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In the paper, the air cavity created by vertical water entry of cylinders with different slenderness ratio (defined as “s=L/D”) is investigated experimentally, theoretically, and computationally. The study is focused on the range of Froude numbers, Fr = V/(gr) 0.5, (12< Fr< 30). Particular attention is given to the effect of slenderness ratios on the surface seal time, the evolution process of the cavities. To understand the water entry physical processes, we conduct several experiments of water entry of different length cylinders. A theory model considering the added mass (induced by the water motion), buoyancy force, gravity, and water-resisting force is developed to predict the relationship between the falling distance and evolution time. Studies show that for the same size bullet the surface seal time of the cavity decreases with the increase of impact speed. Under the identical impact speed, the cavity seal time decreases with the increase of the slenderness ratio. For the consistent impact speed, with the value of “s” increase, the falling distance increase (the same moment). The falling distance captured by the developed theoretical model match with the experimental and numerical data.

Simulation of surface erosion by impact of abrasive water-jet (AWJ) is challenging for traditional mesh-based numerical methods, because it involves complex phenomena related to fluid–solid interaction, material removal and free surface flows. In this study, the surface erosion mechanism of ductile target materials by AWJ is investigated based on the smoothed particle hydrodynamics method (SPH, a mesh-free method). The water-jet, abrasives and solid target are all discretized with a series of SPH particles. The water-jet is modeled as a continuous fluid flow, the target material is modeled as a elastic–plastic material, and the abrasives are modeled as rigid bodies. The SPH model is improved by combining several correction algorithms and techniques, which help us to increase the stability and the accuracy of the simulation. The density diffusion correction term is introduced for water-jet, which reduces the pressure noise and makes the pressure field more stable. The dynamic boundary algorithm is used for the abrasives, and the pressure distribution around the abrasive is improved. The interactions among the water-jet, abrasives and solid target are realized by different contact algorithms. The dynamic process of plastic deformation, material removal and crater generation of the target material under AWJ impact can be simulated by the improved SPH model. The proposed model could be useful in the applications of AWJ machining and metal surface erosion. [ABSTRACT FROM AUTHOR]

Sucker rod constructed of FRP (fiber-reinforced plastic) is currently used in offshore oil and gas industries due to its high tensile strength, lightweight, and resistance to corrosion. Due to the fact that the surface of FRP sucker rod cannot be threaded, it is often attached to steel joints via adhesive technology, and the bonded joint of FRP sucker rod is particularly prone to breaking and coming off. The current research is primarily concerned with the mechanical properties of FRP sucker rods, with little emphasis on the adhesive performance of bonded connections. This research developed a numerical model with a novel bonded joint structure based on the cohesion failure criteria. An indoor test was used to determine and confirm the expected bonded joint failure load. Additionally, an orthogonal test was conducted to maximize the adhesion performance. The findings indicated that a) theaccuracy of numerical model was within 2% and b) when the groove angle was 30°, the length ratio was 2/23, each groove was 14 mm in length based on a triangular groove, and the anticipated failure stress of the bonded joint was around 443 kN, an increase of 10%. [ABSTRACT FROM AUTHOR]

At present, fiberglass sucker rod has been gradually utilized in low permeability reservoirs because of their high strength and strong corrosion resistance. However, the bonding joint of fiberglass sucker rod in high water-content well is particularly prone to break and fall off, which influences the service life and construction safety of recovery operation. Current researches mainly focused on the bonding strength at room temperature, and less consideration was given to the residual strength and failure pattern under immersion. This paper proposed a novel diffusion-structure finite element model (FEM) based on transient dynamic method to simulate the process of water into the joint, and the life-death element method was adopted to study the progressive damage of bonding joints verified by indoor experiment in order to predict residual failure strength and obtain failure mode in submerged environment. As immersion duration extended, the results illustrated that a) the cohesive failure gradually became main failure; b) the maximum von Mises stress, shear stress, and end deformation of bonded joint increased and the maximum interfacial stress barely unchanged within the range of 5%; c) the numerically predicted strength decreased from 21.8 to 11.5 MPa, which was in good agreement with the experimental results within a deviation of 8%. [ABSTRACT FROM AUTHOR]

We conducted an experimental study on the formation of cavity and splash crown during the impact of superhydrophobic and hydrophilic spheres on water and polyethylene oxide solution (non-Newtonian liquid). We investigated the influences of falling speed of spheres on splash crown and cavity formation. In particular, we focused on the evolution time of splash and cavity when spheres with different contact angles fall into different liquids under various speeds and the different behavior of splash curtain. Results show that sphere contact angle and liquid viscosity have a great effect on cavity formation. The increase in contact angle and liquid viscosity induces cavity formation. However, viscosity has a certain inhibitory effect on crown evolution. The faster the falling speed is, the shorter the splash crown's evolution time, but the greater the volume will be. A pinch-off model of cavity has a great impact on the formation of "Worthington jet." [ABSTRACT FROM AUTHOR]