Techsburg and Solar Turbines to present paper at 2023 ASME IGTI Turbo Expo 2023 entitled “Predicting the Performance of Turbine Exhaust Diffuser-Collector Systems Across the Operating Range: Comparison of Lattice-Boltzmann Method Simulations with Experiments”


The predictive capability of the lattice-Boltzmann very large eddy simulation (LBM-VLES) methodology was evaluated for industrial gas turbine exhaust diffuser-collector applications.  The effort focused on evaluating the accuracy of performance predictions against experimental rig data gathered at engine representative conditions including the Reynolds number, Mach number and inlet flow conditions. The performance prediction capability of LBM-VLES simulations was also compared against Reynolds-averaged Navier-Stokes (RANS) simulations. Evaluations were completed for two distinct exhaust rig geometries at conditions indicative of their respective design points, and the performance prediction capability was also evaluated at conditions depicting two off-design cases. The off-design conditions were represented by an increase in inlet swirl angle and associated incidence on the diffuser struts.

Overall, the authors found that LBM-VLES simulations were a suitable approach for predicting the performance of gas turbine exhaust diffuser-collector systems at both on- and off-design conditions. The LBM-VLES simulation accuracy was substantially better than that achieved by RANS simulations, with 66% lower RMS pressure recovery error between CFD and experiments for the four cases studied, and an 89% reduction in error for the furthest off-design case. The computational cost of the transient LBM-VLES simulations was roughly the same as the RANS simulations performed using best practices for that solver.

Techsburg presents paper at AIAA SCITECH Forum 2023 entitled “Experimental and Numerical Investigation of Installed Ducted Propulsor Aeroacoustics”


NASA’s Advanced Air Transport Technology project has spurred development of novel transport aircraft configurations with the goal of reducing noise and greenhouse gas emissions. To this end, a subscale model of a low-solidity electric ducted fan propulsor originally designed for the Ampaire TailwindTM aircraft concept was tested in the Virginia Tech Anechoic Wind Tunnel in three installation configurations: isolated, close-coupled to an upstream airfoil, and planar boundary layer-ingesting. Three aeroacoustic CFD simulations matching the test conditions for a select run of each configuration were conducted using the PowerFLOW lattice-Boltzmann method solver. Acoustic levels from these simulations were compared against microphone measurements from the experiment, and duct modal analysis was performed at the duct inlet plane of the simulations.

Techsburg selected for NASA Phase II SBIR contract entitled “Design Cycle Prediction Software for Wing-Strut Junction Flow Noise”


NASA’s Advanced Air Transport Technology Project has worked with industry over the last decade to develop airframe/propulsion concepts and associated technologies to enable transformative air travel for future generations. Techsburg and AVEC’s proposal “Design Cycle Prediction Software for Wing-Strut Junction Flow Noise” addresses a technology analysis gap in the development of a leading airframe concept, the Transonic Truss Braced Wing (TTBW) airliner. The aeroacoustic signatures of the large bracing strut and jury member features of this configuration need to be captured in reduced-order modeling tools to enable design cycle trade studies/optimization of far field noise due to the wing/strut junction noise source. Building on Phase I success, we propose to train an artificial neural network (ANN) model of this noise source using PowerFLOW lattice-Boltzmann method (LBM) computational aeroacoustic simulations. Phase II will conclude with delivery of the reduced-order software tool Wing-Strut Broadband Acoustic Model, “WiSBAM”.

Techsburg presents paper at the Vertical Flight Society's 78th Annual Forum entitled “Measured Acoustic Characteristics of Low Tip Speed eVTOL Rotors in Hover”


To document noise characteristics and provide validation data for acoustic modeling of rotor systems appropriate for eVTOL/UAM aircraft, the team of Techsburg, AVEC, and Virginia Tech performed an outdoor static test of a subscale 5-blade rotor. The testing was carried out as part of a program to demonstrate feasibility and performance of a quiet rotor system in support of the eVTOL industry. Techsburg designed a low-tip speed rotor to approximate performance required by a 4-5 passenger UAM vehicle. A driving design feature was low-tip speed operation (Mtip ~0.27) at system disk loadings of 7 to 8 psf (~3.7 N/m2). The test article was designed as a ground adjustable pitch 5-blade rotor, and 2-blade and 3-blade versions of this rotor were also tested during this project. The test article size of 3 feet diameter (0.91 m) represented a scale factor of approximately 30% compared to a full size vehicles currently in operation or development today. The aerodynamic performance in hover was consistent with other rotor systems tested in the past at Techsburg (Figure of Merit ~0.70), and the effects of naturally occurring turbulence on rotor acoustics was measured using a 180-deg arc array of ground plane microphones at the Virginia Tech Drone Park test facility. The paper closes with a discussion of simulating the experiment with the PowerFLOW LBM solver with and without flow turbulence.