Xiongliang Yao

Study on Load Characteristics of Underwater Explosion Using RKDG-LS-DGF and BEM

This study numerically investigates the underwater explosion bubble dynamics during the process from detonation to bubble jet with a hybrid algorithm based on Runge Kutta Discontinuous Galerkin-Level Set-Direct Ghost Fluid method (RKDG-LS-DGF) and boundary element method (BEM). RKDG-LS-DGF method is used to simulate the physical process from the detonation of a column charge at one end to the formation of a nonspherical initial bubble and the process of bubble jet. And BEM is adopted to simulate bubble pulsing characteristics. In addition, the numerical results are compared with the experimental results to verify the feasibility of the numerical method. It is found that, during the detonation process of a column charge, the detonation product experiences a shape change from an initial ellipsoid into a sphere during expansion. After the detonation, the bubble experiences expansion and contraction and develops a jet. The jet threads through the bubble in the opposite direction to gravity and induces a high-pressure region. Subsequently, the pressure of this region decreases when the bubble reexpands after being penetrated by the jet. The numerical results agree well with the experimental data, which proves that axisymmetric RKDG-LS-DGF method and BEM are successfully combined to simulate the whole process of underwater explosion.

Research on the Low-frequency Mechanical Characteristics of MR Damper in Ship Isolator

In this paper, by using the fast response, controllable damp, small consume, wide dynamic scope, great adaptation of the MR damper, a new isolator composed of steel rope spring and MR damper is designed and a study on the low-frequency mechanics characteristics of MR damper in isolator is carried out, then the relations between MR damping force and other factors are analyzed with experimental data, it shows that damping force not only has something to do with structural dimension, but also is related to controllable current and vibration frequency. Finally, the experiential formula of damping force is corrected and the relations between corrected coefficients and factors are obtained.

Research on the Mechanics Characteristics of Ship Vibration Reduction and Impact Resistance Isolator Based on MR

In this paper, a new-style isolator system in ship is presented, which is composed of wire rope and MR damper in parallel. By taking advantages of the high damping and damping variability of MR damper, it is possible to make the mechanics characteristics of isolator controllable and then solve the problem of vibration reduction in low frequency and impact resistance in high frequency of ship equipment. In the researches on the impact resistance and vibration reduction performances, numerical experiment and physical experiment are carried out respectively, results indicate that the new isolator has a good active controllable effect on the vibration and impact, especially for controlling resonance and low- frequency vibration of system.

Structure‐borne sound design of typical hull base and underwater model test

Purpose – The structure‐borne sound generated by power equipment can be isolated effectively through vibration absorber under hull base structures. The practical vibration isolation performance is limited due to the weight, size and cost. The dramatic attenuating wave propagation characteristic of hull base without adding weight is essential to the vessel acoustic stealth.Design/methodology/approach – The characteristics of vibration wave propagated from typical shape base link structures have been investigated according to impedance mismatch and wave conversion in non‐homogeneous structure. The hull base is simplified to three degrees of freedom damped system through the mechanical impedance method. The influence of blocking mass weight, as well as location properties to the base vibration isolation performance have been discussed. Furthermore, the structure‐borne sound design of a typical hull base is carried out.Findings – The impedance mismatch of the hull base is further increased by the comprehensiv...

Vulnerability assessment of aircraft guarantee system based on improved FPN

According to the characteristics of vulnerability assessment of aircraft guarantee system on board, a new system vulnerability evaluation method is proposed based on improved fuzzy reasoning algorithm of fuzzy Petri net(FPN). In the improved algorithm, the learning algorithm on unknown weight coefficients is introduced, making the evaluation system get rid of experts or experiences. The results comparison between the presented method and damage tree analysis method demonstrates exhaustiveness and rationality of this model. The model would be applied to the complex ship system assessment.

Experimental Research on the Vibration Reduction and Impact Resistance Performances of Offshore Structure Based on Magnetorheological Damper

This paper presents a new kind of vibration reduction and impact resistance isolator system based on magnetorheological technique, and its experiment results. The vibration and impact experiments were designed using MTS hydraulic loading system. There were many load cases being applied in the experiment with different mass of the model, exciting forces, and controllable electricity of MR damper (Magnetorheological Damper). The experiment results indicate that this isolator system can control the vibration response very well, especially near the natural frequency of the system; and the isolator system has a good performance in the impact experiment too, the response acceleration was evidently reduced, but the characteristic of MR damper was different form its performance in vibration experiment.Copyright