ANALYSIS OF THE WATER IMPACT OF SYMMETRIC WEDGES WITH A MULTI- MATERIAL EULERIAN FORMULATION

2021 ◽  
Vol 154 (A4) ◽  
Author(s):  
S Wang ◽  
C Guedes Soares
Keyword(s):  
Pressure Distribution ◽  
Impact Velocity ◽  
Pressure Coefficient ◽  
Time History ◽  
Maximum Pressure ◽  
Vertical Force ◽  
Force Coefficient ◽  
Explicit Finite Element ◽  
Eulerian Formulation ◽  
The Impact

The two-dimensional hydrodynamic problem of a symmetric wedge vertically impacting in calm water is analysed by using an explicit finite element method based on a multi-material Eulerian formulation. The slam-induced loads on wedges with different deadrise angle at a constant velocity are calculated, including pressure distribution, maximum pressure coefficient, force coefficient and time history of vertical force, which are compared with available theoretical and analytical results. The time evolution of pressure distribution and free surface elevation are presented. Furthermore, the effects of impact velocity are investigated. It shows that this method is capable of predicting the local slamming loads, and as well assessing the effects of the deadrise angle and the impact velocity on the slamming pressure for the wedge-shape section.

Experimental investigation of pressure distribution characteristics of a flying-wing model using PSP

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040088
Author(s):  
Hongbiao Wang ◽  
Baoshan Zhu ◽  
Jian Xiong
Keyword(s):  
Pressure Distribution ◽  
Surface Pressure ◽  
Pressure Measurement ◽  
Pressure Coefficient ◽  
Leading Edge ◽  
Distribution Characteristics ◽  
Characteristic Analysis ◽  
Camera System ◽  
Wing Model ◽  
The Impact

To investigate the static pressure distribution characteristics of a flying-wing model, an advanced binary pressure sensitive paint (PSP) technique is introduced. It has low-temperature sensitivity and can compensate the errors induced by temperature. The pressure measurement test was performed in 0.6 m trisonic wind tunnel at angles of attack ranging from 0[Formula: see text] to 12[Formula: see text] in supersonic condition, adopting a low-aspect-ratio flying wing model. The binary PSP is sprayed on the upper surface of the model while pressure taps are installed on the upper surface of the right wing. Luminescent images of two probes are acquired with a color charge-coupled-device camera system and processed with calibration results. During the test, the surface pressure is measured by PSP and transducer, respectively. The results obtained show that the binary paint is of advantage to the surface pressure measurement and flow characteristic analysis. The high-resolution pressure spectra at different angle of attack clearly reveal the impact of leading edge vortex on the upper surface pressure distributions. The pressure measured by PSP also agrees well with the pressure tap results. The root mean square error of pressure coefficient is 0.01 at [Formula: see text], [Formula: see text].

Study on the Effect of Impact Velocity on Slamming Loads

2014 ◽  
Vol 687-691 ◽  
pp. 432-435
Author(s):  
Peng Yao Yu ◽  
Hui Long Ren ◽  
Hui Li ◽  
Guo Qing Feng
Keyword(s):  
Finite Element Method ◽  
Impact Velocity ◽  
Prediction Method ◽  
Arbitrary Lagrangian Eulerian ◽  
Variable Speed ◽  
Contact Parameter ◽  
Explicit Finite Element Method ◽  
Explicit Finite Element ◽  
Experimental Values ◽  
The Impact

An explicit finite element method which is combined with the Arbitrary Lagrangian-Eulerian (ALE) algorithm is applied to forecast slamming loads during the structure entries into the water. By adjusting the contact parameter, the result of slamming force is improved and this result is compared with the corresponding experimental values to verify the numerical prediction method of slamming loads. By simulating the wedge into the water at a constant speed and evenly variable speed, the effect of the impact velocity on local slamming pressure and global slamming force is studied.

scholarly journals Axial Force Coefficient of APFSDS Projectile

2020 ◽  
Vol 1 ◽  
pp. 1-15
Author(s):  
Ammar Trakic
Keyword(s):  
Kinetic Energy ◽  
Impact Velocity ◽  
Axial Force ◽  
High Impact ◽  
Cfd Model ◽  
Force Coefficient ◽  
Terminal Ballistics ◽  
High Impact Velocity ◽  
The World ◽  
The Impact

