A Computational Framework for Parachute Inflation Based on Immersed Boundary/Finite Element Approach

A computational framework for parachute inflation is developed based on the immersed boundary/finite element approach within the open-source IBAMR library.The fluid motion is solved by Peskin's diffuse-interface immersed boundary(IB)method,which is attractive for simulating moving-boundary flows with large deformations.The adaptive mesh refinement technique is employed to reduce the computational cost while retain the desired resolution.The dynamic response of the parachute is solved with the finite element approach.The canopy and cables of the parachute system are modeled with the hyperelastic material.A tether force is introduced to impose rigidity constraints for the parachute system.The accuracy and reliability of the present framework is validated by simulating inflation of a constrained square plate.Application of the present framework on several canonical cases further demonstrates its versatility for simulation of parachute inflation.

Faster Than Sound, Daredevil Parachute Jumps from the Edge of the Space

This article discusses the kinematics of a parachutist making a very-high-altitude jump. The effect of altitude on the density of air, on the gravitational field strength of the Earth, and on the atmosphere’s temperature has been taken into account in our analysis. The well-known equations of classical mechanics governing the selected topic have been solved numerically by using the mathematical software Mathcad. Especially, the possibility of a person exceeding the speed of sound during their fall has been considered in our analysis. The effect of the sound barrier is taken into account so that the shape factor of the falling body is given as a speed-dependent function, which reaches its maximum value at Mach 1.0. The obtained results have been found to be highly consistent with the available experimental data on some high-altitude jumps. The data published on the famous jump of Captain Joseph Kittinger has been analyzed very carefully, and although our calculations reproduced the reported values for most parts, some interesting inconsistencies were also discovered. Kittinger jumped from a gondola attached to a helium-filled balloon from a record-high altitude of 102,800 ft, or 31,330 m, in August 1960. We also made numerical analysis on the high-altitude jump of Felix Baumgartner. He bailed out from his gondola at the record-high altitude of 39.0 km in October 2012.

改善缺血性心力衰竭的新选择——Parachute左心室重建术

近年来,心力衰竭（心衰）的患病率逐年增高,日渐成为严重的公共卫生问题,有临床症状患者的5年存活率与恶性肿瘤相仿。其病因众多,最常见的病因之一为急性心肌梗死[1]。临床上,尤其是前壁心肌梗死合并室壁瘤的患者更易发生缺血性心衰,左心室壁瘤可改变左室壁曲度和厚度,导致整个心脏的扩张和变形。

CD碟片指南

如果说现今占据音乐市场的众多摇滚乐队中（刨去那些以外表迷惑、过激言论炒作而博得青少年青睐的傻乐队）最具人气的一类音乐形式则非英式摇滚（Britpop)莫属。流畅动听的旋律，洒脱健康的形象是最基本的要素。从上世纪八十年代开始，经过一系列的运动变革后，Britpot至今已经成为一个极具号召务的名词.而分析整个英式的发展阶段最重要的要数八十年代末至九十年代初起源于曼彻斯特的MADCHESTER运动。

经皮左心室室壁瘤PARACHUTE封堵术治疗的护理

总结3例经皮左心室室壁瘤PARACHUTE封堵术治疗的护理体会。护理重点为术前规范化治疗基础疾病,改善心肾功能;术后严密监测生命体征,预防和积极处理异常情况,做好抗血小板抗凝治疗的护理,做好水化治疗护理,预防急性肾功能衰竭;治疗康复过程中重视患者主诉和心理护理,持续强化健康宣教。3例患者经治疗和护理,均治愈出院。

