Spherical-shaped ice simulating hailstones were projected onto woven carbon/epoxy composite panels to determine the damage resistance of thin-walled composite structures to ice impact, and to observe the resulting damage modes that occur over a wide range of velocity. To study the behavior of ice in isolation from the complex response of the composite panel targets, impacts onto a dynamic force measurement device were first conducted. These experiments show a linear relationship between the peak measured force and the projectile kinetic energy, regardless of projectile size. Composite panel impact experiments show a linear relationship between the kinetic energy at which failure initiates, referred to as the failure threshold energy (FTE), and the thickness of the panel. Impacts at kinetic energies greater than the FTE produced a multiplicity of damage modes. Glancing impact tests on composite panels show that the FTE can be accurately estimated using a simple trigonometric scaling relationship.

Experimental investigation of high velocity ice impacts on woven carbon/epoxy composite panels

A comprehensive account of the physical foundations of collision and impact phenomena and their applications in a multitude of engineering disciplines. In-depth explanations are included to reveal the unifying features of collision phenomena in both liquids and solids, and to apply them to disciplines including theoretical and applied mechanics, physics and applied mathematics, materials science, aerospace, mechanical and chemical engineering, and terminal ballistics. Covering a range of examples from drops, jets, and sprays, to seaplanes and ballistic projectiles, and detailing a variety of theoretical, numerical, and experimental tools that can be used in developing new models and approaches, this is an ideal resource for students, researchers, and practicing engineers alike.

Collision phenomena in liquids and solids

Experimentally validated strain rate dependent material model for spherical ice impact simulation

Elementary fluid mechanics

Hailfall: the relationship between radar-derived hail kinetic energy and hail damage to buildings

The design methodology and performance of Loughborough University’s new 1·9m × 1·3m, indraft wind tunnel is discussed in the following paper. To overcome severe spatial and financial constraints, a novel configuration was employed, with the inlet and exit placed adjacent to each other and opened to atmosphere. Using a fine filter mesh, honeycomb, two turbulence reduction screens and a contraction ratio of 7·3, flow uniformity in the working area of the jet at 40ms-1 is shown to be within 0·3% deviation from the mean velocity, with turbulence intensity in the region of 0·15%. Working section boundary layer characteristics are shown to be consistent with that of a turbulent boundary layer growing along a flat plate, which originates at the point of inflection of the contraction. A maximum velocity of 46ms-1 was achieved from a 140kW motor, compared to a prediction of 44ms-1, giving an energy ratio of 1·42. Comparison between theoretical and measured performance metrics indicate differences between the way modules perform when part of a wind tunnel system compared to data gathered from test rigs.

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Design methodology and performance of an indraft wind tunnel

This paper details a method to ascertain the reachability of known emergency landing sites for any fixed wing aircraft in a forced landing situation. With a knowledge of the aircraft's state and parameters, as well as a known wind profile, the area of maximum glide range can be calculated using aircraft equations of motion for gliding flight. A landing descent circuit technique used by human pilots carrying out forced landings called high key low key is employed to account for the extra glide distance required for an approach and landing. By combining maximum glide range analysis with the descent circuit, all the reachable landing sites can be determined. X-Plane flight simulator is used to demonstrate and validate the techniques presented.

Reachability Analysis of Landing Sites for Forced Landing of a UAS

To study hail ingestion of turbofan engines, it is essential to have an understanding about the impact of hailstones upon a solid surface. Basic ice impact characteristics hi terms of postimpact particle size, velocity, and mass distribution were studied experimentally with simulated hailstones. Two techniques were used, i.e., patternator and still photography. The advantages and disadvantages of each technique are discussed and the results from each technique presented. A parametric study was carried out, and the parameters investigated included impact angle, approach speed, and initial size of the simulated hailstones. Based on the experimental results, a set of empirical rules is defined for the basic disintegration characteristics of simulated hailstones upon impact.

Impact characteristics of hailstones simulating ingestion by turbofan aeroengines

Experimental studies into hail impact characteristics

Wind tunnel tests are reported that investigate three aspects of aerodynamic flows through battle damaged airfoils. The first aspect investigated was the effect of camber. This showed that reducing camber weakened the strength of the jet flow through the damage and delayed the onset of strong jet flows to higher incidences. The second investigation used five hole probe measurements to survey the flow field on a battle damaged flat plate airfoil. The measurements indicated that the use of the jet-to-freestream velocity ratio is a poor criteria for determining whether damage flows have undergone transition to strong jets. Finally, the influence of a star shaped hole to simulate more realistic battle damage was investigated. It was shown that in terms of damage flow characteristics and changes in lift, drag, and pitching moment coefficients, the use of a circular hole is a reasonable simulation of battle damage.

Peter M. Render

Papers

Design methodology and performance of an indraft wind tunnel

Reachability Analysis of Landing Sites for Forced Landing of a UAS

Impact characteristics of hailstones simulating ingestion by turbofan aeroengines

Experimental studies into hail impact characteristics

Experimental Investigation into the Aerodynamics of Battle Damaged Airfoils