Thesis (B.A.Hons. 1970) from the Dept. of History, University of Adelaide.

The objectives of the present investigation are to determine the nature of the flow field around bluff parachute canopies, considering the effects of canopy shape parameters on this flow field and hence on the resulting aerodynamic forces and moments which are developed on the canopy surface. In order to relate the flow field developed around bluff parachute canopies to their aerodynamic characteristics, a series of experiments in the Leicester University wind tunnel has been conducted on a family of particularly significant canopy shapes. These cross-shaped canopies have excellent drag and stability characteristics if arm ratios of about 4:1 are selected. Flow visualisation, using both helium bubbles and wool tufts, was used to determine the flow field around the canopy. The most probable description of the wake flow is chains of irregularly-shaped vortex loops which move at about 0.7 times the undisturbed free stream velocity. Aerodynamic forces and moments measured on the various canopies correspond with the observed flow characteristics. Statistical correlation analyses made with hot wire anemometers in their wake indicate the periodic structure of the wakes formed behind these bluff bodies and reveal their basic similarities. Strouhal numbers of about 0.15 were obtained in the wake formed behind an imporous rigid hemispherical canopy. These are increased as canopy porosity is made larger. A useful comparison between a semi-theoretical blockage correction applied to aerodynamic forces and test results was obtained from an ancillary test programme conducted under water in a large cross-sectional area ship tank.

A model for the flow around bluff bodies has been developed. It is applied to an investigation of parachute canopy aerodynamic characteristics. Since the model assumes an axisymmetric incompressible high Reynolds number flow, it is only applicable to the calculation of aerodynamic characteristics at zero angle of attack. The flow is assumed to separate from the canopy at its surface discontinuity, i.e. the canopy hemline. The vorticity created in the boundary layer over the canopy upper surface is carried downstream, forming a free shear layer. In the flow field vorticity is confined to the this shear layer, outside it the flow is irrotational. Consequently, in this part of the fluid field a velocity potential can be defined. The wake flow created by bluff canopies is found to consist of a cluster of vortex rings which are shed periodically to the wake. Consequently, the axial aerodynamic force developed on the canopy will exhibit periodic behaviour. The resulting Strouhal number, has been determined to be about 0.13, based on the canopy projected area diameter. For all axisymmetric bluff canopies considered the calculated mean axial force coefficient, based on the canopy projected diameter, was found to be between 1.20 and 1.45. These values, together with the calculated pressure distribution and the wake flow periodicity, are in good agreement with known experiments. For parachute canopies performing an oscillatory axial motion the calculated results compare well with experimental data. However, it is shown that Morison's formula for this axial force is, generally, inadequate. Limited calculations of axial forces developed on the inflating parachute canopies agree with the sparse experimental data available. In the model the real flow field is simulated, basically, by a potential model. The canopy surface is replaced by a vortex ring panel lattice. Each panel contains a circular bound vortex ring which is located at one quarter panel length. For each panel the flow boundary conditions on the canopy surface are fulfilled along a control circle at three quarters of the panel length. A standing eddy which is generated by the high back-flow developed near the canopy hemline, on the canopy under surface is simulated by a standing vortex ring. The simulation of a two-dimensional discrete vortex separated wake is extended to the axisymmetric case by representing the separated wake with axisymmetric discrete vortex rings. The free shear layer emanating from the canopy hemline is represented by discrete free vortex rings which leave the canopy surface tangentially. At each time step in the calculation process a newly-created vortex ring is shed to the wake. In the vortex modelling of the separated wake a number of new elements have been introduced: -improvement of the near wake simulation by accounting for the standing eddy on the canopy under surface; -a simple method of calculating the newly created vortex ring strength & location; -reduction of the free parameters from two, the time step and the number of panels representing the canopy surface to one, i.e. the number of panels. Further model validation & implementation have been suggested. Methods of model development for asymmetric canopy representation have been discussed.

A polygonal body of revolution consisting of discrete meridional members joined by regular polygons is optimized for maximum drag and drag coefficient. The meridional, or primary members, carryall of the radial loads and the membrane structure transfers applied pressure loads to the primary members. The shape of the secondary membrane is found such that the performance index is optimized. Several methods are utilized to solve for the optimum conditions, and an application of these solutions to a parachute design is shown. The results are presented in parametric form with pressure distributions, structural flexibility, and skirt closure angle being the parameters investigated. In general, the results verified experimental data in several areas and that the current shapes used in design cover the optimum region, although refinements could be made in some areas. Of particular significance is the difference in shape for optimum drag and drag coefficient. For maximum drag force, the fullness or the lobing between meridional members should be a maximum throughout the span of the gore, whereas, for the maximum drag coefficient design, the lobing is a minimum in the region near the vent and gradually increases as the meridional distance increases. It was found that the pressure distribution influences the optimum design. For a typical distribution that increases as the meridional distance increases, the gore width should be increased near the skirt for an optimum drag coefficient. Parameter studies show that by increasing the secondary structure flexibility the drag increases, although it is a secondary effect for present designs. A well-known parameter in optimum parachute design is the suspension line length, and this study verifies that increasing the length improves the drag. Optimum conditions are found by use of the maximum principle, steepest descent, and the Rayleigh-Ritz method. / Ph. D.

