Fluid Mechanics I 1. Introduction & Chapter 1 3rd semester, autumn

Shinichiro YANO Department of Urban and Environmental Engineering, Kyushu University

10 October, 2012

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Who am I ? Instructor: Shinichiro Yano, Dr. of Engineering

– Associate Professor of Sustainable Aquatic Environmental Engneering

– Environmental Fluid Mechanics Lab. – Room 1031, West 2 building (West zone) – tel: 092-802-3414 – yano@civil.kyushu-u.ac.jp

WEB site for this class http://www7.civil.kyushu-u.ac.jp/kankyo/kankyo_en/

lecture_en.html

ｰ PDF file for color version can be downloaded

Career: 1995-1998: Research Associate, KU 1998: Degree of Dr., Engineering, KU 1998-2002: Lecturer, Nagasaki Univ. 2002-2004: Research Fellow, KU 2004-now: Associate Professor, KU 2008-2009: Guest Researcher, TU Delft, the Netherlands

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Research Interests: 1) Environmental Hydraulics: - mechanism of change of aquatic environment - improvement of deteriorated coastal and riverine environments 2) Computational Fluid Dynamics(CFD): - numerical simulation of current and matter transport in an estuary

and a river 3) Hydroinformatics: - to combine GIS(geographical information system) with CFD and Field

Measurement

the upper Chikugo River: Q=4.5m3/s

Effect of stream flow regime change on river ecosystem

the upper Chikugo River: Q=40m3/s

In-situ measurement of tidal current in Ariake Sea: flood tide

上げ潮最強時(09:00～11:00）の水深平均流速平面分布

10km10km10km10km

下げ潮最強時(15:00～17:00）の水深平均流速平面分布

10km10km10km10km

In-situ measurement of tidal current in Ariake Sea: ebb tide

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Numerical hydrodynamics modeling in Ariake Sea: Salinity distribution in flood event in 2006

05:00 HW 12:00 LW 19:00 HW

Komenotu River

Minamata Rive

Minamata Bay Minamata Bay

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Course descriptions (1) Textbook

– Fluid mechanics, 7th edition – By Frank White – International edition (PB) – McGraw-Hill – ISBN:978-0071311212 – used for series of courses, Fluid Mechanics II (Mech. and Aero.),

Hydraulics I and II (Civil)

Prerequisites – Mathematical skills

• Ordinary & partial differential & integral calculations • Linear algebra • Vector analysis

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Course descriptions (2) Attendance

– Attendance of 2/3 of classes (more than 10 classes) is required – Attendance is confirmed via a small exercise to check

understanding level: This is NOT a test!

Grading – Mid-term and final examinations 80% – Attendance 20% – Total score of 60 is necessary for qualification

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1. Introduction 1.1 What is fluid ? What is fluid ? (§1.4)

– Solid can resist shear – Liquid

• Water, oil, alcohol, etc. • Large density with cohesive forces

– Gas • Air, nitrogen, natural gas, etc. • Free movement of molecules

Fluids easily moved by shear (No shear forces at rest)

Temperature

Pres

sure

Solid

Liquid

Gas

Saturation curve

Fig. 1.3

boiling point

melting point

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1. 2 Fluid mechanics as a continuum mechanics Fluid as a continuum (§1.5)

– Density

• Mass per unit volume • δv*~10-9 mm3 (1µm3) at standard condition

– Knudsen number

• Mean free path of gas molecules / representative physical length • Kn <<0.01 Continuum mechanics Fluid dynamics (fluids in motion) Fluid statics (fluid at rest) • Kn >>0.01 Rarefied gas dynamics

Fig. 1.4

vM

vv δρ

δδ ∗→= lim

LKn λ

=

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1. 3 Dimensions & Units (§1.6) Dimensions

– 4 primary dimensions Mass, Length, Time, Temperature {Θ} • Other dimensions can be represented by those four in FM

» ex. Velocity {V}={L/T}, Force {F} ={MLT-2}

Units for quantitative expressions – SI (International system) units

• Kg (Kilo-gram), m (meter), s (second), K (Kelvin) – Other… BG, CGS, EES --- can be converted to SI

Homogeneous dimensions (units) must be used

Table 1.1 Primary dims. Table 1.2 Secondary dims.