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Author: Helmut G. Heinrich Publisher: ISBN: Category : Drag (Aerodynamics) Languages : en Pages : 100
Book Description
Results of wind tunnel studies concerned with transient and steady state performance of single and clustered parachutes in cargo extraction systems are presented. In Part 1, circular flat and ringslot canopies singly suspended and in clusters of 2, 3, and 4, were deployed in freestream, in the wake of an aircraft, and near a simulated ground. As a further means of analysis, wake pressure surveys were performed on the DHC-4 Caribou and the C-130 Hercules aircraft and are presented in Part 2.
Author: Helmut G. Heinrich Publisher: ISBN: Category : Drag (Aerodynamics) Languages : en Pages : 100
Book Description
Results of wind tunnel studies concerned with transient and steady state performance of single and clustered parachutes in cargo extraction systems are presented. In Part 1, circular flat and ringslot canopies singly suspended and in clusters of 2, 3, and 4, were deployed in freestream, in the wake of an aircraft, and near a simulated ground. As a further means of analysis, wake pressure surveys were performed on the DHC-4 Caribou and the C-130 Hercules aircraft and are presented in Part 2.
Author: H. G. Heinrich Publisher: ISBN: Category : Parachutes Languages : en Pages : 108
Book Description
The drag and stability characteristics of single and clustered solid flat and ringslot parachutes as cargo extraction systems in the wake of a model of the Caribou airplane with windmilling and powered propellers are reported. The investigation also includes the effect of actuated wing trailing flaps, and the variation of the parachute performance parameters in midair and near the ground. It was found that in all cases the drag coefficient of the cluster decreases with the increased number of canopies in the cluster, and a single ringslot parachute is more stable than the most stable cluster of solid flat canopies. The effects of the powered propeller slipstream and flap actuation are noticeable but not dominating. Also, wake surveys of the airplane showed characteristic dynamic pressure defects or increases for power off or on flight conditions. The location of these pressure fields was noticeably influenced by flap actuation and ground effects.
Author: Carl W. Peterson Publisher: ISBN: Category : Drag (Aerodynamics) Languages : en Pages : 47
Book Description
An experiment was conducted to evaluate approximate analytical methods for predicting the reduction in parachute drag caused by forebody wake effects. The drag of a 20° conical ribbon parachute was measured at several axial stations behind an ogive cylinder forebody with and without fins. The same parachute was tested in "undisturbed" flow (where wake effects were neligible) so that the effects of suspension line length on parachute drag could be separated from the drag losses caused by the turbulent wake. Total head pressure surveys were made across the forebody wake and integrated scross the canopy skirt area to determine the effective dynamic pressure acting on the parachute. Experimental results confirmed the validity of the underlying physical model of the parachute/wake interaction: the ratio of parachute drag behind a forebody divided by wake-free parachute drag is equal to the ratio of effective dynamic pressure acting on the parachute divided by free-stream dynamic pressure. However, the inability of existing turbulent wake theoretical models to make accurate predictions of wake velocity distributions for arbitrary forebody shapes is a fundamental limitation of the drag-loss analysis. If wake velocity profiles are known, the empirical constants in the turbulent wake theoretical models can be adjusted and accurate estimates of wake-induced parachute drag loss can be obtained from existing theory.
Author: C. W. Peterson Publisher: ISBN: Category : Parachutes Languages : en Pages : 10
Book Description
An experiment was conducted to evaluate approximate analytical methods for predicting the reduction in parachute drag due to forebody wake effects. The drag of a 20° conical ribbon parachute was measured at several axial stations behind an ogive-cylinder forebody with and without fins. The same parachute was tested in "undisturbed" flow (where wake effects were negligible) so that the effects of suspension line length on parachute drag could be separated from the drag losses caused by the turbulent wake. Total head pressure surveys were made across the forebody wake and integrated across the canopy skirt area to determine the effective dynamic pressure acting on the parachute. Experimental results confirmed the validity of the underlying physical model of the parachute/wake interaction: the ratio of parachute drag behind a forebody divided by wake-free parachute drag is equal to the ratio of effective dynamic pressure acting on the parachute divided by freestream dynamic pressure. However, the inability of existing turbulent wake theoretical models to make accurate predictions of wake velocity distributions for arbitrary forebody shapes is a fundamental limitation of the drag loss analysis. If wake velocity profiles are known, the empirical constants in trhe turbulent wake theoretical models can be adjusted and accurate estimates of wake-induced parachute drag loss can be obtained from existing theory.
Author: Sanger M. Burk Publisher: ISBN: Category : Aerodynamics, aircraft Languages : en Pages : 24
Book Description
A drop-test investigation has been conducted to determine the stability and drag characteristics of radially vented (duplex) parachutes. Parachutes of two different designs were tested: a large parachute with high geometric porosity and a small parachute with low geometric porosity designed for the same descent velocity with the same load. The results of the tests show that the large high-porosity duplex parachute was very stable in descent, oscillations averaging about [plus-or-minus]3.40; and the average drag coefficient based on the total canopy area and based on the fabric area alone were approximately 0.38 and 0.55, respectively. The small, low-porosity duplex parachute was also very stable in descent, oscillations averaging about [plus-or-minus]4.50; and the average drag coefficients based on the total canopy area and based on the fabric area alone were approximately 0.62 and 0.79, respectively. The oscillations for the cluster of three solid flat circular parachutes, tested for comparison purposes, were [plus-or-minus]7.10. The average drag coefficients based on the total canopy area and the fabric area alone were approximately 0.64 and 0.65, respectively.
Author: Helmut G. Heinrich Publisher: ISBN: Category : Equations of motion Languages : en Pages : 14
Book Description
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.
Author: Helmut G. Heinrich
Author: Kenneth Bruce Buchanan
Author: Helmut G. Heinrich
Author: H. G. Heinrich
Author: Carl W. Peterson
Author: C. W. Peterson
Author: University of Minnesota
Author: Defense Documentation Center (U.S.)
Author: Sanger M. Burk
Author: 
Author: Helmut G. Heinrich