Modeling of Wind Waves in the Bays of South-West Part of the Crimea Peninsula

Transcription

1 Turkish Journal of Fisheries and Aquati Sienes 12: (2012) ISS DOI: / v12_2_23 Modeling of Wind Waves in the Bays of South-West Part of the Crimea Peninsula Vladimir Vladimirovih Fomin 1, *, Dmitriy Vladimirovih Alekseev 2, lena Vasil evna Ivanha 2 1 Marine Branh of Ukrainian Hydrometeorologial Institute, 61, Sovetskaya st., 99011, Sevastopol, Ukraine. 2 Marine Hydrophysial Institute of the AS of Ukraine, 2, Kapitanskaya st., 99011, Sevastopol, Ukraine. * Corresponding Author: Tel.: ; Fax: ; -mail: v.fomin@ukr.net Reeived 15 Marh 2012 Aepted 02 April 2012 Astrat umerial simulation of waves in the ays of south-west part of the Crimea Peninsula is arried out with high spae resolution. Partiular attention is paid to the loal harateristis of waves in the Sevastopol Bay. The parallel version of wave spetral model SWA is implemented. The steady state waves aused y of different diretions are onsidered. It is otained that the most intensive waves near the Crimea south-west oast and in the Sevastopol Bay are generated y west ; the less intensive ones are aused y east. volution of wave heights, veloities and lengths on different stages of storm on 11 ovemer 2007 are studied. The areas of oast whih are sujeted mostly y storm waves are determined. Keywords: Computing luster, SWA, the Sevastopol Bay. Introdution Bays of the Crimea south-west oast (Figure 1) are intensively used oth for eonomi and military purposes. The ommerial, passenger and fishery ports, shipyards are plaed here as well as navies of Russia and Ukraine. ot infrequently do the storm waves reak funtioning of maritime eonomi omplexes; they ause underflooding or sometimes ollapse of shores, destrution of oastal uildings, signifiant material damage and human losses (Dotsenko, 2000). So the investigation of wave onditions of the Crimea south-west region has the top-priority sientifi and applied interest. The Sevastopol Bay is the largest ay of the Crimea south-west oast. It strethes out in zonal diretion from the west to the east for 7.5 km. The maximal width of the ay is approximately 1 km. Depth dereases from 20 m in the west to 4-5 m in the east. The ay has indented oastline due to the presene of small ays and apes (Figure 2). The mouth of the Sevastopol Bay is ounded y two piers, the distane etween whih equals 550 m. Till now there haven t een any theoretial investigations in whih wave loal peuliarities in the Crimea ays would e resolved and the realisti onditions on their oundaries would e aounted for. In the present work the spae distriution of wave parameters along the south-west oast of the Crimea Peninsula in ase of s with different diretions is studied y using the method of omputer simulation. Partiular attention is paid to the loal harateristis of waves in the Sevastopol Bay. The harateristis of extreme waves in the ay during devastating storm on 11 ovemer 2007 were onsidered. volution of the storm ourred the following way. At night on 10 ovemer 2007 the Mediterranean ylone left the Balkan region and with the veloity of 70 km/h started to move towards the Crimea. At the eginning on 11 ovemer aove the Crimea region the south-east inreased to m/s and y 9 a.m. reahed m/s hanging diretion to south-west. Wind veloity in lasts reahed 32 m/s. On ovemer the ylone enter was moving from the Crimea Peninsula to the north and the aove the Blak Sea water area didn t exeed 7-12 m/s. As a result of the storm the part of a quay etween the Artyleriis ka Bay and Pivdenna Bay (Figure 2) was destroyed, a oat was sumerged in the Artyleriis ka Bay, and some warships were damaged. Mathematial Model Charateristis of waves (signifiant wave height, wave diretion, length and period) are Pulished y Central Fisheries Researh Institute (CFRI) Trazon, Turkey in ooperation with Japan International Cooperation Ageny (JICA), Japan

