skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: CFD Validation of Small Quadrotor Performance using CREATETM-AV Helios
Computational fluid dynamics (CFD) simulations of a small quadrotor were conducted using CREATETM-AV Helios. Two near-body CFD solvers and multiple turbulence models including transition models available in Helios were tested. The DJI Phantom 3 was chosen as a representative configuration because it has been studied extensively and is typical of commercial unmanned aerial vehicles. The airfoil at three-quarters span of the rotor geometry was extracted to perform both two-dimensional (2D) airfoil and three-dimensional (3D) wing studies in order to determine appropriate grid spacings for use with the various models. Isolated rotor simulations for DJI Phantom 3 rotor in hover utilizing appropriate grids were completed for fully turbulent and turbulence transition models. The predicted thrust from all of the methods lie within experimental uncertainty. The Spalart Allmaras model gave consistent results across the two CFD solvers and was most computationally efficient. As such it was chosen for the simulations of the full quadrotor performance in hover. The results indicate that a transition model is not required in order to obtain satisfactory thrust predictions as compared to experiment for a small quadrotor in hover using the Helios package. However, the figure of merit is underpredicted by both fully turbulent and transition models. Therefore, the effect of transition modeling on torque prediction needs further investigation.  more » « less
Award ID(s):
1728277
PAR ID:
10108279
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
VFS 75th Annual Forum & Technology Display
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; (, AIAA Scitech 2021 Forum)
    null (Ed.)
    A memory efficient framework is developed for the aerodynamic design optimization of helicopter rotor blades in hover. This framework is based on a fully-automated discrete-adjoint toolbox called FDOT. The in-house toolbox is capable of computing sensitivity or gradient information very accurately, and uses an operator-overloading technique that takes advantage of a unique expression-template-based approach for memory and computational efficiency while still being fully-automated with minimal user interventions. The main goal of the present work is to "design" helicopter rotor blades with increased figure-of-merit. Therefore, the flow around the Caradonna-Tung rotor in non-lifting and lifting hover conditions is studied in order to validate the primal and adjoint solvers based on a rotating frame of reference formulation. The efficacy of the optimization framework is first demonstrated for drag minimization of a rotating NACA 0012 airfoil, which resembles a Vertical-Axis Wind Turbine (VAWT) configuration. Finally, the single- and multi-point design optimization results for the Caradonna-Tung rotor are presented. It is important to note that the current approach (FDOT) can be directly coupled -- in a "black-box" manner -- to other existing codes in the Helios computational platform, which is part of CREATE-AV. 
    more » « less
  2. ; ; ; ; (, In Advanced Wind Tunnel Boundary Simulation II)
    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. 
    more » « less
  3. (, Fluids)
    One of the key factors in simulating realistic wall-bounded flows at high Reynolds numbers is the selection of an appropriate turbulence model for the steady Reynolds Averaged Navier–Stokes equations (RANS) equations. In this investigation, the performance of several turbulence models was explored for the simulation of steady, compressible, turbulent flow on complex geometries (concave and convex surface curvatures) and unstructured grids. The turbulence models considered were the Spalart–Allmaras model, the Wilcox k- ω model and the Menter shear stress transport (SST) model. The FLITE3D flow solver was employed, which utilizes a stabilized finite volume method with discontinuity capturing. A numerical benchmarking of the different models was performed for classical Computational Fluid Dynamic (CFD) cases, such as supersonic flow over an isothermal flat plate, transonic flow over the RAE2822 airfoil, the ONERA M6 wing and a generic F15 aircraft configuration. Validation was performed by means of available experimental data from the literature as well as high spatial/temporal resolution Direct Numerical Simulation (DNS). For attached or mildly separated flows, the performance of all turbulence models was consistent. However, the contrary was observed in separated flows with recirculation zones. Particularly, the Menter SST model showed the best compromise between accurately describing the physics of the flow and numerical stability. 
    more » « less
  4. ; ; ; (, VFS Aeromechanics for Advanced Vertical Flight Technical Meeting)
    A multirotor trim module is developed for the HPCMP CREATETM-AV Helios rotorcraft simulation code. Trimmed free-flight simulation results are presented for two multirotor configurations, using rotor frequencies and aircraft attitudes as the control variables. The loose-coupling procedure is used to achieve trim, where aerodynamic loading on the rotor blades and fuselage are computed using a simplified aerodynamic model, and modified at each coupling iteration using the airloads computed by the higher fidelity CFD based aerodynamics. Two different optimization methods are tested: a least-square regression algorithm, with the norm of the loads at the center of gravity as the objective function, and a nonlinear constrained optimization code, with the total power as the objective function, and with constraints applied to satisfy trim. First, a commercial small-scale UAV is simulated in forward flight. A reference model for midscale UAM applications is then trimmed in hover to demonstrate the module’s ability to model and trim a complex configuration. 
    more » « less
  5. ; (, 13th European Wave and Tidal Energy Conference, Napoli, Italy)
    In light of the 2018 special report on climate change compiled by the United Nations, there is a renewed urgency to the rapid adoption of renewable energy technologies. A key roadblock to the large-scale/commercial conversion of tidal energy is the question concerning the operational efficiency of existing technologies in the non-homogeneous, turbulent and corrosive marine environment. A thorough understanding of the aforementioned aspects of full-scale deployment is vital in developing robust and cost-effective turbine designs and farm layouts. The current experimental work at Lehigh University aims to better the understanding of turbine performance and near-wake statistics in homogeneous and non-homogeneous turbulent flows, similar to actual marine conditions. A 1:20 laboratory scale tidal turbine model with a rotor diameter of 0.28m is used in the experiments and an active grid type turbulence generator, designed in-house, is employed to generate both homogeneous and non-homogeneous turbulent inflow conditions. To the knowledge of the authors, this is the first experimental study to explore the effects of non-homogeneous inflow turbulence on tidal turbines. From the data collected it was observed that the non-homogeneous inflow condition led to a considerable drop (15-20%) in the measured thrust coefficient. They also resulted in larger torque and thrust fluctuations on the rotor (~40% under the tested conditions). The effect of inflow non-homogeneity was evident in the asymmetric near-wake characteristics as well. Turbulence intensity and Reynolds stresses measured in the wake of the rotor were found to adapt quicker to inflow non-homogeneity than the wake velocity deficit and integral length scales. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email