流体力学A卷2007-7.doc

中山大学工学院二〇〇六学年第二学期期末考试试题（A卷） 系、所、中心/专 业：应用力学与工程系/05土木工程 课 程： Fluid Mechanics 姓 名： 学 号： 成绩评定 评卷人（签名）________________ 考试时间：2007年 7 月 13日 上午 《中山大学授予学士学位工作细则》第六条：“考试作弊不授予学士学位。” 题次 1 2 3 4 5 6 7 8 总分 分数 15 10 15 10 15 10 15 10 100 得分 *Draw diagrams, list governing equations and make proper assumptions for each question [15 marks] A rectangular tank, open to atmosphere, is filled with water(?=103kg/m3) to a depth of 2.5m as shown in Figure 1. A U-tube manometer is connected to the tank at a location 0.7m above the tank bottom. If the zero level of the manometer fluid (mercury, ? =13.5x103kg/m3) is 0.2m below the connection, determine the deflection l after the manometer is connected and all the air has been removed from the connecting leg. If the top of the tank is sealed tightly and the air pressure inside the tank is increased to a gage pressure of 0.5atm. Determine the deflection l. (assume 1atm=10m H2O, cross section of the tank cross section of the manometer) Figure 1 [10 marks] A long square wood block is pivoted along one edge. The block is in equilibrium when immersed in water to depth shown. Evaluate the specific gravity of the wood, if friction in the pivot is negligible. Figure 2 [15 marks] A reducer in a piping system is shown in Figure 3. The internal volume of the reducer is 0.2m3 and its mass is 25kg. Evaluate the total force that must be provided by the surrounding pipes to support the reducer. The fluid is gasoline with?? =0.73x103kg/m3. Patm=101kPa. Figure 3 [10 marks] The water flow rate through the siphon is 0.02m3/s, its temperature is 20oC (vapor pressure 2.33kPa), and the pipe diameter is 50mm. Compute the maximum allowable height, h. Figure 4 [15 marks] Consider a smooth sphere, of diameter D, immersed in a fluid moving with a speed V. The drag force on a 3m diameter weather balloon in air moving at 1.5m/s is to be calcula