Water Jet Velocity Research Articles

Microstructure and topography of laterally confined porous anodic oxides produced with high growth rate in a maskless two-phase jet setup

AbstractMaskless anodic oxidation with a continuous free jet of electrolyte can be used for the local surface functionalization and structuring of aluminum materials. In this study, a two-phase jet was applied with the aim of enhanced lateral confinement of the anodic oxide on the aluminum alloy EN AW-7075. The two-phase jet was realized by a coaxial arrangement. While the inner electrolyte nozzle with a diameter of 100 µm acted as the cathode and was used to provide the electrolyte with a flow rate of 10 ml min−1 resulting in an average jet velocity of approximately 21 m s−1, the outer nozzle with a diameter of 3000 µm was used to provide deionized water with a flow rate of 383 ml min−1 resulting in an average water jet velocity of 1 m s−1, which is sufficient to realize a continuous free two-phase jet. Process voltages from 10 to 60 V were investigated. The realized oxide layers were characterized by non-destructive as well as destructive methods to determine their microstructure and their thicknesses. Optically transparent anodic oxide layers were achieved in the voltage range between 10 and 25 V. Maximum total layer thicknesses between 1.1 µm and 16.9 µm were measured in these cases. Thicknesses of more than 50 µm were determined for higher voltages up to 60 V; however, burning effects and stronger discolorations were determined for voltages ranging from 30 to 60 V. Consequently, 25 V was derived as best suitable voltage for two-phase anodizing with high growth rate leading to oxide layers with low defects. Graphical abstract

Investigation of continuous wave/coaxial waterjet-assisted laser combined machining of micro holes in GH3536

A two-step combined processing technique, combining a continuous-wave laser with a waterjet-assisted nanosecond laser, has been introduced to enhance the quality and efficiency of laser micro-hole processing for nickel-based superalloys. Initially, a through-hole was created using a continuous-wave laser, followed by hole refinement with a coaxial waterjet-assisted nanosecond laser. In the first step, orthogonal testing methods were employed to investigate the impact of various parameters, including power, duty ratio, frequency, defocusing amount, and processing time, on the entrance and exit apertures, as well as the hole taper. Through the analysis of variance (ANOVA) method, the optimal parameter combination A2B1C4D3E1 was identified, achieving the minimal hole taper. This combination comprised a power level of 80 %, a duty ratio of 15 %, a frequency of 400 Hz, a defocusing amount of 2 mm, and a processing time of 10 ms. In the second step, a comparison was made between scanning and trepan drilling machining methods. The results unequivocally demonstrated that scanning drilling achieves superior entrance and exit morphologies. Furthermore, the effect of water jet velocity on the morphology of micropores was thoroughly analyzed. The voltage range of the water pump was adjusted from 10 V to 24 V, revealing that a voltage of 20 V produced the smallest hole taper. The scanning filling diameter was accurately preset according to the preformed hole aperture as well as the thickness of the recast layer. Finally, after coaxial waterjet-assisted laser precision machining, the inner wall of the hole is free of cracks, and the recast layer and oxide layer are effectively minimized. The initial hole prefabrication with the continuous-wave laser took merely 0.01 s, and the subsequent fine-tuning with the coaxial waterjet-assisted laser took 2 min and 25 s.

Experimental and numerical study of a lateral waterjet laser cutting of an SS304 brush seal.

This study explores the application of lateral waterjet laser cutting in the fabrication of brush seals for gas turbine engines, with the aim of optimizing process parameters to enhance cutting quality. Experimental and numerical analyses were conducted to assess the effects of laser power, scanning speed, waterjet velocity, and waterjet standoff distance on key outcomes, such as kerf width, heat-affected zone, and recast layer thickness. The findings indicate that a laser power of 500 W, scanning speed of 15 mm/s, waterjet velocity up to 10 m/s, and waterjet standoff distance of 1 mm are optimal for reducing thermal damage and achieving precise kerfs. Furthermore, numerical simulations highlight the significance of controlled molten flow in realizing these optimal results, providing a comprehensive understanding of the cutting mechanism. These findings position lateral waterjet laser cutting as a better technique for brush seal manufacturing, offering significant improvements over conventional methods.

