Abstract
AbstractThe generation of a fully turbulent boundary layer profile is investigated using analytical and numerical methods over the Reynolds number range 422 ≤ Reθ ≤ 31,000. The numerical method uses a new mixing length blending function. The predictions are validated against reference wind tunnel measurements under zero streamwise pressure gradient. The methods are then tested for low and moderate adverse pressure gradients. Comparison against experiment and DNS data show a good predictive ability under zero pressure gradient and moderate adverse pressure gradient, with both methods providing a complete velocity profile through the viscous sub-layer down to the wall. These methods are useful computational fluid dynamic tools for generating an equilibrium thick turbulent boundary layer at the computational domain inflow.
Highlights
Computational fluid dynamic (CFD) simulations of wall-bounded flows, such as the flow over aircraft high-lift devices, ailerons, the elevators and the rudder, often use a turbulent boundary layer inflow to reduce the computational domain size with respect to a full wing, tailplane or fin simulation
This paper compares the use of analytical correlations and of an auxiliary boundary layer numerical method for generating a turbulent boundary layer inflow for CFD over a wide Reynolds number range
As one aim of this paper is to introduce methods for generating an inflow velocity profile for Reynolds averaged Navier-Stokes (RANS) computations, rather than curve-fitting specific traverses, the authors take κ = 0.384 and B = 4.17 constant
Summary
Computational fluid dynamic (CFD) simulations of wall-bounded flows, such as the flow over aircraft high-lift devices, ailerons, the elevators and the rudder, often use a turbulent boundary layer inflow to reduce the computational domain size with respect to a full wing, tailplane or fin simulation. The interactive boundary layer (IBL) model of Cousteix and Mauss(15,16) consists in a uniformly valid approximation of the velocity field, including the inner and the outer regions, of an incompressible turbulent boundary layer It provides rational mathematical arguments in the form of a method of matched asymptotic expansions (MAE). Österlund(20) reports velocity measurements obtained using the OFI technique in which estimates of the uncertainty in uτ and in the wall-normal distance are given These are used as the main reference velocity profiles in this paper. This uncertainty analysis gives some appreciation of the advances in measurement techniques and efforts made to provide quality benchmark velocity profiles with clearly defined uncertainty margins in support of the on-going boundary layer modelling research. Whereas a monotonic kinetic energy cascade in the kinetic energy spectrum is only one marker of a fully developed turbulent boundary layer, the reference velocity profiles in Table 1 have been selected based on the availability of kinetic energy spectra that document such a feature
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