scholarly journals Cavity Formation during Asymmetric Water Entry of Rigid Bodies

2021 ◽  
Vol 11 (5) ◽  
pp. 2029
Author(s):  
Riccardo Panciroli ◽  
Giangiacomo Minak
Keyword(s):  
Velocity Component ◽  
Water Entry ◽  
Rigid Bodies ◽  
Rigid Body Dynamics ◽  
The Body ◽  
Horizontal Velocity ◽  
Cavity Formation ◽  
Fluid Structure ◽  
Horizontal Velocity Component ◽  
The Stability

This work numerically evaluates the role of advancing velocity on the water entry of rigid wedges, highlighting its influence on the development of underpressure at the fluid–structure interface, which can eventually lead to fluid detachment or cavity formation, depending on the geometry. A coupled FEM–SPH numerical model is implemented within LS-DYNA, and three types of asymmetric impacts are treated: (I) symmetric wedges with horizontal velocity component, (II) asymmetric wedges with a pure vertical velocity component, and (III) asymmetric wedges with a horizontal velocity component. Particular attention is given to the evolution of the pressure at the fluid–structure interface and the onset of fluid detachment at the wedge tip and their effect on the rigid body dynamics. Results concerning the tilting moment generated during the water entry are presented, varying entry depth, asymmetry, and entry velocity. The presented results are important for the evaluation of the stability of the body during asymmetric slamming events.

Experimental investigation of the water entry of a rectangular plate at high horizontal velocity

2016 ◽  
Vol 799 ◽  
pp. 637-672 ◽  
Author(s):  
A. Iafrati
Keyword(s):  
Rectangular Plate ◽  
Velocity Component ◽  
Propagation Velocity ◽  
Velocity Ratio ◽  
Water Entry ◽  
The Body ◽  
Horizontal Velocity ◽  
Initial Growth ◽  
Test Conditions ◽  
Pressure Peak

The water entry of a rectangular plate with a high horizontal velocity component is investigated experimentally. The test conditions are representative of those encountered by aircraft during emergency landing on water and are given in terms of three main parameters: horizontal velocity, approach angle, i.e. vertical to horizontal velocity ratio, and pitch angle. Experimental data are presented in terms of pressure, spray root shape, pressure peak propagation velocity and total loads acting on the plate. A theoretical solution of the plate entry problem based on two-dimensional and potential flow assumptions is derived and is used to support the interpretation of the experimental measurements. The results indicate that, as the plate penetrates and the ratio between the plate breadth and the wetted length measured on the longitudinal plane diminishes, the role of the third dimension becomes dominant. The increased possibility for the liquid to escape from the lateral sides yields a reduction of the pressure peak propagation velocity and, consequently, of the corresponding pressure peak intensity. In particular, it is shown that, at the beginning of the entry process, the pressure peak moves much faster than the geometric intersection between the body and the free surface, but at a later stage the two points move along the body at the same speed. Furthermore, it is shown that the spray root develops a curved shape which is almost independent of the specific test conditions, even though the initial growth rate of the curvature is higher for larger pitch angles. The loads follow a linear increase versus time, as predicted by the theoretical model, only in a short initial stage. Next, for all test conditions examined here, they approach a square-root dependence on time. It is seen that, if the loads are scaled by the square of the velocity component normal to the plate, the data are almost independent of the test conditions.

scholarly journals B-Spline Impulse Response Functions of Rigid Bodies for Fluid-Structure Interaction Analysis

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
S. Zhou-Bowers ◽  
D. C. Rizos
Keyword(s):  
Impulse Response ◽  
Dynamic Models ◽  
Interaction Analysis ◽  
Fluid Structure Interaction ◽  
Rigid Bodies ◽  
The Body ◽  
Impulse Response Functions ◽  
Fluid Structure ◽  
B Spline ◽  
Structure Interaction

Reduced 3D dynamic fluid-structure interaction (FSI) models are proposed in this paper based on a direct time-domain B-spline boundary element method (BEM). These models are used to simulate the motion of rigid bodies in infinite or semi-infinite fluid media in real, or near real, time. B-spline impulse response function (BIRF) techniques are used within the BEM framework to compute the response of the hydrodynamic system to transient forces. Higher-order spatial and temporal discretization is used in developing the kinematic FSI model of rigid bodies and computing its BIRFs. Hydrodynamic effects on the massless rigid body generated by an arbitrary transient acceleration of the body are computed by a mere superposition of BIRFs. Finally, the dynamic models of rigid bodies including inertia effects are generated by introducing the kinematic interaction model to the governing equation of motion and solve for the response in a time-marching scheme. Verification examples are presented and demonstrate the stability, accuracy, and efficiency of the proposed technique.

