问题
单项选择题
在水力模型实验中，要实现有压管流的动力相似，应选用的相似准则是（）。
A.雷诺准则
B.弗劳德准则
C.欧拉准则
D.柯西准则
答案
参考答案：A
解析：本题属于记忆题，应熟知各准则的适用条件。雷诺准则是惯性力与黏滞力之比，在有压管流中，黏滞力成为主要矛盾，因此适用雷诺准则。
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在水力模型实验中，要实现有压管流的动力相似，应选用的相似准则是（）。
A.雷诺准则
B.弗劳德准则
C.欧拉准则
D.柯西准则
参考答案：A
解析：本题属于记忆题，应熟知各准则的适用条件。雷诺准则是惯性力与黏滞力之比，在有压管流中，黏滞力成为主要矛盾，因此适用雷诺准则。
My husband Sid and I were never able to have children. I had always wanted a family and that feeling 36 after his death. He was all I had. When he 37 , I felt like I had lost my entire family. I never 38 I would finally get the family I had always wished for. A few years later I met Tom. When we married, I 39 got four grown children and eight grandchildren. I was 40 about my first meeting with his children. My worries melted away when I realized that they 41 me and were more than willing to bring me into their family. And when his daughters 42 me if their children could call me “Mimi,” I was excited, Tom was divorced, and 43 I was also concerned about the 44 that the children already had two grandmothers. Would the little ones understand 45 I fit into the family？ At our first extended family gathering, I 46 our six-year-old grandson Jim staring at me with a 47 look. He seemed to be thinking about something serious. 48 sporting a big grin(咧嘴笑)，he jumped and said, “I know who you are! You are our 49 grandma!” At that moment, I know it was time to just relax and enjoy my new 50 . People say when a door close, God opens a window. Now I know what that 51 . I lost so much joy when Sid died, 52 now I have a new happy life. I am enjoying so many things I 53 got to experience before like reading bedtime stories. My refrigerator is covered with drawings, and my walls are 54 with photos of the kids. I may be an instant “extra” grandma in Jim’s eyes, but I am just as 55 any other “regular” grandma I know.
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