AeroDynamic Solutions (United States)

This effort focuses on the comparison of unsteadiness due to as-measured turbine blades in a transonic turbine to that obtained with blueprint geometries via computational fluid dynamics (CFD). A Reynolds-averaged Navier–Stokes flow solver with the two-equation Wilcox turbulence model is used as the numerical analysis tool for comparison between the blueprint geometries and as-manufactured geometries obtained from a structured light optical measurement system. The nominal turbine CFD grid data defined for analysis of the blueprint blade were geometrically modified to reflect as-manufactured turbine blades using an established mesh metamorphosis algorithm. The approach uses a modified neural network to iteratively update the source mesh to the target mesh. In this case, the source is the interior CFD surface grid while the target is the surface blade geometry obtained from the optical scanner. Nodes interior to the CFD surface were updated using a modified iterative spring analogy to avoid grid corruption when matching as-manufactured part geometry. This approach avoids the tedious manual approach of regenerating the CFD grid and does not rely on geometry obtained from coordinate measurement machine (CMM) sections, but rather a point cloud representing the entirety of the turbine blade. Surface pressure traces and the discrete Fourier transforms (DFT) thereof from numerical predictions of as-measured geometries are then compared both to blueprint predictions and to experimental measurements. The importance of incorporating as-measured geometries in analyses to explain deviations between numerical predictions of blueprint geometries and experimental results is readily apparent. Further analysis of every casting produced in the creation of the test turbine yields variations that one can expect in both aero-performance and unsteady loading as a consequence of manufacturing tolerances. Finally, the use of measured airfoil geometries to reduce the unsteady load on a target blade in a region of interest is successfully demonstrated.

This effort focuses on the comparison of unsteadiness due to as-measured turbine blades in a transonic turbine to that obtained with blueprint geometries via computational fluid dynamics (CFD). A Reynolds-averaged Navier-Stokes flow solver with the two-equation Wilcox turbulence model is used as the numerical analysis tool for comparison between the blueprint geometries and as-manufactured geometries obtained from a structured light optical measurement system. The nominal turbine CFD grid data defined for analysis of the blueprint blade was geometrically modified to reflect as-manufactured turbine blades using an established mesh metamorphosis algorithm. The approach uses a modified neural network to iteratively update the source mesh to the target mesh. In this case the source is the interior CFD surface grid while the target is the surface blade geometry obtained from the optical scanner. Nodes interior to the CFD surface were updated using a modified iterative spring analogy to avoid grid corruption when matching as-manufactured part geometry. This approach avoids the tedious manual approach of regenerating the CFD grid and does not rely on geometry obtained from Coordinate Measurement Machine (CMM) sections, but rather a point cloud representing the entirety of the turbine blade. Surface pressure traces and the discrete Fourier transforms thereof from numerical predictions of as-measured geometries are then compared both to blueprint predictions and to experimental measurements. The importance of incorporating as-measured geometries in analyses to explain deviations between numerical predictions of blueprint geometries and experimental results is readily apparent. Further analysis of every casting produced in the creation of the test turbine yields variations that one can expect in both aero-performance and unsteady loading as a consequence of manufacturing tolerances. Finally, the use of measured airfoil geometries to reduce the unsteady load on a target blade in a region of interest is successfully demonstrated.

Conjugate heat transfer (CHT) simulations were conducted for five film-cooled flat plates designed to model the pressure side of the High Impact Technologies Research Turbine First Vane (HIT RT1V). The numerical results of the CHT analysis were compared against experimental data. The five test cases consist of one baseline geometry and four different cooling hole geometries applied to a film-cooling hole arrangement that was optimized to achieve a more uniform cooling effectiveness. This optimized film-cooling hole configuration was designed by coupling a genetic algorithm with a Navier-Stokes fluid solver, using source terms to model film holes, starting from a baseline cooling configuration. All five plates were manufactured, and surface temperature measurements were taken using infrared thermography while the plates were exposed to flow conditions similar to the pressure side of the HIT RT1V. CHT simulations were carried out using unstructured meshes for both fluid and solid with all film holes fully resolved. Comparison of experimental data and simulations shows a consistent trend between the optimized configurations as well as correct predictions of the flow characteristics of each hole geometry although the absolute temperatures are underpredicted by the CHT. Both experimental measurements and CHT predictions show the optimized geometry with mini-trenched-shaped holes to give the best cooling effectiveness.

Abstract The experimental investigations presented in this paper deal with an active flow control approach at the rear end of two different three-dimensional generic car configurations. Periodic forcing is used to influence the recirculation area behind these models based on the Ahmed body geometry with slant angles of 25°. and 90°. and hence to achieve a reduction in the total drag. Several forcing parameters (jet angle, forcing frequency and intensity) and their influence on the static pressure distribution at the rear end of the models and the total drag are examined. A model predictive closed-loop actuation approach is presented for one steady blowing excitation configuration. The interaction between the periodic compressed air actuator jet and the shear layer is depicted by means of stereo time-resolved Particle Image Velocimetry. The different actuation concepts lead to a drag reduction of up to 5.7% and demonstrate a good correlation with the static pressure distribution at the rear end of the model.KeywordsParticle Image VelocimetryDrag ReductionModel Predictive ControlStrouhal NumberBluff BodyThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Under‐ and over‐expanded jet flows are calculated for the Euler equations. The solution procedure is based on the two‐stage Runge‐Kutta time‐stepping scheme. The studies of the flow field structure in diffusers, free jets and impinging jets have been investigated for a range of jet‐to‐stream total pressure ratios and for different exit Mach numbers. The resulting flows show a complex shock‐shear expansion structure with Mach discs. Numerical results are compared with available experimental data and with previously published data. An oscillating phenomenon was observed in the case of free jets operating at sonic exit Mach number and in another case of impingement of under‐expanded jets on a flat plate.