Lattice Boltzmann Analysis of Fluid-Structure Interaction with Moving Boundaries

2013 ◽  
Vol 13 (3) ◽  
pp. 823-834 ◽  
Author(s):  
Alessandro De Rosis ◽  
Giacomo Falcucci ◽  
Stefano Ubertini ◽  
Francesco Ubertini ◽  
Sauro Succi
Keyword(s):  
Fluid Flow ◽  
Lattice Boltzmann ◽  
Time Discretization ◽  
Rigid Bodies ◽  
The Body ◽  
Moving Boundaries ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Body Dynamics ◽  
Boltzmann Method

AbstractThis work is concerned with the modelling of the interaction of fluid flow with flexibly supported rigid bodies. The fluid flow is modelled by Lattice-Boltzmann Method, coupled to a set of ordinary differential equations describing the dynamics of the solid body in terms its elastic and damping properties. The time discretization of the body dynamics is performed via the Time Discontinuous Galerkin Method. Several numerical examples are presented and highlight the robustness and efficiency of the proposed methodology, by means of comparisons with previously published results. The examples show that the present fluid-structure method is able to capture vortex- induced oscillations of flexibly-supported rigid body.

scholarly journals Spray deposition within plant canopies

2000 ◽  
Vol 53 ◽  
pp. 248-252 ◽  
Author(s):  
B. Richardson ◽  
M. Newton
Keyword(s):  
Velocity Component ◽  
Spray Deposition ◽  
Horizontal Velocity ◽  
Pteridium Aquilinum ◽  
Fluorescent Tracer ◽  
Bracken Fern ◽  
Plant Canopies ◽  
Plane Normal ◽  
Horizontal Velocity Component ◽  
Arctostaphylos Patula

Spray deposition was measured within canopies of bracken fern (Pteridium aquilinum) and greenleaf manzanita (Arctostaphylos patula) following ground application of a spray mixture containing water a fluorescent tracer and surfactant A high proportion of spray (3538) reached the ground through manzanita canopies whereas only 113 reached the ground through a bracken canopy Spray deposition was closely linked to the quantity of foliage projected on a plane normal to the trajectory of droplets passing through the canopy Droplets that had trajectories with a significant horizontal velocity component were more effectively captured because of an increase in the quantity of foliage in their path

scholarly journals On the Effect of Cavity Formation during the Water Entry of Flexible Bodies

2018 ◽  
Author(s):  
Riccardo Panciroli ◽  
Tiziano Pagliaroli ◽  
Giangiacomo Minak
Keyword(s):  
Fluid Motion ◽  
Free Fall ◽  
Time Frame ◽  
Water Entry ◽  
The Body ◽  
Structural Deformation ◽  
Cavity Formation ◽  
Experimental Conditions ◽  
Flexible Bodies ◽  
The Impact

Elastic bodies entering the water might experience Fluid-Structure Interaction phenomena introduced by the mutual interaction between the structural deformation and the fluid motion. Cavity formation, often misleadingly named cavitation, is one of these. This work presents the results of an experimental investigation on the water entry of deformable wedges impacting a quiescent water surface with pure vertical velocity in free fall. The experimental campaign is conducted on flexible wedges parametrically varying the flexural stiffness, deadrise angle, and drop height. It is found that under given experimental conditions cavity pockets forms beneath the wedge. Their generation mechanism is found to be ruled by a differential between structural and fluid velocities, which is introduced by the structural vibrations. Results show that the impact force during water entry of stiff bodies is always opposing gravity, while in case of flexible bodies might temporarily reverse its direction, with the body that is being sucked into the water within the time frame between the cavity formation and its collapse. Severe impacts might also generate a series of cavity generation and collapses.

Comparison of Driving Rain Index Calculated According to EN 15927-3 to the CFD Simulation and Experimental Measurement

2016 ◽  
Vol 861 ◽  
pp. 239-246 ◽  
Author(s):  
Peter Juras ◽  
Miroslav Jakubcik
Keyword(s):  
Experimental Measurement ◽  
Velocity Component ◽  
Cfd Simulation ◽  
Rain Gauge ◽  
Horizontal Velocity ◽  
Building Science ◽  
Moisture Source ◽  
Horizontal Velocity Component ◽  
Building Facades ◽  
Driving Rain

Wind-driven rain or driving rain is a rain which has given a horizontal velocity component by the wind. It can be the important moisture source for building façades and has been of the great concern in building science. In this article, the normative method described in STN EN ISO 15927-3:2009, was used for calculation of driving rain impact on vertical surfaces. This amount of rain was compared to the CFD simulation for selected location and to the experimental measurement carried out by wind-driven rain gauge.

