Projected area and drag coefficient of high velocity irregular fragments that rotate or tumble

Moxnes, John F.; Frøyland, Øyvind; Øye, Ivar J.; Brate, Tom I.; Friis, Eva; Ødegårdstuen, Gard; Risdal, Tallak Harald

doi:10.1016/j.dt.2017.03.008

Cited by 14 publications

(6 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The path of a fragment moving while being affected by drag and gravitational force can be predicted using the point mass trajectory model based on the Lord Rayleigh's drag equation [5,9,40]:…”

Section: Trajectory Model Of the Fragmentsmentioning

confidence: 99%

Dynamics of flight of the fragments with higher order Haar wavelet method

Kivistik,

Mehrparvar,

Eerme

et al. 2024

PEAS

View full text Add to dashboard Cite

Fragments that have an irregular shape and move at high speeds are difficult to assess since experiments require high-tech solutions, and the differential equations that describe the motion cannot be solved analytically. Different numerical and function approximation methods are used to find the trajectory model. This work uses a state-of-the-art, higher order Haar wavelet method to approximate the trajectory model with empirically determined drag force. The initial conditions of the flight of the fragments are determined by the finite element method. The results obtained by utilizing the Haar wavelet method and the higher order Haar wavelet method are compared. The higher order Haar wavelet method outperforms the Haar wavelet method but allows for keeping the implementation complexity of the method in the same range. Utilizing the higher order Haar wavelet method leads to a reduction in the computational cost since the same accuracy with the Haar wavelet method can be achieved with the use of several order lower mesh.

show abstract

Section: Trajectory Model Of the Fragmentsmentioning

confidence: 99%

Dynamics of flight of the fragments with higher order Haar wavelet method

Kivistik,

Mehrparvar,

Eerme

et al. 2024

PEAS

View full text Add to dashboard Cite

show abstract

“…Twisdale and Vickery (1992) applied modified cross-flow theory to develop the expression for the drag coefficient of the random orientation rectangular parallelepiped as a function of orientation angles and geometrical characteristics. Moxnes et al (2017) showed different novel analytical models for the expected projected area and drag coefficient of fragments that tumble or rotate with the rotational axis normal to the velocity vector. They forecasted a model where the expected drag coefficient depends on the shape and Mach number.…”

Section: *Aerodynamicmentioning

confidence: 99%

Wave drag coefficient of nonaxisymmetric irregular-shaped bodies

Serdarevic-Kadic¹

2022

Int. j. adv. appl. sci.

View full text Add to dashboard Cite

At high speeds, transonic and supersonic, the wave drag coefficient is a significant part of drag coefficients and it depends on the front surface shape and flow velocity. Drag, wave drag, drag coefficient, and wave drag coefficient for four bodies with the same width, height and length, and different shapes are estimated by CFD (ANSYS Fluent). For different front surface curvatures, at high flow velocity, pressure distribution on the front surface of the body, and flow field as a contour of Mach number are analyzed. The influence of front surface curvature on detached shock wave distance is determined.

show abstract

“…Initial angular velocity estimate given here is rather conservative since, as we mentioned, there are reports that initial angular velocity of HE fragments can be in order of around 23 000 rad/s (Moxnes et al, 2017).…”

Section: Flat On Flowmentioning

confidence: 99%

“…8) are determined, we obtained minimum 125 rotations of the body around the center of mass due to the initial angular velocity. Since initial angular velocities of real fragments are much higher (Moxnes et al, 2017), it is reasonable to conclude that fragments could rotate due to the initial disturbance (initial angular velocity) during its whole trajectory, since travel time of these bodies is usually very short due to their high velocities.…”

Section: Flat On Flowmentioning

confidence: 99%

“…It is important to note that research on estimate of initial angular velocity of fragments from detonating warheads is scarce. Recently Norwegian researchers (Moxnes et al, 2017) made numerical simulations of HE warhead detonation using IMPETUS Afea program, where they concluded that in their case (fragment with mass of 0,51 g) initial angular velocity of fragment was in the order of 23 000 rad/s (3650 rev/s). So significant angular velocity can be imparted to fragments in the initial stage of their flight.…”

Section: Flat On Flowmentioning

confidence: 99%

See 1 more Smart Citation

Instability estimation of irregularly shaped bodies moving through a resistive medium with high velocity

Kljuno

Catovic

2017

Int. j. adv. appl. sci.

View full text Add to dashboard Cite

The purpose of the paper was to show an idea how numerical simulations of flow around a stationary irregularly shaped body can be used to estimate instability of the body during a real-world motion of such a body (e.g. a metal fragment). To the best of our knowledge, there is no evidence that such an analysis is available in literature for irregularly shaped bodies. The novelty is in the introduced method for the stability analysis and the fact that a realworld fragment shape was digitized and used for the analysis. However, the disadvantage is in necessity that real fragments need to be scanned and digitized for the analysis, but the future work should give improvements in this direction. The focus was on the rotational part of the motion, particularly on obtaining the period of the motion when the body rotates, but the solving for angles of rotation was not the objective. We showed an idea on how to estimate the period of instability when continuous rotation occurs after the initial projection of the fragment. We assumed that relatively high angular velocity occurs at the initial condition (initial projection of the fragment), which provided an opportunity to assume further that the axis of rotation remains unchanged during the motion. By analyzing the kinetic energy of rotation, we estimated the period of body rotation until it reached a stable orientation during the high velocity motion. To employ this approach that uses the mechanical energy, it was necessary to obtain the work done by the (aerodynamic) moments of resistance forces about the center of mass. These resistance (aerodynamic) moments were obtained for various orientations of the body using simulations of fluid flow around the real geometry of the body, which was obtained by scanning a real-world fragment, digitizing it, and importing it in a CAD software, which provided the inertial properties through moments of inertia. At each rotation, the kinetic energy of rotation is dissipated through work of the aerodynamic moment which was the basis for calculation when the body takes a steady orientation for the rest of the motion.

show abstract

Projected area and drag coefficient of high velocity irregular fragments that rotate or tumble

Cited by 14 publications

References 3 publications

Dynamics of flight of the fragments with higher order Haar wavelet method

Dynamics of flight of the fragments with higher order Haar wavelet method

Wave drag coefficient of nonaxisymmetric irregular-shaped bodies

Instability estimation of irregularly shaped bodies moving through a resistive medium with high velocity

Contact Info

Product

Resources

About