The Use of Advanced Transient Structural Codes to Study Interior Gun Dynamics

1991 ◽  
Author(s):  
Stephen Wilkerson
Keyword(s):  
Kinetic Energy ◽  
Boundary Conditions ◽  
Numerical Models ◽  
Three Dimensional ◽  
Numerical Results ◽  
Numerical Techniques ◽  
Modeling Process ◽  
Numerical Studies ◽  
Areas Of Concern

Abstract Three-dimensional numerical models used to analyze the in-bore dynamics of kinetic energy projectiles are presented. The intricate modeling process, boundary conditions, and assumptions used in the analysis are given. Numerical results are analyzed and presented to show the importance of three-dimensional numerical studies. Finally possible areas of concern and future improvements in the numerical techniques used are reviewed.

Long-term thermal two- and three-dimensional analysis of roller compacted concrete dams supported by monitoring verification

2010 ◽  
Vol 37 (4) ◽  
pp. 600-610 ◽  
Author(s):  
Vladan Kuzmanovic ◽  
Ljubodrag Savic ◽  
John Stefanakos
Keyword(s):  
Thermal Analysis ◽  
Boundary Conditions ◽  
Thermal Field ◽  
Numerical Models ◽  
Three Dimensional ◽  
Roller Compacted Concrete ◽  
Rcc Dam ◽  
Field Investigations ◽  
Good Agreement

This paper presents two-dimensional (2D) and three-dimensional (3D) numerical models for unsteady phased thermal analysis of RCC dams. The time evolution of a thermal field has been modeled using the actual dam shape, RCC technology and the adequate description of material properties. Model calibration and verification has been done based on the field investigations of the Platanovryssi dam, the highest RCC dam in Europe. The results of a long-term thermal analysis, with actual initial and boundary conditions, have shown a good agreement with the observed temperatures. The influence of relevant parameters on the thermal field of RCC dams has been analyzed. It is concluded that the 2D model is appropriate for the thermal phased analysis, and that the boundary conditions and the mixture properties are the most influential on the RCC dam thermal behavior.

An analytical model for the rotational behavior of concrete segmental joints with gaskets

2019 ◽  
Vol 22 (13) ◽  
pp. 2866-2881 ◽  
Author(s):  
Fan Yang ◽  
Shengrong Cao ◽  
Qingbin Li
Keyword(s):  
Analytical Model ◽  
Numerical Models ◽  
Three Dimensional ◽  
Numerical Results ◽  
Rotational Behavior ◽  
Rotational Stiffness ◽  
Bending Tests ◽  
Tightening Force ◽  
Analytical Results ◽  
Joint Section

To investigate the rotational behavior of concrete segmental joints with gaskets, bending tests are performed by detailed three-dimensional continuum numerical models for joints with and without gaskets. Based on the numerical results, an analytical model is proposed to analyze the rotational stiffness of the segmental joint and extend the simulation with related parametric studies. The bending tests reveal that the rotational behavior of the segmental joint with gaskets can be divided into four stages for both the sagging and hogging moment cases. The analytical results reveal that the sealing gasket has little influence on the joint rotational behavior, while the elastic gasket has a significant effect of reducing the joint rotational stiffness. Besides, the rotational behavior of the joint with gaskets is affected by the axial force and the bolt pre-tightening force to a certain degree. The proposed analytical model allows the effect of the properties of bolts and various gaskets, the concrete contact force, the geometry of the joint section, and the subjected loads to be taken into consideration. The analytical results are well consistent with the numerical results, and the analytical model can be adopted for simulation of the segmental joint with various gaskets.

scholarly journals Fixed Grid Numerical Models for Solidification and Melting of Phase Change Materials (PCMs)

2019 ◽  
Vol 9 (20) ◽  
pp. 4334 ◽  
Author(s):  
José Henrique Nazzi Ehms ◽  
Rejane De Césaro Oliveski ◽  
Luiz Alberto Oliveira Rocha ◽  
Cesare Biserni ◽  
Massimo Garai
Keyword(s):  
Numerical Model ◽  
Boundary Conditions ◽  
Phase Change ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Source Term ◽  
Numerical Models ◽  
Fixed Grid ◽  
Numerical Studies ◽  
The Impact

Phase change materials (PCMs) are classified according to their phase change process, temperature, and composition. The utilization of PCMs lies mainly in the field of solar energy and building applications as well as in industrial processes. The main advantage of such materials is the use of latent heat, which allows the storage of a large amount of thermal energy with small temperature variation, improving the energy efficiency of the system. The study of PCMs using computational fluid dynamics (CFD) is widespread and has been documented in several papers, following the tendency that CFD nowadays tends to become increasingly widespread. Numerical studies of solidification and melting processes use a combination of formulations to describe the physical phenomena related to such processes, these being mainly the latent heat and the velocity transition between the liquid and the solid phases. The methods used to describe the latent heat are divided into three main groups: source term methods (E-STM), enthalpy methods (E-EM), and temperature-transforming models (E-TTM). The description of the velocity transition is, in turn, divided into three main groups: switch-off methods (SOM), source term methods (STM), and variable viscosity methods (VVM). Since a full numerical model uses a combination of at least one of the methods for each phenomenon, several combinations are possible. The main objective of the present paper was to review the numerical approaches used to describe solidification and melting processes in fixed grid models. In the first part of the present review, we focus on the PCM classification and applications, as well as analyze the main features of solidification and melting processes in different container shapes and boundary conditions. Regarding numerical models adopted in phase-change processes, the review is focused on the fixed grid methods used to describe both latent heat and velocity transition between the phases. Additionally, we discuss the most common simplifications and boundary conditions used when studying solidification and melting processes, as well as the impact of such simplifications on computational cost. Afterwards, we compare the combinations of formulations used in numerical studies of solidification and melting processes, concluding that “enthalpy–porosity” is the most widespread numerical model used in PCM studies. Moreover, several combinations of formulations are barely explored. Regarding the simulation performance, we also show a new basic method that can be employed to evaluate the computing performance in transient numerical simulations.