Armor-piercing ammunition is primarily used to combat against heavy armored targets (tanks), but targets can be light armored vehicles, aircraft, warehouse, structures, etc. It has been shown that the most effective type of anti-tank ammunition in the world is the APFSDS ammunition (Armor Piercing Fin Stabilized Discarding Sabot). The APFSDS projectile flies to the target and with his kinetic energy acts on the target, that is, penetrates through armor and disables the tank and his crew. Since the projectile destroys target with his kinetic energy, then it is necessary for the projectile to have the high impact velocity. The decrease in the velocity of a projectile, during flight, is mainly influenced by aerodynamic forces. The most dominant is the axial force due to the laid trajectory of the projectile. By knowing the axial force (axial force coefficient), it is possible to predict the impact velocity of the projectile, by external ballistic calculation, in function of the distance of the target, and to define the maximum effective range from the aspect of terminal ballistics. In this paper two models will be presented for predicting axial force (the axial force coefficient) of an APFSDS projectile after discarding sabot. The first model is defined in STANAG 4655 Ed.1. This model is used to predict the axial force coefficient for all types of conventional projectiles. The second model for predicting the axial force coefficient of an APFSDS projectile, which is presented in the paper, is the CFD-model (Computed Fluid Dynamics).

Optimal Design of Axe-Symmetric Diffuser via Genetic Algorithm and Ball-Spine Inverse Design Method

2012 ◽  
Author(s):  
Navid S. Vaghefi ◽  
Mahdi Nili Ahmadabadi ◽  
Mohammad R. Roshani
Keyword(s):  
Genetic Algorithm ◽  
Boundary Layer ◽  
Pressure Distribution ◽  
Pressure Coefficient ◽  
Initial Guess ◽  
Inverse Design ◽  
Numerical Code ◽  
Maximum Pressure ◽  
Optimum Pressure ◽  
Design Algorithm

In this research, an optimal aerodynamic design of an axe-symmetric diffuser is performed via combination of a developed boundary layer numerical code, BSA inverse design Algorithm and genetic optimization algorithm. To do this, developed numerical boundary layer code is incorporated into the genetic algorithm to reach to an optimum pressure distribution on the wall in such a way that the maximum pressure recovery is obtained without separation. To validate the developed boundary layer code, the calculated quantities are compared with Blasius and Howart’s analytical results. Then, the optimized pressure distribution will be the candidate “target pressure distribution” for the inverse design algorithm to find out the relevant optimum geometry. Geometry modification takes place based on the combination of Ball-Spine algorithm and fluent software as the flow field solver. Implementation of this combination is completed through User Defined Function (UDF) feature of Fluent. Fluent advantageous provides the capabilities for extension of the proposed method to turbulent flows, complicated geometries and employment of both structured and unstructured grids. To show the true performance of the proposed method of inverse design, several issues have been investigated for different initial guess. To validate the effect of the presented method, increased pressure coefficient for an optimized diffuser is illustrated.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Some aspects of rock cutting by high speed water jets

1966 ◽  
Vol 260 (1110) ◽  
pp. 295-310 ◽  
Keyword(s):  
Pressure Distribution ◽  
High Speed ◽  
Frictional Heating ◽  
Water Jet ◽  
Short Exposure ◽  
Maximum Pressure ◽  
Steam Turbines ◽  
Target Plate ◽  
Water Jets ◽  
The Impact

