On the Origin of a Maximum Peak Pressure on the Target Outside of the Stagnation Point upon Normal Impact of a Blunt Projectile and with Underwater Explosion

2006 ◽  
Author(s):  
Alexander Gonor
Keyword(s):  
Stagnation Point ◽  
Peak Pressure ◽  
Underwater Explosion ◽  
Normal Impact ◽  
Maximum Peak

Effects of Steel Case on Underwater Shock Wave

2011 ◽  
Vol 52-54 ◽  
pp. 943-948
Author(s):  
Ji Li Rong ◽  
Da Lin Xiang ◽  
Jian Li
Keyword(s):  
Shock Wave ◽  
Peak Pressure ◽  
Underwater Explosion ◽  
Steel Shell ◽  
Cylindrical Charge ◽  
Underwater Shock Wave ◽  
Shock Wave Energy ◽  
Lag Effect ◽  
Underwater Shock ◽  
Different Thickness

The effects of steel case confinement for the aluminized explosive on underwater explosion(UNDEX) were experimentally and numerically investigated. The experimental results using 1kg cylindrical charge cased 6mm steel shell, show that steel case enhance the peak pressure, impulse, shock wave energy and decay time relative to the bare charge. The effect of different thickness of steel case was analyzed. With the increase of the case thickness, the shock wave were enhanced first and weaken later, and there is a lag-effect for the peak pressure of shock wave. There is an optimal case thickness which could maximum enhance the peak pressure. According to dimensional analysis, it's found that the ratio of case mass and charge mass( ) is a better dimensionless parameter to estimate UNDEX for a cased charge.

scholarly journals Influences of High-Speed Train Speed on Tunnel Aerodynamic Pressures

2021 ◽  
Vol 12 (1) ◽  
pp. 303
Author(s):  
Jianming Du ◽  
Qian Fang ◽  
Jun Wang ◽  
Gan Wang
Keyword(s):  
High Speed ◽  
Peak Pressure ◽  
Stage I ◽  
Stage Ii ◽  
Stage Iii ◽  
High Speed Train ◽  
Railway Tunnel ◽  
Maximum Peak ◽  
Train Speed ◽  
Three Stages

To comprehensively investigate the characteristics of aerodynamic pressures on a tunnel caused by the whole tunnel passage of a high-speed train at different speeds, we conduct a series of three-dimensional numerical simulations. Based on the field test results obtained by other researchers, the input parameters of our numerical simulation are determined. The process of a high-speed train travelling through a railway tunnel is divided into three stages according to the spatial relationship between the train and tunnel. Stage I: before train nose enters the entrance; Stage II: while the train body runs inside the tunnel; Stage III: after the train tail leaves the exit. The influences of high-speed train speed on the tunnel aerodynamic pressures of these three stages are systematically investigated. The results show that the maximum peak pressure value decreases with increasing distance from the entrance and increases with increasing train speed in Stage I. There is an approximately linear relationship between the three types of maximum peak pressure (positive peak, negative peak, and peak-to-peak pressures) and the power of the train speed in Stage II. These three types of maximum peak pressure values of the points near tunnel portals increase with increasing train speed in Stage III. Moreover, these three types of maximum peak pressure in the tunnel’s middle section at different train speeds are more complex than those near the tunnel portals, and there is one or more turning points due to the superimposed effects of different pressure waves.

scholarly journals Calibration of Numerical Simulation Methods for Underwater Explosion with Centrifugal Tests

2019 ◽  
Vol 2019 ◽  
pp. 1-19
Author(s):  
Qiusheng Wang ◽  
Shicong Liu ◽  
Haoran Lou
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Peak Pressure ◽  
Bubble Radius ◽  
Three Dimensional ◽  
Underwater Explosion ◽  
Mesh Size ◽  
State Equation ◽  
Pulsation Period ◽  
Bubble Pulsation

The centrifugal underwater explosion tests and corresponding numerical simulations were carried out to study the laws of shock wave and bubble pulsation. A semiempirical method to determine JWL state equation parameters was given. The influence on numerical results caused by factors such as state equation of water, boundary condition, and mesh size was analyzed by comparing with the centrifugal underwater explosion test results. The results show that the similarity criterion is also suitable in numerical simulation; the shock wave peak pressure calculated by polynomial state equation is smaller than that of shock state equation. However, the maximum bubble radius and the pulsation period calculated by the two equations are almost the same. The maximum bubble radius is mainly affected by the boundary simulating the test model box, and the pulsation period is mainly affected by the artificial cutoff boundary. With the increase of standoff distance of measuring point, the mesh size required for the numerical calculation decreases; the size of the two-dimensional model is recommended to take 1/30 ∼ 1/10 explosion radius. In three-dimensional models, when mesh size is 2 times larger than explosion radius, the bubble motion change in the second pulsation period is not obvious. When mesh size is smaller than 1 time explosive radius, the full period of bubble pulsation can be well simulated, but calculation errors increase slowly and computation time greatly increases, so the three-dimensional mesh size is suggested to take the charge radius. Shock wave peak pressure is basically unaffected by gravity. As the gravity increases, the bubble maximum radius and the first pulsation period both decrease.

