Effect of Fluid Dynamic Viscosity on the Strength of Chalk

The surface of an articular cartilage human joint, coated with phospholipid bilayers or multi-layers, plays an important role in the surface-active phospholipid lubrication, friction, and wear during human limb movement. The biological bi-layer is a thin polar membrane composed of two layers of phospholipids that have a hydrophilic phosphate head (from the outside) and a hydrophobic tail (from the inside) consisting of two fatty acid chains. These membranes are flat sheets that form a continuous barrier around all cells. Synovial fluid (SF) in the human joint gap contains glycoprotein, lubricin (proteinglycan 4), and hyaluronidase, i.e. an enzyme that produces hialuron acid and ±10% phospholipids. Because the mechanism of surface articular phospholipid lubrication (SAPL) has been a frequently controversial subject in the past decade, this fact requires showing the hydrodynamic description in the form of a mathematical model of the abovementioned problem and its particular solution. To give a description of this model, it is necessary to recognize the variations of the dynamic viscosity of synovial fluid as a function of parameters depending on the presence of many phospholipid particles. To these parameters belong power (exponent) concentration of hydrogen ions (pH), cartilage wet ability (We), collagen fibre concentration in synovial fluid, and a created electrostatic field on the phospholipid membrane. Based on the Young-Laplace-Kelvin Law, initial achievements presented in scientific papers and our own investigations illustrated in this paper, the decrements, and increments of synovial fluid dynamic viscosities versus pH and wet ability (We) increases, simultaneously taking into account the influence of the intensity of charges in the electrostatic field. Moreover, this study considers the influence of collagen fibre concentration on the dynamic viscosity of synovial fluid. Based on initial considerations performed by virtue of the developed SAPL, it may be stated that the charge increments from low to high values of the electrostatic field is connected with viscosity increases of synovial fluid but only simultaneously with the pH index and cartilage wet ability variations.

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Experimental investigation of proppant clustering in intersected fractures

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-021-01122-4 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1727-1742

Author(s):

Wenpei Ma ◽

Ingrid Tomac

Keyword(s):

Fluid Flow ◽

Flow Rate ◽

Dynamic Viscosity ◽

Visual Analysis ◽

Fluid Dynamic ◽

Fluid Flow Rate ◽

Volumetric Concentration ◽

Fracture Intersection ◽

Reservoir Permeability ◽

Image Velocimetry

AbstractThis paper investigates the dynamics of proppant agglomerations during flow and transport within fractures intersected at the angles typical for the joint of pre-existing and newly formed fractures. The study considers variations and coupling of fluid flow rates, proppant volumetric concentrations, fluid dynamic viscosities and fracture intersection angles. Proppants are widely used during hydraulic fracturing to keep fractures open and enhance reservoir permeability. This study uses plexiglas experimental slots and visual analysis for identifying particle displacements. Geo-Particle Image Velocimetry–Reliability-Guided (GeoPIV-RG) method tracks particle movements among images by comparing the reference and subsequent snapshots at the point and time of interest. Results of this study show that the proppant volumetric concentration and the fluid flow rate are closely correlated with each other for affecting proppant flow, transport, and agglomeration formation. Increasing the proppant volumetric concentration generally promotes particle agglomeration, with different extent when coupled with the fluid flow rate. Proppant volumetric concentration affects the size, shape, and distribution of particle clusters. Increasing the fluid flow rate increases the occurrence of particle agglomerates at low proppant volumetric concentration; however, this trend is absent under high proppant volumetric concentrations. Sizes and shapes of proppant agglomerates change as the fluid flow rate changes. Changes of fracture intersection angle minimally affect shape, size and distance between proppant agglomerates and clusters. Furthermore, increasing the fluid dynamic viscosity strongly promotes proppant agglomeration. Although fluid dynamic viscosity changes do not affect the shape and size of particle clusters, the distance between adjacent clusters decreases at higher fluid dynamic viscosity.

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ON RANDOM EXPECTED VALUES VARIATIONS OF TRIBOLOGY PARAMETERS IN HUMAN HIP JOINT SURFACES

Tribologia ◽

10.5604/01.3001.0015.6898 ◽

2021 ◽

Vol 297 (3) ◽

pp. 45-56

Author(s):

Krzysztof Wierzcholski ◽

Jacek Gospodarczyk

Keyword(s):

Friction Coefficient ◽

Synovial Fluid ◽

Carrying Capacity ◽

Dynamic Viscosity ◽

Fluid Dynamic ◽

Load Carrying Capacity ◽

Friction Forces ◽

Load Carrying ◽

Gap Height ◽

Human Joint

This paper presents recent progress in the knowledge concerning the stochastic theory of bio- hydrodynamic lubrication with a phospholipids bilayer. On the basis of experimental measurements and analytical solutions, the research concerns the determination of the random expectancy values of load carrying capacity, the friction coefficient, and synovial fluid dynamic variations. After numerous measurements, it directly follows that the random density function of the gap height in the human joint usually indicates a disorderly increases and decreases in the height. Such irregular gap height variations have an important influence on the random synovial bio-fluid dynamic viscosity. This finally leads to the friction coefficient and cartilage wear changes of cooperating bio- surfaces. The main topic of this paper relates to the expectancy values of the tribology parameters localized inside the variable stochastic standard deviation intervals of the human joint gap height. The results obtained finally indicate the influence of the random roughness and growth of living biological cartilage surfaces on the expectancy values of the synovial fluid dynamic viscosity, load carrying capacity and friction forces in human hip joints.

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