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This study presents the first 3D two-way coupled fluid structure interaction (FSI) simulation of a hybrid anechoic wind tunnel (HAWT) test section with modeling all important effects, such as turbulence, Kevlar wall porosity and deflection, and reveals for the first time the complete 3D flow structure associated with a lifting model placed into a HAWT. The Kevlar deflections are captured using finite element analysis (FEA) with shell elements operated under a membrane condition. Three-dimensional RANS CFD simulations are used to resolve the flow field. Aerodynamic experimental results are available and are compared against the FSI results. Quantitatively, the pressure coefficients on the airfoil are in good agreement with experimental results. The lift coefficient was slightly underpredicted while the drag was overpredicted by the CFD simulations. The flow structure downstream of the airfoil showed good agreement with the experiments, particularly over the wind tunnel walls where the Kevlar windows interact with the flow field. A discrepancy between previous experimental observations and juncture flow-induced vortices at the ends of the airfoil is found to stem from the limited ability of turbulence models. The qualitative behavior of the flow, including airfoil pressures and cross-sectional flow structure is well captured in the CFD. From the structural side, the behavior of the Kevlar windows and the flow developing over them is closely related to the aerodynamic pressure field induced by the airfoil. The Kevlar displacement and the transpiration velocity across the material is dominated by flow blockage effects, generated aerodynamic lift, and the wake of the airfoil. The airfoil wake increases the Kevlar window displacement, which was previously not resolved by two-dimensional panel-method simulations. The static pressure distribution over the Kevlar windows is symmetrical about the tunnel mid-height, confirming a dominantly two-dimensional flow field.
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CFD-Assisted Calibration of a Multi-Hole Probe for a Small UAS
A method for calibrating a multi-hole probe (MHP) used for inertial wind vector measurements from a small Uncrewed Aircraft System (sUAS) is presented. The first phase of the calibration process is broken into three parts: Obtaining reference airspeed, angle of attacks and side slip angles; calibrating MHPs with experimental data; mitigating bias errors to improve calibrations.The method follows the established wind tunnel calibration procedures and includes two additional steps to increase calibration accuracy. The calibration process begins with a computational fluid dynamics (CFD) study on blockage effects in the wind tunnel. CFD results indicate nontrivial deviations of the mean flow due to blockage in wind tunnel test section. Analysis shows a linear relationship between experimental setup position and the resulting deviation from unidirectional flow. The relationship is incorporated into the routine to develop a calibration model. This augments previously demonstrated techniques by processing experimental data from the probe using CFD results. Then the model is refined by removing experimental bias angles. The next phase is to account for upwash effects caused by the sUAS lifting surfaces. Initial CFD analysis has been conducted to determine the relationship between the perceived airframe orientation measured from the relative wind, and the angle of attack measured by the MHP. Preliminary results show that there is a measurable linear relationship between the perceived and actual angles of attack. The objective these additional steps is to increase the accuracy of MHP calibration and characterize the error in inertial wind vector measured during field experiments.
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- Award ID(s):
- 1824609
- PAR ID:
- 10354754
- Date Published:
- Journal Name:
- AIAA SciTech 2022 Forum
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.2514/6.2022-2400
