Three-dimensional periodic thermoelastichydrodynamic modeling of hydrodynamic processes of a thrust bearing

The article presents the basic principles of three-dimensional mathematical modeling of the operation of a thrust plain bearing with fixed pads of the compressor. The model is based on the periodic thermoelastichydrodynamic (PTEHD) theory which allows calculating the temperature at the inlet to the pad and considering the complete thermal pattern. A description of the main provisions of the numerical implementation is given. In the stationary mode of the bearings operation, using the Sm2Px3Tx program, numerical experiments were carried out aimed at studying different boundary conditions to the Reynolds equation, the physics of the hydrodynamic process in the lubricating and boundary films of the bearing and the heat propagation in the body of the pad and thrust collar.

Three-dimensional integro-differential model of unstationary hydrodynamic process in a liquid-metal pool of underwater arc welding

Wet underwater arc welding is now widely used. At the same time, obtaining high-quality welds with this welding method is an urgent scientific and technical problem due to their saturation with hydrogen and oxygen and the formation of pores. One of the promising directions for solving this issue is the use of an external electromagnetic effect on the liquid metal in the weld pool in order to control the movements of the molten metal flows to improve the degassing processes of welded joints. It is possible to estimate the parameters and efficiency of external electromagnetic influence by means of mathematical modeling of related electromagnetic, hydrodynamic and thermal processes occurring in the welding installation. The article proposes a three-dimensional integro-differential model of a non-stationary hydrodynamic process occurring in the liquid metal of a weld pool in an underwater arc welding system with an external electromagnetic effect. For the equations of hydrodynamics boundary value problems are formed, which, using potential theory, are reduced to a system of integro-differential equations for the vorticity function in the volume of a liquid conductor and a simple vector layer on its surface. For a numerical solution, the resulting system of integro-differential equations is approximated by an algebraic system according to the Krylov-Bogolyubov method. This system of equations makes it possible to determine the velocity field in the liquid metal of the weld pool for any welding modes.

Theoretical Description of the Hydrodynamic Process after Barrier Lake Formation and Emergency Responses Implementation

Barrier lakes are secondary disasters with associated landslides and debris flow that can cause serious damage to the downstream populations and areas. Existing studies are lacking in comprehensive descriptions of the rescue process, where the main channel streamflow varies and topographic erosion develops, as well as engineering disposal performs. This paper aimed to theoretically investigate the formation and emergency responses to barrier lakes using on-the-spot investigation and calculus theory. The results showed that the formation of a barrier lake led to a sudden variation in the flow-change rate (normal to infinite). However, after implementing emergency measures, this rate returned to normal. The whole rescue process could be regarded as the accumulation of disposal effects. Volume changes in the main streams were expressed by a differential equation of the lake surface area and water level variations. In addition, a corresponding theoretical description of flow discharges was also given when engineering measures such as the excavation of diversion channels and engineering blasting were adopted. Specifically, the theoretical expressions of flow discharge were given respectively in the developing stage and breach stable stage after the excavation of diversion channels. The flow discharge through certain sections was also described theoretically when engineering blasting was chosen to widen and deepen the cross-section of the diversion channels. Overall, this paper mathematicizes and theorizes the existing emergency measures, which helps to better understand their implementation principles and application requirements.

Synergistic regulation mechanism of selectin and integrin on leukocyte adhesion under shear flow

In the process of inflammation, the hydrodynamic process of circulating leukocyte recruitment to the inflammatory site requires the rolling adhesion of leukocytes in blood vessels mediated by selectin and integrin molecules. Although a number of experiments have demonstrated that cooperative effects exist between selectins and integrins in leukocyte rolling adhesion under shear flow, the mechanisms underlying how the mechanics of selectins and integrins synergistically may govern the dynamics of cell rolling is not yet fully resolved. Here we present a mechanical model on selectin- and integrin- jointly mediated rolling adhesion of leukocyte in shear flow, by considering two pairs' binding/unbinding events as Markov processes and describing kinetics of leukocyte by the approach of continuum mechanics. Through examining the dynamics of leukocyte rolling as a function of relative fraction of selectin and integrin pairs, we show that, during recruitment, the elongation of intermittent weak selectin bonds consuming the kinetic energy of rolling leukocyte decelerates the rolling speed and enables the integrin pairs to form strong bonds, therefore achieving the arrestment of leukocyte (firm adhesion). The coexistence of selectins and integrins may also be required for effective phase transition from firm adhesion to rolling adhesion, due to dynamic competition in pairs' formation and elongation. These results are verified by the relevant Monte Carlo simulations and related to reported experimental observations.

