A numerical study of the thermally induced stress distribution in a rotating hollow disc heated by a moving heat source acting on one of the side surfaces

2009 ◽  
Vol 223 (8) ◽  
pp. 1877-1887 ◽  
Author(s):  
M S Genç ◽  
G Özşik ◽  
H Yapicr
Keyword(s):  
Thermal Stress ◽  
Heat Source ◽  
Stress Ratio ◽  
Numerical Study ◽  
Three Dimensional ◽  
Side Surface ◽  
Angular Speed ◽  
Moving Heat Source ◽  
Ambient Conditions ◽  
Wide Range

This study presents the effects of a moving heat source (MHS) on a rotating hollow steel disc heated from its one side surface under stagnant ambient conditions. As the disc rotates around the z-axis with a constant angular speed Ω, the heat source moves along from one radial segment to the next radial segment in the radial direction on the processed surface at the end of each revolution of the disc. Three-dimensional (3D) numerical calculations are performed individually for a wide range of thermal conductivity λ of steel and for different Ωs. In order to obtain the thermal stress per heat flux intensity q0, it is assumed that the thermo-physical properties of the disc do not change with temperature. The maximum effective thermal stress ratio varies in the range of 22–134 °C depending on λ and Ω. While the MHS passes from one radial segment to the next radial segment, it causes an additional steeping of the effective thermal stress. However, when the values of λ and Ω are increased, the maximum effective thermal stress ratio can be reduced by a considerable amount.

scholarly journals Numerical study of transient three-dimensional heat conduction problem with a moving heat source

2011 ◽  
Vol 15 (1) ◽  
pp. 257-266 ◽  
Author(s):  
Ivana Ivanovic ◽  
Aleksandar Sedmak ◽  
Marko Milos ◽  
Aleksandar Zivkovic ◽  
Mirjana Lazic
Keyword(s):  
Heat Conduction ◽  
Heat Source ◽  
Numerical Solution ◽  
Numerical Study ◽  
Heat Conduction Problem ◽  
Gaussian Function ◽  
Three Dimensional ◽  
Moving Heat Source ◽  
Input Parameters ◽  
Flux Boundary Conditions

A numerical study of transient three-dimensional heat conduction problem with a moving source is presented. For numerical solution Douglas-Gunn alternating direction implicit method is applied and for the moving heat source flux distribution Gaussian function is used. An influence on numerical solution of input parameters figuring in flux boundary conditions is examined. This include parameters appearing in Gaussian function and heat transfer coefficient from free convection boundaries. Sensitivity of cooling time from 800 to 500?C with respect to input parameters is also tested.

scholarly journals Drops bouncing off macro-textured superhydrophobic surfaces

2017 ◽  
Vol 824 ◽  
pp. 866-885 ◽  
Author(s):  
Ali Mazloomi Moqaddam ◽  
Shyam S. Chikatamarla ◽  
Iliya V. Karlin
Keyword(s):  
Contact Time ◽  
Numerical Study ◽  
Three Dimensional ◽  
Superhydrophobic Surfaces ◽  
Nonlinear Behaviour ◽  
Textured Surfaces ◽  
Texture Density ◽  
Wide Range ◽  
Quantitative Manner ◽  
The Impact

Recent experiments with droplets impacting macro-textured superhydrophobic surfaces revealed new regimes of bouncing with a remarkable reduction of the contact time. Here we present a comprehensive numerical study that reveals the physics behind these new bouncing regimes and quantifies the roles played by various external and internal forces. For the first time, accurate three-dimensional simulations involving realistic macro-textured surfaces are performed. After demonstrating that simulations reproduce experiments in a quantitative manner, the study is focused on analysing the flow situations beyond current experiments. We show that the experimentally observed reduction of contact time extends to higher Weber numbers, and analyse the role played by the texture density. Moreover, we report a nonlinear behaviour of the contact time with the increase of the Weber number for imperfectly coated textures, and study the impact on tilted surfaces in a wide range of Weber numbers. Finally, we present novel energy analysis techniques that elaborate and quantify the interplay between the kinetic and surface energy, and the role played by the dissipation for various Weber numbers.

