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How to sustainably produce bauxite by effective reverse froth flotation of kaolinite at low temperature is an urgent problem to be solved in the field of mineral processing. In this work, a novel amino-based Gemini surfactant butadiyl-1, 4-bis (dimethyl dodecylammonium bromide) (BBDB) was prepared and first utilized as a novel collector for kaolinite flotation. Its flotation performance for kaolinite was compared with that of the common monomolecular surfactant 1-dodecylamine (DDA) by micro-flotation tests. The tests results indicated that 95% kaolinite recovery was obtained using 2.0 × 10−4 mol/L BBDB at 25 ℃, which was half of the dosage when DDA obtained the maximum kaolinite recovery of 81%. At extremely low temperature (0 ℃), 3.0 × 10−4 mol/L BBDB could still collect 91% kaolinite, while DDA showed a frustrating ability. The contact angle tests indicated that BBDB could still significantly improve the hydrophobicity of the kaolinite surface (contact angle 71.7°) than DDA (contact angle only 25.8°) at 0 ℃. The Krafft point comparison tests indicated that BBDB had a much lower Krafft point (below 0 ℃) than DDA. Fourier transform infrared spectroscopy (FTIR)-spectrum analysis and zeta potential measurements showed that BBDB was physically adsorbed on the surface of kaolinite through electrostatic interaction.

In this study, a new hydroxamic-acid molecule - sebacoyl hydroxamic acid (SHA) was synthesized and characterized. It was the first time that SHA with dual hydroxamic acid groups of “crab” structure was used as a collector for wolframite flotation, and its collecting ability was compared with the traditional collector benzohydroxamic acid (BAH) in the presence or absence of lead ions. In micro-flotation experiments, the wolframite recovery using 4 × 10−4 mol/L SHA collector alone was 30% higher than that using 4 × 10−4 mol/L BHA collector and 1 × 10−4 mol/L Pb(NO3)2 activator. The results of bench-scale flotation experiments showed that the WO3 recovery of wolframite concentrate with 180 g/t SHA was 10.05% higher than that with 360 g/t BHA and 300 g/t Pb(NO3)2. Therefore, using SHA collector with “crab” structure for wolframite flotation can not only improve the separation index at a low dosage, but also eliminate the use of Pb(NO3)2.

In many existing works, the seakeeping motions and air dynamics of a surface effect ship (SES) were assumed to be linear under small-amplitude waves (wave amplitude to wave length ratio ≤ 5%) to enhance the computational efficiency. However, according to SES model test results, it was found that even in small-amplitude waves, the fluctuating air cushion pressure shows significantly nonlinear effects. To precisely reveal this distinctive feature, the origin of nonlinearity was carefully investigated and the air leakage was considered as the main source of nonlinearity based on mathematical analysis in this paper. The reason is that the variance of clearance height under seals is comparable to the clearance height at equilibrium state in small-amplitude waves, which makes the air leakage area intermittently equal to zero without any harmonic variance. Therefore, an efficient partial nonlinear numerical model for the SES dynamics was proposed by combining a linear frequency-domain hydrodynamic model based on the efficient 2.5D methods with a nonlinear time-domain air dynamic model. The nonlinear parts of numerical results from the partial nonlinear model, including the fluctuating air pressure and midship accelerations, agree well with experimental results. The results demonstrate the effectiveness of the partial nonlinear model on the SES seakeeping performance prediction, and confirm that its nonlinearity mainly originates from the air leakage.

Phosphorite is generally used in the manufacture of phosphate fertilizer and plays a vital role in the development of agricultural and food production. Nonetheless, how to obtain phosphorite concentrates efficiently and sustainably has become an urgent problem. In this study, a newly designed trisiloxane surfactant, N-(2-Aminoethyl)-3-aminopropyltrisiloxane (AATS), has been prepared and utilized as an emerging collector for reverse flotation of phosphorite ore. Its collecting ability was compared with the conventional surfactant 1-dodecamine (DDA). In the collector concentration tests, AATS with lower concentrations showed stronger collecting ability for quartz. In the pH tests, AATS always performed better than DDA in the acidic or alkaline condition. In bench-scale flotation experiments, the P2O5 recovery of phosphorite concentrates with 150 g/t AATS was 10.77% higher than that with 300 g/t DDA, which proved that AATS can be applied to the sustainable production of phosphorite concentrates. For a 4000 t/d phosphorite ore processing plant, the profit could be increased 7,014,702.07 USD every year by using AATS as the collector. Therefore, this work provides a promising approach to enhance the production efficiency of phosphate fertilizer and to promote the sustainable development of agriculture.

This paper presents an approximate but efficient method for modeling the hydrodynamics and seakeeping performance of partial air cushion supported catamaran (PACSCAT) with planing demihulls. This method takes into account of the effects of the waves on the air–water interface under the air cushion induced by the pulsating pressure in the cushion and by the demihulls, which are ignored by existing approximate methods. Specifically, the new developments are made in two aspects. One is that the governing equations of the heave and pitch motions of the PACSCAT are derived to include the effects of the waves under the air cushion due to the pulsating pressure and the demihulls. Another one is that an approximate method is developed for evaluating the waves due to the pulsating pressure. Better agreement between the experimental data and the numerical results for pressure is achieved.