Study on transient aerodynamic characteristics of parachute opening process

In the research of parachute, canopy inflation process modeling is one of the most complicated tasks. As canopy often experiences the largest deformations and loa-dings during a very short time, it is of great difficulty for theoretical analysis and experimental measurements. In this paper, aerodynamic equations and structural dynamics equations were developed for describing parachute opening process, and an iterative coupling solving strategy incorpo- rating the above equations was proposed for a small-scale, flexible and flat-circular parachute. Then, analyses were carried out for canopy geometry, time-dependent pressure difference between the inside and outside of the canopy, transient vortex around the canopy and the flow field in the radial plane as a sequence in opening process. The mechanism of the canopy shape development was explained from perspective of transient flow fields during the inflation process. Experiments of the parachute opening process were conducted in a wind tunnel, in which instantaneous shape of the canopy was measured by high velocity camera and the opening loading was measured by dynamometer balance. The theoretical predictions were found in good agreement with the experimental results, validating the proposed approach. This numerical method can improve the situation of strong dependence of parachute research on wind tunnel tests, and is of significance to the understanding of the mechanics of parachute inflation process.

Incidence and risk factors associated with injuries during static line parachute training in Royal Thai Army

Background:Incidence and risk factors of parachute injuries has been studied in developed countries,but not in trainees of the airborne forces in the Royal Thailand Army.Methods:A prospective cohort study was conducted among 992 military personnel who attended the basic airborne training program from February to July 2018.Information sheets were used to collect data about(a)personal demographics;(b)environmental conditions surrounding the parachute practice;and(c)parachute-related injuries.The incidence rate of injury was then calculated.Risk factors were examined using multilevel Poisson regression analysis and presented as incidence rate ratio(IRR)and 95%confidence interval(95%CI).Results:A total of 166 parachute-related injuries occurred in 4677 jumps.The incidence rate of injury was 35.50 per 1000 jumps(95%CI 30.04–41.21).Factors significantly related to parachute injury included:jumping with equipment versus without equipment[adjusted IRR(95%CI):1.28(0.88–1.87)],higher wind speed[1.54(1.27–1.87)per knot],airplane versus helicopter exit[1.75(0.68–4.55)],side versus rear exit[2.13(1.43–3.23)],night versus day jumping[2.19(0.81–5.90)],and presence of motion sickness[3.43(1.93–6.92)].Conclusions:To prevent military static line parachute injuries,the following factors should be taken into consideration:type of aircraft,aircraft exit,time of the day,equipment,motion sickness and wind speed.Trial registration:The project was certified by the Research Ethics Committee,Faculty of Medicine,Chulalongkorn University(IRB No.697/60).

Flow Field Characteristics for Parachute-projectile System

In the current research for parachute flow field nowadays,the size of parachutes in previous research are so large compared with their carriers that the effects of the carriers wake flow to parachute are always neglected.Different from such large parachutes,the parachute size in this paper is on the same magnitude with the carrier,thus,the carrier can obviously affect the parachute flow field.In this paper,flow field characteristics of small parachute for projectile decelerating are researched through two approaches,namely,computational fluid dynamics（CFD） simulation and wind tunnel tests.Three parachutes with various sizes are chosen for study.Firstly,the CFD simulation of flow field around these parachutes is carried out,and then the CFD simulation of parachute-projectile systems is executed.According to the simulation results,the phenomenon is observed that in the simulations of parachutes there are two vortex-rings at the wind shadow of parachutes,however,in the second simulations of parachute-projectile systems,two additional vortex-rings emerge inside the parachutes.Due to these two inner vortex-rings,the pressure inside parachutes decreases.As a result,the drag of parachute in simulation of parachute-projectile systems is about 20% smaller compared with the prior one.In order to verify the numerical results of CFD simulations,wind tunnel tests are employed.In terms of the data of the wind tunnel tests,the CFD simulation for flow field characteristics is reasonable and feasible.The results of both CFD simulation and wind tunnel tests demonstrated the influence of projectile wake flow to parachute drag can not be neglected if the parachute size is on the same magnitude with projectile.The influence to parachute drag from the ratio of projectile diameter to parachute diameter is also analyzed both in CFD simulations and wind tunnel tests.The approach combined CFD simulation and wind tunnel tests proposed can be used to guide the design of such parachute whose size is on the same magnitude with carrier.

