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VELOCITY DERIVATIVES IN AN ATMOSPHERIC SURFACE LAYER AT Reλ = 104. FURTHER RESULTS

Michael Kholmyansky
Faculty of Engineering, Tel Aviv University Tel Aviv 69974, Israel

Arkady Tsinober
Department of Fluid Mechanics and Heat Transfer, School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv, Israel; and Institute for Mathematical Sciences and Department of Aeronautics, Imperial College, London, United Kingdom

Svyatoslav Yorish
Faculty of Engineering, Tel Aviv University Tel Aviv 69974, Israel

Résumé

We present a set of new results obtained from a field experiment at Reλ = 104. The emphasis is on the velocity derivatives, both the (tensor of) spatial derivatives dui/dxj and the temporal derivatives dui/dt. In the former we address new aspects of geometrical statistics, reduction of nonlinearity, and comparison of strain dominated regions and regions with concentrated vorticity. In the latter new results are presented on measurements without employing the Taylor hypothesis which allowed to evaluate the local, aldu/dt, and the convective, ac ≡ (u · Δ)u, accelerations, and the relation between al and ac, as well as to assess the feasibility of direct measurements of the streamwise derivative d/dx1 without invoking the Taylor hypothesis.