Fluid Flow and Lateral Fluid Dispersion in Bounded Granular Beds

2002 ◽  
Author(s):  
Azita Soleymani ◽  
Eveliina Takasuo ◽  
Piroz Zamankhan ◽  
William Polashenski
Keyword(s):  
Reynolds Number ◽  
Porous Media ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Numerical Results ◽  
Transition To Turbulence ◽  
Wide Range

Results are presented from a numerical study examining the flow of a viscous, incompressible fluid through random packing of nonoverlapping spheres at moderate Reynolds numbers (based on pore permeability and interstitial fluid velocity), spanning a wide range of flow conditions for porous media. By using a laminar model including inertial terms and assuming rough walls, numerical solutions of the Navier-Stokes equations in three-dimensional porous packed beds resulted in dimensionless pressure drops in excellent agreement with those reported in a previous study (Fand et al., 1987). This observation suggests that no transition to turbulence could occur in the range of Reynolds number studied. For flows in the Forchheimer regime, numerical results are presented of the lateral dispersivity of solute continuously injected into a three-dimensional bounded granular bed at moderate Peclet numbers. Lateral fluid dispersion coefficients are calculated by comparing the concentration profiles obtained from numerical and analytical methods. Comparing the present numerical results with data available in the literature, no evidence has been found to support the speculations by others for a transition from laminar to turbulent regimes in porous media at a critical Reynolds number.

Study of arching behaviour and strength of concrete masonry infills under out-of-plane loading

2019 ◽  
Vol 46 (10) ◽  
pp. 896-908 ◽  
Author(s):  
Ehsan Nasiri ◽  
Yi Liu
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Element Model ◽  
Contributing Factors ◽  
Concrete Frames ◽  
Masonry Infills ◽  
Concrete Masonry ◽  
Wide Range ◽  
Out Of Plane ◽  
Three Dimensional Finite Element

A numerical study using a three-dimensional finite element model was conducted to investigate the arching behaviour and strength of concrete masonry infills bounded by reinforced concrete frames subjected to out-of-plane loading. Physical specimens were concurrently tested to provide results for validation of the model as well as evidence of directional characteristics of arching behaviour of masonry infills. A subsequent parametric study using the model included a wide range of infilled frame geometric properties. The results showed in detail the difference in one-way and two-way arching in terms of both strength and failure mechanism, and the contributing factors to this difference. Evaluation of the two main design equations for out-of-plane strength of masonry infills led to proposal of modifications to provide a more rational consideration of directional behaviour of concrete masonry infills. A comparison study using the available test results showed a marked improvement of strength prediction based on the proposed modification.

A Numerical Study of Three-Dimensional Convective Heat Transfer From a Window Covered by a Simple Partially-Open Plane Blind

2008 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
Murat Basarir ◽  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Three Dimensional ◽  
Side Surface ◽  
Governing Equations ◽  
Three Dimensional Flow ◽  
Buoyancy Forces ◽  
Fluid Properties ◽  
Higher Temperature ◽  
Open Plane

Heat transfer from the room-side surface of a window covered by a plane blind to the surrounding room has been considered. The window is at a higher temperature than the air in the room. There is an open gap between the blind system and the window at the top of the window and the effect of the size of this gap on the window-to-air heat transfer rate has been numerically examined. Three-dimensional flow has been considered. The flow has been assumed to be steady and laminar and it has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. It has also been assumed that the flow is symmetrical about the vertical centre-plane of the window. The solution has been obtained by numerically solving the full three-dimensional form of the governing equations, these equations being written in terms of dimensionless variables. Results have only been obtained for a Prandtl number of 0.7. The effects of the other dimensionless parameters on the window Nusselt number have been numerically determined.

Numerical Study of Impact Penetration Shearing Employing Finite Strain Viscoplasticity Model Incorporating Adiabatic Shear Banding

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Patrice Longère ◽  
André Dragon ◽  
Xavier Deprince
Keyword(s):  
Damage Mechanics ◽  
Numerical Study ◽  
Shear Banding ◽  
Three Dimensional ◽  
Adiabatic Shear ◽  
Deformation Model ◽  
Viscoplastic Material ◽  
Predictive Tool ◽  
Adiabatic Shear Banding ◽  
Wide Range

This work brings forward a twofold contribution relevant to the adiabatic shear banding (ASB) process as a part of dynamic plasticity of high-strength metallic materials. The first contribution is a reassessment of a three-dimensional finite deformation model starting from a specific scale postulate and devoted to cover a wide range of dissipative phenomena, including ASB-related material instabilities (strong softening prefailure stage). The model, particularly destined to deal with impacted structures was first detailed by (Longère et al. 2003, “Modelling Adiabatic Shear Banding Via Damage Mechanics Approach,” Arch. Mech., 55, pp. 3–38; 2005, “Adiabatic Shear Banding Induced Degradation in a Thermo-Elastic/Viscoplastic Material Under Dynamic Loading,” Int. J. Impact Eng., 32, pp. 285–320). The second novel contribution concerns numerical solution of a genuine ballistic penetration problem employing the above model for a target plate material. The ASB trajectories are shown to follow a multistage history and complex distribution pattern leading finally to plugging failure mechanism. The corresponding analysis and related parametric study are intended to put to the test the pertinency of the model as an advanced predictive tool for complex shock related problems.

