Download or read book Dynamics of Parachute Inflation written by H. G. Heinrich and published by . This book was released on 1969 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study is concerned with identification of significant terms in the process of parachute inflation. For finite mass cases, the equations of motion for parachutes inflating in free air and in wind tunnel experiments are established and organized in view of the nonsteady terms of canopy size, systems velocity, included and apparent masses, and the time derivatives of these terms. Wind tunnel experiments are described, the results of which yield graphical and numerical time functions for the significant terms of the equation of motion and the force-time histories. The wind tunnel results are compared with full size test information and certain identities are shown. The sigificant terms are combined to functions unique for the test conditions and substituted in the equation of motion. Force-time functions so derived compare satisfactorily with measured force histories and the contributions of the individual terms to the instantaneous parachute force can be seen.

Download or read book A Contribution to Parachute Inflation Dynamics written by Bryan W. Roberts and published by . This book was released on 1968 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A theoretical model of the inflation process is presented. The resulting stress-displacement equations for the canopy and lines are solved in the steady state condition of uniform descent. Some comments are made on the form of the unsteady pressure distribution on an inflating canopy. A close connection between the parachute stress, displacement and pressure equations has been demonstrated. This relationship is fundamental to any inflation theory. A plastic film parachute is to be used to verify the theoretical work. The permanent set properties of the plastic are to be used to measure the maximum stress history in the inflating canopy. The plastic film parachute will be air-dropped at the conference.

Download or read book Parachute Inflation A Problem in Aeroelasticity written by and published by . This book was released on 1994 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: In parachute research, canopy inflation is the least understood and most complex process to model. Unfortunately, it is during the opening process that the canopy 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 plus payload and the aerodynamics of the surrounding fluid medium. The addition of a computational capability to model the coupled opening behavior would greatly assist in understanding the canopy inflation process. Ongoing research at the U.S. Army Natick Research, Development and Engineering Center (Natick) focuses on this coupled problem. The solution to this problem will assist in the development of future U.S. Army airdrop systems, which include the capability of deploying at low altitudes and high speeds. This report describes research at Natick that currently involves coupling a computational fluid dynamics (CFD) code to a mass spring damper (MSD) parachute structural code. The model is described and results are presented.

Download or read book Inflation and Performance of Three Parachute Configurations from Supersonic Flight Tests in a Low density Environment written by Charles H. Whitlock and published by . This book was released on 1969 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ten flight tests of modified-ringsail, disk-gap-band, and cross parachute configurations with deployment at Mach numbers and dynamic pressures corresponding to conditions expected during entry into a Martian atmosphere have been completed. Comparison of flight results indicates that theoretical snatch force values were never exceeded when the deployment techniques of these tests were used. Opening loads showed no definite trend with Mach number. Values for filling times compared favorably with generally accepted empirical curves based on 15-percent geometric porosity. Canopy stability was good when Mach numbers were below 1.4 for the modified-ringsail and disk-gap-band configurations.

Download or read book Parachute Inflation written by Keith R. Stein and published by . This book was released on 1994 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: In parachute research, canopy inflation is the least understood and most complex process to model. Unfortunately, it is during the opening process that the canopy 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 plus payload and the aerodynamics of the surrounding fluid medium. The addition of a computational capability to model the coupled opening behavior would greatly assist in understanding the canopy inflation process. Ongoing research at the U.S. Army Natick Research, Development and Engineering Center (Natick) focuses on this coupled problem. The solution to this problem will assist in the development of future U.S. Army airdrop systems, which include the capability of deploying at low altitudes and high speeds. This report describes research at Natick that currently involves coupling a computational fluid dynamics (CFD) code to a mass spring damper (MSD) parachute structural code. The model is described and results are presented.

Download or read book The Reduction of Parachute Inflation Time Through Use of an Internal Canopy as Experienced in Laboratory and Full Size Studies written by R. J. Niccum and published by . This book was released on 1964 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: A short opening time and moderate opening force are desirable characteristics of practially all parachute applications. But because of the interdependency between opening time and force, this is one of the most intricate functions in the dynamics of parachute inflation. Particularly, parachutes with rapid inflation usually develop a high opening force. It has been hypothesized that since theoretical and experimental analyses indicate that the maximum force occurs after the canopy has attained one-half or more of its fully inflated size, possibly an acceleration of the initial phase of opening might have the desired effect upon the total inflation.

Download or read book A Method to Reduce Parachute Inflation Time with a Minor Increase of Opening Force written by Helmut G. Heinrich and published by . This book was released on 1960 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: A short opening time and a moderate opening force are desirable characteristics in practically all parachute applications. However, the relationship between opening time and force is one of the most intricate functions in the dynamics of the parachute inflation. In particular, parachutes with a characteristically fast inflation develop in general a high opening force. In the following study, a method has been devised for which, in wind tunnel tests, the duration of the initial phase of the inflation has been reduced, whereas the final phase, during which the maximum force occurs, remains basically unchanged.

