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。

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.

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.

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).

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.

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.

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.

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.

Perturbation Dynamics and Its Application for Parachute-Munition System

The nine-degree-freedom dynamic model of the parachute-munition system is developed by the theories and the analysis methods of parachute dynamics and multibody dynamics.On the basis of the above model,a linear five-degree-of-freedom dynamic model is developed by linearization at the steady state.A new algorithm,which can be fused with submunition kinematics and used in target identification,is developed by the principle of parachute dynamics.The simulation program is developed and used to remove the influence of wind gust on hitting accuracy.The successful airdrop test demonstrates that the new method can be used in the guidance of smart munition.

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.

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.

Availability,Management and Use of Priority Life-Saving Medicines for Under-Five Children in Two Health Districts in Senegal:A Cross-Sectional Study

Under-five mortality remains a major concern in the world and in Senegal. It is mainly due to preventable and treatable diseases with priority life-saving medicines for under-five children. This study evaluated the availability, management and use of these drugs in two health districts in Senegal. A descriptive cross-sectional study was conducted in the health districts of Guediawaye and Pete from 01 November 2018 to 31 January 2019. The health district of Guediawaye is in the region hosting the Senegalese capital while that of Pete is located in the region of Saint Louis, northern Senegal. Nine drugs that can prevent and treat malaria, diarrhea, pneumonia and malnutrition were selected. An inventory form and a self-administered questionnaire were used to collect data that was analyzed with SPSS and expressed as a percentage and average. Drug availability was 50.4% and 54.3% in Guediawaye and in Pete, respectively. Average stock-out duration in the past three months was estimated at 22.6 and 26 days, respectively. The drug management was marked, on the one hand, by a good availability of stock cards in the two districts with proportions equal to 100% and 94.1%, respectively, and on the other hand, by the presence of expired stocks in Pete (12.2%). About 79% and 88% of prescribers reported prescribing the basket drug, respectively. These results show that access to priority life-saving medicines for children remains a challenge. Measures to be taken should include improving the distribution channels and training of health professionals. Further studies should be conducted in other health districts to better understand the barriers to access to child health services.

Knowledge and Skills in Advanced Swimming and Life-Saving Techniques: A Correlational Study

This descriptive-correlational study was conducted to determine the relationship between the knowledge and skills of the BSMT (Bachelor of Science in Maritime Transportation) students in PE (Physical Education) 2 (Advanced Swimming and Life-saving Techniques). The respondents of the study were the 40 second year BSMT students that were taken through purposive sampling. The study utilized a researcher-made questionnaire for both knowledge and skills that had undergone validity and reliability-testing. Descriptive and inferential statistics were used to analyze the data such as mean, standard deviation, and Spearman’s rho. Results revealed that their knowledge on Advanced Swimming and Life-saving Techniques was “Fair” while the skills of the second year BSMT students were “Very good”. Furthermore, the knowledge of the BSMT students had a positive correlation (substantial) with their skills on Advanced Swimming and Life-saving Techniques. The second year BSMT students are encouraged to undergo trainings and upgrading to enhance their knowledge and skills in Advanced Swimming and Life-saving Techniques in order for them to become life-long learners.

Level of Acceptability of the Instructional Guide in Physical Education 2(Advanced Swimming Skills and Life-Saving Techniques)

This descriptive study aimed to determine the level of acceptability of the Instructional Guide in Physical Education 2(Advanced Swimming Skills and Life-Saving Techniques).The respondents of the study were the content experts currently teaching PE(Physical Education)in other universities in Iloilo and Bacolod City,Philippines together with the BSMT(Bachelor of Science Marine Transportation)students who used the instructional guide throughout the duration of the study.The instrument used to evaluate the materials was adopted from Terunez(2008)and included seven evaluation criteria to include physical aspect,language,content,objectives,instructions,learning activities,and evaluation measures.The statistical tools employed were mean,standard deviation,and rank.The results of the study revealed that the level of acceptability of the instructional guide in physical aspect was“High”which means that the material was suited to the level of the intended users.No significant difference was noted in the evaluation result of the content experts and student users.It can be concluded that the development of Instructional Guide in Physical Education 2 is deemed to be highly beneficial in enhancing learning.It is recommended that this instructional material will be utilized by other maritime institutions offering courses in Advanced Swimming and Life-Saving Techniques.

轻小型高可靠回收控制器设计与实现

针对某商用返回式卫星回收系统轻小型、高可靠的约束要求,设计了一种新型回收控制器产品,该装置基于微电子机械系统(Micro Electro Mechanical Systems,MEMS)过载传感器进行弹道过载测量,采用双核四进程“与或”逻辑实现冗余控制,基于容性释能半导体桥点火器起爆技术实现火工品管理。策划了针对返回过程的弹道过载触发验证试验,针对容性释能电容阵列放电特性,开展了容性释能系统不同初始电压、不同电容阵列容值以及不同回路阻值下的点火效能仿真分析。结果表明该回收控制器在轻小型约束下返回弹道过载感知精度达到±0.28 g,可实现开伞逻辑高可靠控制。半导体桥点火器容性释能电路优化参数为初始电压大于24 V、回路阻值小于0.3Ω、初始电容大于22μF,可实现点火器高可靠点火控制。该设计在不显著增加硬件基础上,大大降低产品质量,可为航空航天用同类电子系统设计提供参考。