In all other cases studied, the dilute gas contribution is negligible and the configurational contribution dominates the overall behavior. The dilute gas contribution to the bulk viscosity is seen to be significant only in the cases when intramolecular relaxation times are in the μs range, and for low vibrational wave numbers (<1000 cm-1) This explains the abnormally high values of bulk viscosity reported for CO2. Both atomistic and coarse-grained force fields for water, CO2, and n-decane are considered and tested for their accuracy, and where possible, compared to experimental data. As a benchmark, the Lennard-Jones fluid is studied. The configurational part is calculated using Green-Kubo relations for the fluctuations of the pressure tensor obtained from equilibrium microcanonical molecular dynamics simulations. The dilute gas contribution is evaluated using experimental data for the relaxation times of vibrational and rotational degrees of freedom. The bulk viscosity of molecular models of gases and liquids is determined by molecular simulations as a combination of a dilute gas contribution, arising due to the relaxation of internal degrees of freedom, and a configurational contribution, due to the presence of intermolecular interactions. Furthermore, it was observed that the presence of casing in the wellbore impacted the stress distribution around the casing in such a way that the fracture propagation deviated from the wellbore vicinity. Accordingly, a new parameter, called fracturing power, was introduced to relate fracture geometry to fluid viscosity and injection rate. This resulted in more curved fracture planes. However, when the fracturing energy was transferred to a borehole at a faster rate, the fracture initiation angle also increased. The results indicated that by increasing the fracturing fluid viscosity and injection rate, the fracturing energy increased, and consequently, higher fracturing pressures were observed. In addition, dimensional analyses were performed to correspond the results of lab experiments to field-scale operations. A true tri-axial stress cell was used to simulate real far field stress conditions. Hydraulic fracturing tests were conducted in cased perforated boreholes made in tight 150 mm synthetic cubic samples. In this study, three different fracturing fluids with viscosities ranging from 20 to 600 Pa.s were used to investigate the effects of varying fracturing fluid viscosities and fluid injection rates on the fracturing mechanisms. Various parameters affect such mechanisms, including fracturing fluid viscosity and injection rate. Near Wellbore Hydraulic Fracture Propagation from Perforations in Tight Rocks: The Roles of Fracturing Fluid Viscosity and Injection Rateįull Text Available Hydraulic fracture initiation and near wellbore propagation is governed by complex failure mechanisms, especially in cased perforated wellbores. By introducing a phase transition inthe cosmic fluid, the future singularity can nevertheless in principle be avoided. These solutions mayincorporate a viscosity-induced Big Rip singularity. It is shownthat, based on a natural scaling law for the viscosity, a simple solution can be found forquantities such as the Hubble parameter and the energy density. Analysis assists in design of flow systems for petroleum, coal, polymers, and other materials.ĭirectory of Open Access Journals (Sweden)įull Text Available A bulk viscosity is introduced in the formalism of modified gravity. Fluid is taken to be viscous, non-Newtonian, and incompressible the gas to be ideal the flow to be inertia-free, isothermal, and one dimensional. ![]() Reduced viscosity interpreted for fluid/gas mixturesĪnalysis predicts decrease in fluid viscosity by comparing pressure profile of fluid/gas mixture with that of power-law fluid. ![]() • With this function the rotation of particles are described correctly. • This correction is function of the hydrodynamic concentration of particles. • Coincidence of curves requires a correction of value of viscosity in calculations. Highlights: • Dynamic susceptibility was measured at different temperatures and concentrations. The value of the correction coefficient doesn’t depend on temperature and is the universal function of the hydrodynamic concentration of particles. ![]() Coincidence of normalized dynamic susceptibility curves plotted for different concentrations was obtained only after introducing correction for the value of dynamic viscosity of the magnetic fluid. Lebedev, A.V., E-mail: frequency dependences of dynamic susceptibility were measured for a series of magnetic fluid samples with the same dispersed composition at different temperatures. ![]() Viscosity of magnetic fluids must be modified in calculations of dynamic susceptibilityĮnergy Technology Data Exchange (ETDEWEB)
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