Euler calculations for flowfield of a helicopter rotor in hover

Agarwal, Ramesh K.; Deese, J.

doi:10.2514/3.45431

Cited by 59 publications

(22 citation statements)

References 2 publications

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“…Jameson [1][2][3] has developed high accuracy, low dissipation schemes for fixed-wing applications while Sheffer et al 4 showed that the performance of these numerical schemes in the calculation of helicopter flows are robust and accurate. A lot of work has been done in the field of helicopter simulation in the past decades ranging from potential flow calculations (Caradonna & Isom,5,6 Caradonna & Philippe 7 ), Euler and Navier-Stokes (RANS) calculations (Agarwal & Deese, 8,9 Srinivasan et al, 10,11 Allen, 12-16 Pomin & Wagner [17][18][19] ), and hybrid methods (Hassan et al, 20 Bhagwat et al 21,22 ), just to name a few. Most of the aforementioned computations employed some form of implicit time stepping scheme, mostly the dual time stepping scheme first introduced by Jameson. 23 While this has proved to be accurate for helicopter simulation, the time and computational resources required to compute a complete rotor in forward flight is very high, especially if the aeroelastic effects are to be considered.…”

Section: Introductionmentioning

confidence: 99%

Time Spectral Method for Rotorcraft Flow

Butsuntorn

Jameson

2008

46th AIAA Aerospace Sciences Meeting and Exhibit

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This paper proposes a fast and efficient way to simulate time-periodic unsteady threedimensional rotorcraft flow for both Euler and Reynolds averaged Navier-Stokes equations. Based on the recently developed Time Spectral method, accurate results for hover and forward flight cases were achieved while gaining efficiency on the traditional dual time stepping scheme, and being simpler than the nonlinear frequency domain type solvers. Two new formulations for Vorticity Confinement for compressible flows were explored. The first formulation uses the local velocity magnitude to scale the confinement parameter and the second uses a helicity to determine the strength of the confinement term. The addition of the confinement term has no effect on the surface pressure distribution and negligible errors in the calculations of the coefficients of lift and drag.

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Section: Introductionmentioning

confidence: 99%

Time Spectral Method for Rotorcraft Flow

Butsuntorn

Jameson

2008

46th AIAA Aerospace Sciences Meeting and Exhibit

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“…When the static angle was set at 15 degrees, 20 degrees and 25 degrees, the dynamic angle of attack for the last 3 inches of the rotor blade is less than zero and produces drag and no lift [9].…”

Section: Net Dynamic Angle Of Attack Along the Blade Leading Edgementioning

confidence: 99%

Producing Electric Power from the Wind: A Study of Flow Mechanics and Blade Efficiency

Frost¹

2014

Chronicle of The New Researcher

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Author Summary: In many locations, the installation of windmills to produce electric energy is not economic due to the efficiency of the machine to convert wind energy to electric energy. There is a theoretical limit (Betz's Law) of 59.3% of the energy of the wind that is available for conversion to electric energy. This makes sense since if you extract all of the kinetic energy of the wind, the wind comes to a stop and does not flow over the blade. If the blades of the windmill become more efficient, the windmill could become more economically viable for more installations. This is a study of the flow mechanics and efficiency of the windmill blade in the hopes that some design improvements might push these machine's output closer to the Betz Theoretical Limit. AbstractElectric power generated from the wind can help our society become less dependent upon the production of foreign oil. Windmills of old were made with blades that had a cross-section of a rectangle. These were inexpensive blades sweeping out small circles by today's standards. Windmill rotor blades today have airfoil cross-sections, which reduce drag and increase the performance [1].My hypothesis is that the symmetrical airfoils will outperform the flat-bottomed airfoil and rectangular blades. This is important since increasing the efficiency of the windmill will increase its affordability and use. To test my hypothesis, I created a wind tunnel and windmill to test the different blades. Twelve inch long blades measuring 2 and 5 inches from front to back were used. The length of the blade was 12 inches. The windmill was made out of PVC pipe [2]. To smooth the airflow, I used an array of pre-cut pipes resembling the same in a 2009 US Department of Energy report on windmills and wind energy [3].In each series of experiments, I waited for the wind tunnel and air smoother to reach a steady state flow of air. The airflow speed was 11.2 feet per second and 5.8 feet per second. I set the Static Angle of the blades on the rotor and then put the windmill into the airflow. I waited for the rotors to reach steady state and then recorded power data and measured the rotational speed of the rotor with a strobe light. I averaged the observations and graphed the output results. I calculated the net Dynamic Angle of attack for points along the leading edge of the rotors and graphed the ratio of the coefficients for each calculated net Dynamic Angle.My hypothesis was correct as the symmetrical airfoils out performed the flat-bottomed airfoils and control blades. At the 11.2 ft/sec wind speed, the 2" symmetrical blade produced 28% more power than the 2" flatbottomed blade at a 5-degree static angle; 56% more power at a 10-degree static angle. The 2" symmetrical blade also produced twice the power of the 5" symmetrical blade.At the 5.8 ft/sec wind speed, the 2" symmetrical blade produced 11% more power than the 2" flat-bottomed blade at 5-degree static angle; 84% more power than the flat-bottomed blade at a 10-degree static angle. The 2" symmetrical blade power outpu...

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“…This was followed by the use of the Euler equations [35] and with increase in computational power, codes which solved the Navier-Stokes equations [36]. A common strand to all these solution schemes was the use of wake models to compute the induced effects of the rotor and these methods are also referred to as wakecoupled methods.…”

Section: Computational Workmentioning

confidence: 99%

CFD Analysis of a Slatted UH-60 Rotor in Hover

Ganti

2012

30th AIAA Applied Aerodynamics Conference

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The effect of leading-edge slats (LE) on the performance of a UH-60A rotor in hover was studied using the OverTURNS CFD solver. The objective of the study was to quantify the effect of LE slats on the hover stall boundary and analyze the reasons for any potential improvement/penalty. CFD predictions of 2-D slatted airfoil aerodynamics were validated against available wind tunnel measurements for steady angle of attack variations. The 3-D CFD framework was validated by comparing predictions for the baseline UH-60A rotor against available experimental values. Subsequent computations were performed on a slatted UH-60A rotor blade with a 40%-span slatted airfoil section and two different slat configurations. The effect of the slat root and tip vortices as they convect over the main blade element was captured using appropriately refined main element meshes and their impact on the slatted rotor performance was analyzed. It was found that the accurate capture of the slat root and tip vortices using the refined meshes made a significant difference to the performance predictions for the slatted rotors. The calculations were performed over a range of thrust values and it was observed that the slatted rotor incurred a slight performance penalty at lower thrust and was comparable to the baseline rotor at higher thrust conditions. It was also found that shock induced separation near the blade tip was the limiting factor for the baseline UH-60 rotor in hover, causing an increase in rotor power and resulting in a reduction of figure of merit for the baseline rotor at higher thrust values. The shock induced separation occured outboard of the slat tip and therefore limited the performance of the slatted rotors as well. Overall, the study provides useful insights into effects of leading edge slats on rotor hover performance, aerodynamics and wake behavior.

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Euler calculations for flowfield of a helicopter rotor in hover

Cited by 59 publications

References 2 publications

Time Spectral Method for Rotorcraft Flow

Time Spectral Method for Rotorcraft Flow

Producing Electric Power from the Wind: A Study of Flow Mechanics and Blade Efficiency

CFD Analysis of a Slatted UH-60 Rotor in Hover

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