Introduction to Modern Measurement Technology

Transcription

1 Introduction to Modern Measurement Technology and Applications in Coastal and Ocean Engineering Kuang-An Chang Ocean Engineering Program Department of Civil Engineering Texas A&M University

2 What Do We Need to Measure in Coastal and Ocean Engineering? Water elevation Force Pressure Velocity Concentration

3 Available Tools for Non-Intrusive Quantitative Measurement Techniques: Laser Doppler Velocimetry (LDV) Point velocity measurement, high sampling rate, small sampling volume Particle Image Velocimetry (PIV) Full field velocity measurement, usually low sampling rate Laser Induced Fluorescence (LIF) Flow visualization, scalar field (concentration, heat) measurement, usually qualitative

4 Drawing of Leonardo Da Vinci Structures within a water flow

5 Laser Induced Fluorescence Turbulent round jet under waves

6 How Does LDV Work?

7 LDV Fiber Optical System

8 Measurement of flow field around a 1:5 scale car model in a wind tunnel Photo courtesy of Mercedes-Benz, Germany

9 Measurement of air flow field around a ship model in a wind tunnel Photo courtesy of University of Bristol, UK

10 LDV System at TAMU

11 LDV Measurement

12 How Does PIV Work? Thin sheet of light Water seeded with small particles Camera field of view Mirror Digital camera head Pulsed laser with light sheet optics Light sheet optics

13 PIV Setup Pulsed laser (Nd:YAG) Mirror Light sheet optics Free surface Thin sheet of light Jet seeded with small particles Video Computer

14 Image pair Image pair Camera Trigger signal Laser trigger signal t pixels

15 Naive PIV Technique Frame 1 t = t 0 Frame 2 t = t 0 + t

16 PIV Technique (2-frame/single-pulsed) Frame 1 Frames 2 t = t t = t t

17 Cross Correlation Cross-correlation: R Rs ( ) = f( xgx ) ( + sdx ) sub window y x

18 Instantaneous Velocity Measurements Turbulent Round Jet 1 Turbulent Round Jet 2

19 How Does LIF Work? Thin sheet of light jet mixed with fluorescent dye CW laser with light sheet optics Light sheet optics

20 Fluorescein Characteristics absorption emission

21 LIF Setup Shutter Thin glass Power meter CW laser (Argon-Ion) Connected to constant head reservoir y Mirror Scanning beam galvanometer Free surface Jet mixed with fluorescent dye x FOV Video Computer

22 PIV/LIF Setup Pulsed laser (Nd:YAG) Shutter Mirror Thin glass Power meter CW laser (Argon-Ion) Connected to constant head reservoir y Light sheet optics Thin sheet of light Mirror galvanometer Scanning beam Free surface Jet mixed with fluorescent dye and seeding particles x FOV Video Computer

23 Simultaneous velocity and concentration (Re = 4210)

24 Simultaneous velocity and concentration (Re = 4210)

25 Animation - Turbulent Round Jet Re = 360. Simultaneous PTV-LIF Measurements

26 Laboratory in Action

27 Applications Pollutant transport in coastal water Current structure interaction Wave-structure interaction

28 Jet under Waves Jet under Waves

29 a sewage outfall plume in coastal waters The plume is intruding into a narrow layer. At the time the picture was taken, the mean current field was moving the plume off-shore.

30 tracer-study plume conducted at the mouth of a river entering into an estuary One can clearly see the fine-scale structure of the plume interacting with ambient turbulence and the slow nature of lateral spreading.

31 joining of three different rivers The one on the left, with very high particulate concentration, joins with the two rivers on the right. The larger of the two rivers carries a higher particulate load, thus the darkest (cleanest) smallest river is also visible. Notice how sharp the boundaries are separating the various river flows.

32 Tung-Hsiao, Taiwan

33 Tung-Hsiao, Taiwan

34 Sketch of Horseshoe Vortex System

35 Experimental Setup (a) honey comb 200 cm contraction section meshes 54 cm test section 180 cm stainless flow regulator 885 cm 122 cm 50 cm valve pump 306 cm stainless flow regulator (b) 122 cm 100 cm 200 cm 305 cm 36 cm 122 cm

36 Experimental Setup side wall glass X U 0 W model x Z z side wall glass top view U 0 Y y model h X H x base plate support bottom glass side view

37 cm/s x(mm) PIV Velocity y(mm) y(mm) y(mm) y(mm) y(mm) y (mm) y(mm)

38 cm/s x(mm) y (mm) y(mm) y(mm) y(mm) y(mm) y(mm) y(mm)

39 Cylinder-Plate Juncture Flow Animation

40 Bridge Scour

41 Bridge Scour

42 Bridge Scour

43 Bridge Scour

44 Bridge Scour

45 Navy barge ship model test y Capsizing Position 8 m Wave Absorber x Wave maker SWL h = 0.8 m 0 m Barge 33 m Side View 0.9 m Top View

46 Barge Model

47 Wave Interaction with Barge Light sheet Unit : mm Barge wavemaker // // Absorber 800 Wave Elevation Gauges Mirror FOV Slope : 1/5 // // Side View

48 Sketch of rolling barge and PIV fields of view Condition FOV size (mm 2 ) Spatial resolution (mm 2 ) Fixed Barge (large FOV) Fixed Barge (small FOV) Free Rolling Barge

49 Sample Image Pair

50 Vorticity (Fixed Barge, T=1.0 s)

51 Turbulent kinetic energy (Fixed Barge, T=1.0 s)

52 Vorticity (Rolling Barge, T=2.0 s)

53 Waves runup

54 Instantaneous velocity field

55 Laboratory equipment

56 Wave Tank & High Speed PIV System

57 High Speed PIV System

58 Nd:YAG PIV System

59 LDV System (3D) LDV System

60 Why be a coastal engineer? Can always claim that we are working when going to beach!

61 Our problem of interest

62 Our measurements

63 Our Working Place

64 Our field equipment