Damage evolution of CFRP laminates by normal and oblique impact erosion of pulsating water jets

Impact direction is one of the critical factors affecting the waterdrop erosion behavior of materials. In this paper, rain erosion damage behavior of a typical carbon fiber reinforced polymer (CFRP) laminate is investigated as a function of the impingement angle (0° as normal impact and 15°, 30°, 45° as oblique impact deviated from the normal) and the relative fiber orientation (parallel PA and perpendicular PE to the fiber direction of the surface layer) under the waterjet velocity of 320 m/s and the impact frequency of 50 Hz via a pulsating waterjet erosion test rig. After continuous impact of multiple waterjets, the typical damage of CFRP laminates is mainly composed of the central erosion crater and the upheaval of the surrounding surface layer. The onset and evolution of damage are mainly driven by the shear action of lateral jetting and stress concentration of hydraulic penetration exerted at the surface irregularities. There is no significant difference in the damage modes between the normal and oblique impacts, except for the asymmetric distributions of matrix cracking in PA-orientation and delamination in PE-orientation caused by the angle inclination. With the impingement angle increasing, the volume loss and erosion depth decrease while the incubation period increases mainly due to the decreases of water hammer pressure and contact area. The PA-orientation can cause lower incubation period and larger erosion mass loss than PE-orientation before the surface ply is penetrated, with the underlying mechanism related to the distinct tensile properties of CFRP laminates along longitudinal and transversal directions and the asymmetric properties of fiber–matrix interface. According to the fitting results of erosion curves, it is possible to describe the incubation period and the erosion rate of CFRP laminates under oblique impact using a two-branch equation, and Springer model can give reasonable prediction for the average incubation period and PA-orientation erosion rate of a certain oblique impact occasion with known 0° impact erosion results.

Experiments on droplet production from solitary waves impacting on a vertical wall

This work presents the results of an experimental investigation of solitary waves impacting on a vertical flat wall. The aim of the study was to correlate the wave characteristics and breaking stage before impact to the droplet production after the impact. The main characteristic of these experiments is that the wall height is lower than the wave height. The droplet sizes were obtained by combining 3D particle tracking velocimetry with an in-house code. Droplet diameters between 0.3–22 mm were measured at a distance of 35 cm and 68 cm from the wall. It was found that the breaking stage before the impact has a large influence on the mean size of the droplets produced, especially when there is air trapped between the wall and the wave at the impact moment. It was found that the mean droplet size decreases with the ratio of water jet velocity after impact and the wave speed. The resulting distributions of droplet sizes were compared to three different theoretical models used in other droplet production studies. Results were also compared to previous experimental studies of droplet formation from breaking waves to determine the best fit to the experimentally obtained distribution.

Generation of effective pulsed waterjets by ultrasonic nozzle used for energy exploration

Pulsed waterjet has higher energy efficiency ratio and less energy consumption than a continuous waterjet. To achieve more effective and powerful pulsed waterjets, a new ultrasonic nozzle with more compact structure and less energy loss was developed. By designing a hollow flow channel in the piezoelectric ceramic stack and the amplifier, the nozzle enables axial water inlet and avoids energy loss at the turnaround point. The resonant frequency of the ultrasonic nozzle was validated as 19227 Hz by modal analysis and impedance test, which is a deviation of 3.87% compared with the expected frequency of 20000 Hz. Besides, the pulse characteristics of modulated waterjet were analyzed experimentally by high-speed photography. The pulsed waterjet presented obvious periodic pulses and good clustering, and water slugs of "mushroom" shape can be clearly observed. The difference between the waterjet velocity and the theoretical value is less than 7.7%. And the pulse frequency of the modulated waterjet reaches about 19485.1 Hz, with a deviation of 1.3% compared with the nozzle resonant frequency of 19227 Hz. The new ultrasonic nozzle can be widely used in energy exploration for effective pulsed waterjet generation and less energy consumption.

