流體力學試驗.第七章：壓力中心儀試驗

Abstract

中文摘要

此試驗利用槓桿原理測定容器內的液體產生的靜水壓作用在容器壁所產生的順時針力矩，藉由此順時針力矩可推倒出，將本為隨著水深改變的靜水壓視作為一集中力時，作用於壓力中心點R，並找出R點位於何處? 試驗分成兩個部份:一為儀器在水平的時候所靜壓力作用在壓力中心點R1與靜力學理論公式計算出的理論值R2做比較得出誤差，針對此誤差可做進一步的探討。；二為儀器有著θ角度的旋轉，試比較力矩相同的情況下，儀器在水平及傾斜時，壓力中心的位置是否有不同， 試驗過程中會使用到砝碼、錘鉤、用來調整水位的針筒以及吸管能幫助有效降低試驗誤差。 實驗步驟如下: • 1. 在力臂一端有孔口處懸掛一錘鉤，並利用力臂中端之小水槽裝水，調整儀器使其平衡。 • 2.在錘鉤上增加砝碼，並緩緩加水於圓弧容器中，使水平桿恢復平衡(假如加太多水就用針筒吸取多餘的水) • 3.第一部份:依據水位的高度h分為h≦D及h＞D兩個單元做紀錄，優先紀錄第一單元h≦D之每次試驗的砝碼重及容器內的水位高。完成後再紀錄第二單元。 • 4.第二部份:重複步驟1~3並且詳細記錄試驗數據。 • 5.將試驗數據求出實際的壓力重心，並與理論公式推出之理論壓力中心相互比較，針對兩者之異同做討論。

Abstract The test is using Principle of lever to measure the moment in the clockwise direction stem from hydrostatic pressure of liquid in the container. Let’s consider hydrostatic pressure as concentrated force act on the pressure center called point R and find out its position. This test can be divided into two parts. The first of all, Part I : comparing computed value of pressure center with theoretical value of pressure center that can get error, aim at this error we can discuss this further. Second, Part II : the instrumentation have rotate θ degrees. In the situation while moments are same, trying to compare the position of pressure center when the instrumentation is horizontal with the instrumentation is tilt. In the course of the experiments, we will use weights, balance pan, pneumatic syringre be used to adjust level and straws that can decline experimental error effectively. Step of experiment is listed below: 1. Hanging a balance pan at orifice on the end of force arm. Taking in water with the sink at middle of force arm and adjusting the instrumentation make it balance. 2. Adding weights on the balance pan then putting the water in the circular container make the leveling rod return to equilibrium state. If put too much water in that could use pneumatic syringre to suck out superfluous water. 3. Part I : Taking notes according to the level(called h) can be divided into h≦D and h＞D two units. Recording the weights and level each experiment. Finish Unit 1 first after that finish Unit 2. 4. Part II : Repeat step 1 to step 3 and record experimental data detailed 5. According to experimental data to find out the position of actual pressure center and compare that with the position of theoretical pressure center and discussing the difference between the two.