Round Parachute Research Articles

Gondolatok a katonai ejtőernyőzés jelenéről és jövőjéről

A szerzőt régóta foglalkoztatja a katonai ejtőernyőzés jelene és jövője. Már másfél évtizeddel ezelőtt, 2005-ben megfogalmazta a gondolatait a témáról, „Tanulmány a katonai ejtőernyőzésről” címmel. A dolgozat néhány internetes oldalon1 jelenleg is fellelhető. Az évek során természetesen több pozitív változás történt, ám a szerző úgy látja, a magyar katonai ejtőernyőzés jelenleg is több problémával küzd. Az alábbiakban néhány olyan ötletet, javaslatot vázol fel, melyek megvalósításával szerinte orvosolhatók a gondok.
 KULCSSZAVAK: katonai ejtőernyőzés, körkupolás ejtőernyő, légcellás ejtőernyő, HALO, HAHO, Honvédelmi Sportszövetség, ÖTR

Study on Transient Dynamics and Aerodynamic Characteristics of a New Type of High-Damping Four-Winged Rotating Parachute Inflation Process

To decrease the opening shock as well as improve the resistance coefficient and stability of the parachute of aviation weapon under subsonic conditions, a new kind of high-damping four-winged rotating (HFWR) parachute is investigated in this paper. The transient dynamic behavior and aerodynamic characteristics of the parachute during the inflation process are studied. Considering the permeability, the 3D folded finite element (FE) model of the HFWR parachute is established based on the direct folding modeling technique, and the inflation process of the parachute under subsonic flow is simulated using the multimaterial arbitrary Lagrange–Euler (ALE) method. A series of wind tunnel tests are conducted to verify the numerical results. Besides, the opening performances of the HFWR parachute and the round parachute, which includes the inflation process, the dynamic response of the swing angle, and the opening shock load varying with time, are compared under the same conditions. The results show that the opening performance of the HFWR parachute is superior to the round parachute under specific military background. The fluid-structure interaction (FSI) simulation results show good consistency with the wind tunnel tests, which indicates that the numerical modeling can effectively simulate and predict the opening performance and aerodynamic characteristics of the rotating parachute. The modeling method in this paper can help shorten the development cycle, improve the cost effectiveness, and optimize the design of the parachute.

Interaction of a line vortex with a round parachute canopy

The interaction of a rectilinear vortex with an inflated round parachute canopy model was studied experimentally in a water tunnel where the vortex core was aligned with the axis of the canopy. Three different canopy diameters were used, and the canopy model was attached to a streamlined forebody. Dye flow visualization indicated that vortex breakdown was present when the core trajectory was within the canopy opening. Vortex breakdown occurred about one to two canopy diameters upstream of the canopy opening. The vortex core completely disintegrated when it interacted with the forebody near the canopy centerline . The vortex breakdown and disintegration caused unsteady, asymmetric deformations on the canopy surface. A reduction in the time-averaged drag and an increase in the fluctuating drag was observed when the vortex core was within the canopy opening. The disintegration of the vortex core near the canopy centerline lessened the drag reduction brought on by the presence of the core.

Continuous Disreefing Method for Parachute Opening

Although round parachutes have been used for airdrop for over 60 years, damage to canopy fabric and suspension lines still occurs during parachute opening due to the rapid canopy opening and the associated high opening force. Continuous disreefing of round parachutes to slow down the opening and decrease the peak opening force has been discussed in the literature, but no viable continuous disreefing method has ever been developed. In this paper, we present a practical, effective, and low-cost continuous disreefing method that does not use any external electrical or power source, only the opening force and the weight of the payload. The method was successfully demonstrated in a full-scale test from an aircraft using a 10.7-m (35-ft) diameter round parachute. The kinetic energy of the payload at parachute deployment of that test was 11 times higher than that of the standard deployment that the parachute is designed for. In spite of the severe deployment condition, no damage to the parachute was observed after ground impact.

Geometric Properties of Parachutes Using 3-D Laser Scanning

The technology of gliding parafoils is currently being pursued by the U.S. Army for precision airdrop of cargos and personnel. The performance of parafoils (lift and drag) and round parachutes (drag) is closely related to their 3-D geometry. There have been some studies on the geometry of round parachutes, but hardly any on parafoils. The technology of 3-D whole body scanning provides a viable tool to investigate the 3-D geometry of parachutes. In this paper, we present an investigation on the 3-D geometry, surface area and volume of small-scale models of parafoil, round parachute, ring-slot parachute, and cross parachute using a 3-D laser scanning apparatus. Scan data from these model parachutes were obtained in a climatic chamber with a steady air velocity. Surface areas and volumes of these parachutes were calculated from the scan data using specially developed mathematical methods. In addition, cross sections of the parachute canopies were obtained from the scan images. These cross sections provide valuable information on the relationship between model parachutes and full-scale parachutes, fabric properties on canopy geometry, and parachute canopy design and manufacturing.

