Dependence of Free-Field Impulse on the Decay Time of Energy Efflux for a Jet Flow.
Abstract
Until now, the peak energy efflux at the jet exit was considered the significant parameter in a scaling approach to estimate the peak overpressure, time of arrival, and positive phase duration from guns and shock tubes. The resulting predictions for the peak overpressure, time of arrival were satisfactory but the positive phase duration prediction was poor. This predicted value of the positive phase duration is used with the peak overpressue prediction to obtain an estimate of an important quantity: the impulse. Here we investigate the characteristic exhaust decay time for the energy efflux at the jet exit as a possible additional significant parameter that might be used to improve predictions for the impulse. Numerical simulation was used to establish that the impulse value depends upon this parameter. Comparison between simulation and experiment is satisfactory. This additional parameter wa sused to correlate the available impulse data. It was determined that the additional parameter significantly improves the prediction capability of the scaling method for predicting impulse. An idealized wave form together with the predicted peak overpressure can be used to obtain an estimate of the positive phase duration. This approach yields less satisfactory agreement with the duration data but this fact is relatively unimportant since the impulse is the quantity of importance. Keywords: Gun muzzle blast; Shock waves; Blast wave scaling; Dimensional analysis.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1986
- Accession Number
- ADA168365
Entities
People
- Kevin S. Fansler
Organizations
- Ballistic Research Laboratory