敦煌莫高窟窟前林带防护效应的风洞实验

 洞窟环境包括窟内的温度、湿度、光照、气流等环境因素的适宜程度，对保护洞窟内的壁画和彩塑是十分重要的。洞窟环境不仅因洞窟所处的位置、大小、型制、有无窟门及窟门形式等而异，而且与窟外整个大环境密切相关。不同风况对洞窟内的气流交换起着重要的作用，也是造成石窟壁画彩塑风沙尘粒沉积、崖面风蚀的主要原因。通过风洞模拟实验，从窟前流场、洞窟环流、崖角形状及其受力等几个方面研究了窟前林带的防护效应和崖角防风蚀机理。结果表明：从控制洞窟水汽因素来讲，窟前以通风结构林带最佳，疏透结构林带次之，紧密结构林带欠佳。控制窟前林带灌溉强度，建立多次、少量的窟前林带灌溉制度，同时，在偏东风条件下尽量减少对窟前林带的灌溉，是控制林带生长和底层洞窟侧渗的重要一环。考虑到促进洞窟自然通风的需求，采用一定疏透度的窟门和采取必要的强迫通风，能够较大改善洞窟的自然通风和环境适宜状况。

Experiment in Wind Tunnel on the Sheltering Effect of Forest Belts at Front of the Dunhuang Mogao Grottos

The environments of grottos include temperature, humidity, illumination, air flow and other relative factors, which are very important for protecting the fresco and color modeling in the Mogao Grottos. The environments of grottos not only depend on their location, magnitude, type and the condition of cave door, but also on their external environments. Wind regimes play an important role for the exchanging of air flow in the caves. They are also the main reasons of causing sand accumulation for frescos and color modeling and wind erosion for cliff surface. The authors aim to study the sheltering effects of the forestry belts at the front of Mogao Grottos on the basis of airflow field and circulation in the caves, the shapes of cliff angle, and its stress by the use of simulation in wind tunnel. The results show that aeration-type forestry belt is the best form for controlling the water vapor in the caves, sparse-type one is the second, and the compacted-type is the worst. In addition, to control the irrigation intensity for forestry belts and to build an irrigation system of more times and little quantity are supplemental controlling measures. At the same time, irrigation should be limited under east-slanting wind condition. To adopt a given porosity cave door or to enforce aeration can greatly improve the cave environment proper for natural aeration of caves.