Efficient heat transfer in a regime of elastic turbulence

Abstract

By systematic measurements of the statistics of temperature fluctuations at various positions within a viscoelastic von Karman flow driven at a Reynolds number at which no inertial instability is observed with the pure solvent and cooled from below it is found that within an elastic turbulent flow regime the heat transfer efficiency may locally increase up to 4 times (as compared to the purely conductive state) which is comparable to the efficiency increase observed in the case of inertial turbulence at Re≈1600. In spite of the inhomogeneous rheological properties induced by the temperature gradient, several similarities with the decay of a low diffusivity tracer in a random smooth flow (Batchelor regime) are found: exponential tails of the probability distribution functions, algebraic decay of the power spectra, P∝f-β with β≈-1.1, exponential decay of the second order moment of the fluctuations. The similarity with the passive scalar decay problem is reinforced by a comparative analysis of the isothermal and non-isothermal flow patterns which reveals no significant effect of the heat transfer process on the flow topology.