Papers by Keyword: Numerical Calculation

Abstract: The article deals with the determination of parameters of longitudinal wood cutting by circular saw blade and construction of the cutting tool. A computational model was chosen to determine stress of the rotating circular saw blade. Stress analysis revealed that maximal stress caused by the temperature gradient was approximately ten times higher than the maximum stress extrapolated from centrifugal forces. In this work were determined the critical speed of the circular saw blade and the power needed to spin. The contribution of this work is the algorithm of the power required for longitudinal wood cutting wood by a circular saw blade, which allows optimal machine tool proposal. Moreover, the calculated state of stress is compared to the FEM model.

Abstract: Because of the added mass, the aerodynamic drag of the automobile will increase obviously when accelerating in the still air. In this paper, it firstly gave the definition of the added mass, and presented that there was little research on the calculation of the added mass of automobile. Then through the analysis of the theoretical calculation method for the added mass, it pointed out that, for the added mass of the car-body with a complex shape, there was much difficulty in the theoretical calculation. Alternatively, a numerical calculation method for the added mass of car-body was derived. The simulation model adopted the Ahmed body and the corresponding verification experiment was completed in the Tongji Automotive Wind Tunnel center. The results indicate that the added mass is a constant which is only dependent on the body-shape. For the model investigated, the added mass is 0.0052kg that is approximately equal to the air displaced by the car-body. As the body accelerates to 4m/s², the aerodynamic drag is increased by 1.89% because of added mass. Therefore, it needs to pay more attention to the impact that the added mass has on the dynamic performance of vehicle when proceeding the aerodynamic designs (especially for the high power performance vehicles). Meanwhile, it still makes a correction to the conventional aerodynamic drag formula. This paper also demonstrates that, with the analysis of the flow-field of car-body, the added mass essentially stems from the additionally work done by the car-body to increase the kinetic energy of external fluid as it speeds up.

Abstract: Due to a particular complexity of the phenomenon of an explosion in a gaseous medium (air) the most appropriate approach to address it is using numerical methods. This paper presents a specific numerical solution to the phenomenon of the so-called point charge explosion from a one-dimensional perspective taking into account reflections from non-deformable partitions. Results of the numerical calculations were calibrated based on test results and their correctness was additionally verified using gas dynamics methods.

Abstract: Phase field method (PFM) was employed to investigate the crystal growth of Mg-Al alloy, on the basis of binary alloy model, the fluid field equation was coupled into the phase-field models, and the marker and cell (MAC) method was used in the numerical calculation of micro structural pattern. In the cast process, quantitative comparison of different anisotropy values that predicted the dendrite evolution were discussed in detail, and when the fluid flow rate reaches a high value, we can see the remelting of dendrite arms.

Abstract: As wedge cam contour’s conventional equation of small roller centering three-jaw jig calculated by classic method is complex and difficult to be used for processing directly, a numerical calculation method for the wedge cam contour is proposed. Firstly, structure and working principle of centering small roller jig is introduced. Secondly, a new numerical calculation method sampling for wedge cam contour using equal step is presented, which can be obtained sampling points expression by numerical calculation model. Then,these samples points assignment will be fitting and interpolation in accordance with quadratic polynomial curve. The equation of quadratic polynomial interpolation on these sampling points these sampling will be obtained, which can be directly applied to NC programming. At last, through comparing fitted quadratic polynomial curve calculated by the numerical method with the theoretical curve calculated by classic method, it is found that the comparison tolerance is much smaller than conventional processing tolerance which is produced by using the theoretical curve for processing. The comparison tolerance is analyzed, refining the sampling step length and using piecewise fitting and interpolation loop calculation method is proposed,which can further improve numerical calculation accuracy to satisfy the requirement of higher and higher positioning. Therefore, it can be concluded that the numerical calculation method can effectively solve the difficult processing problem of wedge cam contour, which will produce better economic benefits.

Abstract: The tight rock often has low porosity, low permeability and poor pore connectivity, which it is difficult for formation evaluation. Nuclear Magnetic Resonance (NMR) logging is widely used in fluid typing and reservoir parameters determination to provide the information of porosity, permeability and pore size distribution. NMR relaxation mechanisms are characterized by the pore-scale petrophysical models. Monte Carlo algorithm describes the Brownian motion of fluid molecules in pore space. In the paper we setup a 3D digital core of the tight sandstone with X-ray computer tomography (CT) images to model NMR response with Monte Carlo random walk algorithm. We compared T₂ distributions from the numerical calculated pulse echo trains from the measurements. The results show that the simulated NMR response is consisted with the experiment.

Abstract: Based on the prototype of No. 2307 filling working face in Yuyang mine, using the method of similar simulation combined with numerical simulation, the geological mechanics model is established to simulate and analyze the mechanics evolution law and the deformation and movement process of the surrounding rock and the surface during the filling mining. Research shows that backfilling can effectively control surrounding rock failure and the surface deformation, and the roof doesn’t collapse, but the bed separated fissures appear, and the maximum stagnation lags the working face by 58.5m; in the mining, surrounding rock stress releases and roof stretches, and the stress concentration appears in the front and end of the goaf, which is 1.47~1.78 times larger than that before mining, and the periodic weighting of filling working face is not obvious; the subsidence value is 212.7 mm after excavation, with the factor 0.06, and the ground level deformation and slope deformation shape are similar to the curve shape of roof caving control method with small values. The results have important theoretical guiding significance for controlling surface movement deformation in actual filling mining.

Abstract: With the increase capacity of wind turbines, grounding device's influence on the equipment and personal safety is becoming more and more significant. In order to calculate the grounding resistance of a wind turbine more accurately, in this paper, based on the Neumann integral formula and the average potential method is applied to derive a formula which can calculate the value of grounding resistance. A general MATLAB program corresponding to the calculation formula is compiled. By comparing the numerical value with the empirical analysis results and building a grounding resistance measurement test platform the correctness of the formulas and program is verified.

Abstract: This paper discusses the importance of per-cooling vegetable and fruit, establishes a mathematical model of the solar adsorption refrigeration system collector bed. It applies activated carbon - methanol as working pairs, takes solar vacuum tube－water cooled collector bed for refrigerating, adsorption temperature and adsorption rate versus time are calculated , draw the corresponding curve figure. Analyses solar adsorption refrigeration system performance and puts forward the improvement direction.

Abstract: This paper extends the polynomial function to double logarithmic function, constructing a class of multi parameters iterative function, and uses this function to calculate the fractal interpolated surface for given interpolation points, and establishes the iterative function mathematical model of multi parameters fractal interpolation. In order to verify the effectiveness and reliability of this proposed model algorithm, this paper uses MATLAB numerical simulation method to calculate, and programs the Newton iterative function of multi parameters fractal interpolation surface, finally gets calculation nephogram of multi parameters fractal interpolation curved surface through calculating. Finally, using iterative method reduces the surface grid size, increasing the smoothness of the surface, so the surface is closer to the actual surface. It provides a new computer method research of fractal interpolation function.