PSI - Issue 32

R. Tsvetkov et al. / Procedia Structural Integrity 32 (2021) 209–215

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R. Tsvetkov et al./ Structural Integrity Procedia 00 (2021) 000 – 000

Fig. 4 shows a set of curves obtained at the fixed value of connecting segment ( L = 10 m) and different radii ratios ( r/R varies from 0.5 to 8). It is seen that each set of geometric parameters of the system corresponds to its own minimum stabilization interval and this value is reached at different values of the parameter τ. At large values of characteristic time (area to the right of the minimum point) HLS operates in an oscillatory mode (as shown in Fig. 3a). Aperiodic changes in the liquid level shown in Fig. 3b, take place at small values of the parameter τ (area to the left of the minimum point). When the hydrostatic leveling system is operating, it is desirable that all transients occur in the mode of damped periodic oscillations. In this case, the equilibrium level of the liquid in the measuring vessels is reached faster. In addition, averaging the height of the liquid column over the stabilization period makes it possible to obtain an equilibrium value even before the liquid has completely stopped moving.

Fig. 5. Stabilization time depends on the τ value at different values of L and ratio r / R = 1.

Fig. 5 shows similar dependences T (τ), obtained when the ratio of the radii of the measuring vessel and the connecting tube is constant ( r / R = 1), but the distance between the sensors changes. In accordance with formula 5, the parameter τ is determined by the radius of the connecting segment and the physical properties of the liquid (the ratio of density and viscosity). The Table 1 shows the approximate values of the parameter τ for several types of liquids at a temperature of 20 ° C.

Table 1. Character time τ for different liquids. Liquid

Character time τ (s) at R = 2.5 mm

Character time τ (s) at R = 5 mm

Character time τ (s) at R = 10 mm

Water

0.78

3.12 1.42 0.69 0.57 0.29

12.5 4.09 2.78 2.28 1.17 0.59

36% ethylene glycol water solution 54% ethylene glycol water solution

0.355 0.173 0.142 0.073 0.037

Silicone fluid 5 Silicone fluid 10 Silicone fluid 20

0.148

Comparing the data given in Table 1 and Fig. 4 and Fig. 5, it is possible to select a fluid that provides the best stabilization time for the hydrostatic level with specific geometric dimensions. On the other hand, for the level filled with a specific fluid, it is possible to select such a geometric configuration in which HLS will operate in a mode of periodic oscillations. Silicon fluids (oil) are often used as a working fluid in hydrostatic levels. They have a low freezing point, stable properties and low evaporation. As the table shows, for these liquids character time τ has a value from 0.037 to 2.29 for hoses of different diameters. In accordance with Fig. 5, for hoses less than 10 m long (curves 1 and 2), these