Relationship Between Tectonic Evolutions and Presence of Heavy Oil in The Central Sumatra Basin

Heavy oil is formed through biodegradation process of hydrocarbons, as well as water washing, in which light hydrocarbon fraction disappears and leaves the heavy fraction. Heavy oil is essentially an asphaltic, dense (low API gravity), and viscous that is chemically characterized by its high content of asphaltenes in the oil. Although variously defi ned, 25o API is set the upper limit for heavy oil. Heavy oil in the Central Sumatra Basin is evidently formed as a result of biodegradation and water washing (a hydrodynamic process within oil reservoir) mechanisms. These processes occur as result of tectonic uplift of the reservoir after it has been fi lled with hydrocarbons. Heavy oil reservoir depths in the Central Sumatra Basin are generally shallower than 1,000 feet (300-400 meters), at which surface water may may be associated with the reservoir hence enabling the heavy oil transformation. A combined geology, remote sensing/geographic information system ( GIS), geophysics, stratigraphy, and wellbased analyses is utilized to serve the study. It has been observed that within the northern part of the basin, heavy oil is mainly found in fi elds located within uphill fault blocks such as the up-thrown part of the Sebanga thrust fault with its Duri, Sebanga North, Kulin, Rantau Bais, Batang, Akar, and Genting fi elds. In the western part of the basin there are the Kumis, Kotalama and Pendalian heavy oil fi elds associated with Dalu-Dalu thrust fault and Gadang Island uplift. In total 51 fi elds/structures containing or suspected to contain heavy oil are associated with uplifted geological positions, hence showing the strong relations between tectonic evolutions and present day presence of heavy oil within the basin.

Water exchange in Van Phong bay, Khanh Hoa province by hydrodynamic model

The analysis of the average wind field from 1979 to 2018 showed that in the Van Phong bay area, the hydrodynamic process is mainly influenced by tidal currents when the frequency of weak wind accounts for a high proportion and the wind regime is controlled entirely by locality and less likely to alter tidal currents significantly. Based on the shallow water hydrodynamic finite element model (FEM), a two-dimensional hydrodynamic model has been developed for Van Phong bay to study hydrodynamic features, especially exchange capacity of seawater with the open sea. The results show that the daily average daily exchange of water in Van Phong bay is about 1,845.46 × 106 m3/day, equivalent to 34.7% water volume in the bay. In the rainy season, the typical daily average water exchange in Van Phong bay is about 2,136.04 × 106 m3/day, equivalent to 43.19% of the volume of water in the bay. In the dry season, the typical daily average total water exchange in Van Phong bay is about 1,825.56 × 106 m3/day, corresponding to 34.35% of water volume in the bay.

Peculiarities of the operation of the oil pipeline in the process of its cleaning from paraffin deposition

Purpose: Improving the technology of cleaning the inner surface of the main oil pipelines from paraffin deposition by specifying the hydrodynamic parameters of the movement of the cleaning device in the cavity of the pipeline, by more accurate prediction of the time of its approach to the final point of purification. Design/methodology/approach: Performing theoretical researches and application of mathematical modelling methods in order to establish the regularities of the cleaning device movement in the oil pipeline. Findings: Regularities of changes in the capacity of the pipeline, the speed of the cleaning process, the specific energy consumption for oil transportation as a function of the linear coordinates of the place and time of the cleaning device movement in the pipeline were established. Research limitations/implications: The next stage of research is to establish the influence of the characteristics of the viscoplastic fluid of the paraffin plug on the additional resistance and the mode of the cleaning device movement in the pipeline. Practical implications: It was developed the method that allows predicting the capacity and energy efficiency of the pipeline operation for each point in time of the process of cleaning from paraffin deposition. Originality/value: The originality of the method is the taking into account the additional hydraulic resistance of the paraffin plug and the available energy resources of oil pumping stations on the hydrodynamic process of moving the cleaning device in the oil pipeline.