2 364 V.V. Fomin et al. / Turk. J. Fish. Aquat. Si. 12: (2012) VI V III IV I II Figure 1. Bathymetry of the Crimea south-west oastal zone (m). Bays: I Kozaha, II Komysheva, III Kruhla, IV Strilets ka, V Karantinna, VI Sevastopol. IX VIII I VII VI I II III IV Figure 2. Bathymetry of the Sevastopol Bay (m). Bays: I Martynova, II Oleksandrivs ka, III Artyleriis ka, IV Pivdenna, V Kilen, VI Sukharna, VII Hollandiia, VIII Pivnihna, IX Kostiantynivs ka. V otained y using the spetral wave model SWA (SWA tehnial doumentation, 2007; Booij et al., 1999; Ris et al., 1999). This is the most widely used omputer model for wave simulations in the nearshore region. SWA aounts for all relevant proesses of wave propagation, generation y, nonlinear interations etween the waves and deay. Compared to the deep-water wave models, SWA inludes depth-indued wave reaking and triad wave-wave interations that may e important for near shore wave predition. Diffration is aommodated in an approximate manner in the model. SWA is ased on the wave energy alane equation in spetral form ( gx) ( gy) ( ) ( S ), (1) t x y where (t, x, y,, )/ is the ation density; (t, x, y,, ) is the energy density spetrum; x, y are the horizontal oordinates; t is the time; g is the gravitational aeleration; g 1 g 2kH tanh ( kh) 1 ; 2 k sinh( 2kH) k k x y, gy g ; k k gx, k k x, k } is the wave vetor; 2 2 k k x k y ; { y H is the water depth; gk tanh(kh) is the wave frequeny; is the wave propagation diretion; H H t ; 1 H ; k H m m is a oordinate perpendiular to the wave propagation diretion ; S Sin Snl Sw Sf Sdi is the soure/sink term; S in is the energy transfer from to waves; S nl is the nonlinear transfer of wave energy through three-wave and four-wave interations; S w, S f, S idi are the wave deay due to whiteapping, ottom frition and depth-indued wave reaking orrespondingly. For the terms desriing input, whiteapping and ottom frition SWA provides optional hoie of physial approximations. In the

3 V.V. Fomin et al. / Turk. J. Fish. Aquat. Si. 12: (2012) 365 present work the third-generation mode of model was used with Komen et al. (1984) formulation for exponential wave growth due to the and whiteapping. Aording to Moeini and temad- Shahidi (2007) the use of Komen s formulation for the input leads to the most aurate predition of wave heights. At the JRICHO (Joint valuation of Remote sensing Information for Coastal defene and Harour Organisations) projet (Wolf et al., 2000) for the three near-shore zones with loal morphologial peuliarities the verifiation of SWA model was arried out on the asis of satellite altimeter data y using different ottom frition formulations. The est oinidene of results of numerial simulations with the oservation data was otained when the Grant Madsen (Madsen et al., 1988) approximation for the ottom frition was used. So this approximation was hosen for the present study. In SWA for the depth-indued wave reaking the model of Battjes and Janssen (1978) is applied. To alulate four-wave and three-wave interations approximations of Hasselmann et al. (1985) and ldeerky (1996) were implemented orrespondingly. To validate the results of SWA model with the hosen physis test alulations for region of loation of the gas platform Golitsyno 4 on the north-west shelf of the Blak Sea was arried out (Polonsky et al., 2011). Marine Hydrophysial Institute of the AS of Ukraine otained series of parameters and level osillations during on the platform. The results of wave height simulation for the same period were ompared with the in-situ data and showed quite a good oinidene. On the rigid side oundaries the ondition 0 is used. By the angular variale the periodiity ondition is used ( 0) ( 2 ) and y the frequeny variale the following one is used ( min ) ( max ) 0. By using of the solution of equation (1) the following wave harateristis an e otained: the signifiant wave height 2 H s 4 (, ) dd, (2) the mean wave diretion 2 2, (3) artan sin (, ) dd os (, ) dd the mean wavelength 2 2, (4) 2 (, ) dd k(, ) dd and the mean asolute wave period T 2 (, ) dd (, ) dd. (5) The model was installed onto the omputing luster of Marine Hydrophysial Institute