A New Simulation Model for Recoil Analysis of Deep-Water Drilling Risers After Emergency Disconnection

The recoil response of a deep-water drilling riser following an ED(Emergency Disconnection)scenario is a transient and sensitive process.The recoiling displacement of the riser is the resultant of recoil motion and axial stretch.How-ever,it is typically represented by one variable in recoil simulations.As axial deformation is quite small compared with axial motion in the recoil process,it inevitably introduces numerical errors(i.e.,a large number annihilating a small number).Thus,it is hard to perform a quantitative analysis of axial deformation,although a consensus initial deformation is essential for recoil dynamics.Moreover,the triggered axial natural modes have never been examined before.In this study,the recoil response is decomposed into two parts:recoil motion and axial deformation,and a novel model is developed by Galerkin method.It has demonstrated that the initial stretch has a significant effect at the initial stage in recoil.The existing models underestimate the effects of axial deformation.The new model can capture information of triggered natural modes and figure out the modes undergoing dynamic compression.This study can be beneficial to overpull setting,determination of ED time and anti-recoil control optimization.

Temperature influences of the recoil characteristics for aluminum honeycomb buffer in the tether-net launcher

Fluctuations in outer space's temperature would affect the spacecraft's regular operation.This paper aims to study the temperature influences of the aluminum honeycomb buffer in the tether-net launcher.Firstly,a buffer structure was designed to attenuate the pyroshock generated by the pyrotechnic device.Secondly,the mechanical properties of aluminum honeycomb at different temperatures were obtained through quasi-static compression experiments.Then,the internal ballistic responses of the launcher were gained by the closed bomb tests and the equivalent classical interior ballistic model.Finally,the recoil performance of the launcher with aluminum honeycomb buffer at different temperatures was studied.It is revealed that the aluminum honeycomb crushing force gradually decreases with the temperature increases.The peak pressure,burning rate coefficient and velocity increase while the peak time decreases with the temperature increase for the interior ballistics.For the launcher recoil responses,the average launch recoil decreases if the aluminum honeycomb doesn't enter the dense stage.The impact acceleration,projectile velocity and displacement increase as the temperature increase.The paper spotlights the temperature's influence on the recoil characteristics of the aluminum honeycomb buffer,which provides a new idea for buffering technology of pyrotechnic devices in a complex space environment.

A prediction method for the performance of a low-recoil gun with front nozzle

One of the greatest challenges in the design of a gun is to balance muzzle velocity and recoil,especially for guns on aircrafts and deployable vehicles.To resolve the conflict between gun power and recoil force,a concept of rarefaction wave gun(RAVEN)was proposed to significantly reduce the weapon recoil and the heat in barrel,while minimally reducing the muzzle velocity.The main principle of RAVEN is that the rarefaction wave will not reach the projectile base until the muzzle by delaying the venting time of an expansion nozzle at the breech.Developed on the RAVEN principle,the purpose of this paper is to provide an engineering method for predicting the performance of a low-recoil gun with front nozzle.First,a two-dimensional two-phase flow model of interior ballistic during the RAVEN firing cycle was established.Numerical simulation results were compared with the published data to validate the reliability and accuracy.Next,the effects of the vent opening times and locations were investigated to determine the influence rules on the performance of the RAVEN with front nozzle.Then according to the results above,simple nonlinear fitting formulas were provided to explain how the muzzle velocity and the recoil force change with the vent opening time and location.Finally,a better vent venting opening time corresponding to the vent location was proposed.The findings should make an important contribution to the field of engineering applications of the RAVEN.

Measurement of the prompt neutron spectrum from thermalneutron-induced fission in U-235 using the recoil proton method

A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculation and validation of the response matrix, are presented. The PFNS for ^235U in the energy range 1–12 MeV, induced by thermal neutrons, was obtained. The measured spectrum in the low-energy region was in good agreement with previous work and the ENDF/B-VII library, except for minor differences. In the high-energy region, however, the relative height of the measured spectrum was greater, and an analysis of the experiment indicated uncertainties of 13% at 10 MeV and 24% at 12 MeV. Experimental results showed that the recoil proton method could be used to measure prompt fission neutron spectra. Some directions for future work are included.

