针叶树材纵向气体渗透的三维流阻网络

THE THREE-DIMENSIONAL FLOW-RESISTOR NETWORK FOR LONGITUDINAL GAS PERMEABILITY OF SOFTWOODS

气体在木材中的渗透是通过木材内的孔隙通道进行 ,而木材内的孔隙结构非常复杂 ,在纵向、径向、弦向的连接特性均不相同。以往关于针叶树材气体渗透的模型或理论 ,只考虑针叶树材内气体渗透通道在 1个或 2个方向上的连接。本文根据针叶树材管胞流阻和管胞在纵向、径向、弦向的连接特性 ,建立了一个描述针叶树材纵向气体渗透性的三维流阻网络 ,并运用重正化变换求解出流阻网络的流阻 ,计算了针叶树材气体纵向渗透系数。所得马尾松木材气体纵向渗透系数计算值与其测量结果进行比较 ,两者十分吻合 。

Gas flows through the passages that consist of various pores inside wood. The structure of the pores is complex and changeful, and the connections between the pores are different in the longitudinal, radial and tangential directions. The existing models for gas permeability of softwoods only considered the connection of the pores in one direction of wood grain or two directions. In this paper, a three dimensional flow resistor network was constructed according to the connection of the pores in longitudinal, radial and tangential directions. The flow resistor network could be used to describe the mechanism of gas flow in the longitudinal direction. The equivalent flow resistor of the flow resistor network was work out by means of the real space renormalization approach, and the evaluation of the gas permeability of softwood could be evaluated from the equivalent flow resistor. The calculated values of the longitudinal gas permeability of Masson pine( Pinus massoniana ) was compaered with the corresponding measured values. There is a close agreement between the calculation and the measurement. It shows the validity of the theory on three dimensional flow resistor network.