Physical modeling and numerical simulation of V-die forging ingot with central void

2014 ◽  
Vol 228 (13) ◽  
pp. 2347-2356 ◽  
Author(s):  
Peter Christiansen ◽  
Jesper H Hattel ◽  
Niels Bay ◽  
Paulo AF Martins
Keyword(s):  
Numerical Simulation ◽  
Physical Modeling ◽  
Small Scale ◽  
Pure Lead ◽  
Die Forging ◽  
Multi Stage ◽  
Deformation Mechanics ◽  
Open Die Forging ◽  
Central Void ◽  
Forging Load

Numerical simulation and physical modeling performed on small-scale ingots made from pure lead, having a hole drilled through their centerline to mimic porosity, are utilized to characterize the deformation mechanics of a single open die forging compression stage and to identify the influence of the lower V-die angle on porosity closure and forging load requirements of large cast ingots. Results show that a lower V-die angle of 120° provides the best closure of centerline porosity without demanding the highest forging loads or developing unreasonably asymmetric shapes that may create difficulties in multi-stage open die forging procedures.

Open Die Forging of Large Shafts with Defects – Physical and Numerical Modelling

2013 ◽  
Vol 554-557 ◽  
pp. 2145-2155 ◽  
Author(s):  
Peter Christiansen ◽  
Jesper Hattel ◽  
Niels Bay ◽  
Luis M. Alves ◽  
Paulo A.F. Martins
Keyword(s):  
Laboratory Testing ◽  
Finite Element Modelling ◽  
Physical Models ◽  
Small Scale ◽  
Testing Conditions ◽  
Element Modelling ◽  
Die Forging ◽  
Multi Stage ◽  
Porosity Defects ◽  
Open Die Forging

The aim and scope of this paper is centered to analyze the influence of the geometry of V-shaped dies on the closure of internal centerline porosity defects in ingots during multistep open-die forging. The investigation is performed with small scale physical models made from lead using V-shaped dies with 90º and 120º and a reference pair of flat parallel platens. Holes drilled through the center of these preforms are produced to mimic centerline porosity in full scale cast ingots and intermediate rotation of the preforms replicate a multi-stage forging sequence under laboratory testing conditions. The presentation is supported by finite element modelling using an in-house developed computer program and the overall investigation shows that better results in closure of centerline defects are obtained with a V-shaped die with 120º die angle.

The Numerical Simulation of Conductive Body Forming Process and Mould Design

2011 ◽  
Vol 704-705 ◽  
pp. 177-182
Author(s):  
Jian Xin Gao ◽  
Pei Feng Zhao ◽  
Ke Xing Song ◽  
Qing Wang
Keyword(s):  
Numerical Simulation ◽  
Machining Process ◽  
Forming Process ◽  
Die Forging ◽  
Conductive Body ◽  
Closed Die Forging ◽  
Draft Angle ◽  
Simulation Results ◽  
Open Die Forging ◽  
Ring Blank

T2-copper conductive body is a important part used in high voltage switch, it has poor machining process due to the complex shape. Through Deform numerical simulation, conductive body was formed by open-die forging and closed die forging. In the open-die forging simulation，heat transfer coefficient between blank (880°C) and open-die (200°C) is 11, the surrounding environment temperature is 20°C, friction factor is 0.3. The main open-die forging process parameters is: outer draft angle α=6.5°; inner draft angle β＝10°; bridge width b＝5、8、11mm. punching skin and cylindrical blank. Simulation results show that forging can meet the requirement while properly adjusting mould parameters. The main size of closed-die forging working parts is designed according to the conductive body graph, no draft angle and ring blank of external diameter Φ111mm and inside diameter Φ93mm with the same volume of conductive body. The simulation results shows that forging can be formed using open-die forging, and it is difficult to form product by the process of the closed-die forging for ring blank because of the restriction of solid state metal liquidity, many regions of the filling is not sufficient. Open-die forging and casting blank-closed die forging are both used in actual production. The casting blank-closed die forging is a more reasonable forming process compared with the open-die forging as metal volume of distribution is solved, higher utilization rate of material, more simple process in following work and the like. To make it more suitable for practical production, appropriate adjustments of some parameters was made in the mold design process based on the numerical simulation. Keywords: open-die forging; casting blank–closed die forging; numerical simulation