Flow Characteristics of Double-Cruciform Parachute at Inflating and Inflated Conditions

The fluid-structure interaction (FSI) between the canopy and flow field on the inflating and inflated conditions is investigated based on the arbitrary Lagrange-Euler (ALE) method,in both a single-and double-cruciform parachute systems.The projection area of canopy is calculated in the inflation process.The flow field characteristics and the interaction between canopies are analyzed.Results showed that,with free stream velocity of 50m/s,overinflation phenomenon would not occur during the inflation process of the double-cruciform-parachute system,because the collision and extrusion of the two canopies during inflation obstructed the oscillation of the inner gores.Concurrently,compared with the single-cruciform parachute,the vortex motion in the wake of double-cruciform-parachute is more intense.Thus the double-cruciform parachute system oscillated at a velocity of 50 m/s with an angle of less than 6.8°.By comparison,the oscillation angle of the single-cruciform parachute was within 3.5° at the velocity of 50m/s.The results are consistent with those of the wind tunnel test.

Experimental investigation of the effect of Reynolds number on flow structures in the wake of a circular parachute canopy

In the present study, an experimental study was conducted to characterize the effect of Reynolds number on flow structures in the turbulent wake of a circular parachute canopy by utilizing stereoscopic particle image velocime- try （Stereo-PIV） technique. The parachute model tested in the present study was attached by 28 nylon suspension lines and placed horizontally at the test section center of the wind tunnel. The obtained results showed that with the in- crease of Reynolds number, the intensities of the vortices near the downstream region of the canopy skirt were found to increase accordingly. However, the increase of Reynolds number did not result in a significant change in ensemble- averaged normalized x-component of the velocity, ensembleaveraged normalized vorticity, normalized Reynolds stress, and normalized turbulent kinetic energy distributions in the turbulent wake of the circular parachute canopy. The obtained results are very useful to further our understanding about the unsteady aerodynamics in the wake of flexible circular parachute canopies and to constitute a reference for CFD computation.

Numerical Study of Parachute-Payload Land Site Distribution with Randomize Wind Gust Model

A parachute-payload model with randomize wind gust is developed to study the landing accuracy of the parachute decelerator system,which can be exactly described by the landing site distribution.The research focuses on the steady descent phase of the parachute descent process,so the parachute and the payload suspension formulation during the phase are mainly discussed.In addition,since the wind effects have a significant impact on the land site distribution of the passive decelerator system and it is difficult to obtain the exact wind profile in practice,major features of parachute-payload system are studied via the randomized wind gust formulation.As the randomized wind gust formulation is adopted,the wind effect can be considered without the exact wind gust profile and the parachute aerodynamic simulation can be fulfilled with uncertainties.Finally,the model is validated and discussed,and the parachute land site distributions with different wind randomize profiles are presented for comparison.The results show that when parachute is less stable,the land site tends to have a larger variance.

Study of velocity effects on parachute inflation performance based on fluid-structure interaction method

The inflation of a five-ring cone parachute with the airflow velocity of 18 m/s is studied based on the simplified arbitrary Lagrange Euler （SALE）/fluid-structure interaction （FSI） method. The numerical results of the canopy shape, stability, opening load, and drag area are obtained, and they are well consistent with the experimental data gained from wind tunnel tests. The method is then used to simulate the opening process under different velocities. It is found that the first load shock affected by the velocity often occurs at the end of the initial inflation stage. For the first time, the phenomena that the inflation distance proportion coefficient increases and the dynamic load coefficient decreases, respectively, with the increase in the velocity are revealed. The above proposed method is competent to solve the large deformation problem without empirial coefficients, and can collect more space-time details of fluid-structure-motion information when it is compared with the traditional method.

