共查询到19条相似文献,搜索用时 125 毫秒
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采用数值方法研究了狭缝射流冲击柱状凸形表面的流动换热特性,通过四种湍流模型计算结果与实验数据对比,确定了湍流模型适用性.以压力梯度分布为依据,重点分析了狭缝射流沿柱状凸形表面的流动结构和边界层分离特点及柱状凸形表面的强化换热特性.结果表明:RNG k-ε和Realizable k-ε模型具有预测适应性;狭缝射流冲击至柱状凸形表面,气体沿表面运动,速度降低,并在流动下游发生边界层分离;量纲一的逆压梯度随量纲一的曲率半径(D/B)的减小而增大,使得边界层分离更早出现;驻点区域换热Nu随量纲一的曲率半径(D/B)的减小而获得增强,但流动进入下游后,D/B对换热基本无影响;压力梯度是影响狭缝射流冲击柱状凸形表面换热分布的重要因素. 相似文献
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采用实验的方法研究了单个圆形喷嘴冲击射流冷却高温钢板的瞬态传热特性.实验中喷嘴到被冲击表面距离H/D为4和8,射流Re数为在22 700到31 000的范围内.实验结果表明,提高气体流量可以有效提升圆形喷嘴的换热能力.射流冲击距离H/D和射流Re数对Nu数具有明显的影响.在对瞬态实验结果的分析表明,随着实验工件表面温度的降低,换热系数和Nu数逐步降低,说明被冲击表面温度对气体射流冲击换热系数和Nu数具有一定的影响.在气体射流冲击冷却过程中,被冷却物体表面温度对换热系数的影响不可忽略. 相似文献
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平面射流的数值模拟研究 总被引:7,自引:0,他引:7
冲击射流是一个复杂的流动过程,它不仅与流体的种类、被冲击表面形态和喷嘴的结构形式有关,更与喷嘴的布置及从喷嘴喷出流体的Re数有关。通过建立多柬平面射流的二维数学模型,利用SIMPLE算法计算了冲击换热表面的静压值,并分析了各种情况下的换热强度。数值模拟的结果表明,在多束平面射流条件下,Re=6670~39900,L/B=4~6、H/B=5~7时,可得到较为理想的射流冲击换热效果。 相似文献
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为了确定高雷诺数条件下射流与挡板之间的换热系数,采用理论分析和数值计算的方法,建立流场模型,分析流场各物理量的基本规律、流动特性和对流传热系数分布规律,并与已有实验数据进行比较。结果表明:驻点附近,流体与壁面之间的对流换热系数较低;板面上,随着到驻点的距离增大,对流换热系数增大并出现峰值然后降低,峰值出现在约0.2倍扩散半径处。数值计算与理论分析得到的换热系数较为接近。 相似文献
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气体冲击射流的换热系数是设计喷气冷却装置必需的参数。本文采用实验方法研究了多排密集圆孔气体冲击射流的换热过程,主要考察了射流雷诺数ReD,普朗特数Pr,无量纲喷嘴间距Xn/d,无量纲喷射高度H/d和排气方式对平均对流换热系数的影响。实验结果表明:平均努谢尔数NuD随ReD数的0.69次幂增长,随无量纲数Xn/d的-0.269次幂和无量纲数H/d的-0.273次幂的方式减小,同时设置排气通道会显著提高换热系数。实验数据整理成平均努谢尔数NuD与ReD数、Pr数、无量纲间距Xn/d、无量纲喷射高度H/d的准则关系式,测量值与回归结果偏差在7%的范围内。得到的准则关系式与Martin公式比较,更适合于高开孔率的密集冲击射流。 相似文献
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ListofSymbol cp———Specificheat ,J·kg-1·℃ -1; C1,C2 ,Cμ———Turbulentmodelconstants ; Dnoz———EquivalentdynamicdiameterofSEN ,m ; fs,f1———Solidfractionandliquidfraction ; f1,f2 ,fμ———Turbulentmodelterms ; g———Gravitationalacceleration ,m·s-2 ; k———Turbulencekineticenergy ,m2 ·s-2 ; k1———Laminarthermalconductivity ,W·m-1·℃-1; ks———Thermalconductivityofsolidsteel,W·m-1·℃ -1; p———Pressure ,Pa ; Prt———TurbulentPran… 相似文献
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Tarek M. Salaheldin Jasim Imran M. Hanif Chaudhry 《Canadian Metallurgical Quarterly》2004,130(2):91-100
A three-dimensional numerical model FLUENT is used to simulate the separated turbulent flow around vertical circular piers in clear water. Computations are performed using different turbulence models and results are compared with several sets of experimental data available in the literature. Despite commonly perceived weakness of the k-ε model in resolving three-dimensional (3D) open channel and geophysical flows, several variants of this turbulence model are found to have performed satisfactorily in reproducing the measured velocity profiles. However, model results obtained using the k-ε models show some discrepancy with the measured bed shear stress. The Reynolds stress model performed quite well in simulating velocity distribution on flat bed and scour hole as well as shear stress distribution on flat bed around circular piers. The study demonstrates that a robust 3D hydrodynamic model can effectively supplement experimental studies in understanding the complex flow field and the scour initiation process around piers of various size, shape, and dimension. 相似文献
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建立步进式加热炉内流动、燃烧和传热的数学模型。炉内流场的模拟采用k-ε双方程模型,辐射换热计算采用P-1辐射模型,气相燃烧采用Species Transport模型,流场计算采用Simpler算法。采用上述模型与算法得到了炉内详细合理的温度、速度和浓度分布,并对其中影响板坯加热的温度场进行了实验验证。 相似文献
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The internal structure of continuous casting tundish is complex, and the flow state of molten steel is diverse. Detailed and accurate information of molten steel flow field is the premise of tundish control and optimization. Numerical simulation method has been widely used in the study of molten steel flow field in tundish. The accurate numerical simulation of molten steel flow field is inseparable from the appropriate turbulence model and the corresponding boundary conditions. Based on the CFD open source code OpenFOAM v8, three different types of turbulence models (standard k-ε model, RNG k-ε model, and SST k-ω model) were applied to simulate the molten steel flow in the tundish. Additionally, two boundary conditions of symmetry plane and the free slip were also applied. Comparing the simulation results to the experimental data, it shows the RTD curve obtained by the simulation with the SST k-ω model can successfully predict the "double peaks" that appeared in the experiment. Besides, the response time and peak value time are closest to that of experimental results. For SST k-ω, when changing the type of liquid surface boundary from free slip to symmetrical plane, the error of tracer response time obtained is reduced from 93.89% to less than 8.35%, and the error of peak time is reduced from 100.78% to about 12.32%. It can be concluded that the SST k-ω model and the symmetry boundary are applicable for the simulation of molten steel flow in the tundish. 相似文献
