Scott Backhaus – Capability Leader
A sound wave in a gas is usually regarded as consisting of coupled pressure and motion oscillations, but temperature oscillations are always present, too. When the sound travels in a gas in small channels, oscillating heat also flows to and from the channel walls. Combinations of all such oscillations in three dimensions produce a rich variety of “thermoacoustic” effects.
Our experiments usually involve pressurized inert gases, heat sources and sinks, high-power acoustic drivers, and sensors to measure pressures, temperatures, and sometimes mole fractions. Theory relies on the assumptions that the oscillations of pressure, temperature, density, velocity, and entropy are adequately represented as “small” sinusoidal functions of time. Surprisingly, the results of this approach are usefully accurate even for large oscillations with substantial harmonic content.
Thermoacoustic heat and temperature effects are too small to be obvious in the sound in air with which we communicate every day. However, in intense sound waves in pressurized gases, thermoacoustics can be harnessed to produce powerful engines, pulsating combustion, heat pumps, refrigerators, and mixture separators. Hence, much current thermoacoustics research is motivated by the desire to create new technology for the energy industry that is as simple and reliable as sound waves themselves.
More information about thermoacoustics at Los Alamos may be found at www.lanl.gov/thermoacoustics/
National High Magnetic Field Laboratory/NHMFL
Low Energy Spectroscopy