pressure values depend on the type of valve which it is being closed, and that the network shape is not a relevant factor that it helps to attenuate the transient pressures.

Interference effects on tail characteristics of extreme pressure value distributions

This study investigates the interference effects on the tail characteristics of extreme pressure coefficients. Systematic wind tunnel tests are conducted, from which a large amount of data is generated to describe the tail characteristics of extreme pressure coefficients under interference effects. Through the identification of shape parameter of Generalized Extreme Value distribution (GEVD) function and the estimation of fluctuation level of extreme pressures, optimal peak pressure coefficients are predicted to compare with the Cook and Mayne coefficients. Results show that the design fractiles based on estimated parameters are generally lower than 78%, and the identified concave tail characteristics imply a ceiling coefficient value. The largest negative peak pressure coefficients are found when the interfering building is in the upstream region of the principal building and most of them are along the vertical edges of side faces parallel to the wind direction. By calculating the error percentages due to the assumption of Gumbel tail, the estimation bias is indicated and the significances of both the shape parameter and the fluctuation level of extreme pressures are presented.

Evolution of deviations from the spherical shape of a vapor bubble in supercompression

This paper considers the evolution of small deviations of a cavitation bubble from a spherical shape during its single compression under conditions of experiments on acoustic cavitation of deuterated acetone. Vapor motion in the bubble and the surrounding liquid is defined as a superposition of the spherical component and its non-spherical perturbation. The spherical component is described taking into account the nonstationary heat conductivity of the liquid and vapor and the nonequilibrium nature of the vaporization and condensation on the interface. At the beginning of the compression process, the vapor in the bubble is considered an ideal gas with a nearly uniform pressure. In the simulation of the high-rate compression stage, realistic equations of state are used. The non-spherical component of motion is described taking into account the effect of liquid viscosity, surface tension, vapor density in the bubble, and nonuniformity of its pressure. Estimates are obtained for the amplitude of small perturbations (in the form of harmonics of degree n = 2, 3, ... with the wavelength λ = 2πR/n, where R is the bubble radius) of the spherical shape of the bubble during its compression until reaching extreme values of pressure, density, and temperature. These results are of interest in the study of bubble fusion since the non-sphericity of the bubble prevents its strong compression.

Synthesis, Physicochemical, and Tribological Characterization of Nano Lubricant Contained Cu Nanocolloid as Additive

Monocrystalline Cu nanocolloid with 4.3 nm average particle size and 2.3～9.5 nm particle size distribution was successfully synthesized in situ by liquor-phase reduction synthesis, using copper acetate tetrahydrate as precursor, ascorbic acid as reductant, polyethylene sorbitan monooleate （Tween-80） as modifier, and liquid paraffin as solvent. The as-prepared copper nanocolloid was characterized by XRD, SAED, and TEM. Nano-lubricating oil with excellent dispersibility, chemical stability, and compatibility with other additives verified by TG-DSC, was achieved via adding as-prepared nano-copper into Mobil 1 5w-30 lubricating oil. The nano-lube’s physiochemical properties were characterized according to Chinese national standard. The tribological behavior of nano-lubricant was investigated on ball-on-disk UMT-Ⅱ tribometer and four-ball tribometer. The worn surface morphology was analyzed by means of SEM and EDS. Experimental results show as follows. The Mobil 1 5w-30 lube’s tribological property is markedly enhanced with the as-prepared copper nanocolloid as its additive. The as-prepared nano-Cu agglomerate discontinuous deposited, extrude, melt, spread, and form a film in micro-defects on the worn surfaces, then improve the friction-reducing, anti-wear ability, extreme pressure value, and extreme working ability of Mobil 1 5w-30 lubricant.

Science under Extreme Conditions of Pressures and Temperatures at the ESRF

The last decades have witnessed an unprecedented surge in the study of matter and materials at extreme values of pressure and/or temperature. The fundamental importance of this research stems from the fact that high pressure can deeply modify chemical bonds and induce myriad changes in materials. Many breakthroughs have been achieved at synchrotrons worldwide, in fields ranging from earth and planetary sciences to fundamental physics, chemistry, and materials research, and even in the life sciences, where questions on life and biological function under extreme conditions have been studied.

Towards a complete numerical description of lubricant film dynamics in ball bearings

In this article, we propose a framework for a detailed finite element analysis of elastohydrodynamic lubrication in ball bearings. Our contribution to this field is twofold. First, we present a fully monolithic ALE method for the treatment of fluid---structure interaction. For the lubricant, we use the full Navier---Stokes equations in combination with a pressure-dependent viscosity law and include thermal effects. Second, we introduce a novel method for a fully implicit treatment of the evolution of the lubricants' free surface using Nitsches method. This allows for arbitrarily large time steps independent of the spatial discretization. Despite the variety of numerical challenges present in this application, such as anisotropy and extreme values of pressure, our approach for the first time shows robustness up to high rotational speeds as required in industrial applications. We describe the numerical ingredients we use in detail and present numerical results that validate our approaches and demonstrate its capabilities.

