scholarly journals Pre-impact dynamics of a droplet impinging on a deformable surface

2021 ◽  
Vol 33 (9) ◽  
pp. 092119
Author(s):  
Nathaniel I. J. Henman ◽  
Frank T. Smith ◽  
Manish K. Tiwari
Keyword(s):  
Impact Dynamics ◽  
Deformable Surface

scholarly journals A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear

2021 ◽  
Vol 11 (9) ◽  
pp. 4136
Author(s):  
Rosario Pecora
Keyword(s):  
Numerical Method ◽  
Initial Conditions ◽  
Impact Load ◽  
Numerical Models ◽  
Landing Gear ◽  
Design Stage ◽  
Impact Dynamics ◽  
State Variables ◽  
Adopted Model ◽  
The Impact

Oleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data.

DEFORMABLE MESH FOR AUTOMATED SURFACE EXTRACTION FROM NOISY IMAGES

2004 ◽  
Vol 04 (03) ◽  
pp. 405-432 ◽  
Author(s):  
JUSSI TOHKA ◽  
JOUNI M. MYKKÄNEN
Keyword(s):  
Global Optimization ◽  
Internal Energy ◽  
Optimization Algorithm ◽  
Automatic Segmentation ◽  
Medical Image Analysis ◽  
Surface Extraction ◽  
Deformable Surface ◽  
Surface Models ◽  
Deformable Mesh ◽  
Parameter Values

Surface extraction from noisy volumetric images is a problem commonly encountered in medical image analysis. Deformable surface models can, in principle, solve the problem in an automatic manner. However, it is often essential that a reasonably close initialization and good parameter values for deformable models are provided. In this paper, novel algorithms for global minimization of the energy of deformable meshes are presented. We demonstrate that global optimization by these algorithms reduces the sensitivity of the deformable mesh to its initialization and its parameter values. Consequently, it becomes easier to automate the initialization process and the selection of parameter values. As the second contribution, the internal energy function is derived in a novel way in the framework of deformable surface models. The construction of the internal energy in this way features a simple way to derive the variants of our global optimization algorithm. The experiments with synthetic images are performed to compare variants of the proposed optimization algorithm. Also, we present a practical application of our deformable model to automatic segmentation of positron emission tomography images.

Ball Impact Dynamics of Instep Soccer Kicking

2009 ◽  
Vol 41 (4) ◽  
pp. 889-897 ◽  
Author(s):  
HIRONARI SHINKAI ◽  
HIROYUKI NUNOME ◽  
MASANORI ISOKAWA ◽  
YASUO IKEGAMI
Keyword(s):  
Impact Dynamics ◽  
Ball Impact
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