Abstract
In the process of hydraulic jet fracturing and perforation, fracturing fluid carrying sand is injected through annulus to fracture the pay zone. The numerical simulation analysis with the ...software of ANSYS-Fluent was applied aiming at the problem of low quality of fracturing fluid through the nozzle jet. By means of the analysis and comparison to some important structural parameters of the nozzle, the optimum jet quality through the nozzle was obtained. The research results showed. When the nozzle outlet diameter is from 4.5mm to 4.8mm; the length of the column is from 7mm to 12mm and the inlet radius of curvature is 9mm, the optimum jet quality of the nozzle can be obtained. The jet quality through the nozzle can be improved effectively through the analysis and optimization of the structure of the nozzle, which provides effective technical support for the hydraulic jet fracturing technology.
We examine the tidal deformation of a nonrotating compact body (material body or black hole) in general relativity. The body's exterior metric is calculated in a simultaneous expansion in powers of ...the ratio between the distance to the body and three distinct length scales. The first is the radius of curvature of the external spacetime in which the body is inserted, the second is the scale of spatial inhomogeneity of the curvature, and the third is the scale of temporal variation. The metric is valid in the body's immediate neighborhood, which excludes the external matter responsible for the tidal environment. The body's tidal response is encapsulated in four types of relativistic Love numbers. The first is kℓ, the familiar Love number that measures the linear response to a static tidal field. A second is pℓ, which measures the quadratic response to the tidal field. A third is ˙ kℓ, which is associated with the first time derivative of the tidal field. And the fourth is ¨ kℓ, associated with the second time derivative of the tidal field. All Love numbers are gauge-invariant constants that appear in the body's exterior metric. Their computation (not carried out here, except for black holes) requires extending the metric to the body's interior. The Love numbers acquire an operational meaning through the definition of tidally induced multipole moments. Previously proposed definitions for the moments suffer from ambiguities associated with the subtraction of a "pure tidal field" from the full metric; such subtraction prescriptions are artificial and subjective. A robust operational definition is proposed here. It relies on inserting the body's local metric within a global metric constructed in post-Newtonian theory; the global metric includes the external matter responsible for the tidal environment. When viewed in the post-Newtonian spacetime, the compact body appears as a skeletonized object with a specific multipole structure, moving on a given world line. The tidally induced multipole moments provide a description of this multipole structure. They manifest themselves, for example, in the body's tidal acceleration, which is nonlinear in the tidal field. At leading order in the tidal interaction, the acceleration is proportional to the k2 Love number as calculated in full general relativity. The computation of the multipole moments is carried out to the first post-Newtonian order, but the general method can in principle be extended to higher orders.
•High-velocity impact resistance of doubly curved CFRP sandwich panels is presented.•Impact tests are carried out by using a single-stage air gas gun test machine.•An analytical model is developed to ...describe the ballistic limit velocity.•Parametric analyses are carried out for various radius of curvature of the panels.
This work describes the high-velocity impact behavior of doubly curved sandwich panels. The sandwich panels are manufactured using carbon/fiber epoxy composite face sheets, polyurethane foam core and 3D-printed PLA plastic cellular auxetic (re-entrant) honeycombs. High-velocity impact tests are carried out by using a single-stage air gas gun test machine. A spherical steel projectile with the radius of 5 mm is impacted to the center of the specimens with the speed of 100 m/s. The experimental data are used to validate explicit finite element models of the doubly curved structures. An analytical model is also developed for the ballistic limit of the flat and doubly curved sandwich panels, and the analytical results are compared to those obtained from the numerical ones. Parametric numerical analyses of the high-speed impact of the curved sandwich panels are then carried out considering various radii of curvature of the panels. The results show that the energy absorption is increased as the curvature is decreased for the panels with both foam and re-entrant core. In addition, the core configuration provides a key role in the impact resistance of the sandwich panels. Re-entrant models show an increase in specific energy absorption (SEA) compared to the foam core types.
Display omitted
Abstract
In this work, we present the characterization of a Form 3 Stereolithography (SLA) FormLabs 3D printer which will be used for the fabrication of optical components. The characterization ...consisted of the measurement of the refraction index, absorbance & transmittance values, as well as geometrical parameters like radius of curvature, thickness, roundness, and angles. This study proved that with the Form 3 SLA additive technology components with good quality that meet the design parameters can be fabricated.
Abstract
Research on the behavior of bubble collision has always been one of the focuses in the scientific field. This work focuses on the kinematics and deformation of bubbles when impacting the ...curved boundary with hydrophilicity and hydrophobicity. The impact process of bubbles colliding with the curved wall was recorded by a high-speed camera. The effects of wettability and radius of curvature were analyzed. The results show that when the bubble collides with the hydrophilic curved wall, it will bounce many times until it leaves the wall. Aiming at the phenomenon of liquid film extrusion rupture, a theoretical model is established to deduce the prediction formula of liquid film induction time, which is mainly related to the thickness, the critical rupture thickness, and the compression speed of the liquid film. The prediction error is less than 5.0%.
PDF