Direct numerical simulation of a turbulent jet impinging on a heated wall

2015 ◽  
Vol 764 ◽  
pp. 362-394 ◽  
Author(s):  
T. Dairay ◽  
V. Fortuné ◽  
E. Lamballais ◽  
L.-E. Brizzi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Nusselt Number ◽  
Direct Numerical Simulation ◽  
Temperature Fields ◽  
Heated Wall ◽  
Small Scale ◽  
Turbulent Regime ◽  
High Heat Transfer ◽  
Radial Evolution

AbstractDirect numerical simulation (DNS) of an impinging jet flow with a nozzle-to-plate distance of two jet diameters and a Reynolds number of 10 000 is carried out at high spatial resolution using high-order numerical methods. The flow configuration is designed to enable the development of a fully turbulent regime with the appearance of a well-marked secondary maximum in the radial distribution of the mean heat transfer. The velocity and temperature statistics are validated with documented experiments. The DNS database is then analysed focusing on the role of unsteady processes to explain the spatial distribution of the heat transfer coefficient at the wall. A phenomenological scenario is proposed on the basis of instantaneous flow visualisations in order to explain the non-monotonic radial evolution of the Nusselt number in the stagnation region. This scenario is then assessed by analysing the wall temperature and the wall shear stress distributions and also through the use of conditional averaging of velocity and temperature fields. On one hand, the heat transfer is primarily driven by the large-scale toroidal primary and secondary vortices emitted periodically. On the other hand, these vortices are subjected to azimuthal distortions associated with the production of radially elongated structures at small scale. These distortions are responsible for the appearance of very high heat transfer zones organised as cold fluid spots on the heated wall. These cold spots are shaped by the radial structures through a filament propagation of the heat transfer. The analysis of probability density functions shows that these strong events are highly intermittent in time and space while contributing essentially to the secondary peak observed in the radial evolution of the Nusselt number.

Experimental and Numerical Evaluation of Small-Scale Cryosurgery Using Ultrafine Cryoprobe

2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Junnosuke Okajima ◽  
Atsuki Komiya ◽  
Shigenao Maruyama
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Numerical Evaluation ◽  
Small Scale ◽  
Outer Diameter ◽  
Cooling Performance ◽  
The Heat Transfer Coefficient

The objective of this work is to experimentally and numerically evaluate small-scale cryosurgery using an ultrafine cryoprobe. The outer diameter (OD) of the cryoprobe was 550 μm. The cooling performance of the cryoprobe was tested with a freezing experiment using hydrogel at 37 °C. As a result of 1 min of cooling, the surface temperature of the cryoprobe reached −35 °C and the radius of the frozen region was 2 mm. To evaluate the temperature distribution, a numerical simulation was conducted. The temperature distribution in the frozen region and the heat transfer coefficient was discussed.

Characteristics of Heat Transfer and Flow on a Surface With Small-Scale Concave Spherical Pits

2008 ◽  
Author(s):  
J. S. Wang ◽  
Y. Qiu ◽  
L. Y. Li
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Small Scale ◽  
Heat Transfer Mechanism ◽  
Transfer Enhancement ◽  
Special Effect ◽  
Turbulent Drag Reduction ◽  
Turbulent Drag ◽  
Simulation Results ◽  
Turbulent Coherent Structure

Small-scale concave spherical pits, which have a special effect on heat transfer enhancement and turbulent drag reduction, are investigated by numerical simulation in detail. Two kinds of small-scale concave pits structures are designed on surface of a plate, which are located in the bottom of a rectangle channel. The characteristics of heat transfer and flow in channel are investigated and compared with a same channel with plate bottom by means of LES. Flow structure and temperature distribution near the pits are analyzed. The numerical simulation results indicate that the concave spherical pits disturb the flow field and vortex is induced by the pits. The turbulent coherent structure is affected by the induced vortex. The numerical simulation indicates that small scale pit can generate the vortex in couple. The range of vortex is accord with the array of small scale pit. The small scale pit can enhance the intensity of vortex. As a result, the temperature field near the pit is changed with generation of the vortex. The heat transfer mechanism on plate with small scale concave spherical pit is summarized.

scholarly journals Detection and thermal description of medicanes from numerical simulation