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摘要:连铸中间包内部结构复杂,钢液流动状态多样,详尽准确的钢液流场信息是中间包控制和优化的前提。数值模拟方法已广泛应用于中间包内钢液流场研究,钢液流场的精确数值模拟离不开合适的湍流模型及相应的边界条件。基于CFD开源代码包OpenFOAM v8,分别应用标准k-ε模型、RNG k-ε模型、SST k-ω模型3种湍流模型,对称面边界、自由滑移边界2种液面边界条件,对中间包流场进行了数值模拟。通过与文献中实验结果比较,发现采用SST k-ω模型可以成功预测RTD曲线的“双峰”,且响应时间、峰值时间与实验结果较为接近;应用SST k-ω模型时,将液面边界类型由自由滑移改为对称面,获得的示踪剂响应时间的误差由93.89%降低至8.35%以下,峰值时间的误差由100.78%降低至12.32%左右。因此,SST k-ω模型、对称面液面边界可以较好地描述中间包内钢液流动过程。 相似文献
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《Baosteel Technical Research》2011,5(4):49-53
Mist jet impingement cooling is an enhanced heat transfer method widely used after the continuous galvanizing process.The key of a successful design and operation of the mist jet impingement cooling system lies in mastering heat transfer coefficients.The heat transfer coefficients of high temperature steel plates cooled with multiple mist impinging jets were experimentally investigated,and the effects of gas and water flow rates on heat transfer coefficients were studied.The test results illustrate that the gas flow rate has little effect on the mist heat transfer rate.It is also found that the water flow rate has a great impact on the heat transfer coefficient.When the water flow rate ranges from 0.96m3/h to 1.59 m3/h,an increase in the rate will produce a higher heat transfer coefficient with a maximum of 5650 W/(m2·K).Compared with the conventional gas jet cooling,the heat transfer coefficient of the mist jet cooling will be much higher,which can effectively strengthen the after-pot cooling. 相似文献
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Nils Reidar B. Olsen Richard D. Hedger D. Glen George 《Canadian Metallurgical Quarterly》2000,126(10):949-953
A 3D computational fluid dynamics program was used to calculate the wind-induced accumulation of phytoplankton in Eglwys Nynydd, a water supply reservoir in Wales. The computational fluid dynamics model solved the Navier-Stokes equations for the water velocities using the SIMPLE method to calculate the pressure. Two turbulence models were tested: a zero-equation model and the k-ε model. An unstructured nonorthogonal 3D grid with hexahedral cells was used. The distribution of the blue-green algae Microcystis was calculated by solving the transient convection-diffusion equation for phytoplankton concentration, based on the modeled flow field. The numerical model included algorithms for calculating the growth rate of phytoplankton and simulating the response of the algae to changes in underwater light intensity. The model was validated by comparing the horizontal distribution patterns produced by simulation with those recorded during a field survey of surface concentrations. The results demonstrated reasonable agreement, particularly when using the k-ε turbulence model. The main parameter affecting the results was the effective diameter of the Microcystis colonies. 相似文献
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The scouring process in a plunge pool of loose bed with uniform bed-materials due to a two-dimensional plane impinging jet was simulated computationally. The finite-element-based unsteady three-dimensional model, CCHE3D, with k-ε turbulence closure was employed to solve the flow field. It has long been recognized that the unsteady behavior of the turbulent jet fluctuation plays an important role in scouring and transporting sediment in the plunge pool. In order to model this phenomenon realistically, one has to consider the effects of both shear stress and the life force on sediment particles due to pressure fluctuation. The latter has been taken into account by using empirical relationships of flume data. Both of these effects have been incorporated in the nonequilibrium sediment transport model consisting of sediment pickup rate and step length adopted for the jet scour problem. The model constant relating to the fluctuating lift force was calibrated using an empirical equation to predict the quasi-equilibrium scour depth. The results simulated by the model proposed here agree reasonably well with experimental data. 相似文献
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基于Navier-Stokes动量方程和湍流低雷诺数k-ε方程,综合考虑能量守恒和钢液凝固与糊状区对流动过程的影响,建立了描述结晶器内钢液流动、传热及凝固过程的三维耦合数学模型.以实测温度和结晶器反问题模型计算出的热流为边界条件,模拟计算了结晶器内钢水的流动、传热和凝固行为.钢液流动决定结晶器内的温度和热流分布,铸坯凝固受钢液流动和结晶器热流双重因素的影响.建立的模型以及由此得到的铸坯凝固非均匀特征可为进一步考察浇铸过程中纵裂和其他表面缺陷提供借鉴和参考. 相似文献