Numerical Analysis of Fluid-Structure and Fluid-Rigid Body Interactions Using a Particle Method

2007 ◽  
Author(s):  
S. Koshizuka ◽  
K. Shibata ◽  
M. Tanaka ◽  
Y. Suzuki
Keyword(s):  
Rigid Body ◽  
Elastic Solid ◽  
Particle Method ◽  
Rigid Bodies ◽  
Rigid Body Dynamics ◽  
Volume Integral ◽  
Surface Integral ◽  
Time Step ◽  
Fluid Structure ◽  
Mps Method

An algorithm is presented for fluid-structure and fluid-rigid body interactions using a particle method. The algorithm is based on weak coupling, where fluid and solid analyses are explicitly connected in each time step. Fluid dynamics is solved by the Moving Particle Semi-implicit (MPS) method proposed by Koshizuka and Oka in 1996. Elastic solid dynamics is solved by the MPS method proposed by Song et al. in 2000. Rigid body motion is calculated by the particle method proposed by Tanaka et al. in 2007. The external force from the fluid to the rigid bodies is calculated by either volume integral or surface integral. When the volume integral is employed, both fluid and rigid bodies are calculated as fluid at first in each time step and then the rigid body dynamics is solved and the shapes are reconstructed. For fluid-elastic solid coupling, surface integral is necessary. Calculation examples using the present algorithms are shown.

scholarly journals The Stability of Solutions of Sitnikov Restricted Problem of three Bodies When the Primaries are Triaxial Rigid Bodies

2015 ◽  
Vol 19 (2) ◽  
pp. 76-78
Author(s):  
R.R. Thapa
Keyword(s):  
Restricted Problem ◽  
Principal Axis ◽  
Rigid Bodies ◽  
The Body ◽  
Stability Of Solutions ◽  
Centre Of Mass ◽  
Axis Of Symmetry ◽  
The Stability ◽  
Axes Of Symmetry ◽  
Infinitesimal Mass

The paper deals with the stability of the solutions of Sitnikov's restricted problem of three bodies if the primaries are triaxial rigid bodies. The infinitesimal mass is moving in space and is being influenced by motion of two primaries (m1>m2). They move in circular orbits without rotation around their centre of mass. Both primaries are considered as axis symmetric bodies with one of the axes as axis of symmetry whose equatorial plane coincides with motion of the plane. The synodic system of co-ordinates initially coincides with inertial system of co-ordinates. It is also supposed that initially the principal axis of the body m1 is parallel to synodic axis and are of the axes of symmetry is perpendicular to plane of motion.Journal of Institute of Science and Technology, 2014, 19(2): 76-78

scholarly journals On Air-Cavity Formation during Water Entry of Flexible Wedges

2018 ◽  
Vol 6 (4) ◽  
pp. 155 ◽  
Author(s):  
Riccardo Panciroli ◽  
Tiziano Pagliaroli ◽  
Giangiacomo Minak
Keyword(s):  
Fluid Motion ◽  
Free Fall ◽  
Time Frame ◽  
Water Entry ◽  
The Body ◽  
Structural Deformation ◽  
Cavity Formation ◽  
Experimental Conditions ◽  
Fluid Velocities ◽  
The Impact

Elastic bodies entering water might experience fluid–structure interaction phenomena introduced by the mutual interaction between structural deformation and fluid motion. Cavity formation, often misleadingly named cavitation, is one of these. This work presents the results of an experimental investigation on the water entry of deformable wedges impacting a quiescent water surface with pure vertical velocity in free fall. The experimental campaign is conducted on flexible wedges parametrically varying the flexural stiffness, deadrise angle, and drop height. It is found that, under given experimental conditions, cavity pockets form beneath the wedge. Their generation mechanism might be ascribed to a differential between structural and fluid velocities, which is introduced by structural vibrations. Results show that the impact force during water entry of stiff wedges are always opposing gravity, while, in case flexible wedges temporarily reverse their direction, with the body that is being sucked into the water within the time frame between the cavity formation and its collapse. Severe impact might also generate a series of cavity generation and collapses.

On Singularity of Rigid-Body Dynamics Using Quaternion-Based Models

2012 ◽  
Vol 79 (2) ◽  
Author(s):  
Homin Choi ◽  
Bingen Yang
Keyword(s):  
Dynamic Response ◽  
Rigid Body ◽  
Dynamic Modeling ◽  
Degrees Of Freedom ◽  
Rigid Bodies ◽  
Rigid Body Dynamics ◽  
The Body ◽  
Applied Torque ◽  
Body Dynamics

It is well known that use of quaternions in dynamic modeling of rigid bodies can avoid the singularity due to Euler rotations. This paper shows that the dynamic response of a rigid body modeled by quaternions may become unbounded when a torque is applied to the body. A theorem is derived, relating the singularity to the axes of the rotation and applied torque, and to the degrees of freedom of the body in rotation. To avoid such singularity, a method of equivalent couples is proposed.

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