Measurement of thermo-acoustic waves induced by rapid heating of nickel sheet in open and confined spaces

Numerical Investigation of the Fundamental Mechanism for Entropy Noise Generation in Aero-Engines

“…Although the TTL signal shows astepwise increase the air temperature is increasing with at ime delay and a certain gradient. Hwang et al [10] showed that even rapid heating causes adelayed increase of the wire temperature what explains the delayed increase of the air temperature. The measured time delay of 0.01 si sa lmost consistent with the estimated time delay of 0.0095 s. Signal S1 in Figure 4shows apositive pressure signal generated by the accelerated positive entropyg radient in the nozzle.…”

On the transition from thermoacoustic convection to diffusion in a near-critical fluid

“…Huang and Bau's theoretical modeling of the thermoacoustic effect in gases [5,6] indicated that the thermomechanical waves, linear or nonlinear, ought to have an asymmetrical waveform comprising a sharp front and a long tail, which squarely contradicted prior predictions of a rounded symmetric shape. Experimental measurements of the thermally-induced pressure waves in a gas-filled enclosure were performed by Brown and Churchill [7], Hwang and Kim [8], and Lin and Farouk [9]. Their observations, without exception, seemed to align with the asymmetrical description of the thermoacoustic waves.…”

“…When the temperature ceases increasing, the still expanding boundary layer tends to alleviate the boundary pressure buildup, according to Eq. (8). In the absence of viable pressure forces, the fluid motions can no longer maintain organized.…”

Influence of thermodynamic properties of a thermo-acoustic emitter on the efficiency of thermal airborne ultrasound generation

“…Contrary to existing theoretical approaches [11,[16][17][18][19][20][21][22][23][24] proposed EDF-model is applicable to free hanging as well as to substrate-based TA-emitters and comprise:…”

“…-models for TA-emitters consisting of free hanging films and wirers [11,[16][17][18][19], -models for substrate-based TA-emitters [20][21][22][23][24] and -a generalized model for thermal sound generation, the EDF-model [25].…”