Computing surface area and volume of parachutes from 3D scans

PurposeTo explore three‐dimensional scanning technology in capturing the shape of inflated parachutes for accurate estimation of surface area and volume.Design/methodology/approachThe volume and surface area of an inflated round parachute are important parameters for the design and analysis of its performance. However, it is difficult to acquire the three‐dimensional (3D) surface shape of a parachute due to its flexible fabric and dynamic movement. This paper presents how we collect 3D data with a laser scanner and calculate volume and surface area of parachutes from their scans. The necessary data clean and approximation steps with non‐uniform B‐spline function are introduced and implemented. Numerical integration methods are employed to estimate surface area and volume. The approximation of the parachute based on an ellipsoid is compared with the numerical integration approach in their volumes and surface areas.FindingsIt is found that 3D scanning technology, with help of mathematic program developed, provides a feasible mean to estimate the surface area and volume of inflated parachutes. The numerical integration method derived in this paper is reliable and robust for the computation.Originality/valueIt is the first time that the 3D shape of an inflated parachute has been scanned with a laser scanner. The mathematical methods developed for processing of scan data are useful for others who use 3D scanning technology. The computational approach and results of surface area and volume of inflated parachutes are valuable to parachute performance modeling and design community.

Large deflection analysis of pneumatic envelopes using a penalty parameter modified material model

The computational challenge associated with pneumatic envelopes, such as balloons and parachutes, is due to the complication of their underconstrained and no-compression nature. Underconstrained behavior leads to large displacements without concomitant strain energy; no-compression behavior leads to a degenerate, wrinkled state. In this paper, we discuss issues surrounding modeling such structures. We provide a method to analyze pneumatic envelopes through a penalty parameter-modified constitutive relation embedded in a non-linear finite element code. Such an approach is also adaptable to the user-provided material function port available with many commercial finite element codes. Validation examples given are the inflated cantilever cylinder subjected to transverse tip load, inflated cantilever cylinder subjected to twist moment, and the inflation of a round parachute.

FINE SCALE ANALYSIS OF WRINKLED MEMBRANES

The wrinkling of membranes has been a subject of interset at least since the early part of this century. The standard model for analyzing membrane wrinkling is Tension Field theory, which provides a coarse model of the wrinkled membrane. The traditional Tension Field theory has an obvious shortcoming: the solution of Tension Field problems implies a surface that is continuously wrinkled, i.e., the number of wrinkles goes to infinity and wrinkle wavelength goes to zero. We note this condition is not physically realized in practical membranes, where the wrinkle wavelength has finite value. In this paper, we discuss the approach to provide the details of wrinkles themselves, i.e., the number, wavelength, and the wave amplitude of the wrinkles based on a robust, physically based wrinkling algorithm and a standard eigenvalue analysis. This fine analysis has been experimentally verified on the deformation of a planar sheet subjected to tensile and shear loadings. We then consider the case of a pressurized initially plane circular membrane with elastic boundary restraint. The approach is finally extended to the prediction of wrinkle parameters of an inflated round parachute model.

Parachute fluid–structure interactions: 3-D computation

We present a parallel computational strategy for carrying out 3-D simulations of parachute fluid–structure interaction (FSI), and apply this strategy to a round parachute. The strategy uses a stabilized space-time finite element formulation for the fluid dynamics (FD), and a finite element formulation derived from the principle of virtual work for the structural dynamics (SD). The fluid–structure coupling is implemented over compatible surface meshes in the SD and FD meshes. Large deformations of the structure are handled in the FD mesh by using an automatic mesh moving scheme with remeshing as needed.

Military parachuting injuries: a literature review.

This article is a literature review of the aspects of military parachuting related to occupational medicine and focuses on 'conventional' military static line parachuting using a round parachute. The analysis of injuries resulting from military parachuting provide an excellent example of military occupational medicine practice. The techniques of military parachuting are described in order to illustrate the potential mechanisms of injury, and a number of 'classical' parachuting injuries are described. Finally some recommendations are made for the recording of parachute injuries which would assist in the international comparison of injury rates and anatomical distribution.

Computational fluid-structure interaction model for parachute inflation

In parachute research, the canopy inflation process is the least understood and the most complex to model. Unfortunately it is during the opening process that the canopy often experiences the largest deformations and loadings. The complexity of modeling the opening process stems from the coupling between the structural dynamics of the canopy, lines, and payload with the aerodynamics of the surrounding fluid medium. The addition of a computational capability to model the coupled opening behavior would greatly assist in the understanding of the canopy inflation process. This article describes research that involves coupling a computational fluid dynamics code to a mass spring damper parachute structural code. The axisymmetric codes are coupled with an explicit marching method. The current model is described and results for a round parachute are presented. A comparison of the numerical results to experimental data will be presented. The successful solution of these problems gives us confidence that the computational aeroelastic problem for parachute openings can be solved. This solution allows moving the parachute design process from one of cut and try to one based on experimentally verified computational tools and reduces the reliance on costly and time-consuming testing during development.