Study of air mobility and liquid mass loss during ventilation of an experimental tank

Introduction. Activities related to the repair and maintenance of vertical tanks of various design types are carried out both according to the work plan and unscheduled. Such work is often facilitated by both the expiration of the service life of obsolete tanks and corrosion of the internal surfaces, which is one of the main factors affecting the life of the tank. Goals and objectives. Due to the fact that volatile oil products are often stored in tanks with a pontoon, their repair and maintenance is an extremely fire and explosion hazardous event. To provide an explosion-proof vapor-air environment, forced ventilation is used, and special attention is drawn to recent studies devoted to an innovative "vortex" method of organizing ventilation of the internal space of the tank, which has not been previously used on a tank with a pontoon. Methods. To substantiate the effectiveness of the application of an innovative method of organizing ventilation for a tank with a pontoon, empirical research methods were used, as well as analytical numerical calculations to determine the average theoretical air mobility. Results and its discussion. The article proposes to pay attention to the innovative way of organizing ventilation of a reservoir with a pontoon as the most effective, relative to other methods of organizing ventilation, and the results of a numerical experiment to determine the average theoretical air mobility using the V.M. Elterman formula were compared with experimental ones. Conclusion. The results of experiments on the mass loss of the studied liquids and air mobility inside the experimental tank show that the innovative method is more effective than other ventilation methods. However, the results of numerical experiments cast doubt on the advisability of using the Elterman formula for generalizing experimental data as applied to the ventilation of experimental tanks with small volumes. Keywords: reservoir with a pontoon, forced ventilation, air mobility, liquid mass loss

Experimental Study of Environment-Friendly Underwater Structure-Submerged Floating Tunnel

In order to study the dynamic characteristics of an innovative underwater structure, Submerged Floating Tunnel (SFT), a model test study was carried out in a calibrated experimental tank based on the Qiongzhou Strait cross-sea passage project and considering the effects of wave and current loads. The size of the test tank is 36m (length) x 31m (width) x 3m (depth), which can simulate the effect of wave and current simultaneously. Under the conditions of pure current, pure wave and wave-current coupling, the pressure change of the test pipe is monitored, and the influence of the wave-current load on the surface pressure of the test pipe is analyzed. The experimental results show that the pressure at the inlet side of the test pipe increases with the increase of the current velocity, the wave height and period, regardless of whether the test pipe section is subjected to pure current, pure wave or wave-current coupling.

GRAPHICAL ANALYSIS OF FREE-SURFACE WAVE FIELDS FROM MOVING SHIPS AND A PAIR OF CONSECUTIVE POSTS

The paper presents a comparison of the photographic material of the wave patterns resulted from the movement of a ship in situ and a model ship, as well as from two consecutive posts, their regularities being found through graphical processing. The possibility to find the fore imaginary source of Kelvin wave pattern forming the ship's wave system is given at a distance of one wavelength before the top of the bow retaining wave. The equality of the length of trans-verse waves and divergent waves along the outer boundaries of the latter zone is fixed. It has been assumed that the intermediate waves generated between the main waves in the model ship and the posts are regular, imposition of wave patterns in a pair of consistently moving racks depending on the hit of the rear rack in the wave field of the first rack has been stated. Regularly occurring flows around moving posts are discussed. The bow and stern system of Kelvin waves in a ship wave sys-tem has been illustrated (the angle of the midpoint of diverging wave crests with the ship’s diamet-rical plane and the angle of diverging wave crests with the ship’s diametrical plane). The photo-graphs presented were taken in the experimental tank of Siberian State University of Water Transport (Novosibirsk State Academy of Water Transport) in 2006. A thin film naturally generat-ed on the water surface of the experimental tank and given a structure directed along the tank due to previous runs helped to visualize the distortion of the free water surface in better quality and to obtain clearly outlined contours in lighting.

Colour vision of green turtle (Chelonia mydas) hatchlings: do they still prefer blue under water?