Propagation of positive, negative, and recoil leaders in upward lightning flashes

Leader propagation is a fundamental issue in lightning physics. The propagation characteristics of positive leaders and negative leaders are summarized and compared based on data from high-speed camera and electromagnetic field in rocket-triggered lightning and tower-initiated lightning discharges; available channel base current data recorded in rocket-triggered lightning are also used. The negative leaders propagate in a stepped fashion accompanied by many branches. The stems ahead of the negative leader tip determine the manner and direction of the leader propagation, and even the branching and winding of the lightning channel. The impulsive current, electromagnetic field, and related optical images suggest that the positive leader may develop in a step-like fashion at its initial stage of triggered lightning. However, the stepping processes of the positive leader are obviously different from those of the negative leader. Tower-initiated lightning revealed that the most conspicuous characteristics of the stepwise positive leader involve the intermittent brush-like corona zone in front of the leader tip and the luminosity enhancement of the channel behind the tip. In rockettriggered lightning flashes, the charge transferred during an individual step for the negative leader was nearly an order greater than for the positive counterpart. The successive streamers ahead of the leader tip are essential for both negative and positive leader propagation, and the stems could be formed from one or more streamers in the previous negative streamer zone with the main leader channel dim. High-resolution observation of tower lightning also revealed a new type of bidirectional recoil leader, with polarity contrary to the traditional one, traversing in negative channels associated with tower-initiated and rocket-triggered lightning.

Fast thermometry for trapped atoms using recoil-induced resonance

We have employed recoil-induced resonance（RIR） with linewidth on the order of 10 k Hz to demonstrate the fast thermometry for ultracold atoms. We theoretically calculate the absorption spectrum of RIR which agrees well with the experimental results. The temperature of the ultracold sample derived from the RIR spectrum is T = 84 ± 4.5 μK, which is close to 85 μK that measured by the method of time-of-flight absorption imaging. To exhibit the fast measurement advantage in applying RIR to the ultracold atom thermometry, we study the dependence of ultracold sample temperature on the trapping beam frequency detuning. This method can be applied to determine the translational temperature of molecules in photoassociation dynamics.

CALCULATION AND OPTIMIZATION OF EXPERIMENTAL PARAMETERS IN ELASTIC RECOIL DETECTION (ERD)

Elastic recoil detection (ERD) proposed for the analysis of light elements in a heavier matrix is an appropriate method for its specialities. Optimization of experimental parameters in ERD such as scattering geometry and incident beam energy is very important when using a small accelerator with energy lower than 10 MeV. In this paper a computer program ERDAl is developed for the purpose, and is proved to be useful for practical handling of ERD experiments.

ELASTIC RECOIL DETECTION ANALYSIS OF LIGHT ELEMENTS IN THIN FILMS USING 35 MeV^(35) Cl^(6+) BEAM

In this paper, an elastic recoil detection analysis method is described using 35 MeV 35Cl as incident ions. This method can determine and profile simultaneously H, D, He, C and O or in the other case, H, C, N and O. The depth resolution for the elements heavier than He is better than 20 nm. It has been applied to study the Co/Si and TiN thin films, and the depth profiles of He implanted in monocrystal silicon.

Mathematical analysis of the role of recoil pressure in weld pool dynamics during laser-MIG hybrid welding

A mathematical model was established to simulate the weld pool development and dynamic process in stationary iaser-MlG hybrid welding. Surface tension and buoyancy were considered to calculate liquid metal flow patter, moreover, typical phenomena of MIG welding, such as filler droplets impinging weld pool, electromagnetic force in the weld pool, and typical phenomena of laser beam welding, such as recoil pressure, Inverse Bremsstrahlung absorption, Fresnel absorption were all considered in the model. The laser beam and arc couple effect were introduced into this model by the plasma width during hybrid welding. The role of recoil pressure in the weld formation was discussed. Transient weld pool shape and complicated liquid metal velocity distribution from two kinds weld pool to an unified weld pool were calculated. The simulated weld bead geometry with consideration recoil pressure was in good agreement with experimental measurement.

New spraying process development for inlet deflector roller in a recoiling line

The inlet deflector rollers of a recoiling line are sprayed rollers. Short scratch lines have been found on the surface of steel sheets during commissioning. By adjusting the control parameters of the line and investigating the manufacturing process of inlet deflector rollers, the root cause of the scratches was found. By modifying the manufacturing process of the rollers, the scratches have been thoroughly eliminated, and quality steel sheets have been consistently produced in the recoiling line.