Numerical computation of end plate effect on Taylor vortices between rotating conical cylinders

End plate effect on Taylor vortices between rotating conical cylinders is studied by numerical method in this paper. We suppose that the inner cone rotates together with the end plate at the top and the outer one as well as the end plate at the bottom remains at rest. It is found that the instability sets in at a critical Reynolds number about Re = 80. Increase Re to about Re = 200 the first single clockwise vortex is formed near the top of the flow system. Further increase Re to about Re = 440 another clockwise vortex is formed under the first one. At about Re = 448 the third vortex is formed which rotates in counterclockwise direction between the first two vortices. With increasing of Re the process continues. Finally, a configuration is obtained with an odd number of vortices in the annulus at about Re = 700, which confirms the experimental observation. Moreover, the local extreme values of pressure and velocity are achieved at the adjacent lines between neighboring vortices or at the medium lines of vortices. The effect of gap size on vortices is also considered. It is shown that the number of vortices increases with decreasing of the gap size and the end plates play an important role in the parity of the number of the vortices.

Transition to Taylor vortex flow between rotating conical cylinders

Transition to Taylor vortex flow between two conical cylinders, with the inner one rotating and the outer one stationary, is studied by the numerical method in this article. It is found that the basic flow becomes unstable with increasing of Reynolds number ( Re) above a certain critical value Re c=117 and with the further increase of Re to about Re=300, the first stable vortex is formed near the top of the flow system. The annulus is filled with six pairs of vortices at about Re=800. These are confirmed by experimental observations. Moreover, the local extreme values of pressure and velocity are reached at the adjacent lines between neighboring vortices or at the medium lines of large vortices. The local minimum values of velocity and the local maximum values of pressure are reached at the same point, whereas the local maximum values of velocity of the flow are assumed at the point of inflection for pressure.

Study on application of CeO 2 and CaCO 3 nanoparticles in lubricating oils

The ceria (CeO 2) nanoparticles and calcium carbonate (CaCO 3) nanoparticles were chosen as additives of anti-wear and extreme pressure for lubricating oils, and the morphology and sizes of nanoparticles were examined using Transmission Electron Microscope (TEM). The tribological performance of lubricating oils containing combined nanoparticles were determined by four-ball friction and wear tester, and the chemical composition of steel ball with worn surface were analyzed by X-ray Photoelectron Spectrum(XPS). The results showed that the lubricating oils containing combined nanoparticles had good anti-wear and friction reducing effects, and the tribological properties were optimal when W CeO2+CaCO3=0.6%, W CeO2:W CaCO3=1:1. The extreme pressure value increased by 40.25%, the wear spot diameter reduced by 33.5%, and friction coefficient reduced by 32% compared with 40CD oil. The coordinated action of big and small particles made anti-wear and friction reducing effective. Tribological chemical reactions resulting from the friction surface formed metal calcium, metal cerium and oxides film, and they could fill up the concave surface and protect the worn surface.

Scour of rock due to the impact of plunging high velocity jets Part II: Experimental results of dynamic pressures at pool bottoms and in one- and two-dimensional closed end rock joints

This paper presents the experimental results of dynamic pressure measurements at simulated plunge pool bottoms and underlying rock joints, due to plunging high velocity jet impact. Emphasis is given on the mean and the fluctuating part of the dynamic pressures, to the extreme pressure values, and to the spectral content of the fluctuations. Particular attention is also paid to the relationship between pool bottom pressures and the pressures they generate inside underlying rock joints. Based on data analysis in one- and two-dimensional rock joints, it was found that high velocity plunging jets are able to generate oscillatory and resonance pressure waves inside the joints. These non-linear transient phenomena propagate at wave celerities that depend on the air content of the air-water mixture inside the joint. This air content is directly related to the plunge pool air content and to instantaneous pressure fluctuations inside the joint. The resulting amplification of pool bottom pressures inside rock joints is believed to be a key for a better assessment of scour formation in rock.

The antifriction behaviours of

In this paper, the antifriction behaviours of (3:1) molecules and their crystal powder were evaluated by different methods. It was found that the crystal powder possessed hexagonal close packed (hcp) crystal structure with a = 10.1 Å and c = 16.55 Å, and a transformation of crystal structure from hcp to face centred cubic (fcc) occurred easily during friction (burnishing). It was confirmed that two kinds of process, breakage of powder coagulated by nanoscale single crystals and rearrangement of the molecules along the friction direction, had occurred under the friction force. The extreme pressure (EP) performance of as an additive in paraffin liquid was investigated on an SRV oscillating wear machine. It was found that the extreme pressure load (EP value) of paraffin liquid was increased by dispersion of powder, accompanied by a slight improvement in the antifriction behaviour. it was confirmed that the improvement in EP value and antifriction behaviour of oil was dependent on the crystal structure of powder, but independent of the spherical molecular structure of or . The burnishing experimental results also proved that the antifriction behaviour was determined by the crystal structure and had no relation to the molecular structure. It was also found that fullerenes possessed some physical properties similar to those of graphite. Since the formation of compact fullerenes with high shear strength during friction can be effectively prevented by some other lubricants, it is suggested that fullerenes should be mixed with other lubricants for tribological application.