When rocks are cut in coal mines by steel picks, frictional heating sometimes causes ignition of methane; high speed water jets may provide a method of cutting which is free from this hazard. A high speed water jet emerging from a nozzle slows down with increasing distance from the nozzle and breaks up into water drops. Studies were made of the behaviour of water jets: in most of the experiments the jets were produced by pressures of 600 atm., but some results are given of experiments at pressures up to 5000 atm. The jets were examined by short exposure optical photography with several different methods of illumination (parallel transmitted, diffuse, and schlieren) and by X-ray photography. In order to find out how the jet velocity decays with distance from a nozzle, and to compare nozzle designs, a target plate containing a hole smaller than the jet diameter was placed so that the jet impinged at right angles on to it, and the target plate was moved until the maximum pressure at the hole was found: this was measured for different distances from the nozzle. Nozzle shapes suggested in literature for minimizing jet dispersion were studied and an empirical investigation of a variety of nozzle shapes was carried out. Several nozzle shapes were found which gave good results, i.e. the maximum pressure on the target plate was half the pump pressure at a distance of about 350 nozzle diameters. In many cutting applications the first stage in the process would be the impingement of a water jet on a surface at right angles. The initial cutting would depend upon the stress distribution within the target, which in turn would depend upon the pressure distribution produced by the water jet on the surface. A theory is given of the pressure distribution on the target plate, which predicts that the pressure will fall to zero at about 2.6 jet radii: this was found to be in good agreement with experiments. Preliminary studies were made of the penetration of several types of rock by water jets of velocities up to about 1000 m/s (pressures about 5000 atm). It was found that a 1 mm diameter jet drills a cylindrical hole about 5 mm in diameter. The pressure that the water jet produces at the bottom of such holes was measured and shown to fall off to about one-tenth of the nozzle pressure at a hole depth of about 4 cm.

scholarly journals Influence of the near standing hall for wind flowing around group of circular cylinders

2020 ◽  
Vol 310 ◽  
pp. 00013 ◽  
Author(s):  
Ivana Veghova ◽  
Olga Hubova
Keyword(s):  
Wind Tunnel ◽  
Pressure Distribution ◽  
Pressure Coefficient ◽  
Wind Pressure ◽  
Circular Cylinders ◽  
Wind Flow ◽  
Force Coefficient ◽  
Turbulent Wind ◽  
Wind Speeds ◽  
Wind Pressure Coefficient

This article deals with experimental investigation of air flow around in – line standing circular cylinders and influence of nearby standing hall on external wind pressure distribution. The wind pressure distribution on the structures is an important parameter in terms of wind load calculation. For vertical circular cylinders in a row arrangement only wind force coefficient is possible find in Eurocode. 1991-1-4. External wind pressure coefficient depends on wind direction and the ratio of distance and diameter b. Influence of nearby standing structure is not possible find in Eurocode. The series of parametric wind tunnel studies was carried out in Boundary Layer Wind Tunnel (BLWT) STU to investigate the external wind pressure coefficient in turbulent wind flow. Experimental measurements were performed in BLWT for 2 reference wind speeds, which fulfilled flow similarity of prototype and model. We have compared the results of free in - line standing 3 circular cylinder and influence of hall on distribution of wind pressure at 3 height levels in turbulent wind flow and these results were compared with values in EN 1991-1-4.

Agricultural aircraft wing slat tolerance for bird strike

2017 ◽  
Vol 89 (4) ◽  
pp. 590-598 ◽  
Author(s):  
Adam Deskiewicz ◽  
Rafał Perz
Keyword(s):  
Finite Element ◽  
Impact Velocity ◽  
Structural Response ◽  
Element Model ◽  
Bird Strike ◽  
Element Analysis ◽  
Content Type ◽  
Explicit Finite Element ◽  
Explicit Finite Element Analysis ◽  
The Impact

Purpose The aim of this study is to assess and describe possible consequences of a bird strike on a Polish-designed PZL-106 Kruk agricultural aircraft. Due to its susceptibility to such events, a wing slat has been chosen for analysis. Design/methodology/approach Smooth particle hydrodynamics (SPH) formulation has been used for generation of the bird finite element model. The simulations were performed by the LS-Dyna explicit finite element analysis software. Several test cases have been analysed with differing parameters such as impact velocity, initial velocity vector direction, place of impact and bird mass. Findings Results of this study reveal that the structure remains safe after an impact at the velocity of 25 m/s. The influence of bird mass on slat damage is clearly observable when the impact velocity rises to 60 m/s. Another important finding was that in each case where the part did not withstand the applied load, it was the lug where first failure occurred. Some of the analysed cases indicated the possibility a consequent wing box damage. Practical implications This finding provides the manufacturer an important insight into the behaviour of the slat and suggests that more detailed analysis of the current lug design might improve the safety of the structure. Originality/value Even though similar analyses have been performed, they tended to focus on large transport aircraft components. This investigation will enhance our understanding of structural response of small, low-speed aircraft to a bird impact, which is a realistic scenario for the chosen case of an agricultural plane.

scholarly journals Unsteady Numerical Calculation of Oblique Submerged Jet

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4728
Author(s):  
Weixuan Jiao ◽  
Di Zhang ◽  
Chuan Wang ◽  
Li Cheng ◽  
Tao Wang
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Pressure Coefficient ◽  
High Energy ◽  
Impact Pressure ◽  
Maximum Pressure ◽  
Flow Angle ◽  
Free Jet ◽  
Velocity Flow ◽  
The Impact

A water jet is a kind of high-speed dynamic fluid with high energy, which is widely used in the engineering field. In order to analyze the characteristics of the flow field and the change of law of the bottom impact pressure of the oblique submerged impinging jet at different times, its unsteady characteristics at different Reynolds numbers were studied by using the Wray–Agarwal (W-A) turbulence model. It can be seen from the results that in the process of jet movement, the pressure at the peak of velocity on the axis was the smallest, and the velocity, flow angle, and pressure distribution remain unchanged after a certain time. In the free jet region, the velocity, flow angle, and pressure remained unchanged. In the impingement region, the velocity and flow angle decreased rapidly, while the pressure increased rapidly. The maximum pressure coefficient of the impingement plate changed with time and was affected by the Reynolds number, but the distribution trend remained the same. In this paper, the characteristics of the flow field and the law of the impact pressure changing with time are described.

Collision Simulation Analysis for Space Flexible Probe-Cone Docking Mechanism

2011 ◽  
Vol 138-139 ◽  
pp. 111-116
Author(s):  
Wei Han ◽  
Yi Yong Huang ◽  
Xiang Zhang ◽  
Xiao Qian Chen
Keyword(s):  
Impact Force ◽  
Simulation Analysis ◽  
Dynamic Properties ◽  
Time History ◽  
Buffer System ◽  
Flexible Docking ◽  
Explicit Finite Element ◽  
Initial Deviation ◽  
Docking Mechanism ◽  
The Impact

The nature of buffer system is a very important factor of determining the dynamic properties for the success of docking operation in space. The current buffer system is too large and highly complicated, which is not suitable for microspacecraft for On Orbit Servicing (OOS). In this paper, a new type of probe-cone docking mechanism with flexible docking cone as buffer system was presented, and the impact force was simulated using the explicit finite element code, LS-DYNA. Then, the time history of the impact process such as the velocity of docking probe and the docking cone’s displacement was computed under the given impact velocity and initial deviation. In the end, the influence of the wall thickness of docking cone on the impact force was analyzed. The conclusion that the flexible docking cone can greatly help to reduce the maximum impact force by more than 50% provides a basis for the engineering design of the buffer system.

A Numerical Investigation on Water Slamming of Stiffened Panels

2018 ◽  
Author(s):  
Shan Wang ◽  
C. Guedes Soares
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Mesh Size ◽  
Stiffened Panel ◽  
Fe Model ◽  
Explicit Finite Element ◽  
Numerical Predictions ◽  
Eulerian Formulation ◽  
The Impact ◽  
Element Method

To investigate the slamming pressure on the bottom of a wet-deck structure of a multihull vessel, the water impact problem of a stiffened steel panel is simulated by using a fully coupled ALE/FEM algorithm which is implemented in the commercial software LS-DYNA. The Lagrangian formulation is used to describe plane-strain deformations of the hull panel while the Eulerian formulation is applied to describe the fluid flow. The governing equations of this coupling problem are solved by using finite element method. The explicit finite element method is firstly validated through the comparisons of the slamming pressure and structural deflection between the numerical predictions and the published experimental data, for an elastic horizontal plate. Secondly, the parametric study of the mesh size in the impact domain of the FE model is performed. The total slamming forces obtained from three models are compared. To study the effects of the flexibility of the structure on the slamming load, the predictions of slamming pressure on several locations of the elastic panel are compared with the values obtained by using the rigid body model. The water entries of the stiffened panel with two different deadrise angles, entry velocities, and thickness of plating are simulated. The results of the total slamming force, slamming pressure are presented and discussed.

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