A Numerical Study of Droplet Impingement for In-Flight Ice Accretion Prediction

2016 ◽  
Author(s):  
Hao Zhang ◽  
Chihyung Wen ◽  
Junwei Su
Keyword(s):  
Collection Efficiency ◽  
Numerical Study ◽  
Three Dimensional ◽  
Ice Accretion ◽  
Eulerian Model ◽  
Droplet Impingement ◽  
Basic Module ◽  
Wide Range ◽  
Subsonic Regime ◽  
Finite Volume Approach

Droplet impingement is the basic module in both ice accretion and anti-icing numerical calculation. A three dimensional finite volume approach with the capacity of modeling the in-flight droplet impingement on a wide range of subsonic regime is therefore established in this research, using OpenFOAM®. The Eulerian model is applied to estimate the droplet flow field with the same computational grid sets as those of the air flow calculation. The roughness effect caused by ice accretion is considered in the wall function modeling. Thus, the collection efficiency could be investigated for further icing numerical simulations. This approach is validated on both cylinder and sphere benchmark cases. The results are compared with the corresponding experimental and LEWICE (LEWis ICE accretion program) simulation data.

scholarly journals Heat Source Modeling in Selective Laser Melting

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2052 ◽  
Author(s):  
Elham Mirkoohi ◽  
Daniel E. Seivers ◽  
Hamid Garmestani ◽  
Steven Y. Liang
Keyword(s):  
Temperature Field ◽  
Steady State ◽  
Heat Source ◽  
Material Properties ◽  
Physical Phenomenon ◽  
Three Dimensional ◽  
Moving Heat Source ◽  
Point Heat Source ◽  
Laser Melting ◽  
Source Models

Selective laser melting (SLM) is an emerging additive manufacturing (AM) technology for metals. Intricate three-dimensional parts can be generated from the powder bed by selectively melting the desired location of the powders. The process is repeated for each layer until the part is built. The necessary heat is provided by a laser. Temperature magnitude and history during SLM directly determine the molten pool dimensions, thermal stress, residual stress, balling effect, and dimensional accuracy. Laser-matter interaction is a crucial physical phenomenon in the SLM process. In this paper, five different heat source models are introduced to predict the three-dimensional temperature field analytically. These models are known as steady state moving point heat source, transient moving point heat source, semi-elliptical moving heat source, double elliptical moving heat source, and uniform moving heat source. The analytical temperature model for all of the heat source models is solved using three-dimensional differential equations of heat conduction with different approaches. The steady state and transient moving heat source are solved using a separation of variables approach. However, the rest of the models are solved by employing Green’s functions. Due to the high temperature in the presence of the laser, the temperature gradient is usually high which has a substantial impact on thermal material properties. Consequently, the temperature field is predicted by considering the temperature sensitivity thermal material properties. Moreover, due to the repeated heating and cooling, the part usually undergoes several melting and solidification cycles, and this physical phenomenon is considered by modifying the heat capacity using latent heat of melting. Furthermore, the multi-layer aspect of the metal AM process is considered by incorporating the temperature history from the previous layer since the interaction of the layers have an impact on heat transfer mechanisms. The proposed temperature field models based on different heat source approaches are validated using experimental measurement of melt pool geometry from independent experimentations. A detailed explanation of the comparison of models is also provided. Moreover, the effect of process parameters on the balling effect is also discussed.

Analytical Solution for a Transient Three-Dimensional Temperature Distribution in Laser Assisted Machining Processes

Volume 3 ◽  
2004 ◽  
Author(s):  
Gustavo Gutierrez ◽  
Juan Guillermo Araya
Keyword(s):  
Temperature Distribution ◽  
Analytical Solution ◽  
Heat Source ◽  
Three Dimensional ◽  
Laser Source ◽  
Finite Domain ◽  
Transient Temperature ◽  
Moving Heat Source ◽  
Infinite Domains ◽  
Laser Assisted Machining

Laser assisted machining is a recent technique for machining brittle ceramic materials by first softening them by heating the material with a laser beam, without reaching the melting point and, in this way, minimizing the damage of the workpiece and tool. The use of a laser source is a common procedure in numerous electronic and optical material processes. This research presents a new analytical solution to determine transient temperature distributions in a finite solid when it is heated by a moving heat source. The analytical solution is obtained by solving the transient three-dimensional heat conduction equation in a finite domain by the method of separation of variables. Previous studies focus on analytical solutions for semi-infinite domains. In this study, for a moving heat source, the temperature field is obtained in a finite domain. The purpose of this study is to obtain an analytical solution to predict transient temperature distribution in a finite solid due to a moving heat source.

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