Effect of water jet erosion parameters on erosion rate of WC10Ni5Cr HVOF coated 35CrMo steel

Abstract This research work aims for developing the water jet erosion (WJE) prediction equation and analyzing the optimum water jet erosion parameters such as impingement angle (degree), water jet velocity (m s−1), stand-off distance (mm), and erodent discharge rate (g min−1) for minimizing the water jet erosion of 35CrMo steel coated with WC10Ni5Cr coating. The optimized high velocity oxy fuel (HVOF) process parameters were employed for developing the coating of WC10Ni5Cr on 35CrMo steel. The WJE prediction equations were checked for its validity employing analysis of variance (ANOVA). The water jet erosion was measured as the loss of mass (g) after water jet erosion testing for noncoated and coated 35CrMo steel substrates. From the results it was analyzed that the noncoated and coated 35CrMo steel substrates when subjected to the impingement angle of 60°, water jet velocity of 15 m s−1, stand-off distance of 40 mm, and erodent discharge rate of 1500 g min−1 displayed lower mass loss of 0.0177 g and 0.0079 g. The coated 35CrMo steel substrate showed 55.36 % decrement in erosion compared to noncoated 35CrMo steel substrate. These findings support the employability of WC10Ni5Cr HVOF coating for 35CrMo steel to improve its water jet erosion resistance in engineering applications.

Numerical investigation of the instability of dry granular bed induced by water leakage

AbstractUnderground pipe defects or cracks under transport infrastructure can cause water leakage to upper soil layers (e.g. subgrade and capping), inducing local cavities or even failure of overlying road/railway formation. Although numerous studies on the instability of granular beds induced by injected water have been conducted, most of them focused on the behaviour of saturated granular beds, while research on dry granular beds is still limited. This paper aims to address this gap using a numerical model coupling volume of fluid method with discrete element method. We observed that dry granular beds go through three distinct regimes as water jet velocity increases including stationary, stable deformation with heave and fluidisation. However, the flow velocities required to deform and fluidise dry granular beds are significantly higher than those required for saturated beds. Increasing granular bed thickness can alter its failure mechanism from full depth to localised erosion, leading to cavity formation around pipe cracks prior to the bed fluidisation. The gravitational and frictional components of granular mass are identified as two main resisting forces of dry granular beds against water jet force, evidenced by the increase of critical jet velocities as particle density and friction coefficient increase. Nevertheless, the moblised zone of granular mass is practically independent of both the buried depth of dry granular beds.

Ultrasonic-Vibration-Assisted Waterjet Drilling of [0/45/-45/90]2s Carbon-Fiber-Reinforced Polymer Laminates.

The pure waterjet (WJ) drilling process of carbon-fiber-reinforced polymer (CFRP) laminates causes damage, such as tears and delamination, leading to poor-quality hole-wall. Ultrasonic-vibration-assisted technology can improve the quality of hole walls and repair such damage, particularly the delamination of CFRP laminates. In this study, we conducted a numerical and experimental investigation of a high-pressure pure WJ drilling process of CFRP laminates performed using ultrasonic vibration to improve the delamination phenomena of the pure WJ drilling process. An explicit dynamic model using the smoothed particle hydrodynamics method was employed to simulate the ultrasonic-vibration-assisted WJ drilling of CFRP laminates and ascertain the optimal drilling performance. Thereafter, WJ drilling experiments were conducted to verify the numerical simulation. The results illustrate that the employment of ultrasonic vibration significantly increased the material removal rate by approximately 20%. Moreover, the water-wedging action that induces the propagation of delamination was weakened with an increase in the amplitude of the ultrasonic vibration. The hole-wall quality was optimal with the following drilling parameters: amplitude, 10 μm; frequency, 20 kHz; and WJ velocity, 900 m/s. The delamination zone length was only 0.19 mm and was reduced by 85.6% compared with the values obtained using non-assisted WJ drilling.

