In Situ Velocity Measurements in the Near-Wake of a Ship Superstructure

Brownell, Cody; Luznik, Luksa; Snyder, Murray R.; Kang, Hyung Suk; Wilkinson, Colin

doi:10.2514/1.c031727

Cited by 42 publications

(13 citation statements)

References 21 publications

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“…14. For headwind, the flow moving over the top of the hangar already has residual turbulence from being in the wake of the pilot house and explains the reason why our turbulence intensities show very little variation with elevation above the flight deck (Brownell et al 2012). We do not observe a significant increase in hy 0 y 0 i 1/2 /U ref and hw 0 w 0 i 1/2 /U ref turbulence intensities downstream of the reattachment point, as observed by Tinney and Ukeiley (2009).…”

Section: B Flow On the Flight Deck Behind Hangar Superstructuresupporting

confidence: 53%

Influence of the Atmospheric Surface Layer on a Turbulent Flow Downstream of a Ship Superstructure

Luznik

Brownell

Snyder

et al. 2013

Journal of Atmospheric and Oceanic Technology

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This paper describes a set of turbulence measurements at sea in the area of high flow distortion in the nearwake and recirculation zone behind a ship's superstructure that is similar in geometry to a helicopter hangar/ flight deck arrangement found on many modern U.S. Navy ships. The instrumented ship is a 32-m-long training vessel operated by the United States Naval Academy that has been modified by adding a representative flight deck and hangar structure. The flight deck is instrumented with up to seven sonic anemometers/ thermometers that are used to obtain simultaneous velocity measurements at various spatial locations on the flight deck, and one sonic anemometer at bow mast is used to characterize inflow atmospheric boundary conditions. Data characterizing wind over the deck at an incoming angle of 08 (head winds) and wind speeds from 2 to 10 m s 21 obtained in the Chesapeake Bay are presented and discussed. Turbulent statistics of inflow conditions are analyzed using the Kaimal universal turbulence spectral model for the atmospheric surface layer and show that for the present dataset this approach eliminates the need to account for platform motion in computing variances and covariances. Conditional sampling of mean flow and turbulence statistics at the flight deck indicate no statistically significant variations between unstable, stable, and neutral atmospheric inflow conditions, and the results agree with the published data for flows over the backward-facing step geometries.

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Section: B Flow On the Flight Deck Behind Hangar Superstructuresupporting

confidence: 53%

Influence of the Atmospheric Surface Layer on a Turbulent Flow Downstream of a Ship Superstructure

Luznik

Brownell

Snyder

et al. 2013

Journal of Atmospheric and Oceanic Technology

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“…The purpose of this experiment is to validate the previous wind tunnel results. Onboard measurements are rarely found among the literature, with studies such as Snyder et al 6,7 and Brownwell et al 31 being some of the few examples. In Figure 9, a photograph taken during the onboard measurement acquisition is displayed.…”

Section: Methodsmentioning

confidence: 99%

A spectral analysis of laser Doppler anemometry turbulent flow measurements in a ship air wake

Bardera

Barcala-Montejano

Rodríguez-Sevillano

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part G:

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Helicopters are one of the most important tactical elements in maritime operations. The necessity to improve the conditions in which the landing and takeoff operations are carried out leads to the study of the flow that separates from the ship's superstructure over the flight deck. To investigate this flow a series of wind tunnel experiments have been performed by testing a sub-scale model of a frigate. Measurements of the flow velocity have been taken by means of laser Doppler anemometry in five points that simulate the last path of the landing trajectory. The data obtained in these experiments is analyzed in the frequency domain where the corresponding spectra are calculated. Onboard measurements from an actual full-scale frigate are analyzed and compared with the wind tunnel results. Conclusions obtained consist of a series of illustrative values of turbulent energy frequency ranges, which are valuable for any study in this field. The comparison shows a similarity between both experiments, reasserting the role of the wind tunnel measurements in these kind of studies.

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“…A description of the facility and data for a direct headwind has been discussed previously. 5 For ship airwake flows, flow topology is known to change drastically with sometimes slight changes in incident wind direction. 4 This necessitates full-field validation data from a number of wind directions, to assess the ability of a simulation to capture changes in flow structure and the particular inflow conditions under which those changes occur.…”

Section: Introductionmentioning

confidence: 99%

Velocity Measurements in A Ship Airwake With Crosswind

Brownell

Luznik

Snyder

et al. 2012

42nd AIAA Fluid Dynamics Conference and Exhibit

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In situ air velocity measurements in the near wake of a Navy training ship are presented for an inflow of 15 o to starboard. This data is required for the validation of ship airwake simulations, which are used to determine the launch and recovery envelopes for shipborne rotorcraft and for use in piloted flight simulations. The measurements are taken primarily above an aft flight deck, which sits immediately behind a step-like hangar structure. A description of the mean flow structure is included, as well as the Reynolds stresses at numerous points along the ship centerline. Comparisons are made between the present 15 o case and the case of a direct headwind, presented previously. Compared to the 0 o inflow condition, the flow symmetry is clearly broken with a cross-wind. The port and starboard sides of the deck have very different mean flow profiles and turbulent stress components. An updraft is visible over much of the starboard side of the flight deck, which is not found on the port side, or on either side under a headwind. Along the centerline, the streamwise normal component of the turbulent stresses are much larger in the cross-wind case than in the headwind case, while the shear components have similar magnitudes. This suggests that the wake turbulence is similar, but that in the cross-wind case the flight deck is more heavily burdened by inflow fluctuations from the atmosphere. Nomenclature H= step height of hangar immediately forward of flight deck, approx 1.5-m. = normal, streamwise Reynolds stress component = Reynolds shear stress component = mean velocity in the horizontal plane, measured from above the ship bow = two-point cross-correlation function YP = Navy training vessel, 108-ft long. u,v,w = velocity components in the x,y, and z directions, respectively x = coordinate along the length of ship, with origin at the hangar face, positive aft y = cross-ship coordinate, origin at the ship center, positive starboard z = vertical coordinate, origin at the flight deck surface, positive up

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In Situ Velocity Measurements in the Near-Wake of a Ship Superstructure

Cited by 42 publications

References 21 publications

Influence of the Atmospheric Surface Layer on a Turbulent Flow Downstream of a Ship Superstructure

Influence of the Atmospheric Surface Layer on a Turbulent Flow Downstream of a Ship Superstructure

A spectral analysis of laser Doppler anemometry turbulent flow measurements in a ship air wake

Velocity Measurements in A Ship Airwake With Crosswind

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