In aeroacoustics, Lighthill's eighth power law states that power of the sound created by a turbulent motion, far from the turbulence, is proportional to eighth power of the characteristic turbulent velocity, derived by Sir James Lighthill in 1952.[1][2] This is used to calculate the total acoustic power of the jet noise. The law reads as
where
is the acoustic power in the far-field,
is the proportionality constant (or Lighthill's constant),
is the characteristic length scale of the turbulent source and
is the characteristic velocity scale of the turbulent source.
The eighth power is experimentally verified and found to be accurate for low speed flows, i.e., Mach number is small, . And also, the source has to be compact to apply this law.
Referencesedit
^Lighthill, M. J. (1952, March). On sound generated aerodynamically I. General theory. In Proc. R. Soc. Lond. A (Vol. 211, No. 1107, pp. 564–587). The Royal Society.
^Lighthill, M. J. (1954, February). On sound generated aerodynamically. II. Turbulence as a source of sound. In Proc. R. Soc. Lond. A (Vol. 222, No. 1148, pp. 1–32).
December 15, 2023
lighthill, eighth, power, aeroacoustics, states, that, power, sound, created, turbulent, motion, from, turbulence, proportional, eighth, power, characteristic, turbulent, velocity, derived, james, lighthill, 1952, this, used, calculate, total, acoustic, power,. In aeroacoustics Lighthill s eighth power law states that power of the sound created by a turbulent motion far from the turbulence is proportional to eighth power of the characteristic turbulent velocity derived by Sir James Lighthill in 1952 1 2 This is used to calculate the total acoustic power of the jet noise The law reads as W K r o c o 5 L 2 U 8 displaystyle W K frac rho o c o 5 L 2 U 8 where W displaystyle W is the acoustic power in the far field K displaystyle K is the proportionality constant or Lighthill s constant r o displaystyle rho o is the uniform fluid density c o displaystyle c o is the speed of sound L displaystyle L is the characteristic length scale of the turbulent source and U displaystyle U is the characteristic velocity scale of the turbulent source The eighth power is experimentally verified and found to be accurate for low speed flows i e Mach number is small M lt 1 displaystyle M lt 1 And also the source has to be compact to apply this law References edit Lighthill M J 1952 March On sound generated aerodynamically I General theory In Proc R Soc Lond A Vol 211 No 1107 pp 564 587 The Royal Society Lighthill M J 1954 February On sound generated aerodynamically II Turbulence as a source of sound In Proc R Soc Lond A Vol 222 No 1148 pp 1 32 Retrieved from https en wikipedia org w index php title Lighthill 27s eighth power law amp oldid 991954596, wikipedia, wiki, book, books, library,