方腔内热磁致空气自然对流数值研究

Numerical Study of Magneto-Thermal Natural Convection of Air in a Square Enclosure

建立了处于空间中的孤立永磁体产生的永磁场中的二维方腔热磁自然对流模型,并通过数值计算的方法研究了方腔内空气在重力和磁化力驱动下的自然对流现象.在瑞利数105和磁场强度0.5~3.5T范围内,研究了梯度磁场对自然对流的抑制作用,给出了方腔内磁浮升力场,温度场、流场的变化以及方腔内壁面的换热特性.结果表明：高剩磁钕铁硼永磁体磁场可以明显的抑制方腔内自然对流,与重力场自然对流相比,方腔内流场和温度场发生了明显的变化,剩磁3.5T时Nu减小达47%.

Magneto-thermal natural convection of air in a square enclosure under gravity field and together with a non-uniform magnetic field provided by apermanent Neodymium-Iron-Boron magnet is numerically studied.The physical fields of magnetizing force,velocity and temperature as well as the local distribution characteristics of Nusselt number are all presented in this paper with Rayleigh number 105 and with the residual magnetic flux density ranges from 0.5Tto 3.5T.The results show that the natural convection of air in the square enclosure under the magnetic and gravity fields is quite different from that under the gravity field alone.The natural convection is decreased when the magnetic field is added to the gravity field as the model studied in this paper and the inhibitory effect increases with increase of magnetic filed strength.The velocity and temperature fields and the distribution of the local value of Nusselt number are quite different from that under the gravity field alone.Under the magnetic field supplied by apermanent magnet with a residual magnetic flux density 3.5Tesla,the value of Nu drops by 47%.