Observation of photon recoil effects in single-beam absorption spectroscopy with an ultracold strontium gas

We report on observing photon recoil effects in the absorption of a single monochromatic light at 689 nm through an ultracold ^(88)Sr gas,where the recoil frequency is comparable to natural linewidth of the narrow-line transition 5s^(2) ^(1)S_(0)-5s5p ^(3)P_(1) in strontium.In the regime of high-saturation,the absorption profile becomes asymmetric due to the photon-recoil shift,which is of the same order as the natural linewidth.The lineshape is described by an extension of the optical Bloch equations including the momentum transfers to atoms during emission and absorption of photons.Our work reveals the photon recoil effects in a simplest single-beam absorption setting,which is of significant relevance to other applications such as saturation spectroscopy,Ramsey interferometry,and absorption imaging.

Trigger control characteristics of fuze-recoil simulation system based on electromagnetic launcher

Fuze is the information processing and control unit of the ammunition, so the quality of the fuze becomes one of the most important aspects of ammunition detection. Since using recoil force is a common method to the arm fuze, its dynamic simulation test has always been the focus of the fuze test research. A new fuze recoil environmental simulation method is proposed based on the electromagnetic launcher. Then the trigger control characteristics of the fuze recoil simulation system and the influence of the trigger position on the recoil force are studied. The results of the study show that although the pulse width of the armature force curve can be changed by adjusting the trigger position, due to the limit of the range, there also exists the contradiction that the electromagnetic pulse width gets narrow with the increase of electromagnetic force peak. Thus, it cannot meet the requirements of the fuze launch recoil simulation. In order to make the recoil force close to the actual environment, the multi-stage trigger control characteristics are analyzed, and the influence of trigger position on recoil environmental force characteristics is studied. Then a fuze launch recoil environmental simulation platform is established and continuous electromagnetic force is achieved by using the trigger strategy. Finally, the experiment is performed to simulate the fuze launch recoil environment and show the feasibility and effectiveness of the proposed theoretical analysis. The major research work of this paper includes studying the composition and basic principle of the simulation system, establishing a launch model to analyze the single-stage and multi-stage coil fuze launch recoil characteristics, designing the test device to verify the correctness and validity of the research. This paper draws the conclusions that the feasibility of the fuze launch environmental simulation based on the electromagnetic launcher is verified, the trigger position has a great influence on force peak continuity, the problems of low maximum overload peak and short peak duration in the multi-stage coil fuze launch environmental simulation can be effectively solved through adjusting the trigger position, the system has creative and extensive application prospects.

Neutron response functions and detection efficiency of a spherical proton recoil proportional counter

The neutron response function and detection efficiency of a spherical proton recoil proportional counter (SP) play key roles in precise measurement of neutron spectra of the interior materials.In this paper,the response functions and detection efficiency of three SPs developed at CAEP are simulated by Geant4.The simulated spectra are compared with pulse-height spectra measured at 0.165,0.575,1.4,and 14.1 MeV of incident neutrons.And the calculated detector efficiencies agree within 5%with the data obtained by neutron activation.

Dynamic Simulation of the Tank Gun Recoil Response

By using the ATV module of MSC. ADAMS, the dynamic simulation of recoil response of tank gun is analyzed.How the recoil force affects the bodywork and the suspension during gun firing, as well as the changing status of the gun muzzle's velocity are gained. All results and analyzing methods are offered for the designing basis of optimizing tank vehicle-gun match. The constructive exploration is beneficial to improving the general capability of tank.

