微灌技術(shù)要素對(duì)土壤水分運(yùn)動(dòng)影響的數(shù)值模擬
發(fā)布時(shí)間：2018-11-28 20:42
【摘要】：滴灌作為一種高效的節(jié)水灌溉技術(shù)在新疆等干旱或半干旱地區(qū)得到廣泛應(yīng)用,為減小蒸發(fā)對(duì)土壤水鹽運(yùn)移的影響通常采用地埋的方式,即地下滴灌進(jìn)行灌溉。微潤灌則是以連續(xù)灌溉的方式通過地埋微潤帶將水分緩慢輸送到植物根區(qū)的新型節(jié)水灌溉技術(shù)。數(shù)值模擬具有簡便、快捷、靈活等特點(diǎn),在給定的初始、邊界條件下,可用于模擬各因素及其組合對(duì)土壤水流、溶質(zhì)運(yùn)移、熱運(yùn)移、植物根系吸水等方面的影響。國內(nèi)的大多研究者往往只是證明該模擬值與實(shí)測(cè)值較為接近,在經(jīng)驗(yàn)證模擬數(shù)據(jù)合理并近似于真實(shí)值后利用軟件進(jìn)行多因素、長時(shí)間的模擬試驗(yàn)研究尚不足。探明滴灌系統(tǒng)毛管布置方式和微潤灌土壤水分運(yùn)動(dòng)規(guī)律,對(duì)與科學(xué)設(shè)計(jì)滴灌和微潤灌系統(tǒng),合理控制土壤鹽分的運(yùn)動(dòng)具有重要意義。本文通過應(yīng)用HYDRUS-2D軟件,對(duì)不同灌水方式下土壤水分運(yùn)動(dòng)過程進(jìn)行數(shù)值模擬,重點(diǎn)研究了地下滴灌灌水時(shí)間、滴頭流量、灌水間隔等技術(shù)要素以及地下滴灌和微潤灌兩種不同灌水方式對(duì)水分運(yùn)動(dòng)的影響。得到如下主要結(jié)論:1、隨灌水時(shí)間的增加,濕潤峰垂直向上運(yùn)移到達(dá)表層所用時(shí)間以冪函數(shù)趨勢(shì)減小,垂直向下、水平方向運(yùn)移距離均服從冪函數(shù)遞增;不同方向濕潤峰運(yùn)移距離隨滴頭流量的增大呈冪函數(shù)增長;隨灌水次數(shù)的增加呈對(duì)數(shù)函數(shù)增長。2、隨滴頭流量的增加三個(gè)方向上濕潤峰運(yùn)移距離隨灌水時(shí)間增加的冪函數(shù)系數(shù)和指數(shù)均呈拋物線變化趨勢(shì),其中垂直向上的指數(shù)拋物線開口向下,其他方向的系數(shù)和指數(shù)拋物線均開口向上;且在滴頭流量為1.5L/h處接近峰值。3、濕潤面積隨滴頭流量和灌水時(shí)間增加分別呈線性增大,隨灌水間隔增大呈指數(shù)下降,其中遞增的滴頭流量濕潤面積曲線斜率大于灌水時(shí)間濕潤面積曲線斜率;濕潤面積與滴頭流量和灌水時(shí)間的增大呈正比與灌水間隔的增大呈反比。4、隨著滴頭間距的增加水平方向上濕潤區(qū)交匯的時(shí)間、濕潤區(qū)交匯后形成“鞍部”消失所用的時(shí)間均隨之增加;在滴頭埋深附近,不同灌水時(shí)間、滴頭流量、灌水間隔和滴頭間距組合對(duì)土壤水分運(yùn)動(dòng)影響較大,在以滴頭為中心40cm以外土壤內(nèi)水分運(yùn)動(dòng)受以上四個(gè)因素組合的影響不明顯。5、利用數(shù)值模擬對(duì)比地下滴灌和微潤灌下水分運(yùn)動(dòng)發(fā)現(xiàn),在地下滴灌帶和微潤帶附近(小于5cm)的含水量和土水勢(shì)均呈對(duì)稱分布,之后地下滴灌受重力和其間歇灌溉的特點(diǎn)垂直向下的含水量和土水勢(shì)變化快于其他方向,而微潤灌仍以微潤帶為中心基本呈現(xiàn)對(duì)稱分布。灌水量相同時(shí),地下滴灌濕潤體呈近似橢圓形,而微潤灌濕潤體近似圓形且濕潤面積略大于地下滴灌。地下滴灌濕潤土壤水分分布均勻度隨灌水-間歇呈周期性減小-增大,微潤灌水分分布均勻度隨灌水逐漸增大且大于地下滴灌。
[Abstract]:As an efficient water-saving irrigation technique, drip irrigation is widely used in arid or semi-arid areas such as Xinjiang. In order to reduce the effect of evaporation on soil water and salt migration, underground drip irrigation is usually used to irrigate. Micro-irrigation is a new type of water-saving irrigation technology, which can transport water slowly to the plant root area by the way of continuous irrigation. Numerical simulation is simple, rapid and flexible. Under given initial and boundary conditions, it can be used to simulate the effects of various factors and combinations on soil water flow, solute migration, heat transport, water absorption of plant roots, and so on. Most researchers in China only prove that the simulated value is close to the measured value. After verifying that the simulated data is reasonable and approximate to the real value, the software is used to carry out many factors, and the long time simulation experiment is not enough. It is of great significance to find out the capillary arrangement of drip irrigation system and the law of soil moisture movement in micro-moisturizing irrigation, which is of great significance to scientifically design drip irrigation and micro-moisturizing irrigation system and to control the movement of soil salt reasonably. In this paper, the process of soil water movement under different irrigation modes was simulated by using HYDRUS-2D software, and the time and discharge of drip irrigation were studied. The effects of irrigation interval and two different irrigation methods, such as drip irrigation and micro-water irrigation, on water movement. The main conclusions are as follows: 1. With the increase of irrigation time, the time of vertical upward migration of wetting peak to the surface decreases with power function trend, and the distance of vertical downward and horizontal migration increases from power function; The migration distance of wetting peak in different directions increases by power function with the increase of emitter flow. With the increase of irrigation times, the power function coefficient and exponent of wetting peak migration distance increased with irrigation time in three directions, and the power function coefficient and exponent of wetting peak migration distance increased with the increase of emitter discharge. The index parabola in the vertical direction is open downward, and the coefficients and the index parabola in other directions are all open up. The wetting area increases linearly with the increase of emitter discharge and irrigation time, and decreases exponentially with the increase of irrigation interval. The slope of wetting area curve of increasing drip discharge is larger than that of irrigation time. The increase of wetting area is directly proportional to the increase of emitter discharge and irrigation time, and is inversely proportional to the increase of irrigation interval. The time of formation of "saddle" after the meeting of wet area increased. In the vicinity of emitter depth, different irrigation time, emitter discharge, irrigation interval and emitter spacing have great influence on soil moisture movement. The effects of the above four factors on the soil water movement outside the emitter 40cm were not obvious. 5. The results of numerical simulation were compared with those of the underground drip irrigation and the micro-moisturizing irrigation, and it was found that the soil moisture movement was not affected by the above four factors. The distribution of water content and soil water potential in the vicinity of the subsurface drip irrigation zone and the microwetting zone (less than 5cm) was symmetrical. After that, the vertical downward water content and soil water potential of the underground drip irrigation and its intermittent irrigation characteristics changed faster than those of other directions. However, the microirrigation still centered on the microwetting zone and presented a symmetrical distribution. When the irrigation amount is the same, the wetting body of underground drip irrigation is approximately elliptical, while the moist body of micro-moistening irrigation is round and the area of wetting is slightly larger than that of underground drip irrigation. The soil moisture distribution uniformity decreased and increased periodically with irrigation and intermittent irrigation, and the distribution uniformity of micro-moisture irrigation gradually increased with irrigation and was larger than that of underground drip irrigation.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：S152.7;S275.5
