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Results are presented from a series of laboratory experiments in which the interaction of a turbulent buoyant jet with a localised patch of grid-generated turbulence has been investigated. The experiments show that the effect of the turbulent patch is to arrest the structural development of the buoyant jet at a location determined by the relative values of the r.m.s. turbulent velocities in the patch and jet, respectively. Measurements of the breakdown distance z_c from the jet source have been compared successfully with the predictions of a scaling analysis for the limiting cases of momentum- and buoyancy-dominated regions of the buoyant jet.

The effect of transverse magnetic field on the stability of plane Poiseuille and Couette flow between two parallel flat plates is investigated for Oldroyd-B fluid. The classical Orr–Sommerfeld analysis is extended to electrically conducting fluid for Oldroyd-B model, assuming that the magnetic Prandtl number is sufficiently small. The Chebyshev collocation method with the QZ-algorithm is used for solving the stability equations to find the eigenvalues. The critical values of Reynolds number, wave number, and wave speed are computed. It is found that the magnetic field has a stabilizing effect on Poiseuille flow, while it has both destabilizing and stabilizing effects on the Couette flow.

It is well-known that freely falling or rising objects and self-propelling bodies shed vorticity. It is then a natural question to ask how to define the forces (drag and lift) experienced by the body in terms of the vorticity distribution in the surrounding fluid and the normal velocity of the body surface, since these define the velocity distribution uniquely. In this paper we outline the answer given by Burgers in an almost forgotten paper from 1920, and point at the close relationship of Burgers's ideas in these matters with those of Sir James Lighthill. The connection with more recent work by Kambe and Howe is established and we briefly discuss related issues concerning "vortex methods" and "vortex sound".