Study on the Non-Steady-State Wear Characteristics and Test of the Flow Passage Components of Deep-Sea Mining Pumps

In the process of conveying coarse-grained minerals, the internal flow-through passage components of mining pumps are subject to wear. The flow of coarse particles in such pumps is complex and changes constantly, making it necessary to study the non-steady-state wear characteristics and test the flow passage components. The evolution of the surface wear rate for the flow passage components during one third of a rotation cycle (120°) of a mining pump impeller with small, design, and large flow rates was analyzed in this study based on a discrete phase model (DPM). The flow that occurs during an entire rotation cycle of the impeller was investigated. The wear test was carried out with a small test pump with the same specific speed as and a similar structure to that of the deep-sea mining pump. The test results were compared with the numerical calculation results of the deep-sea mining pump obtained by using the same numerical calculation method and wear model, and the test wear area was found to be more consistent with the numerical calculation wear area. The results show that the numerical calculation method used in this article can more accurately predict the surface wear of the passage components of the mining pump and provides a suitable method for the prediction of the wear characteristics of the mining pump.

Precise grading of surrounding rock based on the numerical calculation of the jointed rock mass

In this study, grading of surrounding rock was based on rock mass basic quality (BQ) values according to the specifications in China. Numerical approach was to construct synthetic rock mass (SRM) model to represent the jointed rock mass, and obtain the strength of the rock mass. It represented intact rock by the bonded particle model (BPM), and represent joint behaviour by the smooth joint model (SJM) to construct the discrete fracture network (DFN). In the Hongtuzhang Tunnel, the micro properties of granite cores with different weathered degrees were determined by the validation process, and the calculation representative elementary volume (REV) of surrounding rock was 15 m×15 m. Five slightly weathered, three slightly to moderately weathered, and two moderately weathered granite surrounding rock mass models were established based on the probability distribution of joint sets in each borehole, the conversion BQ value was acquired according by the calculated strength of rock mass model. It was discussed the differences of surrounding rock grades between the geological survey method and the numerical calculation method, and then found that the geological survey report is higher than the numerical calculation method predicted. And the numerical calculation is consistent with the actual excavation of rock mass at borehole A1388.

Numerical Investigation on Air Film Fusion of Pressure-Equalizing Exhaust around Shoulder Ventilation of Submarine-Launched Vehicle

In order to study the influence of pressure-equalizing exhaust at the shoulder of a submarine-launched vehicle on the surface hydrodynamic characteristics, this paper establishes a numerical calculation method based on the VOF multiphase flow model, the standard RNG turbulence model and the overset mesh technology; the method compares the fusion characteristics of the air film at the shoulder of the underwater vehicle, as well as the distribution of surface pressure along the vehicle’s axial direction. The results show that the approximate isobaric zone derived from air film fusion can greatly improve the hydrodynamic characteristics of the vehicle, and the number of venting holes determines the circumferential fusion time of the air film. The greater the number of venting holes, the sooner circumferential fusion starts.

Parametric modeling compressed ellipsoid of rotation as the analytic surface

The article deals with the shaping of the analytical surface in the form of a compressed ellipsoid of rotation. In the process of research, the principle of the golden section was applied, an ellipsoid of rotation with optimal parameters for the design of a large-span unique building of the exhibition complex was obtained. To solve the problem of choosing a rational analytical surface in the Lira-CAD software package, three variants of constructive solutions for the frame of the exhibition complex have been developed. The finite element method is used, the most popular numerical calculation method for studying the stress-strain state of large-span buildings and structures. The analysis of the calculation results made it possible to choose the optimal variant of the structural solutions of the building frame. The check of the dynamic characteristics of the proposed structural solution of the building frame is carried out. The obtained results of the dynamic calculation showed the correctness and efficiency of the adopted structural solutions of the building frame.

Research on Wind Load Calculation Based on Identical Guarantee Rate Method

Wind load on building surface is one of the main loads for structural design; scholars in this field have put forward some methods to calculate wind load, such as Simiu method and Kasperski method. Based on the basic theory of probability and the systematic analysis of the surrounding environment and turbulence, a random variable model for calculating wind load is established. According to the model, through the analysis of the relationship between guarantee rate and wind load, a numerical calculation method to calculate wind load is proposed based on extreme value analysis and polynomial fitting theory. To verify the performance of the algorithm, wind tunnel experiments were carried out to obtain a large number of first-hand measured data of high-rise building (Shanghai World Financial Center). Based on the measured data, the algorithm is simulated, and calculated results are analyzed, including wind pressure distribution on building and probability distribution of fluctuating wind pressure of some measuring points. The validity and accuracy of the proposed model and algorithm are verified by the comparative analysis and theoretical analysis of the calculation results.

Study on the Characteristics of Self-Stabilizing Height Distribution for Deep Foundation Pit Vertical Sidewall in Binary Strata of Upper Soil and Lower Rock

The self-stability height of the foundation pit sidewall is an important criterion for evaluating the safety degree and designing the supporting structure. The strength reduction elastic-plastic finite element numerical calculation method has been adopted in this paper. Based on comparative analysis of the stability characteristics for deep foundation pit in binary strata of upper soil and lower rock under multiple working conditions, the potential fracture surface of deep foundation pit and the evolution law of corresponding safety factor have been revealed under different Hs and H. A new idea that the vertical soil sidewall height (Hs) and the vertical rock sidewall height (Hr) are used as two independent evaluation indexes, respectively, for deep foundation pit stability in binary strata of upper soil and lower rock has been put forward. The distribution characteristics and variation law of Hs0 and Hr0 under different Hs and different H have been revealed, respectively. The spatial distribution map of the self-stabilizing height for deep foundation pit vertical sidewall in upper soil and lower rock binary stratum has been constructed, and the mathematical fitting equation between Hr0 and Hs has been obtained. Finally, combined with the implementation effect of the deep foundation pit project of Ningxia Road Station for Qingdao Metro Line 3, the rationality of the conclusions is verified. The research results provide theoretical basis for quickly determining the self-stability characteristics of foundation pit vertical sidewall.

Simulation analysis of underwater working condition of ship rudder blade based on Fluent

The rudder blade is an important power plant of the ship. Removing damage and failure is the premise of the normal operation of the ship. In this paper, the numerical calculation method is used, combined with K-ɛ (k-epsilon model) and S-A (spalart allmaras) turbulence model, the underwater working conditions of ship rudder blade are analyzed, and the influence of water flow impact at different angles of attack on the damage failure of rudder blade components is discussed. The simulation results show that when the ship is sailing at constant speed, with the change of water attack angle, the main distribution range of rudder blade stress deviates, and the lift and resistance of rudder blade are also gradually increasing, which is easy to damage the parts with concentrated stress. It has theoretical guiding significance for the protection and repair of rudder blade damage.

Numerical Calculation of Fracture Seepage in Rough Rock and Analysis of Local Pressure Drop

The seepage performance of a rock mass mainly depends on the rock fractures developed in it. Numerical calculation method is a common method to study the permeability properties of fractures. Seepage in rock fractures is affected by various factors such as fracture aperture, roughness, and filling, among which aperture and roughness are the two most widely influenced factors. The Navier-Stokes (NS) equation can be solved directly for the seepage flow in rock fractures with good accuracy, but there are problems of large computational volume and slow solution speed. In this paper, the fracture aperture space data is substituted into the local cubic law as an aperture function to form a numerical calculation method for seepage in rough rock fractures, namely, the aperture function method (AFM). Comparing with the physical seepage experiments of rock fractures, the calculation results of AFM will produce a small amount of error under the low Reynolds number condition, but it can greatly improve the calculation efficiency. The high efficiency of calculation makes it possible to apply AFM to the calculation of large-scale 3D rough fracture network models. The pressure drop of fluid in the fracture has viscous pressure drop (VPD) and local pressure drop (LPD). VPD can be calculated using the AFM. After analyzing the results of solving the NS equation for fracture seepage, it is concluded that the LPD includes the pressure drop caused by area crowding in the recirculation zone (RZ), kinetic energy loss in the RZ, kinetic energy loss in the vortices, and other reasons.

Research on coordination design method of main bearing assembly structure based on the maximum radial deformation of bearing bush

Aiming at the difficulty of control and evaluation of main bearing deformation in the coordination design of the main bearing assembly structure for a high-speed diesel engine, taking MRD (the MRD means the maximum radial deformation of the bearing bush) of the bearing bush as an index to evaluate the out-of-round deformation of the bearing bush was proposed in this paper. The numerical calculation method of the MRD was given and the correctness of the method was experimentally verified. And the influence rules of different design parameters on the MRD were analyzed. On this basis, the coordination multi-objective optimization research of the main bearing assembly structure was carried out, and the optimization results were analyzed based on the influence rules of different design parameters on the reliability indexes. The results show that, when the pre-tightening force of the vertical bolt and the bearing bush interference are 240 kN and 0.17 mm respectively, the MRD reaches the minimum value. If the two values continue to increase, redundant loads can be generated, leading to the increase of the MRD. After optimization, the engine block strength coordination and bearing cap strength coordination had increased by 2.47% and 10.48%, respectively, and the deformation coordination and contact coordination had increased by 46.15% and 14.84%, respectively.