Damage behavior and assessment of aeronautical PMMA subjected to high-velocity water-jet impact

Rain erosion of forward-facing aircraft components such as windshields can lead to a significant reduction in performance, hence a potential hazard to air safety, especially for supersonic fighters exposed to precipitation. To understand such threats, the damage behavior of two types of most commonly used aeronautical PMMA, i.e., oriented and non-oriented, under water droplet impact is investigated. A single-impact jet apparatus based on the one-stage gas gun was established to simulate the rain droplet impact. Two critical variables were evaluated, including water-jet velocities and incident angles. Typical damage characteristic features including annular depression and circumferential cracks were observed on non-oriented PMMA targets. In contrast, on oriented PMMA targets, massive subsurface craze delamination was observed without any sign of surface cracks. The distinct damage features are determined by the different damage behavior of the oriented and non-oriented PMMA targets during the initial stage of the impingement and the shearing effect of the lateral jet. Increasing impact velocity leads to surface peeling and bulk removal, escalating the damage severity. The damage mechanism of subsurface failure was revealed by observing stress wave interaction and the FEM simulation. An impulse method was developed to quantify each impact event and assess the damaged area. A linear relationship between the damaged area and the initial impact stage impulse was established, which can be applied for preliminary evaluation and prediction of the damage caused by high-velocity water droplet impact on aeronautical PMMA.

Study on the Removal of Oxide Scale Formed on 300 M Steel Special-Shaped Hot Forging Surfaces during Heating at Elevated Temperature by a High-Pressure Water Descaling Process

Numerical simulations and experiments were utilized to study the removal of oxide scale formed on 300 M steel special-shaped hot forging surfaces during heating at elevated temperature by a high-pressure water descaling process. Specifically, the experimental setup of the special-shaped hot forging was designed and manufactured according to the descaling parameters and simulation results obtained from the hot rolling process. The force states of three typical hot forging surfaces impinged by high-pressure water jets were analyzed. Moreover, the mechanism of the high-pressure water descaling process was proposed based on the research results. The numerical simulations and experimental results revealed that the velocity distribution of the high-pressure water jets is relatively different in various areas of the special-shaped hot forging surfaces. Therefore, the descaling performance is synergistically influenced by the velocity of the high-pressure water jet and the shape of the special-shaped hot forging. Given a certain spray pressure, the value of impact force Fi plays a significant role in the descaling of the typical hot forging. The larger the value of Fi on the typical hot forging surface, the easier it is to remove the oxide scale, and vice versa. Accordingly, the difficulty of removing the oxide scale formed on the 300 M steel special-shaped hot forging surfaces during heating at elevated temperature by a high-pressure water descaling process is in the following order: plane surface < convex surface < concave surface. Additionally, only the inner-layer FeO of the oxide scale remained after the high-pressure water descaling process due to the appearance of FeO-Fe2SiO4 eutectic in the FeO layer.

Experimental investigation on submerged water jet wrapped in an annular gas jet

To reduce the energy dissipation of the submerged water jet, a series of experiments of the submerged water jet wrapped in an annular gas jet are performed under different gas ventilation rates, annular sizes, water jet nozzle diameters, and water jet velocities in a transparent water tank. In the experiments, a ventilated cavity is created by the annular gas jet that encloses the submerged water jet. The submerged water jet is separated from the surrounding water within a certain distance after leaving the nozzle exit by the ventilated cavity, which contributes to the effective working length of the submerged water jet significantly increasing, referring to the energy dissipation decrease. Furthermore, the geometry of the ventilated cavity changes periodically, i.e., the cavity length and diameter decrease after increasing to the peak values in each cycle. Moreover, the ventilated cavity development process can be mainly divided into formation, collapse, and intermission stages. The maximum cavity length of the ventilated cavity decrease with the per unit time momentum ratio between the water jet and the gas jet. Namely, the per unit time momentum ratio between the water jet and the gas jet is the dominating parameter of the cavity geometry.

