Analysis of water entry impact load characteristics of rigid spheres based on experiments

2021 ◽  
Author(s):  
Long Meng ◽  
Jingping Xiao
Keyword(s):  
Impact Load ◽  
Water Entry ◽  
Rigid Spheres ◽  
Load Characteristics

scholarly journals Analysis and Testing of Load Characteristics for Rotary-Percussive Drilling of Lunar Rock Simulant with a Lunar Regolith Coring Bit

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Peng Li ◽  
Hui Zhang ◽  
Shengyuan Jiang ◽  
Weiwei Zhang
Keyword(s):  
Impact Load ◽  
Rotational Velocity ◽  
Lunar Regolith ◽  
Drilling Process ◽  
Percussive Drilling ◽  
Analytic Equation ◽  
Lunar Rock ◽  
Rotary Drilling ◽  
Drilling Parameters ◽  
Load Characteristics

Based on an optimized lunar regolith coring bit (LRCB) configuration, the load characteristics of rotary-percussive drilling of lunar rock simulant in a laboratory environment are analyzed to determine the effects of the drilling parameters (the rotational velocity, the penetration rate, and the percussion frequency) on the drilling load. The process of rotary drilling into lunar rock using an LRCB is modeled as an interaction between an elemental blade and the rock. The rock’s fracture mechanism during different stages of the percussive mechanism is analyzed to create a load forecasting model for the cutting and percussive fracturing of rock using an elemental blade. Finally, a model of the load on the LRCB is obtained from the analytic equation for the bit’s cutting blade distribution; experimental verification of the rotary-impact load characteristics for lunar rock simulant with different parameters is performed. The results show that the penetrations per revolution (PPR) are the primary parameter influencing the drilling load. When the PPR are fixed, increasing the percussion frequency reduces the drilling load on the rock. Additionally, the variation pattern of the drilling load of the bit is in agreement with that predicted by the theoretical model. This provides a research basis for subsequent optimization of the drilling procedure and online recognition of the drilling process.

scholarly journals Water entry of deformable spheres

2017 ◽  
Vol 824 ◽  
pp. 912-930 ◽  
Author(s):  
Randy C. Hurd ◽  
Jesse Belden ◽  
Michael A. Jandron ◽  
D. Tate Fanning ◽  
Allan F. Bower ◽  
...  
Keyword(s):  
Material Properties ◽  
High Speed ◽  
Large Scale ◽  
Hydrodynamic Pressure ◽  
Oscillation Period ◽  
Water Entry ◽  
Effective Diameter ◽  
High Speed Imaging ◽  
Rigid Spheres ◽  
Velocity Change

When a rigid body collides with a liquid surface with sufficient velocity, it creates a splash curtain above the surface and entrains air behind the sphere, creating a cavity below the surface. While cavity dynamics has been studied for over a century, this work focuses on the water entry characteristics of deformable elastomeric spheres, which has not been studied. Upon free surface impact, an elastomeric sphere deforms significantly, giving rise to large-scale material oscillations within the sphere resulting in unique nested cavities. We study these phenomena experimentally with high-speed imaging and image processing techniques. The water entry behaviour of deformable spheres differs from rigid spheres because of the pronounced deformation caused at impact as well as the subsequent material vibration. Our results show that this deformation and vibration can be predicted from material properties and impact conditions. Additionally, by accounting for the sphere deformation in an effective diameter term, we recover previously reported characteristics for time to cavity pinch off and hydrodynamic force coefficients for rigid spheres. Our results also show that velocity change over the first oscillation period scales with the dimensionless ratio of material shear modulus to impact hydrodynamic pressure. Therefore, we are able to describe the water entry characteristics of deformable spheres in terms of material properties and impact conditions.

