Low-Mach-number preconditioning applied to turbulent helicopter fuselage flowfield computation

Application is presented of a low-speed preconditioning technique for solving the compressible Reynolds averaged Navier-Stokes equations to low-speed external aerodynamic problems. The methodology adopted, which follows that of Merkle and Choi, is explained in detail, including its numerical implementation. Simple test cases around a NACA0012 airfoil in inviscid and viscous flow illustrate the efficiency of the method, both for the convergence as well as on the, quality the solution. Application to realistic helicopter fuselage configurations shows the improvements brought by the method for complex configurations, the preconditioned solution being indispensable to correlate well with experiment at very low Mach numbers.