Monte Carlo Study on Spontaneous Recoil of Confined DNA Chain

长 DNA 链的部分被一个电场驾驶进限制环境，当剩余的留在高熵的区域时。在这个领域的移动之上，链自发地撤退到高熵的区域。这个动态过程被蒙特卡罗模拟调查。模拟复制 DNA 链的 recoil 是开始慢的并且逐渐地由于 confinement-entropic 力量的存在处于速度增加的试验性地观察的现象。结果与增加尺寸或减少显示出那 DNA 链的 recoil 速度将增加的 nanopillars 的间距。进一步的分析建议典型的熵与在监禁的免费部分的区域部分每在监禁的单体成正比。

The Numerical Simulation of Recoil Caused by Blasting Demolition of High Buildings

On the basis of recoil in the process of blasting demolition of high buildings, this thesis applies dynamics theory to predict whether the phenomena of recoil will occur or not by simulation and calculation of the recoil and the pressure suffered from the rudimental supporter in the process of demolition. The criterion of recoil relies on whether recoil can be overcome by the intensity of reservation or friction. To take the obliquity as increment, and to calculate the recoil and the pressure suffered from the rudimental supporter in correspondence with the every obliquity in the demolition by VC program, the relation curve can be obtained between recoil and obliquity. By means of examples testified with programs, the obtained results are consistent with those of practice.

Study of relationship between motion of mechanisms in gas operated weapon and its shock absorber

The article deals with the motion of the breech block carrier and the weapon casing of an automatic weapon mounted on a flexible carriage and the base of the weapon.Earlier works,which did not consider the dynamic properties of the base of the weapon,did not allow to reconcile the calculated and experimental results of the weapon casing displacement when shooting from firing rests.For the analysis of the motion of individual parts,the methods of mathematical modelling and firing experiments using a high-speed camera were chosen.Calculations show the best accord with experiment when modelling the system with 4 degrees of freedom.The oscillation of the system regarding the movement of the breech block carrier and the weapon casing was investigated under changed conditions of rate of fire,the use of a muzzle brake and different types of shock absorbers.The velocities and displacements of the weapon casing and the breech block carrier at different values of the impulse of the gases to the breech block carrier were determined.

Determination of responses of liquid xenon to low energy electron and nuclear recoils using a PandaX-Ⅱ detector

We present a systematic determination of the responses of PandaX-Ⅱ,a dual phase xenon time projection chamber detector,to low energy recoils.The electron recoil(ER) and nuclear recoil(NR) responses are calibrated,respectively,with injected tritiated methane or 220Rn source,and with 241Am-Be neutron source,in an energy range from 1-25 keV(ER) and 4-80 keV(NR),under the two drift fields,400 and 317 V/cm.An empirical model is used to fit the light yield and charge yield for both types of recoils.The best fit models can describe the calibration data significantly.The systematic uncertainties of the fitted models are obtained via statistical comparison to the data.

适应火工装置冲击环境的铝蜂窝缓冲特性研究

针对火工装置发射过程中对卫星平台产生的冲击,设计了一种基于铝蜂窝的新型空间发射缓冲结构,通过火药密爆试验和铝蜂窝准静态压溃试验分别建立了空间火工发射装置内弹道模型和铝蜂窝压溃模型,在此基础上建立了发射后坐动力学模型,并重点研究了火药药量和铝蜂窝内径对发射后坐特性的影响。研究结果表明:当火药药量增大0.3 g,后坐力平均值增大了1.95%,牵引体发射速度增大了5.10%,后坐位移增大了7.64%,后坐力持续时间减小10.3%。当铝蜂窝内径从148 mm分别减小1 mm和2 mm时,后坐力平均值增大了4.06%和9.08%,牵引体发射速度增大了0.22%和0.54%,后坐位移增大了3.38%和15.24%。同时以上参数的合理选择可以有效降低发射后坐力并保证牵引体的发射性能。

基于热源网络法的永磁式电磁制退机热特性研究

永磁式电磁制退机以磁场为能量传输介质,有望彻底解决传统液压式制退机液体泄漏、阻力规律稳定性差等问题。然而电磁制退机工作过程中的热特性变化规律尚未探明,限制了电磁制退机的进一步发展。依据电磁制退机的结构,建立了热源网络温度场分析模型,计算了电磁制退机各主要部件的热参数,结合热路传播路径编写了温度场计算程序,得到了火炮后坐过程中电磁制退机不同时刻的瞬态节点温度,探究了电磁制退机瞬态工作过程中的温度传播规律与分布特性。同时建立有限元模型,对热源网络分析模型进行了验证。最后充分利用热源网络模型计算效率高的优势,开展了连发射击工况下电磁制退机的热特性研究、失效预测和冷却措施探究,为电磁制退机的工程设计提供了参考。