Numerical evaluation of the hydrodynamic impact characteristics of the air launched AUV upon water entry

2020 ◽  
Vol 34 (14) ◽  
pp. 2050149
Author(s):  
Ahmad Zamir Chaudhry ◽  
Guang Pan ◽  
Yao Shi
Keyword(s):  
High Speed ◽  
Impact Load ◽  
Research Work ◽  
Computational Cost ◽  
Water Entry ◽  
Structure Design ◽  
Hydrodynamic Characteristics ◽  
Ale Method ◽  
The Impact ◽  
Selection Of

In this paper, water entry process of air launched AUV is investigated by employing fully coupled finite element method and arbitrary Lagrange–Euler formulation (FEM-ALE) and using penalty coupling technique. Numerical model is established to describe the hydrodynamic characteristics and flow patterns of a high-speed water entry AUV. The effectiveness and accuracy of the numerical simulation are verified quantitatively by the experiments of the earlier study. Selection of suitable advection method and mesh convergence study is carried out during experimental validation process. It is found that appropriate mesh size of impact domain is crucial for numerical simulations and second-order Van Leer advection method is more appropriate for high speed water entry problems. Subsequently, the arbitrary Lagrange–Euler (ALE) algorithm is used to describe the variation laws of the impact load characteristics with water entry velocities, water entry angles and different AUV masses. Dimensionless impact coefficient of AUV at different velocities calculated using ALE method is compared with SPH results. This reveals that ALE method can also simulate the water entry process accurately with less computational cost. This research work can provide beneficial reference information for structure design of AUV and for selection of the water entry parameters.

scholarly journals Numerical and experimental investigation on the oblique water entry of cylinder

2020 ◽  
Vol 103 (3) ◽  
pp. 003685042094088
Author(s):  
Longquan Sun ◽  
Duliang Wang ◽  
Yingyu Chen ◽  
Guoxun Wu
Keyword(s):  
Water Entry ◽  
Initial Time ◽  
Lagrange Method ◽  
Simulation Research ◽  
Motion State ◽  
Slamming Load ◽  
Load Characteristics ◽  
Air Cavities ◽  
The Relationship ◽  
Good Agreement

The study of water entry cavity and the analysis of load characteristics are hot topics in water entry research. The coupled Euler–Lagrange method is used to carry out simulation research on the water entry process of a cylinder. Aiming at the water vapor mixing phenomenon caused by structure slamming on the water at the initial time of water entry, the slamming load is further studied by correcting the sound speed in the water. The differences between the calculated results obtained by adjusting the number of units in the numerical simulation prove the convergence of the numerical method. Water entry experiments of a cylinder were carried out, and the results are in good agreement with the simulation data. The motion state simulation and analysis are carried out for the process of water entry with different initial speeds and angles. The changes in the structure’s positions, air cavities, and slamming loads are obtained. The rule of slamming pressure with the water entry angle and the relationship between pressure and acceleration are determined.

scholarly journals Numerical simulation of cavitation characteristics in high speed water entry of head-jetting underwater vehicle

2021 ◽  
Vol 39 (4) ◽  
pp. 810-817
Author(s):  
Hairui Zhao ◽  
Yao Shi ◽  
Guang Pan
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Impact Load ◽  
Underwater Vehicle ◽  
Water Entry ◽  
Engineering Practice ◽  
Entry Angle ◽  
Air Jet ◽  
Entry Velocity ◽  
The Impact

Autonomous underwater vehicle will be subjected to a huge impact load during high speed water entry, which will damage the structure and the internal instruments of the vehicle. Therefore, it is of great significance to study the buffer mechanism of the vehicle during the process of water-entry. In this paper, a kind of head-jetting device with disk cavitation is used. The complex cavitation forms, under the three-phase coupling of gas, liquid and solid, in the water entry process of the vehicle on which the device is installed. In this paper, the numerical simulation of high-speed water entry of the vehicle equipped with head jet device is carried out. Through the analysis of water entry cavitation under typical working conditions, the following conclusions are obtained. After the installation of head jet device, the water entry cavity of the vehicle changes gradually from cone to spindle shape. The air jet, compared with that without jet, can promote the formation of water inlet supercavitation, decrease the interaction area between the vehicle and water, and reduce the impact load during water entry. At the same water entry depth, the diameter of cavitation increases with the amount of air jet. The water entry velocity has a great influence on the difference of cavitation shape. The water entry depth closure phenomenon, when the water entry velocity is less than 100 m/s, can be observed in the depth of 3.5 times of the projectile length. The water entry angle has a significant effect on the cavitation shape. The cavity shows obvious asymmetry when the vehicle slants into the water, and the diameter and length of the bubbles decrease with the increase of the water entry angle. The research content of this paper provides technical support for the engineering practice of high-speed water entry and load reduction, and the conclusions are of great significance in related fields.

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