Theme: Anaylisis of the paragliding rescue parachute opening Aims: To contribute safety in paragliding comunity by comparing rescue parachute speed openings.We will test different types and brands and focus mainly on speed of openings from the time of deployment to fully inflated rescue parachute. We will try to simulate it as close to the real situations as possible. Methodology: For our test we used a swing bridge where we attachad a rope. Pilot would always swing on the rope and deploy the rescue parachute. Each test was recorded on the camera so we could evaulate the speed of openings and stability. Each test was split in to 5 parts - drop in (rebound), swing, dead point (stall point), deployment, mening. Another method was experimental personality characteristics of the person conducting the investigation. Results: Results : After full analysis of the survey we found that a main factor of the reserve opening is the pilot as the direction and the strenght of the throw are the key factors for the reserve to open.Fastest open parachute in our test was cirus delta it opened in 3.17 seconds from the start of throw to open. Key words: paragliding, speed, rescue parachute, process of opening

The thesis is focused on the small UAV’s rescue system design. The thesis is divided into related sections reflecting the design process. The first part deals with general problems of parachute equipment. Another part is evaluating critical situations in manual and autonomous control of the airplane. The deceleration device is based on this critical situations as well as the calculated structure loading. Next is the description and evaluation of experiments to verify the performance of modern parachutes. The thesis also includes a simplified proposal ejection mechanism designed in 3D software and documentation of the of model aircraft construction for testing and predicting behaviour in autonomous flight mode.

The velocity field in the wake of a small scale flexible parachute canopy was measured using two-dimensional particle image velocimetry. The experiments were performed in a water tunnel with the Reynolds number ranging from 3.0-6.0 x 104. Both a fully inflated canopy and the inflation phase were investigated in a constant freestream (i.e. an infinite mass condition). The fully inflated canopy experienced a cyclic“breathing" which corresponded to the shedding of a vortex ring from the canopy. The normalized breathing frequency had a value of 0.56 +/- 0.03. The investigation of the canopy inflation showed that during the early stages of the inflation, the boundary layer on the canopy surface remains attached to the canopy while the canopy diameter increases substantially. The boundary layer begins to separate near the apex region when the diameter is ~68% of the fully inflated diameter. The separation point then progresses upstream from the canopy apex region toward the canopy skirt. During this time period, the force rapidly increases to its maximum value while the separation point of the boundary layer moves upstream towards the skirt. The force then declines rapidly and the separated boundary layer rolls-up into a large vortex ring near the canopy skirt. At the same time, the canopy is drawn into an over-expanded state after which the cyclic breathing initiates. The unsteady potential force was estimated from the rate of change of the canopy volume. It contributed no more than 10% of the peak opening force and was only significant during the early stages of inflation. The majority of the opening force was the result of the time rate of change of the fluid impulse. It accounts for approximately 60% of the peak opening force. This result shows that the formation of the viscous wake is the primary factor in the peak drag force of the canopy.

This PhD thesis describes parachute rescue systems for small planes and focuses on their functionality in the border areas of the flight envelope, especially at very low altitudes and low airspeeds of flight (fall). For extending the functionality of the rescue system in extreme areas of usability envelope, was founded an innovative dividable parachute slider, which works normally at high speed, but at the low airspeeds does not limit the opening time of the canopy. Structural design of this slider is the subject of a new patent application “Parachute opening speed regulation device”, filed with Industrial property Office in Prague on August 14, 2014 under number 2014-543 PV. The PhD thesis further contains computational principle of circular parachute opening and the structural design. For verification of the dividable slider functionality, a parachute model has been constructed and subjected to a series of drop tests. The main benefit of the PhD thesis is extending the usability of rescue system into its statistically most frequent use, i.e. into low altitudes and low airspeeds of flight (fall).

Title: History of skydiving - precision landing Objectives of work: The aim of this work is to map complexly and integraly the history of skydiving with a focus on racing discipline of precision landing. Due to insufficient number of relevant compact resources and web sites, so the work becomes the first file that holds the issue in a comprehensive manner and develop a unified overview of the analysis problem. Method: This is a theoretical work, the kernel of the work will be at tracing specialized publications and websites, collecting information, filtering the relevant data in their comprehensive use. Results: Objective of thesis was largely achieved. It turned out that the topic is very broad to draw up a detailed summery of the entire history of the research question. The topic was therefore processed generally and is more like a preview than a perfect description. Intended overview was given. Key words: Skydiving, parachute, competitive discipline, precision landing, history.

Title: Progress of discipline precision landing based on the development of a circular parachute Objectives of work: The aim of this work is to map the history of skydiving with a focus on racing discipline of precision landing and on the development of a circular parachute. Due to insufficient number of compact resources and web sites, so the work becomes the file that holds the issue in a comprehensive manner and develop a unified overview of the analysis problem. Method: This is a theoretical work, the kernel of the work will be at tracing specialized publications, journals and websites, collecting information, filtering the relevant data in their comprehensive use. Results: Objective of thesis was largely achieved. It turned out that the topic is very broad to draw up a detailed summery of the entire history of the research question. The topic was therefore processed generally and is more like a preview than a perfect description. Intended overview was given. Key words: Skydiving, parachute, competitive discipline, precision landing, history.