A review of velocity and pressure fluctuations in turbulent flows around bluff bodies

Abstract

This paper is firstly a review of the theory for the changes in the velocity fluctuations in a turbulent floq as it passes around a bluff body with a simple shape such as prism or sphere. Detailed results are given for the ideal cases where the scale of the incident turbulence is much smaller or much larger than the body's diameter, but it is shown that the results are also applicable to many practical flows, including bluff bodies in the wake of others. This review gives new, simple derivations for the spectra and variances of velocity and pressure fluctuations near the surface of bluff bodies, showing why on different shapes of body and for different scales there are different distributions of pressure variance. A new approach is described for simulating realisations of the random velocity field, using the technique of ‘kinematic simulation’. Experimental results are also briefly reviewed for bluff bodies placed in homogeneous turbulence, and in inhomogeneous shear flows. The outstanding problem remains of understanding how incident turbulence interacts with the turbulence and vortex shedding in the wake of a bluff body, though there has been some progress in identifying and understanding some of the mechanisms.