Slope- watershed coupling simulation under different vegetation coverage based on GAST model

A non-equilibrium sediment transport soil erosion model based on finite volume method (FVM) coupled with two-dimensional hydrodynamic process is proposed, application of the GPU techniques in the numerical model, making it possible to simulate the sediment transport and bed evolution in a high resolution but efficient way. The first-order Gudonov format FVM is used to discreting the control equation. The variables on both sides of the unit interface are obtained by limiting slope interpolation. An efficient and robust non-negative depth reconstruction algorithm is used to solve the dry-wet boundary problem. This algorithm makes the model have second-order accuracy in space, and also effectively suppresses the numerical oscillation. Harten, Lax van Leer Contact (HLLC) approximate Riemann solver is used to calculate mass and momentum flux, and the friction source term is calculated by the proposed split point implicit method. These values are evaluated by a novel 2D edge-based MUSCL scheme. The code is programmed using C++ and CUDA, which can be run on GPU to greatly accelerate the calculation speed. In this paper, two numerical experiments show that the model performs well in accuracy and robustness of the algorithm in the process of slope erosion and watershed erosion. The constructed model can simulate the soil erosion of slope and watershed gully under different vegetation coverage, and characterize the erosion process of interaction between slope and gully.

Management of trickle irrigation for banana: Hydrodynamic processes and sensor placement at the root zone

ABSTRACT Information on soil hydrodynamic processes assists in explaining the soil-water-plant relationship and has practical applications to irrigation management, such as the definition of soil water sensor placement. The objective of this study was to detail the hydrodynamic process in the soil root zone and to define the location for placement of soil water sensor under different configurations of trickle irrigation in banana crops. Three micro-sprinkler emitters with flow rates of 70 (T1), 53 (T2), 35 L h-1 (T3), and two drip system, one with one drip line per row of plants (T4), and another with two drip lines per row of plants (T5) were evaluated. The experiment was conducted in a randomized block design with five repetitions. Higher water extraction was found for irrigation systems with higher flow rates for all configurations of trickle irrigation systems. Soil moisture sensors in drip systems should be placed at distances of 0.75 to 0.81 m from the pseudo stem and at depths of 0.33 to 0.44 m. Under micro-sprinkler systems, soil water sensors should be placed at 0.75, 0.77 and 0.83 m from the pseudo stem towards to the emitter and at depths of 0.33, 0.48 and 0.55 m for emitter flow rates of 35, 53 and 70 L h-1, respectively.

Controls on the sedimentary characteristics of shelf-edge deltas in a source-to-sink context

<p>Shelf-edge deltas constitute important components of source-to-sink (S2S) systems. They distribute sediment to continental slopes and basin floors from rivers that have prograded across shelves, and due to their scale they form significant sediment accumulations at shelf margins. Because of their intimate relationship with regressive conditions, several geological controls govern their evolution, including relative sea-level changes, sediment budgets, river hydrology, and hydrodynamic processes; these factors are themselves influenced by characteristics of terrestrial catchments and continental shelves, and by climate. Despite their important role in sediment dispersal to shallow- and deep-marine environments, shelf-edge deltas are commonly overlooked in models that describe S2S systems, perhaps because of their relative paucity during the present-day highstand conditions. In subsurface and outcrop, their recognition can be difficult in cases where information with which to constrain the physiographic environment is limited, such that the spatial position of a delta relative to the shelf margin cannot be determined unequivocally.</p><p>This study aims to improve our understanding of controls on the sedimentary characteristics of shelf-edge deltas. For this purpose, >40 shelf-edge deltas of Late Triassic to late Quaternary age from >30 globally-distributed shelf-margin successions have been investigated, utilising literature-derived seafloor-, subsurface- and outcrop data. Following a database approach, sedimentary records have been quantitatively analysed in terms of geometry (e.g. dimensions, thickness, gradients) and facies characteristics (e.g. lithology, sedimentary structures) of depositional environments (e.g. delta top, delta front) and architectural elements (e.g. delta lobes, distributary mouth bars). Specific consideration has been given to assessment of palaeoenvironmental setting (e.g. hydrodynamic process regime, margin type, bathymetric setting, palaeolatitude). Moreover, scaling relationships between these properties and attributes of the S2S system (e.g. fluvial-system and catchment attributes, shelf configuration, shelf-slope transition) have been evaluated. Accordingly, the relative importance of controls on the sedimentary characteristics of shelf-edge deltas has been assessed.</p><p>This analysis demonstrates that environmental factors influence the sedimentary record of shelf-edge deltas via a complex interplay of dynamic processes and physiography of the S2S segments catchment, shelf and slope. Based on these findings, new facies models for shelf-edge delta types are developed, which are placed in the context of S2S linkages. Outcomes of this study aid the identification and classification of shelf-edge deltas and their preserved deposits, as well as the reconstruction of associated environmental conditions from stratigraphic records.</p>