2014 ◽  
Vol 14 (5) ◽  
pp. 1059-1070 ◽  
Author(s):  
M. A. Picornell ◽  
J. Campins ◽  
A. Jansà
Keyword(s):  
Numerical Simulation ◽  
Thermal Structure ◽  
Weather Prediction ◽  
Weather Forecast ◽  
Small Scale ◽  
Medium Range Weather Forecast ◽  
Warm Core ◽  
Strong Winds ◽  
Nwp Model ◽  
Ecmwf Model

Abstract. Tropical-like cyclones rarely affect the Mediterranean region but they can produce strong winds and heavy precipitations. These warm-core cyclones, called MEDICANES (MEDIterranean hurriCANES), are small in size, develop over the sea and are infrequent. For these reasons, the detection and forecast of medicanes are a difficult task and many efforts have been devoted to identify them. The goals of this work are to contribute to a proper description of these structures and to develop some criteria to identify medicanes from numerical weather prediction (NWP) model outputs. To do that, existing methodologies for detecting, characterizating and tracking cyclones have been adapted to small-scale intense cyclonic perturbations. First, a mesocyclone detection and tracking algorithm has been modified to select intense cyclones. Next, the parameters that define the Hart's cyclone phase diagram are tuned and calculated to examine their thermal structure. Four well-known medicane events have been described from numerical simulation outputs of the European Centre for Medium-Range Weather Forecast (ECMWF) model. The predicted cyclones and their evolution have been validated against available observational data and numerical analyses from the literature.

scholarly journals Flow topologies in bubble-induced turbulence: a direct numerical simulation analysis

2018 ◽  
Vol 857 ◽  
pp. 270-290 ◽  
Author(s):  
Josef Hasslberger ◽  
Markus Klein ◽  
Nilanjan Chakraborty
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Volume Fraction ◽  
Fluid Velocity ◽  
Small Scale ◽  
Flow Topology ◽  
Two Phase ◽  
Local Flow ◽  
Interface Curvature

This paper presents a detailed investigation of flow topologies in bubble-induced two-phase turbulence. Two freely moving and deforming air bubbles that have been suspended in liquid water under counterflow conditions have been considered for this analysis. The direct numerical simulation data considered here are based on the one-fluid formulation of the two-phase flow governing equations. To study the development of coherent structures, a local flow topology analysis is performed. Using the invariants of the velocity gradient tensor, all possible small-scale flow structures can be categorized into two nodal and two focal topologies for incompressible turbulent flows. The volume fraction of focal topologies in the gaseous phase is consistently higher than in the surrounding liquid phase. This observation has been argued to be linked to a strong vorticity production at the regions of simultaneous high fluid velocity and high interface curvature. Depending on the regime (steady/laminar or unsteady/turbulent), additional effects related to the density and viscosity jump at the interface influence the behaviour. The analysis also points to a specific term of the vorticity transport equation as being responsible for the induction of vortical motion at the interface. Besides the known mechanisms, this term, related to surface tension and gradients of interface curvature, represents another potential source of turbulence production that lends itself to further investigation.

scholarly journals Profitability of Small Scale Vegetable Production in Southern District, Botswana

2017 ◽  
Vol 5 (1) ◽  
pp. 35
Author(s):  
Sekgopa T. Kealeboga ◽  
Lagat K. Job ◽  
Tselaesele M. Nelson
Keyword(s):  
Rural Households ◽  
Sampling Technique ◽  
Small Scale ◽  
Vegetable Production ◽  
Eradication Programme ◽  
Gross Margin ◽  
Production Program ◽  
Extreme Poverty ◽  
Pests And Diseases ◽  
Multi Stage

Government determination to eradicate extreme poverty and food insecurity among Batswana through small scale vegetable production program appears not to transform their economic stance. Rural households that are part of Poverty Eradication Programme were investigated to determine if backyard gardens were profitable enough to improve incomes, reduce extreme poverty, and increase food security. The study aimed at analysing profitability and identifying factors that affect profitability of backyard gardening. Multi-stage sampling technique was used to collect data from 100 rural households who are part of the backyard garden scheme. Data was analysed using descriptive statistics, gross margin analysis and regression analysis. Results indicated that backyard gardening was a viable activity though profitability was affected by amount of fertilizer applied, market availability and area planted. Beneficiaries indicated that the production and marketing constraints they faced included pests and diseases, lack of water, lack of market and poor prices. Program leaders must recognize the production and marketing constraints themselves as well as plan for the possibility that continual financial support for investment in the initial years of operation.

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