A Conservative Overset Mesh Scheme via Intergrid Boundary Reconnection on Unstructured Meshes

Numerical simulation of unsteady flows around a complete helicopter was conducted, and the effect of rotor downwash on the behavior of free-flight rockets air-launched from the helicopter and their plume was investigated. For this purpose, a three-dimensional inviscid flow solver based on unstructured meshes was developed, and an overset mesh technique was adopted to handle the relative motion of the main rotor, tail rotor, fuselage, and traveling rockets. The flow solver was coupled with six-degrees-of-freedom equations of motion to describe the trajectory of the free-flight rockets. To validate the flow solver for simulating the plume flow from the rocket nozzle, calculations were made for a jet flow impinging on flat plates. To demonstrate the accuracy of the flow solver for predicting rotor downwash, a rotor-fuselage aerodynamic interaction flow was calculated, and the results were compared with available experimental data. The trajectory simulation of an external store released from a fixed wing was also performed to validate the present flow solver coupled with the six-degrees-of-freedom equations of motion. Then the present method was applied to the simulation of free-flight rockets air-launched from a complete helicopter configuration. It was found that rotor downwash has nonnegligible effects on the trajectory of the air-launched rockets and their plume development, which may potentially affect the safety and the reliability of other equipments installed on the mother helicopter.Nomenclature A e = area of the rocket nozzle exit A 0 = collective pitch angle A 1 = longitudinal cyclic pitch angle B 1 = lateral cyclic pitch angle= mass flow rate at the rocket nozzle exit p e = pressure at the rocket nozzle exit p 1 = pressure of free stream Q = solution vector of the conservative variables R = rotor radius T = temperature U e = velocity at the rocket nozzle exit u, v, w = Cartesian velocity components x, y, z = Cartesian coordinate directions i = induced inflow normal to tip-path plane = advancing ratio i = induced inflow parallel to tip-path plane = density = solidity of rotor blade = azimuth angle

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Section: Unstructured Overset Mesh Techniquementioning

confidence: 99%

Numerical Simulation of Free-Flight Rockets Air-Launched From a Helicopter

Lee

Choi

Kwon

2011

Journal of Aircraft

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“…For unstructured meshes, the search should be performed for all nodes of all mesh blocks, because the nodes and the cells are randomly distributed. To overcome the large computational overhead involved in this search process, a fast and robust neighbor-to-neighbor search technique was implemented by utilizing the property of the linear shape functions [14]. Under parallel computing environment, the search may develop across the subdomain block boundary, and the amount of data information assigned to each processor may change at each iteration.…”

Section: Unstructured Overset Mesh Techniquementioning

confidence: 99%

Numerical Simulation of Rotor-Fuselage Aerodynamic Interaction Using an Unstructured Overset Mesh Technique

Lee¹,

Jung²,

Kwon³

et al. 2010

International Journal of Aeronautical and Space Sciences

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Numerical simulation of unsteady flows around helicopters was conducted to investigate the aerodynamic interaction of main rotor and other components such as fuselage and tail rotor. For this purpose, a three-dimensional inviscid flow solver has been developed based on unstructured meshes. An overset mesh technique was used to describe the relative motion between the main rotor, and other components. As the application of the present method, calculations were made for the rotorfuselage aerodynamic interaction of the ROBIN (ROtor Body INteraction) configuration and for a complete UH-60 helicopter configuration consisted of main rotor, fuselage, and tail rotor. Comparison of the computational results was made with measured time-averaged and instantaneous fuselage surface pressure distributions for the ROBIN configuration and thrust distribution and available experimental data for the UH-60 configuration. It is demonstrated that the present method is efficient and robust for the simulation of complete rotorcraft configurations.

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“…The coupling procedures are quite well developed for unstructured solvers, which allow a number of different strategies, including mesh reconstruction. Economon et al (2013) and Jung and Kwon (2009) describe a conservative scheme with mesh reconstruction as well. When structured solvers are considered, it seems that conservative flux-based techniques were applied in the past to a limited amount of test cases, and a coupling procedure suitable for generic three-dimensional (3D) sliding meshes was never discussed.…”

Section: Introductionmentioning

confidence: 99%

A conservative sliding mesh coupling procedure for U-RANS flow simulations

Vitagliano

Minervino

Quagliarella

et al. 2016

Aircraft Eng & Aerospace Tech

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Purpose-Simulate unsteady flows with surfaces in relative motion using a multi-block structured flow solver. Design/methodology/approach-A procedure for simulating unsteady flows with surfaces in relative motion was developed, based upon a structured multi-block U-RANS flow solver1. Meshes produced in zones of the flow field with different rotation speed are connected by sliding boundaries. The procedure developed guarantees that the flux conservation properties of the original scheme are maintained across the sliding boundaries during the rotation at every time step. Findings-The solver turns out to be very efficient, allowing computation in scalar mode with single core processors as well as in parallel. It was tested by simulating the unsteady flow on a prop fan configuration with two counter-rotating rotors. The comparison of results and performances with respect to an existing commercial flow solver (unstructured) are reported. Originality/value-This paper fulfils an identified need to allow for efficient unsteady flow computations (structured solver) with different bodies in relative motion.

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A Conservative Overset Mesh Scheme via Intergrid Boundary Reconnection on Unstructured Meshes

Cited by 5 publications

References 20 publications

Numerical Simulation of Free-Flight Rockets Air-Launched From a Helicopter

Numerical Simulation of Free-Flight Rockets Air-Launched From a Helicopter

Numerical Simulation of Rotor-Fuselage Aerodynamic Interaction Using an Unstructured Overset Mesh Technique

A conservative sliding mesh coupling procedure for U-RANS flow simulations

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