Ships: Loads, stability and erosion

Transcription

1 Ships: Loads, stability and erosion Chapter 9 ct4310 Bed, bank and shoreline protection H.J. Verhagen June 3, 2012 Faculty of Civil Engineering and Geosciences Section Hydraulic Engineering 1 Vermelding onderdeel organisatie

2 Introduction In inland waterways ships may cause waves primary wave secondary waves propeller wash June 3,

3 flow around fixed object & moving object in stagnant water June 3,

4 Phenomena around a moving ship in a waterway June 3,

5 Return current and primary wave Ship in Elbe river, courtesy prof. Erik Pasche, TU Hamburg June 3,

6 propeller wash June 3,

7 Definition in 1-d approach gt 2 h c tanh gl 2 h 2 L Vl c tanh 2 L L ct June 3,

8 limit speed Bernoulli : continuity: dq dz 2 v v s s u h h z 2g 2g b hv b h B D b z v u Q s s r Maximum speed is reached when return flow becomes critical, i.e. when derivative of return flow to waterlevel becomes zero Combine this with Bernoulli: d v u Ac As bz s dz A V 3 V 1 A gh gh 2 2/3 s l l 1/3 c 2 2 r 0 2 June 3,

9 limit speed a a function of blockage A s /A c A V 3 V 1 A gh gh 2 2/3 s l l 1/3 c 2 2 June 3,

10 limit speed as a function of waterdepth and blockage June 3,

11 primary waves 2 vs 2 z/ h 2 gh 1 A / A z / h 1 u r gh 1 1 As / Ac z / h s c 1 v s gh June 3,

12 waterlevel depression as a function of blockage June 3,

13 return flow velocity as function of blockage June 3,

14 deviation from the 1-d case 2y y z 1 z u 1 u b b ecc r ecc r z max 1.5z ecc June 3,

15 origin of diverging and transverse waves June 3,

16 secondary wave pattern June 3,

17 Kelvin wave Christian Eskelund US Navy June 3,

18 Kelvin Duck wave M.S.Cramer, Virginia Tech Duck Pond June 3,

19 secondary wave height measurements June 3,

20 example (1) Given: ship 10 m wide, draught 3 m canal 40 m wide, 5 m deep Limit speed: A s /Ac = (10*3) / (40*5) = 0.15 fig 9.4 V l /gh = 0.55 V l = 3.8 m/s design speed 0.9*3.8=3.4 m/s Use fig. 9.6 z/h=0.083 z=0.42 m Ship sails 10 m from bank (y= 5 m), so eq. 9.6 and 9.7 z max =1.5((1+2*5/40)*0.42 = 0.78 m u r = 0.15 *gh = 1.04 m incl. excentricity: (1+5/40)*1.04 = 1.17 m/s H = 1.2 h(s/h) *v 4 /(gh) 2 = eq *5*(10/5) *3.4 4 /(10*5) 2 = 0.27 m June 3,

21 standard values in the Netherlands Lakes Canals Rivers Small waters Wave heights (m) Currents (m/s) Wind waves Ship waves Natural current Return current n.a n.a. Data from CUR 197 Breuksteen in de praktijk June 3,

22 Propeller action June 3,

23 turbulence in propeller wash and in free circular jet June 3,

24 equations for propeller jets u 2.8u 0 m x/ d r 2.8u x b 0.21x u e u u e m r 0.69 b 2 x/ d 2 June 3,

25 velocity distribution in propeller wash and free jets June 3,

26 velocities behind propeller u P 1.15 d 0 2 u bmax 0 1/3 d 0.3u z b see also section June 3,

27 measured flow in a propeller jet data from thesis Schokkink, 2003 June 3,

28 Turbulence in a propeller jet data from thesis Schokkink, 2003 June 3,

29 Flow caused by a propeller on an inclined slope data from thesis Schokkink, 2003 June 3,

30 erosion due to bowthrusters data from thesis Schokkink, 2003 Plofsluis, Amsterdam Rijn kanaal June 3,

31 Ship engines 3000 power main propulsion system - resistance y = 0,661x R 2 = 0,5882 installed power ship lenght*(2*draught+beam) Type of ship Small ships Spits Kempenaar Dortmund-Ems Kanal Rhein-Herne Kanal Large Rhine vessel 2 barge pushboat Power of engine (kw) P mean =0.66L(2D+B) P 10% =1.25 P mean June 3, Data from Verheij (2010)

32 Simulation of a propeller jet Model by De Jong [2003], measurements by Schokking [2002] June 3,

33 Model simulation with Phoenicx Data from Van der Laan [2005] June 3,

34 The physical model Van der Laan [2005] June 3,

35 Dieptegemiddelde horizontale stroomsnelheid (ū in cm/s) Mathematical vs. Physical model EMS 1 Fysisch model EMS 1 Numeriek model EMS 3 Fysisch model EMS 3 Numeriek model Initiële stroomsnelheid (Uo in m/s) Van der Laan [2005] June 3,

36 flow under ship Egbert van Blaaderen, 2006 June 3,

37 Data of all inland vessels - P mean =A 1 LD+A power bow thruster - lateral resistance 10% exceedance lines Container vessels General cargo Tankers Cruise liners installed power bow thruster [kw] lateral resistance L*D [m2] June 3, Data from Verheij (2010)

38 stability of bed protection important are: return flow stern wave (depression) secondary waves propeller wash Relations based on Izbash + experimental data Hartelkanaal tests provided good data M Q Dipro June 3,

39 bow thrusters P A ( LD) A v d p 1 2 D P d 0.5 Pd D0 D vb 1.03vp z 0 p 1/3 P d = Power of engine L = lenght of ship D = draught of ship D 0 = diameter of propeller v p = velocity behind thruster v b = velocity near the bed = loss factor = 0.9 z p = distance propeller axis and bottom of channel The axis of the thruster is D p above the bed, but for there is no default given. June 3,

40 stability (primary waves) d n50 2 ur g sin 1 sin 2 2 z max d n50 1.8cot 0.33 June 3,

41 stability (secondary waves) H cos55 H d d n50 n50 June 3,

42 stability (propeller wash) d n50 2 ub g sin 1 sin 2 2 June 3,

43 given: depression = 0.78 m H = 0.27, T = 1.8 s u r = 1.17 m/s tan=1/3 stern wave effect: zmax cot d n50 dn example (2) *1.8* m return flow effect: 2 ur 1 dn g sin 1 sin secondary wave effect: H d d n50 n June 3, dn * *2*9.81* m 1.65* m

44 example (3) stern wave dominates problem action of stern wave only at waterline at deeper water return flow dominates at more spacious water bodies secondary waves become dominant June 3,

45 example (4) Ship 10 m wide, d3 m draught, 1000 kw engine (1370 hp), propeller diameter 1.4 m, propeller 1.5 m above bed Effective jet = 70% of real diameter, so d = 1 m d n50 1/3 P u d d ubmax 0.3u0 z 2 ub g sin 1 sin b 2 2 u 0 2 ub June 3, m / s 1000* * m / s *2.25 dn m 60/300kg 1.65*9.8

46 Optimal depth of a channel Dredge level Free channel depth 2d n50 June 3,

47 erosion h y h0 cos tan h0 June 3,

48 bed erosion due to propeller wash ux c ln 5.6 ud hs x zb June 3,

49 Dipro - Cress June 3,