of the AS of Ukraine. To do this parallel version of SWA model uilt on the MPI tehnology for omputers with distriuted memory was used (MPI Douments, 2009). To refine the spae resolution of the model the alulations of wave fields were arried out on four nested grids. These grids over the Blak Sea and the Sea of Azov asin, the Crimea west oastal zone, the Crimea south-west oastal zone (Figure 1), and the Sevastopol Bay (Figure 2) with spae resolution of km, m, 4948 m, and 1011 m orrespondingly. When alulating wave harateristis in the Sevastopol Bay the effet of diffration was taken into aount. Angular resolution while determining wave spetrum equals 10. Throughout the frequeny oordinate the grids with 32 nodes in frequeny range Hz in ase of stationary and with 70 nodes in frequeny range Hz in ase of non-stationary were used. Results and Disussion Aording to the oservations on the marine hydrometeorologial station Sevastopol, the s of four main diretions (north, south, east and west) as well as north-east one are the most frequent during the year aove the Sevastopol Bay. The east (23.1%) and south (19.6%) s dominate among them, ut the veloity of the east is minimal. As to the strong s, the south one is most frequent (1%). Let s onsider the steady state waves aused y stationary and spae homogeneous of four main diretions. In numerial alulations the veloity equals 10 m/s. This value is lose to the maximum of monthly mean veloity for the Crimea south-west oast. The most intensive waves near the Crimea south-west oast are aused y west (Figure 3a) due to the longest feth in this ase. Signifiant wave height reahes 1.7 m in the open part of the water area and 1.3 m in the oastal zone. In ase of east the feth is shortest and as a result maximal wave height eomes more then two times smaller (up to 0.8 m) in omparison with the west effet. So the east auses the weakest waves (Figure 3). In entral part of the water area wave heights vary insignifiantly in ase of west and in ase of east they are haraterized y signifiant spae variaility. Maximal heights of waves generated y south and north s are lose to eah other and equal 1.6 m and 1.4 m orrespondingly (Figure 3, 3d). But near the ay mouths the wave heights differ greatly due to the sreen effet of Crimea Peninsula for the south. Diretion of wave propagation is determined y harateristis and y peuliar properties of oastline and ottom. ear the Crimea south-west oast diretion of wave propagation oinides with

4 366 V.V. Fomin et al. / Turk. J. Fish. Aquat. Si. 12: (2012) a d Figure 3. Signifiant wave heights (m) near the south-west oast of the Crimea in ase of west (a), east (), north () and south (d) s. the diretion only in ase of west (Figure 4a). In ase of east due to refration in the southern shallow region near shore the waves deflet to the south following the oastline shape (Figure 4). In other parts of the water area waves follow the diretion. Under the effet of north and south s the wave defletion to the east shallow region appears almost everywhere (Figure 4, 4d). But in ase of south these defletion is more signifiant than in ase of north one. Intensive penetration of waves into the Sevastopol Bay ours under the effet of west. The other ays are more sujeted y the waves generated y the north. The longest waves (up to 26 m) are generated in the open part of the water area y west. In ays wave lengths vary from 6 to 16 m. In ase of north far from the shore wave lengths are shorter (up to 20 m) and in the ays (with the exeption of the Sevastopol Bay) they are longer (from 10 to 18 m) then in ase of west. Maximal wave lengths generated y south have approximately the same values as in ase of north one ut the range of their variaility is wider (from 4 to 20 m). ast effet auses the shortest waves (from 2 to 10 m) among all onsidered diretions. Wave period spae distriutions are qualitatively similar to the wave length ones. The longest waves generated y west have the iggest periods of 4.6 s. In the ays the periods take on the values of 1-4 