Torpedo pile penetration by combined water jet and mechanical vibrations in cohesive sedimentary beds

The penetration efficiency and safety of piles on the seabed affect the cost of offshore structures and the reliability of relevant equipment, which entails to the success or failure of the development and utilization of ocean resources. However, the traditional methods of pile penetration, including pressing method, impact driving method and vibro-driving method, are difficult to adapt to the complex marine environment. In this study, the torpedo pile penetration in cohesive sedimentary bed was investigated by applying downwardly directed vertical water jet and mechanical vibrations. The experimental work was developed in the laboratory through a series of pile penetration tests in different types of cohesive sediments. During the penetration processes of the torpedo pile, the relevant influencing factors such as water content of cohesive sediment, vibration intensity and water jet velocity were considered. The experimental results show that the penetration depth of the torpedo pile increases with the increase of water jet velocity, vibration intensity and water content of cohesive sediment. Based on the dimensionless analysis and data regression, a formula for the critical penetration depth of the torpedo pile in cohesive sediment is proposed, which is correlated with the water jet velocity and vibration intensity, as well as the torpedo pile and soil properties. In addition, the formula is verified by the experimental data of other study, which presents good consistency.

On the damage behavior of poly(methyl methacrylate) impacted by high-velocity water jet

The damage behavior of poly(methyl methacrylate) targets subjected to water jet impact was experimentally studied. Parameters including water jet velocity, incident angle and target thickness were considered. Three damage modes are observed for thin targets based on different jet velocities and incident angles: (i) penetration; (ii) radial cracks; (iii) surface damage. Besides, with the increase in incident angle, the mechanism that triggers the damage changes from stress wave to flexure. For thicker targets, only surface damage and subsurface ring crack are observed and the surface damaged area increases parabolically with the increase in impact velocity. A modified damage mechanism is presented and the significance of subsurface ring crack is identified as the root cause of surface ring crack and bulk removal. The damaged area is correlated with an empirical equation, and the obtained material coefficient can be used for the preliminary assessment of the damage caused by waterdrop impact.

Depth of Penetration Model in AWJ Cutting Process Considering the Effect of Frictional Drag of Kerf Wall on the Water-Jet Velocity

Abstract Analytical modeling and experimental verification for the process are vital for selecting an optimum range of process parameters in abrasive water-jet (AWJ) cutting. Many numerical models for the prediction of depth of penetration in the AWJ machining process have been presented by various researchers in the past years. However, very little work that has been represented has taken into account the effect of kerf wall frictional drag on the AWJ velocity. The present paper aims to develop a modified mathematical model for penetration depth using a dimensional analysis approach. The kerf wall frictional drag coefficient has been included in the proposed model to explain the variation of particle velocity at a particular depth of penetration. The results predicted with the theoretical model are validated under various process parameters through the AWJ machining experiments. The predicted values of depth of penetration using the proposed model agree well with the experimental data.

An experimental measurement research on impact load of high speed water jet acting on a rigid target by a Hopkinson pressure bar

A high speed water jet generation device based on explosion in a cylindrical cavity is introduced, which can eject a well-characterized water jet with a velocity around 100 m/s. The evolution characteristics and impact phenomenon of water jet act on a rigid target are observed by a high speed camera and the impact load is measured by a Hopkinson pressure bar. The top shape of water jet develops from a convex spherical surface to a flat plane as the stand-off increases under the influence of air resistance. When the top of water jet contacts the target plate, a transient high-pressure zone appears at the liquid-solid interface. A horizontal annular splashing jet generates and the velocity of splashing jet is much higher than that of incident jet as the result of high-pressure zone. The impact load is measured by the Hopkinson pressure bar, including transient “water hummer” pressure and subsequent hydrodynamic load. The “water hummer” pressure of water jet with a flat top is twice that with a convex spherical top, while the subsequent hydrodynamic pressure is equivalent at a comparable transient impact velocity. The measurement results by a Hopkinson pressure bar are in good agreement with the theory formulas in terms of both “water hummer” pressure and hydrodynamic pressure. It is certified that the Hopkinson pressure bar has a credible measuring capacity for both transient and steady-state pressure. By controlling cavity depth, charge amount and stand-off distance, the different top shape and velocity of water jet can be obtained.

