Browse Topic: Computational fluid dynamics (CFD)
Despite advances in CFD, wind tunnel testing remains indispensable for aerodynamic validation, correlation, and homologation. Increasing configuration complexity, shortened development cycles, and stringent result robustness and documentation requirements demand a shift from isolated facilities to integrated, data-driven ecosystems within the overall development and company-wide test processes. We present a software-centric approach integrating wind tunnel operations into a strategic element of the Digital Thread. By orchestrating test planning, execution, data acquisition, and documentation within a unified framework, experimental data becomes reusable across projects and traceable for compliance and homologation. The interaction between CFD and physical testing is important. Such approach systematically improves simulation models with wind tunnel tests. And CFD results guide efficient test matrix definition. Extended measurement methodologies include automated actuation of active
High-speed maglev trains are recognized for their superior velocity, environmental benefits, and enhanced passenger comfort, positioning them as a key area of interest in modern transport research. Nonetheless, tunnel operations introduce complex aerodynamic challenges that can impede performance. This research examines the aerodynamic load behaviors of maglev trains in single and double-track tunnel settings, with particular emphasis on transient drag variations in lead and trail cars during solo and passing operations. A computational fluid dynamics model was constructed to capture detailed flow field attributes, including pressure wave propagation, reflection, and superposition. Findings indicate that aerodynamic loads intensify with increasing speed. When velocity rises from 300 km/h to 600 km/h during solo tunnel transit, the lateral force on the head-car and the drag on the trail-car both surge approximately fivefold. During meets in double-track tunnels, the head-car’s lift
This SAE Aerospace Recommended Practice (ARP) document establishes criteria and recommended practices for the use of airborne icing tankers to aid in design and certification of aircraft ice protection systems and components. Several icing tankers are described, along with their capabilities and suggested use. Sample data for these tanker spray systems are included, shown with 14 CFR Parts 25 and 29, Appendix C icing envelopes for continuous maximum and intermittent maximum icing conditions. (Note: In the remainder of this document, the phrase “Appendix C icing envelopes” will be used for brevity.) This ARP is intended as a guide toward standard practice and is subject to change to keep pace with experience and technical advances.
The validity of using comprehensive analysis (CA) tools coupled with computational fluid dynamics (CFD) to predict the aeromechanics of classical rotor blades was proven in the literature. This paper aims to enhance this validation for the complex double-swept planform ERATO blade under high-thrust level-flight condition. In order to do so, HOST comprehensive analysis tool and elsA/HOST high-fidelity loose coupling are compared to the results of the experimental campaign of the ERATO rotor carried out by ONERA in 1998 at the S1MA transonic wind tunnel. Trim commands and airloads are reviewed and enhanced with respect to a previous publication and structural loads (flap bending moment, chord bending moment and torsion moment) are used to validate the numerical simulations. The results highlight the need for high-fidelity methods in order to improve the accuracy of both the aerodynamic and structural responses.
Rotor blade design is a fundamental problem in rotorcraft aerodynamics. Conventional design methods rely on high-fidelity simulations such as Computational Fluid Dynamics (CFD) that are computationally prohibitive at the early design stage, while low-fidelity methods lack the accuracy required to capture complex aerodynamic interactions. This paper presents a surrogate-based framework for a rotor blade design with multiple airfoil geometries along the span. An efficient design of experiments strategy based on Sobol sampling with unique airfoil identifiers reduces the effective sampling dimension during data generation. Training data is generated using an in-house linear inflow model, which provides a computationally inexpensive yet representative dataset. The primary objective of this work is to demonstrate a complete end-to-end methodology for surrogate model development for high-dimensional rotor blade design with varying spanwise airfoil geometries. The linear inflow model is
This study evaluates the predictive accuracy and computational efficiency of a mid-fidelity Lattice-Boltzmann Method (LBM) framework in simulating the complex aerodynamic interactions of a tilting proprotor–wing configuration. The analysis focuses on the tiltrotor conversion maneuver, investigating a range of proprotor tilt angles from forward towards edgewise and vertical flight. To resolve the interactional flow physics, the LBM framework was integrated with two distinct proprotor modeling approaches, an Actuator Line Method (ALM) and an unsteady Actuator Disk Method (ADM), and two wall model boundary conditions, the explicit power-law and Reichardt’s log-law. The computational models were compared with experimental wind tunnel measurements and high-fidelity computational fluid dynamics (CFD) simulations. The ALM significantly outperformed the ADM in capturing discrete tip vortices and wake turbulence, which were critical for resolving the complex flow fields and wing surface
This paper presents a computational fluid dynamics (CFD) investigation of vertipad surface configurations for mitigation of e-VTOL rotor outwash. The outwash is modelled as a coherent vortex train embedded in a wall jet, simulated using 2D and 3D Large Eddy Simulation (LES). In 2D simulations, a tilted vane surface is shown to break up the coherent vortex train and induces recirculation beneath the vertipad, producing a sustained viscous energy dissipation rate approximately four times higher than the no-vertipad case. 3D simulations evaluate a novel fractal panel concept, comparing it against flat surface, grated panel, and no-vertipad configurations. The fractal panel produces the highest rates of vortex fragmentation and viscous energy dissipation, with sustained rates 90% higher than the no-vertipad configuration, and 30% higher than the next-best-performing grated panel. The results demonstrate that passive vertipad surface modification is an effective outwash mitigation strategy.
