CONTENTS & ABSTRACTS
InEnglish. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Engineering
Volume 9 No. 2June 2003
Directionaland extreme wind properties in the Gulf of Finland; 73–90
Tarmo Soomere and Sirje Keevallik
Abstract. The wind regime of the Gulf of Finland, Baltic Sea, combines consists of SWgloballydominating and north winds dominating in thewhole Baltic Sea basin with and of local east and west winds blowingalong the axis of the gulf. The angular structure of strong winds does notmatch the structure of all winds since they sometimes. Strong winds blow from directions where winds generallyare infrequent. Extreme wind speeds are estimated on the basis ofthe parameters of the Weibull distribution. The 3-hour mean windspeed in the most severe south and SW storms, estimated on the basis of theWeibull distribution, is about 24 m/s once in a century, thus by2–3 m/s less than in the Baltic Propermay reach.The mean wind speed in the strongest east and north storms may reach21–23 m/s or 19–22 m/s once in a century, respectively. The frequency and intensitythemaximum speed of east and north winds decrease is relatively small inthe eastern directionpart of the gulf.SE winds are infrequent and weak.
Key words: wind climate, extreme wind speed, Baltic Sea meteorology,marine winds.
Observed thermohaline fields and low-frequencycurrents in the Narva Bay; 91–106
Janek Laanearu and Urmas Lips
Abstract. This article analyses hydrophysical processes in the NarvaBay, a sub-basin of the Gulf of Finland, on the basis of measurements collectedduring April–August
2001. The fields oftemperature and salinity are determined from the measurement data, and theprogressive-vector diagrams are constructed for the currents. Surface-watercharacteristics and spreading of the Narva River water were affected by thewinds. Large vertical displacements of the coastal waters associated with theEkman transport away from the shore were observed in the western part of thebay. The currents at the buoy stations revealed the signals of near-inertialfluctuations in the surface layer. Theoretical analysis of low-frequencymotions is based on the integrated Ekman equations, which use the wind stressand include the Rayleigh friction. The bursts of the inertial oscillations inthe mixed layer observed in the open-sea side of the bay during strong windsare qualitatively well reproduced by numerical calculations.
Key words: Gulf of Finland,Narva Bay, temperature, salinity, Ekman transport, inertial oscillation.
A seaice dynamics model for the Gulf of Riga; 107–125
Keguang Wang, Matti Leppäranta, and TarmoKõuts
Abstract. A model for simulatingand forecasting the drift of sea ice in the Gulf of Riga, Baltic Sea, ispresented. The basin size and ice thickness scale to 100 km and30 cm, respectively. The model is based on the conservation and momentum lawsof ice with a three-level ice state and viscous-plastic rheology. Thesteady-state momentum equation is employed; the ice state levels are open water,undeformed ice, and deformed (ridged) ice,together with a dynamic constraint controlling the redistribution process. Themodel parameters have been estimated by comparing the model outcome with thedatabase of ice charts. Ridging was allowed for ice thicker than 10 cm andthinner ice rafting in compression.
Key words: sea ice dynamics,model, ice thickness distribution, constitutive law, Gulf of Riga.
Microstructuraleffects on wear of non-homogeneous hardmetal materials;126–136
Irina Hussainova and Mart Viljus
Abstract. Microstructure and composition of ceramic–metal alloys havebeen investigated using scanning electron microscope and energy-dispersiveX-ray analysis. It is shown that microstructural variables play even moreimportant role in the tribological performance of multiphase materials than themeasured mechanical properties.
Key words: non-homogeneous materials, microstructure, tribology, SEM,X-ray analysis.
Formation of aerosolparticles by low-frequency sound-stimulated combustion;137–147
Veera Dushenko, Medhat Hussainov, IgorShcheglov, and Toomas Tiikma
Abstract. This paper presents theresults of an experimental study of the formation of aerosol particles at theoutlet of a flue gas duct of power equipment under the influence of low-frequencysound fluctuations (acoustic field) by burning a gaseous fuel. To measure theconcentration and velocities of the aerosol particles in the flue gas, a laserDoppler anemometer, adapted to the conditions of the test rig, was used. Theapplied technique allowed to detect signals of solid aerosol particles with asize of 4–70 μm directly in a flue gas duct.In our experiments the existence of particles with a size over40 μm was not detected. That is, there were no large agglomerates ofaerosol particles in the flow. Besides, thestudy of aerosol particles enabled us to explain the increased content of CObecause of the CO2 decay. Thus, monitoringof aerosol particles allowed to receive additionalinformation about the combustion process.
Key words: combustion,low-frequency sound fluctuations, aerosol particles, LDA.
Instructionsto authors; 148–150
CopyrightTransfer Agreement; 151
