Verification of a Constraint Force Equation Methodology for Modeling Multi-Body Stage Separation

Tartabini, Paul V.; Roithmayr, Carlos M.; Toniolo, Matthew D.; Karlgaard, Christopher D.; Pamadi, Bandu N.

doi:10.2514/6.2008-7039

Cited by 6 publications

(4 citation statements)

References 13 publications

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“…The ρij vector defines the j th joint connection position relative to the center of mass of vehicle i. Details regarding the formulations are available in the literature [17,18].…”

Section:   mentioning

confidence: 99%

Strap-On Boosters Separation Analysis Using Coupled Simulation of Constraint Dynamics and Time Dependent CFD

Jafari¹,

Toloei²

2022

JSST

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A numerical dynamic-aerodynamic interface for simulating the separation dynamics of constrained strap-on boosters jettisoned in the atmosphere is presented in this paper. Two commercial solvers: a 6DOF multi-body dynamic solver and a numerical time-dependent flow solver are integrated together with an interface code to constitute a package that presents realtime dynamic/aerodynamic coupled analysis. Dynamic unstructured mesh approach is employed using local remeshing methods in respect of bodies' motion with a second-order upwind accurate 3D Euler solver. This interface can simulate the interaction of multi body separation dynamics with aerodynamic effects to complete separation mechanisms like springs, thrusters, joints, and so on. The flow solver is validated by the Titan IV launch vehicle experimental data. The separation integration is used for a typical launch vehicle with two strap-on boosters using spring ejector mechanism and spherical constraint joints acting in the dense atmosphere. Hence, the aim of the presented interface is to facilitate the integration of complicated separation mechanisms with a full numerical CFD aerodynamic solver.

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“…The ρij vector defines the j th joint connection position relative to the center of mass of vehicle i. Details regarding the formulations are available in the literature [17,18].…”

Section:   mentioning

confidence: 99%

Strap-On Boosters Separation Analysis Using Coupled Simulation of Constraint Dynamics and Time Dependent CFD

Jafari¹,

Toloei²

2022

JSST

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“…Although CFE is in wide using for various types of multibody mechanisms under different initial and boundary conditions, the main disadvantage of that is the external forces applying on a mechanism should be determined during the procedure as a known function and cannot be dependent on the spatial location of each part/component of a multibody mechanism. The constraint forces in the CFE method are computed based on the external forces, so the values of external forces should be known independent of the spatial positions, which is in contrast with the usual performance of the ANSYS Fluent ® software, where the external forces at each moment are estimated by the spatial position of the mechanism and complex numerical analysis corresponding to finite element method (FEM) and computational fluid dynamics (CFD) [12][13][14]. Therefore, using CFE seems costly as it needs to be performed in two different software, one for dynamic coupling, e.g., Matlab ® (MathWorks, Natick, MA, USA) and one for solving aerodynamic equations and simulating the multibody system, e.g., ANSYS Fluent ® (ANSYS Fluent ® Software: CFD Simulation, Canonsburg, PA, USA).…”

Section: Introductionmentioning

confidence: 99%

A Nonlinear CFD/Multibody Incremental-Dynamic Model for A Constrained Mechanism

Rahmati

Karimi

2021

Applied Sciences

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Numerical analysis of a multibody mechanism moving in the air is a complicated problem in computational fluid dynamics (CFD). Analyzing the motion of a multibody mechanism in a commercial CFD software, i.e., ANSYS Fluent®, is a challenging issue. This is because the components of a mechanism have to be constrained next to each other during the movement in the air to have a reliable numerical aerodynamics simulation. However, such constraints cannot be numerically modeled in a commercial CFD software, and needs to be separately incorporated into models through the programming environment, such as user-defined functions (UDF). This study proposes a nonlinear-incremental dynamic CFD/multibody method to simulate constrained multibody mechanisms in the air using UDF of ANSYS Fluent®. To testify the accuracy of the proposed method, Newton–Euler dynamic equations for a two-link mechanism are solved using Matlab® ordinary differential equations (ODEs), and the numerical results for the constrained mechanisms are compared. The UDF results of ANSYS Fluent® shows good agreement with Matlab®, and can be applied to constrained multibody mechanisms moving in the air. The proposed UDF of ANSYS Fluent® calculates the aerodynamic forces of a flying multibody mechanism in the air for a low simulation cost than the constraint force equation (CFE) method. The results could have implications in designing and analyzing flying robots to help human rescue teams, and nonlinear dynamic analyses of the aerodynamic forces applying on a moving object in the air, such as airplanes, birds, flies, etc.

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“…where T  is the total angle of attack of the aeroshell, Using equations [5] and [6], the pre-flight aerodynamic model, and assuming the point of rotation lies at the midpoint of the inner-most torus on the axis of symmetry, a deflection of 3.75 deg is required for an aeroshell trim angle of attack of 5 deg.…”

Section: Trim Angle Of Attackmentioning

confidence: 99%

“…The connection between the two parts was modeled as a spherical joint with torsional stiffness and freeplay modeled in thee axes. The constraints equations associated with this idealized joint are enforced by using the constraint force equation (CFE) methodology 4,5,6 , which provides a framework for adding joint modeling capabilities to the POST2 simulation framework. CFE computes the forces and moments required to maintain user-specified kinematical constraints acting between POST2 vehicles (in this case two parts of the same vehicle).…”

Section: Irve-ii Model Reconciliationmentioning

confidence: 99%