Error in bending wave power measurements resulting from longitudinal waves

Bending wave power in the "far field" of a beam is often estimated with two closely spaced accelerometers. When measuring power in flows consisting of bending waves only, this method has been shown to provide reliable results. However, in most practical measurement cases some level of longitudinal wave flow will be present. Measuring bending wave power flow in a beam that has a significant level of longitudinal wave flow can provide inaccurate results, particularly when techniques using measurements on only one side of the beam are used. To determine the limitations of one of the most commonly used one-sided bending power measurements (the two-accelerometer two-position linear finite difference estimate), a measurement on a beam is modeled for combined longitudinal and bending wave power flow. This information is used to predict the sensitivity of the basic two-accelerometer technique to longitudinal wave errors in bending wave measurements on a 1.524 m×0.1016 m×0.1016 m 7075-T651 aluminum beam.