Simulation of Pilot Control Activity During Helicopter Shipboard Operations

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

Burks

2013

This paper provides current results of a multi-year research project that involves the systematic investigation of ship air wakes using an instrumented United States Naval Academy (USNA) YP (Patrol Craft, Training). The objective is to validate and improveComputational Fluid Dynamics (CFD) tools that will be useful in determining ship air wake impact on naval rotary wing vehicles. This project is funded by the Office of Naval Research and includes extensive coordination with Naval Air Systems Command. Currently, ship launch and recovery wind limits and envelopes for helicopters are primarily determined through at-sea in situ flight testing that is expensive and frequently difficult to schedule and complete. The time consuming and potentially risky flight testing is required, in part, because computational tools are not mature enough to adequately predict air flow and wake data in the lee of a ship with a complex superstructure. The top-side configuration of USNA YPs is similar to that of a destroyer or cruiser, and their size (length of 108 ft and above waterline height of 24 ft) allows for collection of air wake data with a Reynolds number that is the same order of magnitude as that of modern naval warships, an important consideration in aerodynamic modeling. A dedicated YP has been modified to add a flight deck and hangar-like structure to produce an air wake similar to that from a modern destroyer. Three-axis acoustic anemometers have been installed at various locations, including a large vertical array on the ship's bow to measure atmospheric boundary layers. Repeated testing on the modified YP is being conducted in the Chesapeake Bay, which allows for the collection of data over a wide range of wind conditions. Additionally, a 4% scale model of the modified YP has been constructed and tested in the USNA recirculating wind tunnel. Comparison of YP in situ data with similar data from wind tunnel testing and CFD simulations shows reasonable agreement for a headwind condition and for relative winds 15° and 30° off the starboard bow. Analysis also indicates that CFD simulations require modeling the velocity profile in the atmospheric boundary layer to improve simulation accuracy. Finally, off-ship turbulence data collected using an instrumented 4.5 ft rotor diameter radio controlled helicopter show that the detected off-ship air wake is present where predicted by CFD simulations.

Section: Introductionmentioning

confidence: 99%

Validation of Computational Ship Air Wakes for a Naval Research Vessel

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

Burks

2013

“…However, validation of the CFD tools has proven challenging, and often it has been hard to reconcile CFD, full-scale in-situ testing, and wind tunnel results. [8][9][10][11] The air wakes of ships that deploy aircraft have been the subject of numerous research programs with the central focus to quantify the flowfield along the aircraft approach paths. Subtle changes and protuberances in hull/deck/superstructure can have significant changes in the external flow characteristics and these flow features can be severe.…”

Section: Introductionmentioning

confidence: 99%

Ship Air Wake Wind Tunnel Test Results (Invited)