Squeeze and Entraining Motion in Nonconformal Line Contacts. Part II—Elastohydrodynamic Lubrication

1989 ◽  
Vol 111 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Rong-Tsong Lee ◽  
B. J. Hamrock
Keyword(s):  
Transient Process ◽  
Peak Pressure ◽  
Initial Conditions ◽  
Hydrodynamic Lubrication ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Profile ◽  
Maximum Pressure ◽  
Steady State Condition ◽  
Maximum Peak ◽  
Line Contacts

A fast numerical approach to the solution of elastohydrodynamic lubrication (EHL) of line contacts in combined entraining and normal squeeze motion is developed. The initial conditions for the pressure profile, the central normal squeeze velocity, and the location of the outlet boundary at any specified dimensionless load and dimensionless entraining velocity were obtained from the hydrodynamic lubrication study in Lee and Hamrock (1988). The pressure and film thickness were obtained by solving the transient Reynolds, elasticity, rheology, and time-dependent central squeeze velocity equations. The squeeze effect on this transient EHL problem has been proved in that the maximum peak pressure was always higher than the maximum pressure calculated at the steady-state condition. The needle-shaped pressure profile during the transient process produced a dimpled shape near the center of the contacts. In general, the maximum peak pressure increased with increasing dimensionless load, decreasing dimensionless entraining velocity, and increasing dimensionless materials parameter. The dynamic performance parameters were plotted and are a function not only of the dimensionless velocity parameter (as described in Lee and Hamrock, (1988)), but also of the dimensionless load, the dimensionless entraining velocity, and the dimensionless materials parameter. The major factor causing the pressure gradient to be infinity during the transient process was the viscosity. A non-Newtonian fluid is suggested to execute the problem for high load and low entraining velocity.

The Effects of Wearing High Heeled Shoes on Pedal Pressure in Women

Foot & Ankle ◽  
1992 ◽  
Vol 13 (2) ◽  
pp. 85-92 ◽  
Author(s):  
Rebecca E. Snow ◽  
Keith R. Williams ◽  
George B. Holmes
Keyword(s):  
Uniform Distribution ◽  
Peak Pressure ◽  
Foot Pressure ◽  
Maximum Peak ◽  
Heel Height ◽  
Quantitative Studies ◽  
Rate Of Loading

The purpose of this study was to investigate the effects of increased heel height in women's shoes on foot pressure during walking. An increase in heel height increased the maximum peak pressure under the metatarsal heads in the forefoot, decreased the time to maximum peak pressure under the metatarsal heads, and increased the rate of loading to the metatarsals during early support. The higher pressures noted with increased heel height were accompanied by a more uniform distribution of pressure beneath the forefoot. These findings may denote increased stress to the various tissues in the foot when walking in high heeled shoes, which may contribute to deleterious orthopaedic changes. Quantitative studies need to be conducted to determine whether orthopaedic changes occur with prolonged wearing of high heeled shoes.

Based on the Technology of Shaped Charge Numerical Simulation Research of the Ice Model's Combination Blasting

2013 ◽  
Vol 753-755 ◽  
pp. 1002-1006 ◽  
Author(s):  
Wen Yuan Meng ◽  
Jun Qiang Hu ◽  
Xin Liu
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Large Scale ◽  
Peak Pressure ◽  
Yellow River ◽  
Underwater Explosion ◽  
Shaped Charge ◽  
Simulation Research ◽  
Finite Element Software ◽  
Set Up

Combination of ice blasting model is set up with the program of blasting with technology of shaped charge, numerical calculation is carried out, and the shockwave peak pressure in ice medium is obtained based on the large-scale finite element software ANSYS/LS-DYNA . This paper analyzes the stress distribution of ice in the combination of underwater explosion loads, and studies the process of the underwater explosion. The article aims to promote the application and research of underwater explosion in Yellow River and Hei Long Jiang River ice blasting, etc.

scholarly journals Remarks On Deformation In Snow With Residual Stress And Gravitational Force By Detonation Impact

