The paper describes a combined experimental and computational study of laminar and turbulent flow between contra-rotating discs. Laminar computations produce Batchelor-type flow: radial outflow occurs in boundary layers on the discs and inflow is confined to a thin shear layer in the mid-plane; between the boundary layers and the shear layer, two contra-rotating cores of fluid are formed. Turbulent computations (using a low-Reynolds-number k-ε turbulence model) and LDA measurements provide no evidence for Batchelor-type flow, even for rotational Reynolds numbers as low as 2.2 × 104. Whilst separate boundary layers are formed on the discs, radial inflow occurs in a single interior core that extends between the two boundary layers; in the core, rotational effects are weak. Although the flow in the core was always found to be turbulent, the flow in the boundary layers could remain laminar for rotational Reynolds numbers up to 1.2 × 105. For the case of a superposed outflow, there is a source region in which the radial component of velocity is everywhere positive; radially outward of this region, the flow is similar to that described above. Although the turbulence model exhibited premature transition from laminar to turbulent flow in the boundary layers, agreement between the computed and measured radial and tangential components of velocity was mainly good over a wide range of nondimensional flow rates and rotational Reynolds numbers.

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