s for this. In ase of north and south s, maximal periods in the open part of the water area are 4 and 4.2 s orrespondingly, and in the ays they lie in the ranges of s and 1-2 s with the exeption of the Sevastopol Bay. For the east periods are smallest and do not exeed 2.8 s. Further we onsider peuliarities of waves in the Sevastopol Bay. As in the open part of the Crimea south-west oastal zone the maximal waves are generated here y the west and minimal ones are aused y east. In ase of west intensive waves penetrate along the ay axis up to the east oundary. But etween the Artyleriis ka Bay and the Pivdenna Bay and in the Pivnihna Bay there are loal regions where intensive waves reah the south and north oasts orrespondingly. Under the effet of north the maximal wave heights our near the south-west oast of the Sevastopol Bay and under the effet of south they our near the north-west oast. Wave diretion generally oinides with the one in the Sevastopol Bay in ase of west and east s. Defletion to the north and south ours only near the north and south oasts of the ay orrespondingly. In ase of north and south s wave diretion deflets to the east on the whole ay water area due to the depth dereasing from the west to the east. Wave lengths in the Sevastopol Bay are shorter then in the open part of the Crimea south-west oastal zone. In ase of west signifiant variations of wave lengths our alone the whole ay in zonal diretion from 14 to 3 m. This orresponds to the wave period hanging from 3.7 to 1.5 s. Under the effet of north wave lengths vary in the range from 10 to 3 m only near the mouth of the ay. In ase of east and south s wave lengths in the Sevastopol Bay lie in the range from 1 to 3 m and insignifiantly vary in spae. As to the wave periods, their values are etween 0.8 and s. ow let s onsider the results of simulation of

5 V.V. Fomin et al. / Turk. J. Fish. Aquat. Si. 12: (2012) 367 a d Figure 4. Wave diretion near the south-west oast of the Crimea in ase of west (a), east (), north () and south (d) s. wave field evolution in the Sevastopol Bay on ovemer In numerial experiments veloity values otained from the SKIRO regional prognosti model (ational and Kapodistrian University of Athens, 2007) were used as atmospheri foring. Wind field resolution was 1010 km. Calulation was arried out from 5 ovemer 2007 to provide adjustment of wave field with the ondition at the moment of storm egin. By the end of 10 ovemer 2007 wave fields in the Sevastopol Bay were formed y the south-east, whih predominated all the day. The veloity was inreasing not monotonially from 6 m/s to 10 m/s. Spae distriution of wave heights was haraterized y the inrease of their values from 0.1 m in the south-east to 0.28 m in the north-west of the ay with the maximal gradients near the south oast and minimal ones near the north oast. Wave diretion oinided with the one in the most part of the ay. But near the south oast waves propagated predominately to the west. Wave length range was quite narrow from 0.5 m in the east to m in the west. It orresponds to period variations from 0.8 s to s. After midnight on 11 ovemer inreasing with time eame more intensive due to eginning of atmospheri ylone moving aove the Crimea Peninsula. At the first stage of atmospheri disturane moving (up to 2 a.m.) the south-east diretion remained predominant, ut its southern omponent was inreasing gradually. The strength eame strong and one veloity reahed 13 m/s. As a result of preserving of predominant diretion the peuliar features of wave height spae distriution remained the same as on 10 ovemer. In partiular the wave heights inreased from the southeast to the north-west and had signifiant gradients near the south oast. But the intensifiation of veloity resulted in small inreasing of maximal wave height value up to 0.34 m in the north-west in the Kostiantynivs ka Bay and minimal value up to 0.1 m in the east end of the ay (Figure 5a). The waves from the south oast propagated to the north-west as in the entral part of the ay (Figure 6a). ear