Measurement of the flow structures in the wakes of different types of parachute canopies

We measured flow structures with stereoscopic particle image velocimetry(stereo-PIV) in the turbulent wakes of three parachute canopies, which had the same surface area, but different geometries. The tested parachute canopies included ribbon canopy, 8-branches canopy, and cross canopy. The obtained results showed that the geometry of the parachute canopies had significant influences on the flow structures in the wakes of these three canopies. In addition, the variation of Reynolds number did not lead to a dramatic change in the distributions of velocity, vorticity,Reynolds stress, and turbulent kinetic energy.

Epidemiology and injury patterns of aerial sports in Switzerland

BACKGROUND Airborne sports have become more popular in recent years.The number of accidents has increased linearly as athletes take increasingly greater risks to experience the adventurous spirit of this kind of sports.AIM To investigate the variety of injuries in airborne sport accidents,as well as which acute treatment these patients receive,both before and after admission to a levelone-trauma center.METHODS We performed a retrospective chart analysis at a major level-one-trauma center in Switzerland for 235-patients who were admitted following airborne sports injuries between 2010 and 2017.Patients’demographic data,injury patterns,emergency primary care procedures and intra-hospital care were recorded.RESULTS Overall,718-injuries in 235-patients were identified;the spine was the most commonly affected region with 46.5%of injuries(n=334/718)in 143-patients.In 69-patients(15.5%),the(non-spine)thorax was affected,followed by the lower and upper extremity,pelvis,head/face and abdominal injuries.Eleven-patients had to be intubated at the trauma site.Three patients were resuscitated after onset of pulseless-electrical-activity.Two-patients died in the resuscitation room.In 116-cases,surgery was indicated including 55-emergency surgeries.Another 19 patients(8.1%)were transferred to the intensive care unit.CONCLUSION Paragliders are most commonly affected,although the highest injury severities were identified for Building,Antenna,Span and Earth-jumping athletes.First responders,treating physicians and pilots should be aware of the risk for potentially serious and life-threatening injury with an in-hospital mortality of 0.9%.

A study of a supersonic capsule/rigid disk-gap-band parachute system using large-eddy simulation

The aerodynamic performances and flow features of the capsule/rigid disk-gap-band(DGB)parachute system from the Mach number 1.8 to 2.2 are studied.We use the adaptive mesh refinement(AMR),the hybrid tuned center-difference and weighted essentially non-oscillatory(TCD-WENO)scheme,and the large-eddy simulation(LES)with the stretched-vortex subgrid model.The simulations reproduce complex interaction of the flow structures,including turbulent wakes and bow shocks,as well as bow shocks and expansion waves.The results show that the calculated aerodynamic drag coefficient agrees well with the previou simulation.Both the aerodynamic drag coefficient and the aerodynamic drag oscillation of the parachute system decrease with the increase of the initial Mach number of the fluid.It is found that the position and angle of the bow shock ahead of the canopy change as the Mach number increases,which makes the flow inside the canopy and the turbulent wake behind the canopy more complex and unstable.

Analysis of Buoyancy Module Auxiliary Installation Technology Based on Numerical Simulation

To reduce the requirement for lifting capacity and decrease the hoist cable force during the descending and laying process of a subsea production system(SPS), a buoyancy module auxiliary installation technology was proposed by loading buoyancy modules on the SPS to reduce the lifting weight. Two models are established, namely, the SPS lowering-down model and the buoyancy module floating-up model. The main study results are the following: 1) When the buoyancy module enters the water under wave condition, the amplitude of tension fluctuation is twice that when SPS enters water; 2) Under current condition, the displacement of SPS becomes three times larger because of the existence of the buoyancy module; 3) After being released, the velocity of the buoyancy module increases to a large speed rapidly and then reaches a balancing speed gradually. The buoyancy module floats up at a balancing speed and rushes out from the water at a pop-up distance; 4) In deep water, the floating-up velocity of the buoyancy module is related to its mass density and shape, and it is not related to water depth; 5) A drag parachute can reduce floating-up velocity and pop-up distance effectively. Good agreement was found between the simulation and experiment results.

