预埋式注灌装置充水过程水力特性数值模拟

Numerical simulation of hydraulic characteristics of pre-embedded irrigation device in water filling process

为了解预埋式注灌装置对土体局部冲刷的原因,采用k-epsilon Realizable湍流模型和VOF多相流模型相结合的方法对在进口压强P=13.8 kPa这一物理试验工况条件下预埋式注灌装置充水过程中的水气二相瞬态流动进行数值模拟,模拟结果表明:在该工况条件下,0~0.9 s时段预埋式注灌装置出水流道内的水流为瞬变流,出水流道内压强大小随时间产生剧烈波动。各监测点的瞬时压强均大于进口压强,最大压强值是进口压强的3.27倍。出水孔流量变化规律与压强随时间变化规律一致,压强峰值对应瞬时流量峰值,为充水过程结束后恒定流出流量的1.66倍。充水过程中出水流道内反复出现的极端压强使孔口出流流量瞬时陡增,造成出水孔周围的局部土体严重冲刷。研究成果可为优化预埋式注灌装置结构体型,减少出流对果树根区土体冲刷提供指导,对预埋式注灌装置在干旱区节水灌溉领域进一步推广提供技术支撑。

To understand the reason of local soil erosion caused by pre-embedded irrigation device,in this paper,k-epsilon Realizable turbulence model and VOF multiphase flow model were used to simulate the water-air two-phase transientflow in the water-filling process of pre-embedded irrigation device under the physical testcondition of inletpressure P=13.8kPa.The simulation results show as follows:Under this work-ing condition,the water flow in the outletrunner of the pre-embedded irrigation device is transientflow from 0 to 0.9s,and the intensity of pressure in the outletrunner fluctuates sharply with time;The instantaneous pressure ateach monitoring pointis greater than the inletpressure,and the maximum pressure is 3.27 times the inletpressure;The changing law of the outletflow is consistentwith the changing law of the pressure over time,and the instantaneous peak flow corresponding to the peak pressure is 1.66 times the constantout-flow after the filling process.In the process of water filling,extreme pressure occurred repeatedly in the outletrunner,which made the outletflow suddenly increase sharply,causing severe erosion of local soil around the outlet.The research results are expected to provide guidance for optimizing the structure shape of the pre-embedded irrigation device and reducing the soil erosion by outflow in the rootarea of fruittrees,and have importantsignificance for the further promotion of the pre-embedded irrigation device in the field of water-saving irrigation in arid areas.