题目内容
范宁公式只适用圆形直管内层流流动时的阻力计算
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材质一定的管子,管壁粗糙度一定。
层流时,摩擦系数与管壁粗糙度无关,湍流时,雷诺数逐渐增大,此时壁面粗糙度对摩擦系数的影响越来越大。
流体层流流动时,摩擦系数既与雷诺数有关,也与管壁粗糙度有关。
Conversation One (Questions 1-4)• Look at the note below.• You will hear a man making a call about a delivery.Telephone MessageTo: John WhiteDate:19/10/00Patrick Fisher rang to say our new (1)........................................................ would be deliveredtomorrow. You need to tell Sarah Robbins, the (2)......................................., where to (3).................................................. them.Please phone Mr. Fisher on (4)................................................................. if there are any problems.Conversation Two (Questions 5-8)• Look at the note below.• You will hear a man telephoning his personnel officer.MessageDate: 12 November 00From: Roshan Singh, (5) .......................................................... Department.Message: He has received an interesting job (6) ..................................and wants to discuss his (7)...............................................He has to reply by (8) ................................................morning range.Conversation Three (Questions 9-12)• Look at the note below.• You will hear a woman calling a company about a possible order.TELEPHONE ENQUIRY RECORDCaller: Julie Ventnor from Polareach LtdShe's interested in our (9) ...........................................................Requires details of our (10) ......................................... termsTotal monthly order, approx. (11) £...........................................................Meeting on: 30th (12) ............................................................
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