An investigation of ship airwakes using Detached-Eddy Simulation

Forrest, James S.; Owen, I.

doi:10.1016/j.compfluid.2009.11.002

Cited by 119 publications

(82 citation statements)

References 28 publications

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“…2 Assistant Professor, Mechanical Engineering Department, 590 Holloway Rd 11/C, Annapolis, MD 21402. 3 Permanent Military Professor, Mechanical Engineering Department, 590 Holloway Rd 11/C, Annapolis, MD 21402, AIAA Member. 4 Research Associate, Mechanical Engineering Department, 590 Holloway Rd 11/C, Annapolis, MD 21402, AIAA Member.…”

Section: Introductionmentioning

confidence: 99%

“…Validated, real-time simulations of the airflow over naval vessels would facilitate the determination of safe operating envelopes, greatly reducing both cost and pilot risk. [1][2][3] The simulation of the airwake from a ship superstructure is challenging because of a number of factors. 4 Reynolds numbers based on ship length can be 10 9 or higher, meaning the range of relevant length scales is 1 Assistant Professor, Mechanical Engineering Department, 590 Holloway Rd 11/C, Annapolis, MD 21402, AIAA Member.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

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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“…The ship airwake environment poses a significant risk to flight operations with helicopters due to the generally unsteady nature of the airwake and the significant variations of downwash and upwash experienced by the helicopter due to vortices and dead-air regions behind the vessel's superstructure 1,2,5,6,9,10,13 . Characterization of the ship airwake environment for safer aircraft launch and recovery is therefore a vivid area in international research, as are the operational and simulation aspects of helicopters flying in the airwakes of ships.…”

Section: Introductionmentioning

confidence: 99%

Computational ship airwake determination to support helicopter-ship dynamic interface assessment

Muijden

Boelens

Vorst

et al. 2013

21st AIAA Computational Fluid Dynamics Conference

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A highly important aspect of safe sea-based helicopter operation is the establishment of ship-helicopter operational limits for current and future helicopter/ship combinations. The capabilities of Computational Fluid Dynamics for the determination of ship airwakes have been investigated, aiming at complementing existing experimental data acquisition techniques consisting of wind tunnel and on-board full-scale measurements. In this paper, computed airwakes based on the Reynolds-averaged Navier-Stokes (RANS) equations as well as on a hybrid RANS-Large Eddy Simulation (LES) approach are compared with experimental data. The resulting airwakes have been converted for usage in a helicopter flight simulator to enable additional feed-back on the reality level of the computational approaches from experienced pilots. It is shown that, from a practical point of view, a useful first impression of the average flow characteristics in the ship airwake can be obtained from steady RANS flow modeling, although the more computationally intensive hybrid RANS-LES approach has an inherently better potential for capturing all of the physical content of the fluctuating flow fields. Nomenclature C v = ratio of local velocity to free-stream velocity, defined as (u 2 + v 2 + w 2 ) 0.5 h = characteristic mesh cell size k = turbulent kinetic energy L = reference length of the ship t = physical time t * = non-dimensional time, in CTS units u = velocity component in x-direction, scaled with U U = reference velocity of the free-stream flow v = velocity component in y-direction, scaled with U w = velocity component in z-direction, scaled with U x, y, z = orthogonal Cartesian coordinate directions β = sideslip angle of reference flow vector β local = local sideslip angle Δt = time step Δt * = non-dimensional time step = vertical deviation of local flow vector from the horizontal plane χ = horizontal deviation of local flow vector from the oncoming flow direction, β local -β ω = specific turbulent dissipation rate CFD = Computational Fluid Dynamics CFL = Courant-Friedrichs-Lewy number, stability criterion for numerical integration CTS = Convective Time Scale, defined as L/U, average time required for a fluid particle to pass the ship

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“…A parametric study using landing helicopter assault (LHA) was conducted by Polsky and Bruner (2000), who showed that the flowfield structure is insensitive to the Reynolds number within a certain range of wind speed. Comparisons of numerical methods on airwake simulation using Reynolds-averaged Navier-Stokes (RANS), Detached Eddy Simulation (DES) and hybrid RANS-LES (Large Eddy Simulation) methodologies have been performed in recent studies (Forrest & Owen, 2010;Lawson, Crozon, Dehaze, Steijl, & Barakos, 2012;Muijden, Boelens, Vorst, & Gooden, 2013;Thornber, Starr, & Drikakis, 2010). The results illustrate that the RANS solver is capable of predicting the fundamental flow characteristics of ship airwake, although there are some deficiencies in detail simulations of turbulent fluctuation.…”

Section: Introductionmentioning

confidence: 99%

“…For the numerical simulation of ship airwake, the near-wall boundary condition (y+) is usually within the range of 50 ∼ 500 (Forrest & Owen, 2010). In the calculation, y+ is set as 50 and the first wall unit value is set as 2 mm in order to meet the requirement of standard wall function in turbulence model calculation.…”

Section: Numerical Setupmentioning

confidence: 99%

An investigation of coupling ship/rotor flowfield using steady and unsteady rotor methods

Shi

Zong

et al. 2017

Engineering Applications of Computational Fluid Mechanics

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A coupling numerical methodology has been developed using the Navier-Stokes solver for ship/rotor flowfield simulation during the helicopter shipboard launch. The steady rotor model (SRM) based on the momentum source approach and unsteady rotor model (URM) based on the moving overset mesh method are respectively employed to account for rotor operations. Studies of coupling ship/rotor flowfield on two typical ships highlight complex interactions over the flight deck. It is shown that the rotor-shipboard vortex interaction and recirculation zone are more serious for small-sized-deck destroyers, while on the straight-through-deck ship the helicopter operations are sensitive to asymmetric distribution of lateral velocity caused by the island. Qualitative and quantitative comparisons in terms of vorticity and velocity between SRM and URM solvers have been conducted. The results demonstrate that both methods can capture complex interactions well. The velocity difference is within 1 m/s in most flowfield areas, except the rotor-wake dominant region. With the consideration of computational efficiency, the momentum source approach could be used to effectively conduct the study of helicopter shipboard operations. ARTICLE HISTORY

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An investigation of ship airwakes using Detached-Eddy Simulation

Cited by 119 publications

References 28 publications

Velocity Measurements in A Ship Airwake With Crosswind

Velocity Measurements in A Ship Airwake With Crosswind

Computational ship airwake determination to support helicopter-ship dynamic interface assessment

An investigation of coupling ship/rotor flowfield using steady and unsteady rotor methods

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