When a surface effect ship (SES) sails in waves, the unsteady velocity potential of water can be decomposed into incident potential, sidehull radiation potential, sidehull diffraction potential and radiation potential due to fluctuating air pressure. The potentials related to sidehulls satisfy Neumann boundary conditions (BC) and have been successfully addressed using the 2.5D method. In contrast, the potential related to fluctuating air pressure satisfies mixed BC consisting of homogeneous Neumann BC on the wetted surface of sidehulls and nonhomogeneous Dirichlet BC on the interface between air and water, which has never been studied using the efficient 2.5D method. In this paper, the 2.5D method is firstly proposed to solve the mixed boundary value problem (BVP), which can deal with the coupling between the fluctuating air pressure and sidehulls. By using the 2.5D method, the radiation wave and other relative hydrodynamic parameters of a SES due to the fluctuating air pressure are evaluated. The numerical results on motion response and the fluctuated air pressure of the SES show acceptable agreement with the experimental ones.

In froth flotation separation process, the collector molecular design has a crucial effect on potash processing to ensure sustainable production of potassium fertilizer (KCl) that is important to secure food supply in human society. Carnallite is an important source of KCl fertilizer production in industry. Reverse flotation has been used to separate halite (NaCl) impurities from carnallite (KCl·MgCl2·6H2O) for carnallite resources. However, progress in the carnallite resource reverse froth flotation has been constrained by the inherent limitation of traditional collector molecules with a single hydrophilic head and single hydrophobic chain per molecule. Herein, a novel morpholine-based Gemini molecule with double hydrophilic heads and hydrophobic chains, butanediyl-α, ω-bis (morpholino tetradecylammonium bromide) (BMTB) was synthesized and applied as the flotation collector in the reverse flotation separation for carnallite mineral. The better flotation performance of Gemini BMTB was achieved, compared to the traditional monomeric surfactant N-(n-Tetradecyl) morpholine (TDM). The bench-scale froth flotation separation results revealed that BMTB exhibited outstanding affinity and selectivity for NaCl crystals from carnallite at natural pH, resulting in less collector dosages – only 1/3 of TDM molecules. In contrast with traditional monomeric surfactant TDM (120 g/t), less amount of Gemini BMTB (40 g/t) – only one third of TDM molecules, was needed to obtain higher KCl recovery (KCl recovery raised by 4.69%). Meanwhile, the grade of NaCl with 40 g/t BMTB collector (2.19%) was lower than that with 120 g/t TDM collector (3.91%), and the grade of KCl with BMTB collector (22.59%) was higher than that with TDM collector (22.12%). Therefore, this work demonstrated the next-generation of flotation collector for the reverse froth flotation separation of the carnallite resources.

When operated under large water immersion, surface piercing propellers are prone to be in heavy load conditions. To improve the hydrodynamic performance of the surface piercing propellers, engineers usually artificially ventilate the blades by equipping a vent pipe in front of the propeller disc. In this paper, the influence of artificial ventilation on the hydrodynamic performance of surface piercing propellers under full immersion conditions was investigated using the Computational Fluid Dynamics (CFD) method. The numerical results suggest that the effect of artificial ventilation on the pressure distribution on the blades decreases along the radial direction. And at low advancing speed, the thrust, torque as well as the efficiency of the propeller are smaller than those without ventilation. However, with the increase of the advancing speed, the efficiency of the propeller rapidly increases and can be greater than the without-ventilation case. The numerical results demonstrates the effectiveness of the artificial ventilation approach for improving the hydrodynamic performance of the surface piercing propellers for high speed planning crafts.

A novel time-domain body-nonlinear Green’s function method is developed for evaluating large-amplitude roll damping of two-dimensional floating bodies with consideration of viscous dissipation effects. In the method, the instantaneous wetted surface of floating bodies is accurately considered, and the viscous dissipation effects are taken into account based on the “fairly perfect fluid” model. As compared to the method based on the existing inviscid body-nonlinear Green’s function, the newly proposed method can give a more accurate damping coefficient of floating bodies rolling on the free surface with large amplitudes according to the numerical tests and comparison with experimental data for a few cases related to ship hull sections with bilge keels.

The mean water surface (interface) under the air cushion of a surface effect ship (SES) or an air cushion supported platform (ACSP) is generally lower than the outside water surface due to the overpressure of the air cushion. To precisely analyze the hydrodynamics under the air cushion, multiple water levels should be considered in numerical models. However, when using free surface Green’s functions as numerical methods, the water level difference cannot be taken into account, because free surface Green’s functions normally require users to set in the whole water domain a unique datum water surface that completely separates the air domain and the water domain. To overcome this difficulty, a multi-domain approach is incorporated into a 2.5D method that is based on a time domain free surface Green’s function with viscous dissipation effects in this paper. In the novel multi-domain 2.5D method, the water domain is partitioned into inner and outer domains, and the interface is located in the inner domain while the outside water surface is placed in the outer domain. In each domain there exists only one unique water level, while water levels in different domains are allowed to be different. Benefited from this characteristic, the multi-domain 2.5D method is able to precisely consider the water level difference and its influence on hydrodynamics. The newly proposed multi-domain 2.5D method is employed to predict the hydrodynamics of an SES, and it is confirmed that the multi-domain 2.5D method can give better numerical results than the single-domain one for the given case.

