Numerical simulations of separated flows at moderate Reynolds numbers appropriate for turbine blades and unmanned aero vehicles

Castiglioni, Giacomo; Domaradzki, J. Andrzej; Pasquariello, Vito; Hickel, Stefan; Grilli, Muzio

doi:10.1016/j.ijheatfluidflow.2014.02.003

Cited by 12 publications

(7 citation statements)

References 23 publications

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“…In cases of relaminarization in transitional flows, the predictions are often inconveniently sensitive to model parameter selection. More recently, the detailed effect of numerical dissipation in immersed boundary/LES methods has been examined in [30,31]. The numerical dissipation may exceed viscous or sub-grid scale model dissipation in transitional flows with laminar separation bubbles, so turbulence quantities and dissipation rates may agree with other computations or experiment only after suitable tuning of model coefficients.…”

Section: The Naca 0012 As a Standard Test Casementioning

confidence: 99%

On the possibility (or lack thereof) of agreement between experiment and computation of flows over wings at moderate Reynolds number

2017

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The flight of many birds and bats, and their robotic counterparts, occurs over a range of chord-based Reynolds numbers from 1 × 10 to 1.5 × 10. It is precisely over this range where the aerodynamics of simple, rigid, fixed wings becomes extraordinarily sensitive to small changes in geometry and the environment, with two sets of consequences. The first is that practical lifting devices at this scale will likely not be simple, rigid, fixed wings. The second is that it becomes non-trivial to make baseline comparisons for experiment and computation, when either one can be wrong. Here we examine one ostensibly simple case of the NACA 0012 aerofoil and make careful comparison between the technical literature, and new experiments and computations. The agreement (or lack thereof) will establish one or more baseline results and some sensitivities around them. The idea is that the diagnostic procedures will help to guide comparisons and predictions in subsequent more complex cases.

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Section: The Naca 0012 As a Standard Test Casementioning

confidence: 99%

On the possibility (or lack thereof) of agreement between experiment and computation of flows over wings at moderate Reynolds number

2017

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“…On the other hand, for this particular flow configuration, it seems that the excess of numerical dissipation, with respect to the sub-grid-scale dissipation, is not enough to be appreciable in the chosen metrics (Pressure and skin friction coefficients, separation and reattachment points). These findings also explain why there is a negligible difference in the results when an explicit LES model is added (see Figure 2) (Castiglioni et al, 2014). The numerical dissipation is dominant over the SGS dissipation, therefore adding an explicit model does not improve the results.…”

Section: Resultsmentioning

confidence: 76%

“…The application of the method to this specific simulation enabled the quantification of previously reported qualitative findings (Castiglioni et al, 2014). Two important observations have been quantified.…”

Section: Discussionmentioning

confidence: 99%

A numerical dissipation rate and viscosity in flow simulations with realistic geometry using low-order compressible Navier–Stokes solvers

Castiglioni¹,

Domaradzki²

2015

Computers & Fluids

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Recently it has become increasingly clear that the role of numerical dissipation, originating from the discretization of governing equations of fluid dynamics, rarely can be ignored regardless of the formal order of accuracy of a numerical scheme used in either explicit or implicit Large Eddy Simulations (LES). The numerical dissipation inhibits the predictive capabilities of LES whenever it is of the same order of magnitude or larger than the subgrid-scale (SGS) dissipation. The need to estimate the numerical dissipation is most pressing for low-order methods employed by commercial CFD codes. Following the recent work of Schranner et al. (2015) the equations and procedure for estimating the numerical dissipation rate and the numerical viscosity

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“…Recent publications have demonstrated that the IB method is able to accurately reproduce the flow around airfoils even at medium-tolarge Reynolds numbers whenever adequately fine fluid meshes are adopted. Castiglioni et al [21] performed a LES of a NACA 0012 with a fixed angle of attack at Re c ¼ 5 Â 10 4 and achieved good agreement of aerodynamic coefficients computed with the IB method compared with those obtained from body-fitted model simulations. Tay et al [22] studied different IB methods for the simulation of flapping wings and showed, when comparing the results to experimental measurements, that the accuracy of their IB model is similar to that of a body-fitted model.…”

Section: Introductionmentioning

confidence: 93%

Effect of Blade Cambering on Dynamic Stall in View of Designing Vertical Axis Turbines

Ouro

Stoesser

Ramírez

2018

Journal of Fluids Engineering

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This paper presents large eddy simulations (LESs) of symmetric and asymmetric (cambered) airfoils forced to undergo deep dynamic stall due to a prescribed pitching motion. Experimental data in terms of lift, drag, and moment coefficients are available for the symmetric NACA 0012 airfoil and these are used to validate the LESs. Good agreement between computed and experimentally observed coefficients is found confirming the accuracy of the method. The influence of foil asymmetry on the aerodynamic coefficients is analyzed by subjecting a NACA 4412 airfoil to the same flow and pitching motion conditions. Flow visualizations and analysis of aerodynamic forces allow an understanding and quantification of dynamic stall on both straight and cambered foils. The results confirm that cambered airfoils provide an increased lift-to-drag ratio and a decreased force hysteresis cycle in comparison to their symmetric counterparts. This may translate into increased performance and lower fatigue loads when using cambered airfoils in the design of vertical axis turbines (VATs) operating at low tip-speed ratios.

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Numerical simulations of separated flows at moderate Reynolds numbers appropriate for turbine blades and unmanned aero vehicles

Cited by 12 publications

References 23 publications

On the possibility (or lack thereof) of agreement between experiment and computation of flows over wings at moderate Reynolds number

On the possibility (or lack thereof) of agreement between experiment and computation of flows over wings at moderate Reynolds number

A numerical dissipation rate and viscosity in flow simulations with realistic geometry using low-order compressible Navier–Stokes solvers

Effect of Blade Cambering on Dynamic Stall in View of Designing Vertical Axis Turbines

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