Experimental investigation on effect of water jet erosion parameters on HVOF sprayed Cr3C2-NiCr coatings on stainless steel: a mathematical approach

Chromium carbides are major components in turbine blades due to their high wear resistance, low friction coefficient, and corrosion resistance at high temperature, typically manufactured by thermal spraying for coating applications. For their excellent oxidation and corrosion tolerance, high-speed thermal spray cermet coatings are commonly used to reduce wear at high temperatures and in corrosive conditions. Coatings based on Cr3C2-NiCr have been deposited by means of the HVOF thermal spraying technique on an AISI 304 steel substrate. Furthermore, the erosion behavior of the substrate and coated samples was tested using a water jet erosion test. The effect of water jet parameters, including angle of impingement, water jet velocity, standoff distance, and erodent discharge, on the erosion rate was systematically investigated. Experiments were conducted on the basis of the core composite architecture and the surface response approach for the creation of multiple regression models. Through the analysis of variance, the precision of the regression models was sufficient to establish associations between input parameters and responses. Results revealed that the most prevailing factor impacting the erosion rate of the coatings, followed by water jet velocity, standoff distance, and eroding discharge, was the angle of impingement.

Investigating the Water Jet Erosion Performance of HVOF-Sprayed WC-10Co Coatings on 35CrMo Steel Utilizing Design of Experiments

To enhance the surface of a material with the desired qualities for diverse applications in service, a variety of thermal and thermo-chemical surface treatment processes are used. Due to the high-velocity impact inherent in the process, high-velocity oxy-fuel (HVOF) spray is now frequently employed in industrial applications for its ability to generate a high-quality coating with appropriate hardness and low oxide content. In this investigation, a high-velocity oxy-fuel (HVOF) thermal spraying process was utilized to coat WC-10Co powders on a 35CrMo steel substrate. A water jet erosion test was also used to examine the substrate and coated samples’ erosion behavior. The erosion rate was systematically investigated using water jet variables such as the angle of impingement, water jet velocity, standoff distance, and erodent discharge. For the development of multiple regression models, experiments were performed utilizing the central composite rotatable design and the response surface methodology. The angle of impingement had the most impact on the rate of coating erosion, leading to the water jet velocity, standoff distance, and erodent discharge.

Numerical study of the boiling heat transfer characteristics of bluff body quenching in cylindrical tube

The present study numerically investigates the characteristics of the forced immersion quenching widely used in material manufacturing processes. The numerical simulation considers the boiling heat transfer occurring at the surface of the hot cylindrical specimen heated at 870 °C during the quenching process with a 20 °C water jet. It also examines the influence of water jet velocity on the forced-immersion quenching process. Once the water flow initially impinges on the top side of the hot steel specimen, a large amount of vapor gets generated but disappears from all sides within a few seconds. The amount of vapor decreases with increased water jet velocity due to the high convective heat transfer, leading to vapor condensation. Moreover, a larger recirculation region appears at the sidewall with high water flow velocity because water vapor formed near the wall escapes. Therefore, the cooling performance of the specimen can primarily be attributed to the boiling and convective heat transfer that occurs within a few seconds. The heat flux and heat transfer coefficient increase with the inlet velocity. Moreover, the cooling rate and uniformity are enhanced owing to the increased boiling and convective heat transfer.

Effect of Nozzle Outlet Type on the Flow Field Velocity and Impact Pressure of High-Pressure Water Jet Peening

Abstract Water jet peening can effectively improve the fatigue strength of metal materials, and the outlet shape of nozzle greatly affects the effect of water jet peening. In this paper, the effects of nozzle outlet shape on water jet velocity and impact pressure are studied by numerical simulation, and the jet velocity and dynamic pressure for different standoff distances are also discussed. The results show that the water jets of square, circular, and triangular nozzles are highly concentrated, and the water jet of elliptical nozzles is the most divergent. The axial velocity attenuation of the square nozzle along the axis is slower than that of the other three nozzles. The water axial velocity of the elliptical nozzle attenuates fastest, and the length of the core segment of the water jet is the smallest. Within a certain axial distance, the dynamic pressure area in the central area of the elliptical water jet is obviously larger than that of the other three nozzles, and the effective treatment range is large, which is more suitable for the welding surface strengthening operation.