A novel time-domain Green’s function is developed for dealing with two-dimensional interaction between water waves and floating bodies with considering viscous dissipation effects based on the “fairly perfect fluid” model. In the Green’s function, the temporal (lower order viscosity coefficient term) and spatial (higher order viscosity coefficient term) viscous dissipation effects are fully considered. As compared to the methods based on the existing time-domain Green’s functions that could not account for the spatial viscous dissipation, the method based on the new time-domain Green’s function can give much better numerical results and overcome instability problems related to the existing Green’s function, according to the numerical tests and comparison with CFD modeling data for a few cases related to floating bodies with a flare angle.

The partial air cushion supported catamaran (PACSCAT) is a type of air cushion assisted catamaran with planing demihulls. Both the air cushion and the demihulls can strongly affect the seakeeping performance. Although there exist some methods for analyzing the seakeeping of other air cushion supported vessels considering the effects of both the air cushion and demihulls, they can take considerable computational time. In this paper, an efficient numerical method is presented, which is formed by combining the 2.5D theory for solving hydrodynamics of demihulls with simplified wave-equation for solving aerodynamics of pressurized air to analysis the seakeeping performance of the high-speed PACSCAT. In the method, the cushion pressure is determined by using adiabatic gas law together with boundary conditions including the craft motion, free surface elevation, fan flows and air leakage. Two models are proposed for air leakage: constant leakage area and varying leakage area linearly related to ship motions and free surface elevation. The results obtained by the newly formulated method are compared with the experimental data, showing that the numerical results have reasonable agreements with experimental ones.

The Transformable-Craft (T-Craft) is an innovative vessel serving as a connector between sea base and beachheads. When operatingat seas, the T-Craft is a surface effect ship (SES) with compartmented air cushions. To analysis the seakeeping performance of the T-Craft SES, a high efficient 2D/2.5D analytical model has been developed by combining the one dimensional waveequation for solving aerodynamics of pressurized cushion air with the STF/2.5D method for solving hydrodynamics of demihulls at low/high speeds. To enhance the computational efficiency, the entire model is linearized except the dynamics of air leakage, which is strongly nonlinear and inappropriate for linearization. Results obtained from the proposed seakeeping analysis model show reasonable agreement with experimental data, while the proposed model hascompetitiveness in the computational efficiency as compared with some 3D models from public works.

The Partial Air Cushion Supported Catamaran (PACSCAT) is an innovative design which combines both the characteristics of hovercraft and catamaran. Further, it provides a high-speed and efficient solution with excellent performance, particularly for shallow water. In this paper, experimental and numerical method are carried out for research of motion attitude and resistance characteristics, which provide a reference for further research and hull optimization work. By model towing test and data interpretation, and the resistance, trim, and heave varying law with increasing speed is summarized. From the view of total resistance, the impacts of the cushion pressure and air flow on resistance performance of PACSCAT are analyzed. Based on the theory of viscous fluid mechanics, a numerical simulation method with high prediction accuracy is established. The flow field around and inside the hull is simulated, the simulating results show good agreements with the testing data. Finally, the effect of the cushion compartment improving the resistance performance is studied. The results show that the cushion compartment is significant for adjusting the pressure distribution of the air cushion. And the average resistance reduction ratio at the high-speed segment can even reach 22%.

The transmission of water waves under vertical thin plates, e.g., offshore floating breakwaters, oscillating water column wave energy converters, and so on, is a crucial feature that dominates the hydrodynamic performance of marine devices. In this paper, the analytical solution to the transmission of water waves under multiple 2D vertical thin plates is firstly derived based on the linear potential theory. The influences of relevant parameters on the wave transmission are discussed, which include the number of plates, the draft of plates, the distance between plates and the water depth. The analytical results suggest that the transmission of progressive waves gradually weakens with the growth of the number and draft of plates, and under the conditions of given number and draft of plates, the distribution of plates has significant influence on the transmission of progressive waves. The results of this paper contribute to the understanding of the transmission of water waves under multiple vertical thin plates, as well as the suggestion on optimal design of complex marine devices, such as a floating breakwater with multiple plates.

Axial fans with the advantages of its simple structure, large amount of wind, widely used in agriculture that respect, but agricultural cross flow fan in the size range of big, prone to resonance problems. In this paper, to a certain type of agricultural pipeline fixed shaft flow fan shell as the research object, using the ANSYS Workbench for the modal analysis. Analysis showed that: When the external excitation frequency is within the range of 102Hz~161Hz and 354Hz~356Hz, the large deformation displacement of the shell is in the direction of the X and Y direction; The analysis results provided theoretical basis for the optimum design of the shell of the axial fan and the selection of the drive motor.