Download or read book Wind tunnel Investigation of Inflation of Disk gap band and Modified Ringsail Parachutes at Dynamic Pressures Between 0 24 and 7 07 Pounds Per Square Foot written by Charles H. Whitlock and published by . This book was released on 1969 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Exploratory wind-tunnel tests of the disk-gap-band and modified ringsail parachute configurations have been conducted at dynamic pressures between 0.24 and 7.07 lb/ft2 (11 and 339 N/m2). Both parachutes exhibited positive inflation characteristics over the range of the tests within technique limitations. The disk-gap-band configuration required less time and distance to inflate than the modified ringsail configuration did.

Download or read book A Simplified Dynamic Model of Parachute Inflation written by D. L. Wolf and published by . This book was released on 1973 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes a dynamic inflation model for parachutes which predicts increased dimensionless inflation times and increased dimensionless inflation forces observed at high altitudes. As altitude is increased, greater relative parachute inertia results in increased inflation times, and greater relative forebody inertia results in increased maximum inflation forces. Upper limit effects of Mach number on inflation time and force are also predicted by the inflation model.

Download or read book New Structural Model for Parachute Inflation Simulations written by and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this project has been to develop a new robust structural model that is being coupled with existing computational fluid dynamics (CFD) codes to accurately simulate the dynamics of parachute and parafoil systems. This research will allow the Army to reduce the time and cost of developing new airdrop systems and retrofitting existing systems for new applications. Parachute dynamics is an extremely complex process. This process is governed by nonlinear time dependent coupling between the parachute and surrounding airflow and involves large canopy shape changes and unconstrained motion of the parachute in the fluid medium. To successfully simulate this complex process, a robust structural model is essential. The following capabilities were added to the structural model: (1) membrane wrinkling, (2) material orthotropy, (3) local bending and damping elements, (4) user defined time dependent element properties, (5) various nonlinear transient solution algorithms, (6) approximate fluid forces, (7) stress projection algorithms, and (8) local nodal coordinate systems. It has been demonstrated that large scale finite element modeling of parachute dynamics is feasible using this structural model. Significant transfer of this basic research was accomplished. New structural model features have continuously been incorporated into a finite element code which has been used extensively by Army engineers to perform simulations of Army parachute systems.

Download or read book Investigation of the Flow Field During the Inflation of Clustered Parachutes written by R. J. Niccum and published by . This book was released on 1966 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Clustered parachutes during the period of inflation were simulated by elliptical cylinders in potential flow and so-called O'Hara shape parachutes in water flow and wind tunnel experiments. The results are presented in the form of streamline and pressure distribution plots around the respective bodies. Results show that when geometric symmetry is disturbed, the flow field becomes unsymmetrical and strong attractive or repulsive forces are developed. This allows a variety of inflation modes to occur and, hence, poor cluster opening performance.

Download or read book Opening Dynamics of a T 10 Parachute with Inflation Aids written by Helmut G. Heinrich and published by . This book was released on 1970 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: The characteristic times and opening forces were studied for various inflation aid configurations of a model T-10 parachute. Finite mass wind tunnel tests were conducted in the horizontal return wind tunnel at a snatch velocity of 70 fps with a suspended load of 1.1 lbs. Relative to results of the standard T-10 parachute, the percentage decrease in the characteristic time and the corresponding percentage increase in the peak force were presented for five centerline, three internal parachutes and two centerline-internal combinations.

Download or read book Analysis of Parachute Opening Dynamics with Supporting Wind Tunnel Experiements written by Helmut G. Heinrich and published by . This book was released on 1968* with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study is concerned with identification of significant terms in the process of parachute inflation. For finite mass cases, the equations of motion for parachutes inflating in free air and in wind tunnel experiments are established and organized in view of the nonsteady terms of canopy size, systems velocity, included and apparent masses, and the time derivatives of these terms. Wind tunnel experiments are described, the results of which yield graphical and numerical time functions for the significant terms of the equation of motion and the force-time histories. The wind tunnel results are compared with full size test information and certain identities are shown. The significant terms are combined to functions unique for the test conditions and substituted in the equation of motion. Force-time functions so derived compare satisfactorily with measured force histories and the contributions of the individual terms to the instantaneous parachute force can be seen.

Download or read book Drag Coefficients for Partially Inflated Flat Circular Parachutes written by Stanley H. Scher and published by . This book was released on 1971 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Free-body tests were made in the Langley spin tunnel to determine drag coefficients for 1.07-meter-diameter (3.5-foot) flat circular parachutes when restrained by wire frames in a series of shapes representing those that parachutes assume during the inflation process. Both high-porosity (stable) and low-porosity (unstable) parachutes were investigated. The results obtained should be applicable to inflation analyses for flat circular parachutes.

