Session: 34-01 High-fidelity CFD – turbines

Paper Number: 152719

Simulation Approach for High-Lift, High-Work Low Pressure Turbine Aerodynamics Using the Lattice-Boltzmann Method 

A simulation approach was established for the application of lattice-Boltzmann method (LBM) CFD to low pressure turbine (LPT) aerodynamics for 2.5D linear cascades of LPT airfoils at low Reynolds numbers. This methodology was evaluated for six LPT airfoil geometries developed at AFRL (four high-lift, two high-lift/high-work) over realistic Reynolds lapse ranges. Predicted loss, loading, and suction surface boundary layer state were compared against prior linear cascade wind tunnel measurements acquired in the AFRL Low Speed Wind Tunnel Facility.

The chief computational strategy for the LBM simulations was to achieve direct numerical simulation (DNS)-level fidelity across the Reynolds range using LBM-LES, as implemented in the PowerFLOW commercial solver developed by Dassault Systèmes SIMULIA Corporation. This DNS-level fidelity was achieved by maintaining isotropically-fine near-wall grid spacing (x⁺,y⁺,z⁺ <1) across the Reynolds number range, and was demonstrated with a grid sensitivity study and the calculation of established grid resolution quality metrics for scale-resolving simulations. Recent enhancements to PowerFLOW’s subgrid turbulence model were leveraged to achieve accurate predictions of laminar separation/reattachment.

Particular attention was paid to capturing the sensitivity of LPT airfoil cascade performance to freestream turbulence, accomplished via the introduction of synthetic resolved turbulence at the inlet of the LBM computational domain. Despite the DNS-level fidelity that was achieved, overall computational cost was compatible with industrial LPT airfoil design cycles, owing to careful scaling of the 2.5D span and simulation physical time as a function of Reynolds number. Several challenges were identified, including the occurrence of Reynolds lapse hysteresis for certain airfoils and relatively higher computational cost at the highest Reynolds numbers studied.

Presenting Author: Matthew Langford Techsburg, Inc.

Presenting Author Biography: Matt Langford is the Chief Engineer at Techsburg, Inc. (located in Christiansburg VA), where he has worked since 2003. His technical focus over that time has been on aerodynamics and aeroacoustics of aircraft propulsion systems, including fans, propellers, vertical lift, and gas turbines. He has split time between experimental and computational projects, but efforts since 2020 have focused on unsteady computational fluid dynamics and computational aeroacoustics using the lattice-Boltzmann method.

Authors:

Matthew Langford Techsburg, Inc.
Stephen Guillot Techsburg, Inc.
Nathan Fletcher U.S. Air Force Research Laboratory
Molly Donovan U.S. Air Force Research Laboratory
Christopher Marks U.S. Air Force Research Laboratory
John Clark U.S. Air Force Research Laboratory
Avinash Jammalamadaka Dassault Systèmes SIMULIA Corporation
Gregory Laskowski Dassault Systèmes SIMULIA Corporation