This paper assesses the capabilities and limitations of mid-fidelity computational fluid dynamics (CFD) approaches when resolving the complex aerodynamic interactions for a generic model-scale proprotor-wing configuration across the tiltrotor conversion maneuver. The Helios mid-fidelity Reduced Order Aerodynamic Model (ROAM) is evaluated against prior extensively validated high-fidelity Helios-OVERFLOW assessments for the proprotor-wing configuration. The ROAM actuator line model (ALM), which represents the proprotor blade via source terms injected into the off-body Cartesian domain, is assessed for the isolated proprotor configuration at several mesh resolutions to understand the requirements to accurately resolve the proprotor physics across the conversion maneuver. The impact of adaptive mesh refinement (AMR) on ROAM's ability to resolve the proprotor physics is also investigated. Next, the flow characteristics and wing loads are evaluated using the ROAM immersed boundary method
In this study, a novel rotorcraft comprehensive analysis (CA) framework is constructed for the aeromechanics analysis of various rotorcraft configurations such as single main/tail rotors, coaxial rotors, and tilt rotors. The framework incorporates numerous solution procedures that include trim, blade response, loads, and vibration with external interfaces to computational fluid dynamics (CFD) analysis. The structural module is characterized by a displacement-based geometrically exact beam (GEB) model and multibody formulations while the internal aerodynamics module is developed using a lifting-line representation of blades with simple inflow models. A series of validation on static benchmark examples showed excellent correlations with published records, particularly in the context of large deformation behavior of heavily loaded beams. The rotorcraft aeromechanics analyses of various configuration rotors such as single main rotor and lift-offset coaxial rotor types are performed next to
This study investigates the aerodynamics and performance of aerial screw rotors in axial climb and off-axis flight for the first time. Additionally, this work highlights comparisons between a hover-efficient aerial screw and a two bladed conventional rotor in various flight states. Using high-fidelity Computational Fluid Dynamics (CFD) analysis, the research identifies the formation of the "da Vinci vortex"—a shape-conforming helical structure to be crucial to thrust generation and performance. Investigations of linear and bilinear variations of the screw pitch and taper reveal nuanced effects on loads on the screw surface and climb efficiency. The effect of the pitch rate is found to dominate over the effect of the taper rate in axial and off-axis climbs. Efficiency in axial flight states is heavily dependent on the pitch rate of the aerial screw. Investigation of all forces on the aerial screw surfaces identifies significant phase differencing in loading between linear and bilinear
This paper presents an analytical prediction of rotor blade–wake interaction (BWI) noise using a newly developed turbulence intensity model. The new model is developed using high-fidelity computational fluid dynamics (CFD) results and is validated against experimental data for a BO105 rotor, showing good agreement. Compared to the Glegg model, the proposed approach predicts sound pressure levels approximately 3 dB higher at 600 Hz and about 2 dB higher below 800 Hz, highlighting the contribution of turbulence outside the vortex core. Furthermore, high-fidelity CFD simulations of tip vortex impingement on a downstream wing are performed using Large Eddy Simulation (LES), fully turbulent Improved Delayed Detached Eddy Simulation (SST-IDDES), and Gamma Transitional IDDES (GT-IDDES). Both LES and GT-IDDES capture detailed unsteady and boundary layer transitional flow features, whereas SST-IDDES fails to capture transition and produces a RANS-dominated, time-averaged flow field. The swirl
A new modeling and simulation approach for uncrewed aerial vehicles (UAVs) for shipboard operations, as well as other complex airwake environments, is introduced. The approach couples an aerodynamic modeling framework, expanded with a closed-loop flight controller, with a flight dynamics solver to assess UAV responses in highly complex airwakes. Using high-fidelity wall-modeled large eddy simulation airwakes, the approach has been evaluated for two traditional naval approaches on a generic destroyer. As part of this effort, a new metric to ensure accurate flight modeling is introduced, along with proposed UAV safety mapping. These predictions can support mission planning by evaluating unique prescribed approaches for nontraditional small UAV, and can aid in early controller design by highlighting specific failure modes based on the airwake environment.
Rotorcraft airfoils often feature a tab which aides in the manufacturing of composite rotor blades, but also has aerodynamic merits. This study performs a comprehensive analysis of the impact of this tab on the 2D airfoil performance, structural adjustments and 3D rotor performance. The aerodynamics are evaluated using CFD, with CFD/CSD coupled results for the rotor performance. The structural data is adjusted using an FEM based in-house process. The HART II model rotor has been taken as a baseline and modified according to the tab variation studies. These included the comparison of a sharp trailing edge versus a tabbed airfoil, various tab thicknesses, lengths, and angles. The studies showed a variation of peak Figure of Merit between 66% to 68% and peak rotor L/D from 4.2 to 4.6 The careful design of the airfoil tab is therefore advised, but similarly the structural design of rotor blades.
A challenge in establishing rotor performance map for sizing tool during design cycle is the rotor performance uncertainty for full vehicle. Sometimes, simplified tests at different setup/scale are conducted to guide performance map, but this introduces another uncertainty due to configuration difference from full vehicle. To aid insights, validated computational fluid dynamics simulations (using CREATE-AV™ Helios) were carried out to examine hovering rotor performance prediction variations at different design stages, or different modeling/testing setup with identical blade design. Quantitative rotor figure of merit differences has been demonstrated along with descriptions of underlying physical reasons. The examined model setup includes isolated rigid blades with and without flapping, elastic blades, model-scale blades, whirl-tower conditions, blades installed on fuselage, and full-vehicle including tail rotor. Both fully turbulent flow and laminar-turbulence transition flow
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