### Abstract

Using measurements of all three components of the temperature dissipation χ in a laboratory boundary layer, the measured probability density p(χ_{r}) of χ_{r}, or χ averaged over a distance r, is found to be closely log-normal over a significant range of r. The variance σ^{2} of lnχ_{r} follows the relation σ^{2} = A + μln(L/r), with μ= 0.35, where L is an integral scale of turbulence. High order moments, up to order 5, of χ_{r} show a power-law variation with r/L. With increasing order of the moment, the power-law exponents become increasingly smaller than the corresponding values implied by assumed log-normality of p(χ_{r}) but are consistent with the bounds given by Novikov's theory. It is suggested that the observed close agreement with log-normality of p(χ_{r}) may be misleading when sufficiently high order moments of χ_{r} are considered.

Original language | English (US) |
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Pages (from-to) | 1800-1804 |

Number of pages | 5 |

Journal | Physics of Fluids |

Volume | 20 |

Issue number | 11 |

DOIs | |

State | Published - 1977 |

### ASJC Scopus subject areas

- Computational Mechanics
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
- Fluid Flow and Transfer Processes

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## Cite this

*Physics of Fluids*,

*20*(11), 1800-1804. https://doi.org/10.1063/1.861795