Curvature Effects in the Curved Duct for the Compressible Viscous Flow With Heat Transfer

2003 ◽  
Author(s):  
Kougen Ozaki ◽  
Hiroshi Maekawa
Keyword(s):  
Boundary Conditions ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Numerical Results ◽  
Outlet Section ◽  
Duct Flow ◽  
Reynolds Number Flow ◽  
Curvature Effects ◽  
Numerical Tests ◽  
Curved Duct

In this paper, non-reflecting boundary conditions based on the NSCBC method for three-dimensional compressible viscous flows, especially outlet boundary conditions, are examined and numerical tests for a curved duct flow are made. Using the subsonic non-reflecting outflow boundary conditions, curvature effects for compressible flow are investigated. First, numerical flows in a straight duct was tested for the stability of the solution and the efficiency of the subsonic non-reflecting outflow conditions extended to 3D problems. Numerical tests show that the non-reflecting NSCBC method provides accurate results for very low Reynolds number flow with isothermal no-slip walls. Second, the unsteady Navier-Stokes equations in cylindrical coordinates were numerically solved using the non-reflecting outflow conditions for a curved duct flow with isothermal no-slip walls. The numerical results show the consistency of the solution. Finally, analyzing the curved duct flow results, effects of the duct curvature were studied. A comparison of the numerical results between two curved ducts, the curvature is 102 times larger than smaller one, shows that the maximum intensity of secondary flow appeared at the outlet section of the more curved duct is about 102 times larger.

Three-Dimensional Analysis of the Free Vibration of Thick Rectangular Plates With Depressions, Grooves or Cut-Outs

1996 ◽  
Vol 118 (2) ◽  
pp. 184-189 ◽  
Author(s):  
P. G. Young ◽  
J. Yuan ◽  
S. M. Dickinson
Keyword(s):  
Kinetic Energy ◽  
Free Vibration ◽  
Boundary Conditions ◽  
Dimensional Analysis ◽  
Thick Plate ◽  
Three Dimensional ◽  
Rectangular Plates ◽  
Algebraic Polynomials ◽  
Elasticity Equations ◽  
Three Dimensional Elasticity

A solution is presented for the free vibration of very thick rectangular plates with depressions, grooves or cut-outs using three-dimensional elasticity equations in Cartesian coordinates. Simple algebraic polynomials which satisfy the boundary conditions of the plate are used as trial functions in a Ritz approach. The plate is modelled as a parallelepiped, and the inclusions are treated quite straightforwardly by subtracting the contribution to the strain and kinetic energy expressions of the volume removed, before minimizing the functional. The approach is demonstrated by considering a number of square thick plate cases, including a plate with a cylindrical groove, a shallow depression or a cylindrical cut-out.

scholarly journals The Influence of Symmetrical Boundary Conditions on the Structural Behaviour of Sandwich Panels Subjected to Torsion

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2093 ◽  
Author(s):  
Zbigniew Pozorski ◽  
Szymon Wojciechowski
Keyword(s):  
Boundary Conditions ◽  
Numerical Models ◽  
Sandwich Panels ◽  
Structural Response ◽  
Numerical Results ◽  
Beam Model ◽  
Structural Behaviour ◽  
High Agreement ◽  
Various Boundary Conditions ◽  
Support Conditions

The paper discusses the influence of load and support conditions on the behaviour of sandwich panels subjected to torsion. 3-D numerical models are presented, in which various boundary conditions have been defined. The case of the load causing the concentrated torque in the span is analyzed, and the load definition affects the structural response. The numerical results were compared with the results obtained for the analytical beam model, which included both free torsion and secondary warping torsion. The conditions under which the models achieve a high agreement between the results were determined, but the significant sensitivity of the solution was also indicated. In each case of the considered load and boundary conditions, the structural response shows appropriate symmetry.

scholarly journals Numerical models development for unidirectional air flow diffusers with lobed and circular orifices

2019 ◽  
Vol 111 ◽  
pp. 01049
Author(s):  
Laurentiu Tacutu ◽  
Ilinca Nastase ◽  
Florin Bode ◽  
Cristiana Croitoru ◽  
Catalin Lungu
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Numerical Study ◽  
Numerical Models ◽  
Ventilation System ◽  
Numerical Results ◽  
Airflow Distribution ◽  
Numerical Grid ◽  
Computational Resources ◽  
Real Scale

In order to achieve more realistic boundary conditions on the inlet of a ventilation system it is necessary to study the influences of the air diffuser orifices geometry on the airflow distribution in the enclosure. Integrating these orifices directly in a real scale air diffuser for a numerical study will result in a huge computational grid which will translate in huge computational resources and a much larger calculation time. The solution, in this case, was the numerical simulation of the airflow through small parts of the studied air diffuser. Later, the numerical results will be implemented as boundary conditions in the unidirectional diffuser of a numerical simulation that represents a real scale operating room (OR). In the current study two diffusers with different orifices were studied, one having circular („O”) and the other one lobbed („+”) orifices. The initial numerical model had 25 orifices on the diffuser, but because of the very large numerical grid resulted for the initial meshes (>35 million tetrahedral cells), a solution with only 4 orifices was chosen for this study. A mesh independency study was made for these two types of air diffusers. The numerical studies were made using RANS method, with SST k-ω turbulence model in steady state conditions. The numerical results obtained with the first step models showed very good agreement with the PIV stereoscopic experimental measurements.

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

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