the north oast of the Sevastopol Bay waves reahed the length of 2 m and period of 1.4 s. From 3 a.m. to 4 a.m. diretion eame lose to southern due to passing of ylone entral part with the minimal veloity in the west from the Sevastopol Bay. Wind strength aove the ay dereased insignifiantly to 11 m/s, varying from the south to the north oast less then on 1 m/s. After short time predomination of south the areas with high gradient of wave heights widened from the south oast to the enter of ay and meridional omponent of wave veloity inreased. After 4 a.m. the Sevastopol Bay was sujeted y the effet of the storm south-west with the predominant west omponent. At 8 a.m. veloity reahed the maximal strength of 25 m/s and varied insignifiantly from the west to the east of the ay. There was the most dangerous stage of the storm evolution onneted with the passing of rear of ylone. At that stage signifiant reuilding of the wave height field ourred. The highest waves were oserved along the ay axis ut etween the Artyleriis ka Bay and the Pivdenna Bay and in less degree in the Pivnihna Bay intensive waves reahed the oast. The proess of wave intensifiation with time was developing the following way. At first the area with the highest waves for the definite moment of

6 368 V.V. Fomin et al. / Turk. J. Fish. Aquat. Si. 12: (2012) 2 a.m. 9 a.m. a p.m. 6 p.m. d Figure 5. Signifiant wave heights (m) in the Sevastopol Bay on 11 ovemer 2007 at 2 a.m (а), at 9 a.m. (), at 1 p.m. () and at 6 p.m. (d). 2 a.m. a a.m Figure 6. Wave diretion in the Sevastopol Bay on 11 ovemer 2007 at 2 a.m. (а) and at 9 a.m. (). time appeared etween two piers in the mouth of the ay. Then this area widened predominantly along the Sevastopol Bay axis toward the Sukharna Bay. For instane at 6 a.m. the wave height etween the piers was 1.5 m and in the Sukharna Bay one was 0.5 m. At 8 a.m. these values were 3.5 and 1.5 m orrespondingly. Due to the sluggishness of wave development proess in omparison with the hange the most intensive waves ourred at 9 a.m. (Figure 5) when the south-west weakened to the value of 23 m/s. As a result of the ommon effet of, oastline shape and athymetry starting from 6 a.m. waves in the distane from oast propagated from the west to the east. ear the north and south oasts waves defleted to the north and south orrespondingly (Figure 6). Wave length and period ranges inreased signifiantly with the strengthening. For example, at 9 a.m. wave lengths varied from 5 m in the east to 40 m in the west and for the wave periods this limits were 2 and 7 s orrespondingly. After 9 a.m. the weakening ontinued with further ylone moving ut until 11 a.m. veloity exeeded 20 m/s. Area with the wave heights more then 2 m still overed signifiant part of the water area from piers to the Artyleriis ka Bay (Figure 5). The oast etween the Artyleriis ka Bay and the Pivdenna Bay was sujeted y effet of waves whih were not higher then 1.5 m and etween the Pivnihna Bay and Sukharna Bay waves near the oast were aout 1 m height. Spatial distriution of wave veloity diretion was in general unhanged in omparison with the situation depited in Figure 6 and remained the same till the morning on 12 ovemer. Only in the Pivdenna Bay diretion of wave propagation was defleting gradually to the south. Ranges of wave length and period variations redued signifiantly as a result of weakening and to the moment under onsideration were 3-25 m and s. After 2 p.m. eame strong again (13 m/s) with the diretion lose to western. This diretion remained predominant till 10 p.m., ut the veloity was dereasing gradually to the value of 6 m/s. Wind ondition hange didn t ause the qualitative reuilding of wave height and diretion fields. Only dereasing of wave height and veloity values ourred. At 6 p.m. intensive waves whih

