Charles Y. Warner

AN EXPERIMENTAL INVESTIGATION OF TURBULENT NATURAL CONVECTION IN AIR AT LOW PRESSURE ALONG A VERTICAL HEATED FLAT PLATE

Abstract An experimental investigation of turbulent natural convection in air is described. The results of this study show good agreement with early investigations and remarkable agreement with the analytical correlation of Bayley [4]: Nu = 0·10 Ra 1 3 for Rayleigh numbers up to 1012. Extensive measurements of the temperature field indicate a good similarity in the temperature profiles when compared on the basis of the natural coordinate ty. The use of power law temperature profiles is shown to be undesirable for the case of turbulent natural convection.

Interrelationship of velocity and chest compression in blunt thoracic impact to swine

As part of a continuing study of thoracic injury resulting from blunt frontal loading, the interrelationship of velocity and chest compression was investigated in a series of animal experiments. Anesthetized male swine were suspended in their natural posture and subjected to midsternal, ventrodorsad impact. Twelve animals were struck at a velocity of 14.5 plus or minus 0.9 m/s and experienced a controlled thoracic compression of either 15,19,or 24%. Six others were impacted at 9.7 plus or minus 1.3 m/s with a greater mean compression of 27%. For the 14.5 m/s exposures the severity of trauma increased with increasing compression, ranging from minor to fatal. Injuries included skeletal fractures, pulmonary contusions, and cardiovascular ruptures leading to tamponade and hemothorax. Serious cardiac arrhythmias also occurred, including one case of lethal ventricular fibrillation. The 9.7 m/s exposures produced mainly pulmonary contusion, ranging in severity from moderate to critical. Cardiac arrhythmias occurred but were typically minor. In contrast to the lower compression impacts at 14.5 m/s, there were no rib fractures or cardiovascular ruptures. In general, peak sternal acceleration and applied force correlated with impact velocity but not with normalized compression; and spinal acceleration did not correlate with any parameter. Overall, the high velocity exposures, produced higher mechanical responses, more severe gross trauma and more serious cardiac arrhythmias despite lower compression levels. The results of this study while reconfirming normalized compression as one correlate of injury, emphasize the importance of loading velocity in determining the overall severity of blunt thoracic impact.

FRICTION APPLICATIONS IN ACCIDENT RECONSTRUCTION

The determination of appropriate friction coefficient values is an important aspect of accident reconstruction. Tire-roadway friction values are highly dependent on a variety of physical factors. Factors such as tire design, side force limitations, road surface wetness, vehicle speed, and load shifting require understanding if useful reconstruction calculations are to be made. Tabulated experimental friction coefficient data are available, and may be improved upon in many situations by simple testing procedures. This paper presents a technical review of basic concepts and principles of friction as they apply to accident reconstruction and automobile safety. A brief review of test measurement methods is also presented, together with simple methods of friction measurement to obtain more precise values in many situations. This paper also recommends coefficient values for reconstruction applications other than tire-roadway forces.

INACCURACIES IN THE CRASH3 PROGRAM

The CRASH3 computer program, a well known and useful tool in accident reconstruction, is shown to be inaccurate by comparison with car-to-car crash test data. Claims for accuracy of about 10 percent cannot be validated. Both the impact model and the damage only model yield results which are in error. Cases involving error well in excess of 20 percent are demonstrated. These inaccuracies are due primarily to the omission of terms in the formulation of the energy equation and to the sensitivity of the solution to the input estimate of principle-direction-of-force.

Sensitivity of Porcine Thoracic Responses and Injuries to Various Frontal and A Lateral Impact Site

Twelve anesthetized pigs were subjected to various blunt frontal or a right-side impact to asses biomechanical and injury response differences in a living animal model. For frontal impacts, thoracic compliance and injury were significantly affected by the location of the sternal load. Impacts above midsternum (to a relatively stiff thorax) produced infrequent skeletal damage but serious mediastinal hemorrhaging and lung laceration; whereas, impacts below midsternum (to a more compliant thorax) resulted in extensive skeletal damage and liver laceration. For lateral impacts, large penetration into the rib cage produced serious liver injuries with extensive near-side skeletal damage in one case and no fractures in the other. The evaluation of functional response to impact was enhanced by analysis of potential heart dysfunctions and of variations in blood catecholamines.

A Perspective on Automobile Crash Fires

The relatively rare occurrence of injury or fatality in fuel-fed fires has received considerable attention in automotive safety rulemaking and products liability litigation. The literature related to fatalities associated with fire is confirmed by recent FARS data, and there are no reliable field data which confirm a need for further injury-reducing effect related to FMVSS 301. NHTSA has acknowledged this by removing crash fire rulemaking from its priorities plan. The police-reported crash fire data now available must be supplemented with in-depth investigation by trained teams before informed judgements can be made regarding further safety improvements with respect to crash fire injury.

Postural influences on thoracic impact

The influence of body posture, and inherently support, on thoracic impact response was investigated in an animal model. Twelve anesthetized and postmortem domestic swine were exposed to blunt, midsternal loading while supported in their natural quadrupedal posture, and the results were compared with previously reported data from similar tests involving an upright body orientation. Measured mechanical responses included applied load, sternal and spinal accelerations, thoracic compression and aortic overpressure. Injury response was assessed from a thoracico-abdominal necropsy as well as pre- and post-impact electrocardiogram traces. Language: en