2012 ◽  
Vol 12 (5) ◽  
Author(s):  
Siavosh Ahmadi
Keyword(s):  
Strain Energy ◽  
Gravitational Force ◽  
Present Model ◽  
Peak Pressure ◽  
Underwater Explosion ◽  
Computational Aspect ◽  
Detonation Pressure ◽  
Material Parameters ◽  
Flow Parameters ◽  
Nature Studies

Estimation of strain (deformation) and strain energy at the time of an explosion has been undertaken in the present investigation. A basic concept of explosive pressure which is required for the estimation of strain and strain energy has been drawn from the underwater explosion with suitable modification to the present studies. One of the most significant aspects of the present investigation is to augment the model by accounting it for gravitational force and residual stresses which are of realistic in nature. Studies consist of computational aspect by observing the variation of strain and strain energy with respect to material parameters such as Elastic modulus (E), poisons ratio (?), density (?), and flow parameters such as peak pressure (Pm), sound velocity (Vs), and length of snow slab (L). One of the interesting observation found in the computational aspect is, the deformation is found to decrease as the velocity of sound (Vs) in snow increases which appears to be strange but found factual. The model has been compared with the other existing papers in the literature and found that, the present model yields to better results. ABSTRAK: Anggaran regangan (canggaan) dan tenaga regangan pada masa letupan diambil kira dalam kajian ini. Konsep asas tekanan letupan yang diperlukan untuk anggaran regangan dan tenaga regangan diperolehi daripada letupan bawah air dengan pengubahsuaian yang sesuai dalam kajian terkini. Antara aspek penting dalam kajian ini adalah penambahan model dengan mengambil kira daya graviti dan tegasan sisa yang sebenar. Kajian terdiri daripada aspek pengiraan, dengan memerhatikan variasi regangan dan tenaga regangan terhadap parameter bahan seperti modulus anjal (E), nisbah Poisson’s (?), ketumpatan (?), dan parameter aliran seperti tekanan puncak (Pm), halaju bunyi (Vs), dan panjang papak salji (L).  Antara pemerhatian menarik yang ditemui dalam aspek pengiraan ialah, canggaan didapati berkurangan ketika halaju bunyi (Vs) salji bertambah.  Walaupun ini nampak asing, tetapi ianya terbukti benar.  Model dibandingkan dengan kertas kerja lain dan didapati bahawa, model terkini memberikan keputusan yang lebih tepat.KEYWORDS: avalanche dynamics; fracture mechanics; detonation pressure

Reducing peak pressures under the saddle at thoracic vertebrae 10-13 is associated with alteration in jump kinematics

2018 ◽  
Vol 14 (4) ◽  
pp. 239-247 ◽  
Author(s):  
R.C. Murray ◽  
R. Mackechnie-Guire ◽  
M. Fisher ◽  
V. Fairfax
Keyword(s):  
Motion Analysis ◽  
High Speed ◽  
Peak Pressure ◽  
Video Data ◽  
Flexion Angle ◽  
Thoracic Vertebrae ◽  
Kinematic Data ◽  
Maximum Peak ◽  
Peak Pressures ◽  
Positive Effect

There is little information about horse-saddle interaction at take-off for a fence, although there is potential that this could have an influence on performance. It was hypothesised that (1) maximum peak pressure under the saddle would occur in the phase of maximum thoracolumbar flexion prior to hindlimb take-off; and (2) limb and trunk kinematics at take-off over the fence would be affected by reducing peak pressure at Thoracic vertebrae (T)10-13 at the point in the stride where peak pressures occur. The peak pressures under the usual saddle (Saddle S) and a saddle modified to reduce peak pressures at T10-13 (Saddle F) were measured during approach and take-off over a 1.30 m upright fence in 12 elite jumping horses. The timing of peak pressures was determined by comparison with simultaneous video data. Shoulder, carpal flexion angle and trunk angle to the horizontal at hindlimb take-off, take-off distance from the fence and fetlock height above the fence were determined using high speed motion analysis. Peak pressures under the saddle at T10-13 and kinematic data were compared between Saddles S and F. Maximum peak pressures occurred at forelimb vertical, during hindlimb protraction, consistent with thoracolumbar ventroflexion. Saddle F was associated with significantly lower peak pressures at T10-13, greater shoulder and carpal flexion, a steeper trunk angle, and higher fetlock height above the fence than Saddle S. Forelimb take-off distance from the fence was not different between saddles, but hindlimbs were significantly closer to the fence with Saddle F, indicating potential increase in ventroflexion through the thoracolumbosacral region. These findings suggest that reducing peak pressures under the saddle at T10-13 are associated with altered kinematics during the approach and take-off over a fence, which may have a positive effect on jumping performance.

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