本文選題：沉積物 + 采樣器��； 參考：《安徽工業(yè)大學(xué)》2015年碩士論文

【摘要】：了解沉積物是認(rèn)識(shí)環(huán)境變遷歷史和預(yù)測(cè)未來環(huán)境變化的基礎(chǔ)。作為流域地表物質(zhì)遷移的主要宿體,湖泊較差的流動(dòng)性,使得其中的環(huán)境物質(zhì)沉積相對(duì)穩(wěn)定,沉積物的層次結(jié)構(gòu)中蘊(yùn)含了豐富的環(huán)境信息,因而成為目前諸多自然環(huán)境變遷記錄研究的熱點(diǎn)。由于現(xiàn)有的采樣器通常破壞了沉積物的原始層序,導(dǎo)致了對(duì)沉積時(shí)期研究的準(zhǔn)確度普遍偏低。本文總結(jié)了現(xiàn)有沉積物采樣器的不足,依據(jù)結(jié)構(gòu)功能原理,設(shè)計(jì)了內(nèi)嵌螺管式冷凍沉積物采樣器的詳細(xì)結(jié)構(gòu)并制作出了樣機(jī)�；贔luent軟件對(duì)該采樣器的凍結(jié)規(guī)律進(jìn)行了數(shù)值模擬,通過室內(nèi)試驗(yàn)與數(shù)值模擬結(jié)果進(jìn)行了對(duì)照,檢測(cè)了該采樣器的基本性能,并制定了野外采樣的操作方案。樣機(jī)的基本結(jié)構(gòu)參數(shù)為:采樣管長1000mm,內(nèi)徑137mm;冷源寬度250mm,冷源下邊界距采樣管口距離200mm。采樣管材質(zhì)為201不銹鋼,螺旋冷凍管材質(zhì)為銅管,防水保護(hù)套管材質(zhì)為UPVC給水管。對(duì)采樣器的凍結(jié)規(guī)律進(jìn)行了數(shù)值模擬,得出了模擬條件下采樣管腔近壁面呈弓形,中心處呈“H”形的對(duì)稱溫度分布特征以及樣品的對(duì)稱弓形相變特征。獲取了樣品理論閉合點(diǎn)的位置,并繪制出樣品軸向閉合高度隨時(shí)間的變化曲線。開展清水試驗(yàn)并與數(shù)值模擬的結(jié)果進(jìn)行了對(duì)照,得出理論閉合點(diǎn)凍結(jié)過程經(jīng)歷了“勻速期”、“平臺(tái)期”、“跌落期”和“減速期”,各時(shí)段占比依次為22.2%、44.4%、11.1%和22.2%,其中“平臺(tái)期”對(duì)整個(gè)冷凍周期起控制作用。開展了室內(nèi)模擬湖泊沉積物采樣試驗(yàn),試驗(yàn)進(jìn)行了8小時(shí),從初始水溫為12.7℃的環(huán)境中采集到了界面清晰的沉積物及其上覆水凍結(jié)樣品。其中沉積物厚164.8mm,上覆水厚151.4mm,樣品直徑137mm,表明了該采樣器實(shí)施冷凍采樣可行。進(jìn)行了含水率與冷凍膨脹率以及融化收縮率的關(guān)系試驗(yàn),并制定了野外采樣操作方案。含水率與冷凍膨脹率的相關(guān)系數(shù)為0.81,與融化收縮率的相關(guān)系數(shù)為0.97。沉積物樣品的冷凍膨脹率小于5%而融化收縮率總體介于10%到40%之間。
[Abstract]:Understanding sediment is the basis of understanding the history of environmental change and predicting future environmental change. As the main host of surface matter migration, the poor fluidity of lakes makes the deposition of environmental materials relatively stable, and the stratification of sediments contains rich environmental information. As a result, it has become a hot spot in the research of many natural environment change records. Because the existing samplers usually destroy the original sequence of sediments, the accuracy of the study on sedimentary period is generally low. In this paper, the shortcomings of the existing sediment sampler are summarized. According to the principle of structure and function, the detailed structure of the snail tube frozen sediment sampler is designed and a prototype is made. The freezing law of the sampler is numerically simulated based on Fluent software. The basic performance of the sampler is tested by comparing the results of indoor test and numerical simulation, and the operation scheme of field sampling is worked out. The basic structural parameters of the prototype are as follows: the length of the sampling tube is 1000mm, the inner diameter is 137mm, the width of the cold source is 250mm, and the distance between the lower boundary of the cold source and the sampling port is 200mmm. The sample tube is 201 stainless steel, the screw freezing tube is copper tube, the waterproof protective casing is UPVC feed pipe. The freezing law of the sampler is numerically simulated, and the symmetrical temperature distribution characteristics of the sampling tube cavity near the wall, the "H" shape at the center and the symmetrical arch phase transition of the sample are obtained under the simulated conditions. The position of the theoretical closure point of the sample was obtained and the curve of the axial closure height of the sample with time was plotted. The results of clean water test and numerical simulation show that the freezing process of the theoretical closed point has experienced "constant velocity period", "platform period", "drop period" and "deceleration period". The proportion of each period was 22.2and 44.4%, respectively, and the "platform period" controlled the whole freezing cycle. The indoor simulated lake sediment sampling test was carried out, and the samples with clear interface and frozen water were collected from the initial water temperature of 12.7 鈩，

本文編號(hào)：1789327