Time-accurate CFD predictions for the JDAM separation from an F-18C aircraft

Sickles, W. L.; Denny, A.; Nichols, R.

doi:10.2514/6.2000-796

Cited by 27 publications

(9 citation statements)

References 10 publications

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“…The time-accurate computational fluid dynamics (CFD) technique is often used to predict store separation events [8][9][10][11]. The CHIMERA scheme [12] is ideally suited to perform calculations with moving bodies.…”

Section: Nomenclaturementioning

confidence: 99%

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Prediction of Ballistic Separation Effect by Direct Calculation of Incremental Coefficients

Kim

Kwon

Park

2010

Journal of Aircraft

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The ballistic separation effect in an aircraft flowfield was predicted via the direct calculation of incremental coefficients. A highly robust flow solver, including a Chimera grid module, was used to create the trajectory of a released store and to calculate incremental coefficients. The incremental coefficients were computed according to the difference between the aerodynamic coefficients in the aircraft flowfield and in the freestream condition. Two different calculations can be executed simultaneously in a parallel computing environment. The aircraft flowfield effect was measured using the incremental coefficients. This method of direct calculation of the incremental coefficients was tested in the case of released stores in two-dimensional subsonic and supersonic flow regions. The accuracy of the unsteady trajectory calculation was verified through comparisons with the captive trajectory system data in the Eglin wing/pylon/store separation problem. The method was then applied to a generic bomb released from a full-body aircraft. The computational results show that the current method is capable of simulating the store trajectory and investigating aircraft flowfield effects. NomenclatureC l , C m , C n = store rolling, pitching, and yawing moment coefficients= contravariant velocities along the generalized coordinates U g = grid velocity u, v, w = Cartesian velocity components C x = incremental force coefficient in the x direction , p, e = density, pressure, and total energy , , = roll, yaw, and pitch angles

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Section: Nomenclaturementioning

confidence: 99%

“…The calculation of the aerodynamic load is fully coupled with the dynamics of the released bomb. This technique is commonly applied to short-range predictions after separation due to its high computing cost [9][10][11]. Recent advances in computing environments have increased the reliance of CFD methods to simulate store separations.…”

Section: Nomenclaturementioning

confidence: 99%

Prediction of Ballistic Separation Effect by Direct Calculation of Incremental Coefficients

Kim

Kwon

Park

2010

Journal of Aircraft

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“…Furthermore, in many publications of this type, strict validations against experiments are lacking. Based on these observations, a different approach was taken in the current study: rather than using computational fluid dynamics (CFD) to create a few time-accurate trajectories, similar to those of captive trajectory system (CTS) testing [5], an aerodynamic database of quasi-static solutions was created, in order to "fly" the nose shroud through the flowfield. This allows the simulation of virtually unlimited trajectories offline, including parametric studies, with merely a six-degree-of-freedom (DOF) code.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Shroud Release Applied for High-Velocity Missiles

Dagan

Arad

2014

Journal of Spacecraft and Rockets

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A detachable missile nose was designed, tested, and implemented in a new missile. This design enables the use of lowdrag supersonic configurations for the major part of the flight, with the application of blunt seekers that are active during the end game. The configuration of the ejected shroud was designed using a novel approach, which included only a small amount of wind-tunnel experiments, coupled with an aerodynamic model produced by computational fluid dynamics. A simulation of flow dynamics, coupled with rigid-body dynamics, was developed and tested. Databases of aerodynamic forces and moments were produced using quasi-steady computations, for hinged and free flight of the shroud, at very demanding conditions of supersonic flight and large angles of attack. These databases were used by rigid-body dynamic simulations, in one-and six-degree-of-freedom modes, in order to predict the shroud's trajectories. Very good agreement with experimental data has been achieved. The present methodology enabled the analysis of hundreds of trajectories at a reasonable computation effort.Nomenclature CD 0 = zero-lift drag coefficient Cm x , Cm y , Cm z = roll, pitch, and yaw-moment coefficients C x , C y , C z = axial, side, and normal force coefficients D = missile base diameter, m F x , F y , F z = axial, side, and normal forces, N I b = moment of inertia with respect to center of gravity, N · m 2 L, M, N = roll, pitch, and yaw moment about the center of gravity, N · m L∕D = projectile length to diameter ratio l = shroud length, m m = total mass of a shroud half, kg p, q, r = angular velocity in roll, pitch, and yaw, rad∕s t ref = reference time scale, s V b = velocity vector of the shroud in a coordinates system attached to the missile, m∕s w = induced wind velocity, m∕s x, z = axial and normal coordinate, m X cg , Z cg = center of gravity location measured from the nose tip, m X NP = center of pressure location measured from the nose tip, m α, β = angle of attack and side-slip angle, deg θ = deflection angle, deg _ θ 0 = initial angular deflection velocity, rad∕s ω = angular velocity vector in a missile's attached coordinate system, rad∕s

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“…Cenko [7,8]) . The JDAM separation provides an attractive demonstration case because it contains a complex aircraft geometry, flight telemetry and photographic-derived quantitative data, and also because it has been simulated by numerous other CFD methods [9][10][11][12][13][14][15]. These previous CFD simulations can be broken into two broad classes; those which computed a set of static solutions which were used with a store trajectory simulation package, and those which computed the trajectory of the store within the CFD simulation process.…”

Section: Introductionmentioning

confidence: 99%

Simulations of 6-DOF Motion with a Cartesian Method

Murman

Aftosmis

Berger

et al. 2003

41st Aerospace Sciences Meeting and Exhibit

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Coupled 6-DOF/CFD trajectory predictions using an automated Cartesian method are demonstrated by simulating a GBU-31/JDAM store separating from an F/A-18C aircraft. Numerical simulations are performed at two Mach numbers near the sonic speed, and compared with flight-test telemetry and photographic-derived data. For both Mach numbers, simulation results using a sequential-static series of flow solutions are contrasted with results using a time-dependent approach. Both numerical approaches show good agreement with the flight-test data through the first 0.25 seconds of the trajectory. At later times the sequential-static and time-dependent methods diverge, after the store produces peak angular rates, however both remain close to the flight-test trajectory. A computational cost comparison for the Cartesian method is included, in terms of absolute CPU time, and relative to computing uncoupled 6-DOF trajectories through a pre-computed matrix of simulations. A detailed description of the 6-DOF method is provided in an appendix, along with verification studies confirming its numerical accuracy.

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Time-accurate CFD predictions for the JDAM separation from an F-18C aircraft

Cited by 27 publications

References 10 publications

Prediction of Ballistic Separation Effect by Direct Calculation of Incremental Coefficients

Prediction of Ballistic Separation Effect by Direct Calculation of Incremental Coefficients

Analysis of Shroud Release Applied for High-Velocity Missiles

Simulations of 6-DOF Motion with a Cartesian Method

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