| Popis: |
The schlieren method, based on Raman-Nath scattering by ultrasonic waves, is extended to pressures up to 8.8t106 Pa (about 5 KW/cm2 for 4 MHz CW waves) by capturing up to the 16th order diffraction harmonics in water. Given the high spatial resolution (~100 mm); this kind of measurement is not possible with conventional hydrophones. Working under partially applicable Raman-Nath regime (thin grating, Qa0.016L2p but 0lnl2000), the theoretical description fails beyond the first few orders. However, we demonstrate that an empirical calibration is possible as long as plane waves are used and the short interaction length is maintained. Examples of beams and measurements are presented and compared with the basic theory |
