A computational study of unsteady ship airwake

Polsky, Susan; Bruner, Christopher William Stuteville

doi:10.2514/6.2002-1022

Cited by 71 publications

(40 citation statements)

References 1 publication

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“…The reality level of RANS for the airwake determination is regarded as acceptable. In addition, another numerical study for the airwake of LHA ship model has been carried out by Polsky and Bruner (2001), using both the RANS (using SST k -ω turbulence model) and Monotone Integrated Large Eddy Simulation (MILES) methods. The result also indicates that the URANS is capable of capturing the unsteady flowfield characteristics.…”

Section: Cfd Methodsmentioning

confidence: 99%

Numerical investigation of rotor loads of a shipborne coaxial-rotor helicopter during a vertical landing based on moving overset mesh method

Huang³

et al. 2019

Engineering Applications of Computational Fluid Mechanics

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Coupled ship/coaxial-rotor simulations have been conducted to investigate the rotor loads of a shipborne coaxial-rotor helicopter during a vertical landing based on Reynolds-averaged Navier-Stokes (RANS) solver. In order to achieve two-way coupling and overcome the limitations of the momentum source method in solving the unsteady aerodynamic problems, the moving overset mesh method is employed to simulate the complex highly unsteady aerodynamic interactions between the lower/upper rotor, flight deck and hangar-door through the vertical descent. To identify pilot workload and control strategy during this phase, the results in terms of time-averaged and rootmean-square (RMS) rotor loads are discussed. The time-averaged loads show that the coaxial-rotor helicopter suffers an increase in thrust and a sharp decrease in torque difference between lower and upper rotors during the vertical landing. It suggests that the pilot has to reduce not only the collective control input, but also the differential collective pitch, to stabilize the heading of the coaxial rotors helicopter. The RMS results indicate that the aerodynamic loads of the lower and upper rotors could couple with each other, and may eventually magnify the overall unsteady loading levels of the coaxial rotor. In addition to the ground effect, the recirculation flow regime will get stronger and lead to a sharp increase in RMS roll as the rotor moves along the vertical descent path. Furthermore, the influences of hangar-door state and the location of landing spot are investigated. The findings imply that opening the hangar-door can significantly reduce the pilot workload, and descending a helicopter to a landing spot which is more closed to the hangar can decrease the RMS load levels, especially during the latter stage of vertical descent. However, the helicopter tends to be pulled towards hangar-door more easily due to greater reduction in pitch moment.

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Section: Cfd Methodsmentioning

confidence: 99%

Numerical investigation of rotor loads of a shipborne coaxial-rotor helicopter during a vertical landing based on moving overset mesh method

Huang³

et al. 2019

Engineering Applications of Computational Fluid Mechanics

View full text Add to dashboard Cite

show abstract

“…15,16,17,18 Solutions often use time-accurate calculations and agree with wind tunnel and flight test data fairly well. In one case 19 the CFD solution is used with a flight simulator enabling a pilot to fly through the airwake.…”

Section: Airwake Analysismentioning

confidence: 96%

Active and Passive Flow Control over the Flight Deck of Small Naval Vessels

Shafer

Ghee

2005

35th AIAA Fluid Dynamics Conference and Exhibit

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Helicopter operations in the vicinity of small naval surface vessels often require excessive pilot workload. Because of the unsteady flow field and large mean velocity gradients, the envelope for flight operations is limited. This experimental investigation uses a 1:144 scale model of the U.S. Navy destroyer DDG-81 to explore the problem.Both active and passive flow control techniques were used to improve the flow field in the helicopter's final decent onto the flight deck. Wind tunnel data was collected at a set of grid points over the ship's flight deck using a single component hotwire. Results show that the use of porous surfaces decreases the unsteadiness of the flow field. Further improvements are found by injecting air through these porous surfaces, causing a reduction in unsteadiness in the landing region of 6.6% at 0 degrees wind-over-deck (WOD) and 8.3% at 20 degrees WOD. Other passive configurations tested include fences placed around the hangar deck edges which move the unsteady shear layer away from the flight deck. Although these devices cause an increase in unsteadiness downstream of the edge of the fence when compared to the baseline, the reticulated foam fence caused an overall decrease in unsteadiness in the landing region of 12.1% at 20 degrees WOD.

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“…Airwake datasets for seven WOD azimuths were computed: 000, 030, 045, 060, 090, 180 and 330 degrees. Six WOD speeds were considered: 15,20,25,30,35, and 45 knots. All cases, with the exception of 000, were run using a steady atmospheric boundary layer profile applied as an inflow boundary condition.…”

Section: Cfd Analysismentioning

confidence: 99%

Development and Application of the SAFEDI Tool for Virtual Dynamic Interface Ship Airwake Analysis

Polsky

Wilkinson

Nichols

et al. 2016

54th AIAA Aerospace Sciences Meeting

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Dynamic interface refers to shipboard aircraft launch and recovery operations including the testing required to determine flight envelope limits as a function of wind speed and direction. Ship-based flight operations must contend with challenges unique to the maritime environment such as ship motion and airwake turbulence created by the ship's superstructure. Ship airwake affects aircraft performance and handling qualities characteristics which in turn impact pilot workload. Ship airwake characteristics vary from ship to ship and also from one relative wind angle to the next for the same ship. The ability to assess ship airwake severity in a simulation environment allows airwake related design considerations, such as ship geometric layout and aircraft flight control design, to be addressed during the design process. NAVAIR has developed a desktop airwake analysis tool to model the handling characteristics of an aircraft when subjected to time accurate ship airwake velocities created with Computational Fluid Dynamics (CFD). The tool has been applied to multiple ship configurations to assess airwake impact on both rotary wing and fixed wing aircraft. This work describes the real-time aircraft flight dynamics models and CFD airwake models that make up the airwake evaluation tool, summarizes verification and validation efforts, and describes the comparative process used to evaluate ship airwake severity for an example ship configuration.

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A computational study of unsteady ship airwake

Cited by 71 publications

References 1 publication

Numerical investigation of rotor loads of a shipborne coaxial-rotor helicopter during a vertical landing based on moving overset mesh method

Numerical investigation of rotor loads of a shipborne coaxial-rotor helicopter during a vertical landing based on moving overset mesh method

Active and Passive Flow Control over the Flight Deck of Small Naval Vessels

Development and Application of the SAFEDI Tool for Virtual Dynamic Interface Ship Airwake Analysis

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