问题 问答题 简答题

简述局部流动损失是怎样形成的?

答案

参考答案:

在流动的局部范围内,由于边界的突然改变,如管道上的阀门、弯头、过流断面形状或面积的突然变化等,使得液体流动速度的大小和方向发生剧烈的变化,质点剧烈碰撞形成旋涡消耗能量,从而形成流动损失。

阅读理解

根据短文内容,选择最佳答案。

    Dinner, for English people, is the richest meal of the day and is very formal (正式的) meal. Many people even

wear special clothes for dinner, so, if you are asked out to dinner, you must find out whether you are expected

to wear a dinner suit. When you get there and you find you are the only person in ordinary clothes, you will feel

unhappy and worried. Dinner is usually served at about half past seven. All the members of the family sit down

together and are on their best behavior (举止). The head of the family sits at the other. If there is a guest (客人),

he usually sits on the right of the lady of the house. If there are several guests, the most important one is asked

to sit there. While the meal conversation is carried on, you should try to get into conversation with the person on

your right or left, but you should not try to talk to someone who is long way from you.

1. In England, if your family are asked out to dinner, _____ will sit on the right of the housewife. [ ]

A. your sister

B. your father

C. your mother

D. you

2. When you go to dinner together with other guests, you should try ______ at table. [ ]

A. to talk only with the lady of the house

B. to talk as loudly as you can

C. to talk with each of the other guests

D. to talk with the person beside you

3. In England if you wear special clothes for dinner, it shows that _______. [ ]

A. you are a special person

B. you are a rich man

C. you are a man with good behavior

D. you are the most important guest

4. Which of the following shows English dinner is different from Chinese dinner? [ ]

A. People have rich dinners when they celebrate their festivals.

B. The important guest usually sits on the right of the lady of the house.

C. The guests usually wear special suits for formal meals.

D. The dinner is usually served in the middle of the day or the evening.

5. From this passage, we may know _______. [ ]

A. English families often serve dinners to guests

B. English people are too rich

C. the person with good behavior is often asked to dinner

D. English people are usually on good behavior at dinner

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