Miklosovic

29th AIAA Applied Aerodynamics Conference

2011

As part of a larger program to develop analytic and computational tools to predict the air wake characteristics of naval vessels, an experimental effort has been undertaken to map the air wake of a scaled patrol craft modified with a representative hangar structure and stern flight deck. A 4% scaled model of a United States Naval Academy YP (Patrol Craft, Training) was fabricated for wind tunnel testing at 0, 15, and 30 degrees of yaw at a Reynolds number of 7.6 million. The topside configuration of the vessel simulates that of larger destroyers and cruisers, which service rotorcraft from stern hangars and flight decks. Flow measurements were made in station planes from 0.45 to 5.14 hangar-heights downstream of the aft hangar face using an 18-hole Omniprobe. The 3D velocity measurements indicated that a recirculation zone occurred over the flight deck and extended from 1.5-3 hangar-heights downstream. The effect of yaw angle on the air wake was to consolidate and shift the rotationality of the flow into a large, leeward vortex with a size on the order of the superstructure height. Furthermore, the unsteadiness of the flow was independent of the survey plane position at zero yaw, but increased by 57% at 30 deg yaw, with a large band of high vorticity where the shear layer separated and rolled up. The velocity distributions, flow angles, and vorticity will be used to compare with computational fluid dynamics (CFD) and full-scale, in-situ measurements to portray a complete, Reynoldsscaled picture of the air wake. NomenclatureCCWT = closed-circuit wind tunnel CFD = computational fluid dynamics CG = guided missile cruiser CVN = multi-purpose aircraft carrier (nuclear) DDG = guided missile destroyer ESP = electronically-scanned pressure H = hangar reference height  = model reference length LHA = amphibious assault ship (general purpose) p = fluid pressure q = dynamic pressure, ( ) 2 2 V ρ T = fluid temperature U = Measurement uncertainty estimate V  = velocity vector V = velocity magnitude u = x-component of velocity v = y-component of velocity w = z-component of velocity x = distance aft of the hangar face y = distance starboard of the vessel centerline z = distance above the flight deck surface 2 WISP = wake interactive survey probe YP = Naval class designation for "patrol craft, training" Greek α = flow pitch angle β = flow yaw angle δ = probe bias error ∆ = differential ε = test section blockage correction factor ζ  = vorticity, V ∇ ×  ρ = fluid density ω  = angular velocity, 2 ζ  Subscripts corr = measurement corrected for bias error p ∆ = pertaining to probe pressure differential probe = measurement referenced to probe position and mount orientation T = stagnation (total) condition V = pertaining to velocity SB = solid blockage WB = wake blockage ∞ = freestream condition

“…The risk and cost could be mitigated through the use of computational tools, but current methods are insufficiently validated for ships with a complex superstructure, such as a destroyer, cruiser or Littoral Combat Ship (LCS). [2][3][4][5][6][7][8][9] This paper presents an update of a multiyear project to develop and validate Computational Fluid Dynamics (CFD) tools to reduce the amount of at-sea in situ flight testing required and make rotary wing launch and recovery envelope expansion safer, more efficient, and affordable.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Experimental and Computational Ship Air Wakes for YP Class Patrol Craft

AIAA Centennial of Naval Aviation Forum "100 Years of Achievement and Progress"

2011

This paper provides second year results from a multi-year research project that involves a systematic investigation of ship air wakes using an instrumented United States Naval Academy (USNA) YP (Patrol Craft, Training). The objective is to validate and improve Computational Fluid Dynamics (CFD) tools that will be useful in determining ship air wake impact on naval rotary wing vehicles. This project is funded by the Office of Naval Research and includes extensive coordination with Naval Air Systems Command. Currently, ship launch and recovery wind limits and envelopes for helicopters are primarily determined through at-sea in situ flight testing that is expensive and frequently difficult to schedule and complete. The time consuming and potentially risky flight testing is required, in part, because computational tools are not mature enough to adequately predict air flow and wake data in the lee of a ship with a complex superstructure. The top-side configuration of USNA YPs is similar to that of a destroyer or cruiser, and their size (length of 108 ft and above waterline height of 24 ft) allows for collection of air wake data that is in the same order of magnitude as that of modern naval warships, an important consideration in aerodynamic modeling. A dedicated YP has been modified to add a flight deck and hangar structure to produce an air wake similar to that on a modern destroyer. Three axis acoustic anemometers, fog generators and an Inertial Measurement Unit (IMU) have been installed. Repeated testing on the modified YP is being conducted in the Chesapeake Bay, which allows for the collection of data over a wide range of wind conditions.Additionally, a scale model of the modified YP has been constructed for testing in the 42×60×102 inch USNA wind tunnel. Significant wind tunnel measurements are scheduled for fall 2010. Comparison of YP in situ test data with wind tunnel data will be useful for validation of wind tunnel test methods and scale effects, as well as CFD models that could help predict ship air wake effects. The project involves USNA midshipmen who are participating in test planning, collecting and analyzing data, and in CFD modeling, providing the midshipmen with valuable professional and research experience. Additionally, the flight deck has been designed to allow operation of a 400-500 lb class rotary wing Unmanned Aerial Vehicle for direct measurement of the dynamic interface between the ship and helicopter.Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents ...