Numerical Prediction of Cavitation Erosion Intensity in Cavitating Flows around a Clark Y 11.7% Hydrofoil

Abstract

A numerical prediction method of cavitation erosion is proposed. In this method, the analysis of bubbles in cavitating flows is performed and the intensity of cavitation erosion is evaluated by the impact pressure induced by spherical bubble collapse. In the present study, two-dimensional cavitating flow around the Clark Y 11.7 % hydrofoil is used to examine the proposed numerical prediction method. The proposed numerical method predicts that the intensities of cavitation erosion in noncavitating, attached cavitating and pseudo-supercavitating flows are far weaker than the intensity of cavitation erosion in a transient cavitating flow, and the intensity in the vicinity of the sheet cavity termination is high. These results correspond well to experimental results, and it is confirmed that systematic erosion characteristics are generally captured by this method. Furthermore, the velocity dependence of cavitation erosion is examined, and it is found that the exponent n in the relation between the intensity I and main flow velocity U in (I ∝ U n in) becomes large when the bubble radius is large and ranges between 4.3 and 7.0 in the present study. According to the bubble dynamics, the ambient pressure and the rate of increases in pressure increase as the main flow velocity, and the maximum internal pressure increase. Therefore, it is thought that smaller bubbles cause cavitation erosion when the main flow velocity is large.

Experimental Study on the Cavitation Characteristics of an Oil Jet Pump With Multiple Nozzles for the Lubrication System in a Steam Turbine

“…Figure 10 shows the sche matic of pressure pulses filtered by a threshold. After that, the cav itation characteristics are characterized by the cavitation intensity [19], which is similar to the acoustic intensity [24], Its expression is shown as follows: Figure 11 shows the influence of pressure threshold on the cavi tation intensity of three points with m = 7.47 and P0 = 2.4 MPa. As shown, the three points show a similar tendency with increas ing pressure threshold.…”

“…Then an experimental rig was constructed to simulate the environment of an oil jet pump with multiple nozzles for the lubrication system of the steam tur bine in a power plant. This study adopted the "cavitation intense" [19] to characterize the cavitation with high frequency response pressure transducers. Finally, this study provided quantitative crite ria for the determination of working oil pressure, area ratio, and pressure ratio, which ensures the relative safety and high efficiency of an oil jet pump with multiple nozzles.…”

Thermal unfolding of myoglobin in the Landau-Ginzburg-Wilson approach

“…Moreover, the experiments have mainly concentrated on the heme-free apomyoglobin [31][32][33][34][35][36][37][38][39][40][41][42][43]. The heme containing myoglobin has also been investigated [44][45][46][47][48][49] but due to apparent complications with the binding of the heme, the studies have been limited to the unfolding process. In both cases the unfolding of the native state proceeds in stages with several folding intermediates.…”

“…In the case of apomyoglobin, the folding appears to proceed inversely to the unfolding. The dynamics is also very similar in both cases, except that in the apomyoglobin the F helix [10] is initially disordered [35] while in the heme containing myoglobin the F helix is initially stable but the first to become disordered when temperature and/or denaturation increases [44][45][46][47][48][49]. The unfolding of the F helix is followed by an intermediate molten globule, in both cases [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49].…”

“…When denaturation and/or temperature increases further, the overall helicity of the molten globule rapidly decreases as the helices B,C,D and E start to unfold. Finally, the remaining helices A, G and H loose their stability and the structure becomes a random chain [44][45][46][47][48][49].…”