Numerical Simulation of ATPS Parachute Transient Dynamics Using Fluid-Structure Interaction Method

In order to simulate and analyze the dynamic characteristics of the parachute from advanced tactical parachute system(ATPS),a nonlinear finite element algorithm and a preconditioning finite volume method are employed and developed to construct three dimensional parachute fluid-structure interaction(FSI)model.Parachute fabric material is represented by membrane-cable elements,and geometrical nonlinear algorithm is employed with wrinkling technique embedded to simulate the large deformations of parachute structure by applying the NewtonRaphson iteration method.On the other hand,the time-dependent flow surrounding parachute canopy is simulated using preconditioned lower-upper symmetric Gauss-Seidel(LU-SGS)method.The pseudo solid dynamic mesh algorithm is employed to update the flow-field mesh based on the complex and arbitrary motion of parachute canopy.Due to the large amount of computation during the FSI simulation,massage passing interface(MPI)parallel computation technique is used for all those three modules to improve the performance of the FSI code.The FSI method is tested to simulate one kind of ATPS parachutes to predict the parachute configuration and anticipate the parachute descent speeds.The comparison of results between the proposed method and those in literatures demonstrates the method to be a useful tool for parachute designers.

Epidemiological investigation of military training injuries for sea trainingand parachuting training

Objective: To study epidemiological characteristics of the military training injuries (MTI) during parachuting training of the air force and sea training of the navy. Methods:The subjects of this study were 1382, including 971 navy soldiers (300 recruits and 671 soldiers) and 411 for force recruits. Navy: Each of injured soldiers was investigated by the trained battalion surgeon; Air force: When the parachuting training finished , two doctors in specific field screened and investigated them one by one. Results: The incidence of injury in for force recruits was 16.3% and in navy recruits was 18. 7%. The incidence of navy soldiers was 5.5%, which was significantly lower than that of navy recruits. There was a peak of incidence in the 2nd training month of navy recruits. The peak of incidence of navy soldiers was in 1st training month. The incidence of air force maintained at a high level except 2nd training month. The incidences of lower legs and ankles were higher than those of other sites in navy with percentage of 42.9% and 17.9% respectively. The incidences of ankles and lumbar region were higher than those of other sites in air force with percentage of 26.9% and 23.9% respectively. Incidence of acute traumatic injuries was highest during special course. Conclusion: The result showed the incidence of injury in sea and parachuting training varied. Different preventive measures should be adopted during special training.

Study on conditions of internally carried air-launched launch vehicles based on the virtual prototype technology

A method based on the virtual prototype technology simulating the separation of a launch vehicle from its aircraft in the aircraft wake was proposed based on the internally carried air-launched launch vehicle program.In this method,the full-scale model of the aircraft,the vehicle and the parachute are constructed.Then,they are imported into the ADAMS software,constraint solutions and driving forces are then added for visual dynamic simulation.The unsteady aerodynamic forces of the vehicle in the aircraft wake are calculated by CFD and the moving grid technique.The forces generated by the parachute can be derived from the Kirchhoff motion equation.Through comparing and analyzing the simulation results under different launch conditions,it has been proven that this method simulates the separation of a launch vehicle from the aircraft in the aircraft wake accurately.It provides the foundation for the aggregate project of internally carried air-launch vehicles,and offers a new referenced method for multi-body dynamic simulation.

Transcatheter Decompression of the Left Atrium in an Adolescent with a Double Inlet Left Ventricle, Severe Parachute Mitral Valve Stenosis and Pulmonary Hypertension

A 17-year-old adolescent with non-operated double inlet left-ventricle and severe stenosed parachute mitral valve is reported. He was admitted with repetitive syncope related to intermittent atrial fibrillation. Life-threatening syncope combined with pre- and post-capillary pulmonary hypertension together with his single ventricle pathophysiology led to the decision for left atrial decompression by percutaneous static atrial septum ballooning after transseptal needle perforation. Aiming to create a restrictive atrial septum defect, unloading of the left atrium without disturbing the balanced hemodynamics was directed for a long-term palliation or as a basis for a further surgical follow-up approach.