本文編號(hào)：2364203
[Abstract]:As an efficient water-saving irrigation technique, drip irrigation is widely used in arid or semi-arid areas such as Xinjiang. In order to reduce the effect of evaporation on soil water and salt migration, underground drip irrigation is usually used to irrigate. Micro-irrigation is a new type of water-saving irrigation technology, which can transport water slowly to the plant root area by the way of continuous irrigation. Numerical simulation is simple, rapid and flexible. Under given initial and boundary conditions, it can be used to simulate the effects of various factors and combinations on soil water flow, solute migration, heat transport, water absorption of plant roots, and so on. Most researchers in China only prove that the simulated value is close to the measured value. After verifying that the simulated data is reasonable and approximate to the real value, the software is used to carry out many factors, and the long time simulation experiment is not enough. It is of great significance to find out the capillary arrangement of drip irrigation system and the law of soil moisture movement in micro-moisturizing irrigation, which is of great significance to scientifically design drip irrigation and micro-moisturizing irrigation system and to control the movement of soil salt reasonably. In this paper, the process of soil water movement under different irrigation modes was simulated by using HYDRUS-2D software, and the time and discharge of drip irrigation were studied. The effects of irrigation interval and two different irrigation methods, such as drip irrigation and micro-water irrigation, on water movement. The main conclusions are as follows: 1. With the increase of irrigation time, the time of vertical upward migration of wetting peak to the surface decreases with power function trend, and the distance of vertical downward and horizontal migration increases from power function; The migration distance of wetting peak in different directions increases by power function with the increase of emitter flow. With the increase of irrigation times, the power function coefficient and exponent of wetting peak migration distance increased with irrigation time in three directions, and the power function coefficient and exponent of wetting peak migration distance increased with the increase of emitter discharge. The index parabola in the vertical direction is open downward, and the coefficients and the index parabola in other directions are all open up. The wetting area increases linearly with the increase of emitter discharge and irrigation time, and decreases exponentially with the increase of irrigation interval. The slope of wetting area curve of increasing drip discharge is larger than that of irrigation time. The increase of wetting area is directly proportional to the increase of emitter discharge and irrigation time, and is inversely proportional to the increase of irrigation interval. The time of formation of "saddle" after the meeting of wet area increased. In the vicinity of emitter depth, different irrigation time, emitter discharge, irrigation interval and emitter spacing have great influence on soil moisture movement. The effects of the above four factors on the soil water movement outside the emitter 40cm were not obvious. 5. The results of numerical simulation were compared with those of the underground drip irrigation and the micro-moisturizing irrigation, and it was found that the soil moisture movement was not affected by the above four factors. The distribution of water content and soil water potential in the vicinity of the subsurface drip irrigation zone and the microwetting zone (less than 5cm) was symmetrical. After that, the vertical downward water content and soil water potential of the underground drip irrigation and its intermittent irrigation characteristics changed faster than those of other directions. However, the microirrigation still centered on the microwetting zone and presented a symmetrical distribution. When the irrigation amount is the same, the wetting body of underground drip irrigation is approximately elliptical, while the moist body of micro-moistening irrigation is round and the area of wetting is slightly larger than that of underground drip irrigation. The soil moisture distribution uniformity decreased and increased periodically with irrigation and intermittent irrigation, and the distribution uniformity of micro-moisture irrigation gradually increased with irrigation and was larger than that of underground drip irrigation.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：S152.7;S275.5
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