Computation of steady and unsteady vortex dominated flows

Kandil, Osama A.; Chuang, Andrew H.

doi:10.2514/6.1987-1462

Cited by 8 publications

(3 citation statements)

References 9 publications

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“…Its advantage is that the same relative position between each object of the helicopter in the reference frame simplifies grid generation, but the governing equations become too complex during coordinate transformation. 17,18) In particular, the energy equations, which should be rearranged for a rotating coordinate system, produce too many terms to implement for numerical code. The second uses a translating reference frame with rotating object as shown in Fig.…”

Section: Coordinate Framesmentioning

confidence: 99%

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Numerical Analysis of Maneuvering Rotorcraft Using Moving Overlapped Grid Method

Yang

Aoyama

2008

Trans. Japan Soc. Aero. S Sci.

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In transient flight, rotor wakes and tip vortex generated by unsteady blade air-loads and blade motions are fully unsteady and 3-dimensionally-aperiodic, giving rise to significant complicity in accurate analysis compared to steady flight. We propose a hybrid approach by splitting the motions of a maneuvering helicopter into translation and rotation. Translation is simulated using a non-inertial moving (translating) coordinate for which new governing equations are derived, and rotations are simulated by moving each grid in the frame. A flow simulation (CFD) code is constructed by using the hybrid approach, then two simple cases (accelerating/decelerating flight and right-turn flight) for maneuvering helicopter are calculated using the moving overlapped grid method, which is now one of the most advanced techniques for tip-vortex capture. The vortex bundling phenomena, which is a main characteristic of right-turn flight, is well captured by the simulation code. The results of the present study provide better understanding of the characteristics for maneuvering rotorcraft, which can be valuable in full helicopter design.Key Words: Rotor Wake, Maneuver, CFD, Overlapped Grid System Nomenclaturẽ V V: absolute velocity in inertial frame XYZ V V r : relative velocity in non-inertial frame xyz V V t : translation velocity of origin of xyz V V T : transformation velocity of xyz from absolute to relative

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Section: Coordinate Framesmentioning

confidence: 99%

“…Then, the governing equations above are modified for coordinates fixed to a rotating rotor blade of the helicopter during hovering or level flight, which is accelerating relative to the fixed coordinates. In this case, the governing equations are expressed as follows: 17) Continuity:…”

Section: Coordinate Framesmentioning

confidence: 99%

Numerical Analysis of Maneuvering Rotorcraft Using Moving Overlapped Grid Method

Yang

Aoyama

2008

Trans. Japan Soc. Aero. S Sci.

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“…Whenever the mesh distortion reaches a specified value which the solver cannot handle, the solution is proceeds by generating a new local mesh automatically and the solutions on the new mesh are calculated. When the moving the body reaches a position sufficiently far from the effect of the fixed body, our parallel solver (FAPeda) [3] automatically switches itself to the relative coordinate solution [4][5]. In this way, there is no need for either deforming mesh or blanking and remeshing.…”

Section: Introductionmentioning

confidence: 99%

An Approach for Parallel CFD Solutions of Store Separation Problems

Oktay¹,

Merttopçuoglu

Akay

2008

Lecture Notes in Computational Science and Engineering

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A new fast and accurate parallel algorithm is developed for solution of moving body problems, with specific reference to store separation problems. The algorithm starts with the development of separate meshes for the moving body (store) and the aircraft wing, which are then connected by using mesh blanking and mesh filling algorithms automatically. Following the partitioning of the connected meshes for parallel computing and obtaining a steady state flow solution, the separation starts by using a dynamically deforming mesh algorithm coupled with the six-degree of freedom rigid body dynamics equations for the store. The solutions continue until severe mesh distortions are reached after which automatic remeshing and partitioning are done on a new mesh obtained by blanking and filling operations to continue with the solutions. As the store reaches far enough distances from the aircraft, the algorithm switches to a relative coordinates eliminating any need for mesh deformations and remeshing. The developed algorithms and the results are discussed with a sample problem, including the parallel efficiency on distributed computers.

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Results from a conical Euler methodology developed for unsteady vortical flows

Lee

Batina

1993

AIAA Journal

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Computation of steady and unsteady vortex dominated flows

Cited by 8 publications

References 9 publications

Numerical Analysis of Maneuvering Rotorcraft Using Moving Overlapped Grid Method

Numerical Analysis of Maneuvering Rotorcraft Using Moving Overlapped Grid Method

An Approach for Parallel CFD Solutions of Store Separation Problems

Results from a conical Euler methodology developed for unsteady vortical flows

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