7 V.V. Fomin et al. / Turk. J. Fish. Aquat. Si. 12: (2012) 369 height didn t exeed 1 m still reahed the oast in the east from the Artyleriis ka Bay (Figure 5d). Later the wave effet on the oast was eoming less signifiant and to 10 p.m. waves higher then 0.6 m were not oserved near the oast. Maximal wave length at 10 p.m. was near the mouth of the Sevastopol Bay and equaled 10 m. Waves with suh length had the periods aout 3.6 s. Conlusion Wind waves in the ays of south-west part of the Crimea Peninsula are studied y using of SWA spetral model. ffet of stationary s with different diretions is onsidered. For the largest Sevastopol Bay the evolution of storm on 11 ovemer 2007 is simulated. The most intensive waves near the Crimea south-west oast and in the Sevastopol Bay are aused y west ; the less intensive ones are aused y east. Diretion of wave propagation near the Crimea south-west oast oinides with the diretion only in ase of west. Under the effet of east the wave diretion deflets to the south in the southern shallow region. In ase of north and south s the wave defletion to the east shallow region appears almost everywhere inluding the Sevastopol Bay. In ase of west and east s in the Sevastopol Bay the wave diretion deflets from the diretion to the north and south near the north and south oasts orrespondingly. Waves with the maximal lengths arise near the Crimea south-west oast and in the Sevastopol Bay under the effet of west ; ones with the minimal lengths arise under the effet of east. The most signifiant variaility of lengths our near the Crimea south-west oast in ase of south and in the Sevastopol Bay in ase of west. During the storm on 11 ovemer 2007 the maximal waves in the Sevastopol Bay ourred at 9 a.m. when the rear of ylone with south-west s moved over the water area. In ase of west s the part of oast etween the Artyleriis ka Bay and the Pivdenna Bay is mostly sujeted y wave effet. This onlusion is onfirmed y the quay destrution on mentioned part of oast on 11 ovemer At the moment, regular instrumental measurements of the waves in ays of southwest part of the Crimea Peninsula aren t arried out and numerial simulation is the only way to estimate possile danger for oastal zones in different situations. The SWA model has een verified in the onditions of the Blak Sea north-west shelf, ut its further improvement is restrited y the lak of in-situ oservation diretly in the region under onsideration. Referenes Battjes, J.A. and Janssen, J.P.F.M nergy loss and set-up due to reaking of random waves. Proeedings of 16 International Conferene of Coastal ngineering, ASC: Booij,., Ris, R.C. and Holthuijsen, L.H A thirdgeneration wave model for oastal regions. Model desription and validation. J. Geophys. Res, 104(C4): Dotsenko, S.F Analysis of the intensifiation of tsunami waves near the South Coast of Crimea. Physial Oeanography, 6: ldeerky, Y onlinear transformation of wave spetra in the nearshore zone. PhD thesis, Den Haag: Delft University of Tehnology, The etherlands. Hasselmann, S., Hasselmann, K., Allender, J.H. and Barnett, T.P Computations and parameterizations of the nonlinear energy transfer in a gravity wave spetrum. Parameterizations of the nonlinear transfer for appliation in wave models. Journal of Physial Oeanog., 15(11): Komen, G.J., Hasselmann, S. and Hasselmann, K On the existene of a fully developed -sea spetrum. Journal of Physial Oeanography, 14: Madsen, O.S., Poon, Y.-K. and Graer, H.C Spetral wave attenuation y ottom frition: Theory. Proeedings of 21 International Conferene of Coastal ngineering, ASC: Moeini, M.H. and temad-shahidi, A Appliation of two numerial models for wave hindasting in Lake rie. Applied Oean Researh, 29(3): MPI Douments, ational and Kapodistrian University of Athens Polonsky, A.B., Fomin, V.V. and Garmashov, A.V Charateristis of the waves in the Blak Sea. Reports of the ational Aademy of Siene of Ukraine, 8: Ris, R.C., Booji,. and Holthtuijsen, L.H A thirdgeneration wave model for oastal region, Part II: Verifiation. J. Geophys. Res., 104(C4): SWA Tehnial Doumentation Delft University of Tehnology. etherlands, 98 pp. Wolf, J., Hargreaves, J.C. and Flather, R.A Appliation of the SWA shallow water wave model to some U.K. oastal sites. Pol Report: 57, UK, 56 pp.