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LAGRANGEAN ACCELERATION MEASUREMENT IN FULLY DEVELOPED TURBULENCE

Yoshiyuki Tsuji
KTH Mechanics, Royal Institute of Technology, 100 44 Stockholm, Sweden; Department of Energy Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8503, Japan

Abstract

Pressure is a fundamental quantity contained in the dynamical equation of fluid motion. In a usual notation, pressure relates to the acceleration vector, which is decomposed into the contributions from the pressure gradient and viscous force while the fluid density is constant. Although the acceleration may be important and basic representation of fluid motion, and Lagrangian acceleration is the core of the kinematic theory of turbulent dispersion, its direct measurement was very difficult. In this paper, we evaluate the acceleration by means of pressure fluctuation because, at large Reynolds numbers, the viscous contribution to the acceleration can be ignored. Accordingly, the acceleration is evaluated as the pressure gradient. Measured data are compared with direct numerical simulation. And the shear effect on the acceleration is discussed.