A Study to Investigate the Viscosity Effect on Micro-Confined Fluids Flow in Tight Formations Considering Fluid–Solid Interaction

Understanding different fluids flow behavior confined in microscales has tremendous significance in the development of tight oil reservoirs. In this article, a novel semiempirical model for different confined fluid flow based on the concept of boundary layer thickness, caused by the fluid–solid interaction, is proposed. Micro-tube experiments are carried out to verify the novel model. After the validation, the viscosity effect on the flow rate and Poiseuille number considering the fluid–solid interaction is investigated. Furthermore, the novel model is incorporated into unstructured networks with anisotropy to study the viscosity effect on pore-scale flow in tight formations under the conditions of different displacement pressure gradients, different aspect ratios (ratio of the pore radius to the connecting throat radius), and different coordination numbers. Results show that the viscosity effect on the flow rate and Poiseuille number after considering the fluid–solid interaction induces a great deviation from that in conventional fluid flow. The absolute permeability is not only a parameter related to pore structures but also depends on fluid viscosity. The study provides an effective model for modeling different confined fluid flow in microscales and lays a good foundation for studying fluid flow in tight formations.

Examination of Viscosity Effect on Cavitating Flow inside Poppet Valves Based on a Numerical Study

The higher susceptibility to cavitation in poppet valves due to the lower viscosity of water than the traditionally used mineral oil poses a challenge in fluid transmission technology. To reveal the underlying mechanism of cavitating flow physics associated with the variation in viscosity effect, the current paper examines both the water and oil cavitating flow dynamics inside poppet valves with varied structures through a numerical study. The simulation results are validated with a comparison to previous experimental data in terms of cavitation morphology and pressure distribution. According to the predicted cavitation distribution, three kinds of cavitation occurred at separated positions in both water- and oil-flow cases. The vortex cavitation, which in the oil-flow case displays a remarkable paired structure with favorable coherence, is featured with a scattered dispersion in the water-flow case, while the profound attached cavitation at the poppet trailing edge in the water-flow case almost disappears in the oil-flow case. Furthermore, the attached cavitation within the chamfered groove has higher stability in the oil-flow case, compared to the thorough detachment behavior featured with profound 3-dimensionality in the water-flow case. According to the potential core and vortex evolution, the strong 3-dimensionality due to the violent laminar-turbulent transition in the water-flow case together with the produced puff pattern of the potential core, to a large extent, interrupts the periodic behavior of cavitation, which is essentially preserved in the oil-flow case featured with favorable coherence.

Boundary Layer Flow of Dusty Williamson Fluid with Variable Viscosity Effect Over a Stretching Sheet

Numerical investigation of the boundary layer flow of Williamson fluid with the presence of dust particles over a stretching sheet is carried out by taking into account the variable viscosity effect and Newtonian heating boundary condition. The genuinely two-phase flow model which has been proved to be compatible to present the mutual relationship between non-Newtonian fluid and solid particles is considered in this present study. To be precise, the governing equations are initially transformed into ordinary differential equations through formulation process before proceeding further with the numerical computation by using Keller-box method. The resulting equations are then programmed in Matlab software. The obtained numerical results are validated with existing study found in open literature and a good agreement is achieved. The influence of pertinent parameters on velocity and temperature profiles, skin friction coefficient together with Nusselt number is presented in graphical and tabular forms. Results revealed that the increasing Williamson parameter decreases the fluid velocity of both fluid and dust phases. It is expected that the present numerical results could conceivably help in predicting the boundary layer problem arising in two-phase flow in the future.

Experiments and mechanistic modeling of viscosity effect on a multistage ESP performance under viscous fluid flow

Assembled in series with multistage, Electrical Submersible Pumps (ESP) are widely used in offshore petroleum production due to the high production rate and efficiency. The hydraulic performance of ESPs is subjected to the fluid viscosity. High oil viscosity leads to the degradation of ESP boosting pressure compared to the catalog curves under water flow. In this paper, the influence of fluid viscosity on the performance of a 14-stage radial-type ESP under varying operational conditions, e.g. rotational speeds 1800–3500 r/min, viscosities 25–520 cP, was investigated. Numerical simulations were conducted on the same ESP model using a commercial Computational Fluid Dynamics (CFD) software. The simulated average pump head is comparable to the corresponding experimental data under different viscosities and rotational speeds with less than ±20% prediction error. A mechanistic model accounting for the viscosity effect on ESP boosting pressure is proposed based on the Euler head in a centrifugal pump. A conceptual best-match flowrate QBM is introduced, at which the impeller outlet flow direction matches the designed flow direction. The recirculation losses caused by the mismatch of velocity triangles and other head losses resulted from the flow direction change, friction loss and leakage flow etc., are included in the model. The comparison of model predicted pump head versus experimental measurements under viscous fluid flow conditions demonstrates good agreement. The overall prediction error is less than ±10%.