Download or read book A Computational Model that Couples Aerodynamic and Structural Dynamic Behavior of Parachutes During the Opening Process written by Keith R. Stein and published by . This book was released on 1993 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: In parachute research, the canopy inflation process in the least understood and most complex to model. Unfortunately, it is during the opening process that the canopy often experiences the largest deformations and loadings. The complexity of modelling 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.

Download or read book Parachute Inflation Process Wind tunnel Study written by Edwin Pounder and published by . This book was released on 1956 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The report presents results of an experimental study of the parachute inflation process. The investigation was carried out in a low speed wind tunnel using small cloth models, and an analysis is presented which gives a basis for extrapolation of the data recorded to any reasonably low Mach number case. The drag of the parachutes and the shapes of the canopies during the inflation process are studied in considerable detail, and some qualitative studies of the flow fields are conducted. The principle variables studied are parachute type, velocity (dynamic pressure), and canopy porosity. The theoretical analysis develops a procedure by which full scale characteristics can be predicted from wind tunnel data, and several examples are computed to illustrate the technique.

Download or read book Modeling and Simulation of the Inflation of Supersonic Parachute for Mars Landing written by Zhengyu Huang and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The numerical simulation of nonlinear fluid-structure interaction problems is significant in many engineering and scientific applications. Examples include aircraft flutter in transonic flows, underwater implosions, pipeline explosions, flapping wings for micro aerial vehicles, and biomedical flows in heart and blood vessels, reactor fuel performance and so on. These problems are generally highly nonlinear, feature multiple scales and strong coupling effects, and might require heterogeneous discretizations for the various physics subsystems. Developing high-fidelity multidisciplinary models for such problem, with an emphasis on real world applications, is the motivation of the thesis. More specifically, the goal is to understand the supersonic parachute inflation dynamics for Mars landing. In 1972, NASA recorded the 1st known instance of a successful parachute operation in the wake of a blunt object at supersonic speeds, during the preparation for the Viking missions to Mars. However, the problem still remains open. "The stress analysis of the canopy cloth is extremely complicated, since maximum stresses occur during opening, which is when the shape and load change rapidly." (Houmard, the Goodyear Aerospace Corporation, 1972) "Technology in parachute structural analysis is far from desirable and no authoritative individual and/or company can really be said to exist." (Alley, NASA, 1972) "No information exists fully explaining parachute behavior in supersonic flow." (Lingard, UK-based Vorticity Ltd, 2010) This thesis first describes an embedded boundary framework for highly nonlinear fluid-structure interaction problems. This is based on the Finite Volume method with Exact two-material Riemann Problems (FIVER), developed in Farhat Research Group [1], and capable of handling evolving material interfaces, including structural fracture. The framework further incorporates a parallel adaptive mesh refinement based on newest vertex bisection, therefore, becomes more efficient for problems with large structure deformations and evolving shock waves. And several modifications are proposed to relieve the ill-conditioning near the fluid-structure interface due to extrapolations, hence, the framework becomes mesh position and orientation independent and delivers smooth pressure coefficient and skin-friction coefficient. Furthermore, this thesis makes a variety of contributions to make the framework more suitable for the parachute inflation simulations. These contributions include a homogeneous porous wall model to capture the porous effect of the canopy on the fluid, and a suspension line treatment that allows for the interactions of the sub-grid scale suspension lines with the flow. Finally, several full-size parachute inflation simulations in the low-density, low-pressure Mars atmosphere are conducted. The computed drag performance is in good agreement with the data collected by the NASA Curiosity Rover during its Mars atmospheric entry. Besides, basic material failure analysis is conducted, which indicates the parachute decelerator system of Curiosity survives with a safety factor about 5.0. This framework demonstrates the potential of using CFD and FSI based simulation tools for the future supersonic parachute design. In addition to the parachute project, several other related projects are reported in this thesis. The first one is a new approach to learning constitutive relations from indirect observation data and its uncertainty quantification for material coupons, such as parachute fabric. In contrast to direct input-output data curve-fitting, this approach focuses on problems, where obtaining comprehensive model input-output data is difficult. But indirect data, like deflections of the structure coupon under different load conditions, are available. Traditional approaches, such as the finite element method, bridge the indirect data with neural network-based~(or its counterparts) constitutive relation models. Its mathematical properties, like accuracy and applicability properties of the approach and the strength of neural networks, are thoroughly studied. Another project aims to extend the multiphysics framework to higher order. Arbitrarily high-order, stable, partitioned solvers are constructed, where different subsystems are modeled and discretized separately, and the resulting equations are solved independently. These solvers are used with the discontinuous Galerkin method for fluid-structure interaction problems with moderate structure deformations.