fluid

摘要： In astrophysics, when studying rotating fluid systems (such as stars or gas giant planets), the rotation effect is most often neglected. This is explained by the fact that the various stars that populate our universe revolve around themselves at relatively low speeds. However, when trying to describe the internal structure of an astrophysical body, the speed of rotation of the fluid contained in the core of the star can reach very high values. It, therefore, becomes impossible to neglect centrifugal forces in the equation of fluid motion. In this work, we carry out a simplified but above all general study of rapidly rotating fluid systems. Euler’s equation then contains a centrifugal force term. The resolution of this equation leads to a solution that reveals a very particular property of this type of system: “the catastrophe of rapidly rotating fluids”.

摘要： Advances in numerical simulation techniques play an important role in helpingmining engineers understand those parts of the rock mass that cannot be readily observed.The Material Point Method(MPM)is an example of such a tool that is gaining popularity for studying geotechnical problems.In recent years,the original formulation of MPM has been extended to not only account for simulating the mechanical behaviour of rock under different loading conditions,but also to describe the coupled interaction of pore water and solid phases in materials.These methods assume that the permeability of mediums is homogeneous,and we show that these MPM techniques fail to accurately capture the correct behaviour of the fluid phase if the permeability of the material is heterogeneous.In this work,we propose a novel implementation of the coupled MPM to address this problem.We employ an approach commonly used in coupled Finite Volume Methods,known as the Two Point Flux Approximation(TPFA).Our new method is benchmarked against two well-known analytical expressions(a one-dimensional geostatic consolidation and the so-called Mandel-Cryer effect).Its performance is compared to existing coupled MPM approaches for homogeneous materials.In order to gauge the possible effectiveness of our technique in the field,we apply ourmethod to a case study relating to a mine known to experience severe problems with pore water.

摘要： The difference of composition in extracellular fluid in brain parenchyma and CSF suggests that CSF-brain barrier(CBB)is objective,which is necessary to maintain the stability of their internal environment.However,the information exchange between brain and CSF is also objective.For example,CSF is changes during diseases,the application of drugs(such as lumbar anesthesia)or tissue transplantation via the CSF pathway may also produce central(cerebral)effects.Who breaks through the barrier and mediates brain-CSF communication?Since 1992,we have found that the peripheral nerve tracer CB-HRP injected into the lateral ventricle of mice,rats and macaques is blocked in the ventricle wall and can only run in CSF,but a large number of CB-HRP-positive labeled neurons can be seen in specific parts of the brain stem parenchyma.Understandably,these neurons touch markers in CSF.Otherwise,they cannot be tagged.

摘要： Fluid and solid simulation is to generate a realistic simulation of fluids and solids,in particular for the fluids such as water and smoke,with computation of Euler equations or Navier-Stokes equations conducted to govern the real fluid physics.Fluid simulation is an important field by its wide applications in many fields and industries,such as film and game simulation,weather forecasting,natural disaster simulation and protection,simulation in maritime and aviation.There are basically two main categories of methods for fluid simulation,data-driven methods and physically-based methods.The data-driven models establish a direct mapping between variables and extract their relationship from historically measured data by the algorithms developed in the fields of statistics,computational intelligence,machine learning,and data mining.

摘要： Tight sandstone gas reservoirs have characteristics of low porosity and low permeability,complex pore structure.In the paper,we consider the pore and micro-fracture systems in tight sandstone reservoir and perform rock physics modeling of sandstone gas reservoirs based on Chapman.Then we analyze the effects of relaxation time,and difference fluid types on dispersion and attention,and seismic responses.We found that the magnitude of the relaxation time is related to the gas saturation and the viscosity coefficient of the fluid.The magnitude of the relaxation time affects the frequency range of the velocity dispersion and attenuation,and the type of fluid affects the magnitude of the velocity dispersion and attenuation.As the relaxation time decreases,the calculated amplitude deceases.And the amplitude and the waveform of the synthetic seismic record are related to different fluid types and formation thickness.

摘要： COVID-19 spreads through patients’exhalation droplets,hence a comprehensive understanding of muco-saliva fragmentation provides crucial insight.This paper scrutinizes a study of the breakup of mimic of contagious viscoelastic exhalation fluid,conducted by MIT researchers:“Visualization of sneeze ejecta:steps of fluid fragmentation leading to respiratory droplets”,in which the authors profoundly contributed to the understanding of hazardous sneeze ejecta caused by sneezing.In this article,some of their nicely incorporated experimental methods and break through will be described and analyzed with the integration of fluid dynamics.

摘要： Dear Editor,Clinical and anatomic investigations strongly suggest that a low orbital cerebrospinal fluid pressure (CSFP), parallel to an elevated intraocular pressure (IOP), may have a role in the pathogenesis of optic neuropathy (Ren et al., 2011, Wang et al., 2012). Optic neuropathy including glaucoma demonstrated structural alterations in the optic nerve head (ONH)and retinal nerve fiber layer (RNFL), as well as functional abnormalities such as visual field (VF) that eventually cause severe visual impairment and blindness.

摘要： In this study,a series of numerical calculations are carried out in ANSYS Workbench based on the unidirectional fluid–solid coupling theory.Using the DTMB 4119 propeller as the research object,a numerical simulation is set up to analyze the open water performance of the propeller,and the equivalent stress distribution of the propeller acting in the flow field and the axial strain of the blade are analyzed.The results show that FLUENT calculations can provide accurate and reliable calculations of the hydrodynamic load for the propeller structure.The maximum equivalent stress was observed in the blade near the hub,and the tip position of the blade had the largest stress.With the increase in speed,the stress and deformation showed a decreasing trend.

摘要： In this paper,we investigate the regularity criterion via the pressure of weak solutions to the micropolar fluid equations in three dimensions.We obtain that for 0<α<1 if p€L^(2/a)(0,T;B^α∞,∞),then the weak solution(u,ω)is regular on(0,T).

摘要： Focal adhesions are polyproteins linked to extracellular matrix and cytoskeleton,which play an important role in the process of transforming force signals into intracellular chemical signals and subsequently triggering related physiological or pathological reactions.The cytoskeleton is a network of protein fibers in the cytoplasm,which is composed of microfilaments,microtubules,intermediate filaments,and cross-linked proteins.It is a very important structure for cells to maintain their basic morphology.This review summarizes the process of fluid shear stress transduction mediated by focal adhesion and the key role of the cytoskeleton in this process,which focuses on the focal adhesion and cytoskeleton systems.The important proteins involved in signal transduction in focal adhesion are introduced emphatically.The relationship between focal adhesion and mechanical transduction pathways are discussed.In this review,we discuss the relationship between fluid shear stress and associated diseases such as atherosclerosis,as well as its role in clinical research and drug development.