底面局部加热条件下热湍流的流场变化及传热规律  

Flow field and heat transfer properties in turbulent convection with local heating condition at the bottom wall

作　　者：胡瑾 章盛祺 夏振华 HU Jin;ZHANG Shengqi;XIA Zhenhua(State Key Laboratory of Fluid Power and Mechatronic Systems,Zhejiang University,Hangzhou 310027,China;School of Aeronautics and Astronautics,Zhejiang University,Hangzhou 310027,China;Guangdong Provincial Key Laboratory of Turbulence Research and Applications,Southern University of Science and Technology,Shenzhen 518055,China;State Key Laboratory for Turbulence and Complex Systems,Peking University,Beijing 100871,China)

机构地区：[1]浙江大学流体动力与机电系统国家重点实验室,杭州310027 [2]浙江大学航空航天学院,杭州310027 [3]南方科技大学广东省湍流基础研究与应用重点实验室,深圳518055 [4]北京大学湍流与复杂系统国家重点实验室,北京100871

出　　处：《空气动力学学报》2022年第2期208-214,I0004,共8页Acta Aerodynamica Sinica

基　　金：国家自然科学基金(92152101);广东省重点实验室项目(2019B121203001)。

摘　　要：在实际的自然对流现象与工业对流换热设备中常常存在非均匀热边界问题,底面局部加热就是其中的一类。本文使用直接数值模拟方法研究了 Pr = 2、Ra = 1×10^(8)条件下,加热长度 l = 0.5 时,不同加热位置对二维方腔内热湍流流场变化及传热规律的影响。其中,下壁面为恒温加热及绝热条件共存的混合边界条件,而上壁面依然为等温条件。将局部加热计算结果与经典 Rayleigh-Benard 对流(RBC)进行比较,结果表明:局部加热条件会对冷热羽流混合和系统下壁面角涡的生长产生抑制作用,从而抑制了大尺度环流的反转;同时,加热位置越靠近下壁面中心,对应总动能和角动量的绝对值越大、振幅越小;局部加热系统通过调整加热位置可令系统传热效率最大化,最高可达 RBC 系统的 73.2%。In Rayleigh-Bénard convection (RBC), the flow is confined in an enclosed box heated from below and cooled from above. However, in many natural and engineering problems, the flow is not always heated on the whole bottom wall. In this paper, turbulent convection with local heating at the bottom wall in a two-dimensional square box is studied through direct numerical simulations. Here, the local heating is realized by setting a constant temperature at a local wall region of the bottom wall, and leaving the rest of the bottom wall to be adiabatic. The non-dimensional length of local heating region l = 0.5 is fixed. Three cases with X = 0, 0.125 and 0.25, where X is the non-dimensional location of the far-left point of the local heating region, as well as the RBC case are simulated at Rayleigh number Ra = 1×10^(8) and Prandtl number Pr = 2. The results show that the local heating conditions can restrain the growth of corner flow near the bottom wall, which leads to the suppression of large-scale circulation (LSC) reversal. Meanwhile, the closer the heating position is to the center of the wall, the greater the absolute values of angular momentum and the total kinetic energy, and the smaller the fluctuation amplitude of them. It is found that the total kinetic energy and the heat transfer efficiency of the three local heating cases reach 62.5%~72.5% and 68.1%~73.2%, respectively, of those of the RBC system, though the heating length is only half of the latter. In addition, the heat transfer efficiency can be maximized by properly adjusting the heating position, and it is increased by 7.4% for the case with X = 0.25 as compared with the X = 0 case. The temperature contours also show that the behavior of the raising hot plumes is quite different in the three cases.

关 键 词：热湍流 局部加热 流动结构 总动能 传热 

分 类 号：O375.5[理学—流体力学]