Background Several anatomical studies provide evidence that green turtles (Chelonia mydas) possess the necessary anatomy for colour vision. Behavioural experiments have previously been conducted with newly emerged hatchlings, concluding that they are attracted to shorter wavelengths compared to longer wavelengths within a terrestrial environment, suggesting a possible attraction towards blue. This paper assessed the colour vision of hatchlings within an aquatic environment, and investigated whether the attraction for shorter wavelengths remains consistent within water, whether the colour saturation of the chromatic stimuli was an important factor, and whether rearing and testing individual animals in different coloured housing tanks has an impact on their visual choices. Methods Forty-one hatchling green turtles were presented with a three-choice experiment where food was attached to three different coloured plates. The plates (blue, yellow, and red) were randomly arranged in the turtle’s tank and four different colour saturations were tested (100, 75, 50, and 25%). Turtles were individually placed into their housing tanks (coloured either red, white, blue or grey) with three different colour plates in front of them, from the same saturation level. The colour of the plate with food first approached and bitten by the turtle was recorded. Results The colour of the tank in which an individual was reared, and where experiments were conducted, significantly influenced which food item was selected on the different coloured plates. While individual turtles preferred to select the food items associated with blue plates across the entire experiment (66.1% of the time compared to 18.2% and 15.7% for yellow and red plates respectively), the preference for blue plates was influenced by the colour of the rearing/experimental tank. Individuals raised in red, white or blue tanks appeared to consistently prefer food on blue plates, but there appeared to be no plate colour preference by turtles in grey tanks. There was no significant effect of either colour saturation or the spatial arrangement of the three colours within an experimental tank on colour choice, and no significant interaction between tank colour and colour saturation. Discussion Thesefindings confirm that the terrestrial preference towards shorter wavelength colours, such as blue, compared to longer wavelength colours remains consistent within an aquatic environment. This preference for blue continues even as the colour saturation reduces from 100% down to 25%, and the colours become darker. Thus, it is suggested that green turtle hatchlings have a strong attraction towards blue. This attraction, however, is influenced by the colour of the tank the turtles were raised in. While this supports the notion that environmental colour may influence individual turtle visual capabilities, it suggests that this relationship is more complicated, and requires further investigation.

Rearing of Mud Crab, Scylla tranquebarica Larvae with Different Stocking Densities

Mud crab (Scylla tranquebarica) is an important aquaculture species, especially in Southeast Asian Countries. However, the larval rearing of this species faces problems resulted in low survival caused not only by intensif canibalism but also by prolonged in larval rearing period. The stocking density during ealy life stages is proposed to influence the crablet production in the larvae rearing tanks. The objective of this research was to evaluate the effect of stocking densities on larval stage development and crablet production of mud crab, S. tranquebarica. Four different initial stocking densities of larvae were tested using 200 L fibre glass tank, namely: A). 30 ind,/L, B). 45 ind./L, C). 60 ind./L and D). 75 ind./L. Rotifer, Brachionus sp, and Artemia nauplii were fed to the larvae with additional commercial diet. Water exchanged in the rearing tank was performed since 7 days post hatching (dph) to 20 dph at a rate of 10 to 40%. Larvae from each experimental tank was sampled periodically (2 to 4 days interval) in order to calculate larvae population, larvae development index (LDI). Megalopa occurences index (MOI), and crablet production were also monitored. The result showed that the highest of LDI and MOI were obtained from treatment B and D which were significantly different (P<0.05) to the other treatments. Furthermore, the highest of crablet production was obtained from treatment D = 495.3+22.48 ind./tank, which was significantly higher (P<0.05) compared to treatment A (48.5+4.94 ind./tank), treatment B (167.5+10.61 ind./tank) and treatment C (218.33+10.41 ind./tank). Therefore, the stocking density of 75 ind./L is optimum for mud crab S. tranquebarica larvae and recommended to be applied for commercial larvae production in hatchery. Keyword: Production, crablet, stocking density, larvae, Scylla tranquebarica