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411.
To simulate two-dimensional free-surface flows with complex boundaries directly and accurately, a novel VOF (Volume-of-fluid) method based on unstructured quadrilateral mesh is presented. Without introducing any complicated boundary treatment or artificial diffusion, this method treated curved boundaries directly by utilizing the inherent merit of unstructured mesh in fitting curves. The PLIC (Piecewise Linear Interface Calculation) method was adopted to obtain a second-order accurate linearized reconstruction approximation and the MLER (Modified Lagrangian-Eulerian Re-map) method was introduced to advect fluid volumes on unstructured mesh. Moreover, an analytical relation for the interface’s line constant vs. the volume clipped by the interface was developed so as to improve the method’s efficiency. To validate this method, a comprehensive series of large straining advection tests were performed. Numerical results provide convincing evidences for the method’s high volume conservative accuracy and second-order shape error convergence rate. Also, a dramatic improvement on computational accuracy over its unstructured triangular mesh counterpart is checked. 相似文献
412.
CHANG Xin ZOU Jing-xiang HUANG Sheng GUO Chun-yu 《船舶与海洋工程学报》2007,6(4):32-36
To design a more effective blade pitch adjustment mechanism,research was done on changes to the hydrodynamic characteristics of VVPs(Variable Vector Propeller) caused by different rules for changing pitch angle. A mathematical method for predicting the hydrodynamic characteristics of a VVP under unsteady conditions is presented based on the panel method. Mathematical models for evaluation based on potential flow theory and the Green theorem are also presented. The hydrodynamic characteristics are numerically predicted. To avoid gaps between panels,hyperboloidal quadrilateral panels were used. The pressure Kutta condition on the trailing edge of the VVP blade was satisfied by the Newton-Raphson iterative procedure. The influence coefficients of the panels were calculated by Morino's analytical formulations to improve numerical calculation speed,and the method developed by Yanagizawa was used to eliminate the point singularity on derivation calculus while determining the velocities on propeller surfaces. The calculation results show that it's best for the hydrodynamic characteristics of the VVP that pitch angle changes follow the sine rule. 相似文献
413.
Jinseong Kim Gisu Kim Yeong-il Park 《International Journal of Automotive Technology》2018,19(4):743-749
In designing a parallel hybrid electric vehicle, it is essential to select the optimal capacity of power sources and the optimal gear ratio of the torque coupler. The capacity of the power sources and the gear ratio of the torque coupler should be optimized simultaneously. However, since this process is excessively time-consuming, previous studies have selected the gear ratio of the torque coupler and then selected the capacity of power source. However, this approach cannot guarantee global optimization. In this paper, a feasible region is defined to satisfy the required performance of vehicle such as maximum speed, hill-climbing. and feasible points are selected inside the feasible region. In the conventional technique, the global optimal solution is obtained by simulating all feasible points. In the optimization technique, optimal points are simulated within the feasible region using several optimal search algorithms, such as the golden section search algorithm and the hillclimbing search algorithm. And using these algorithms, the number of simulations is reduced and the capacity of the power source and the gear ratio of the torque coupler are optimized simultaneously. Finally, the validity of the component sizing results is verified by comparing the global optimal solution obtained by applying the conventional technique with the solution obtained by applying the proposed optimization technique. 相似文献
414.
Ibrahim Elbadawy Mohamed Elsebay Mohamed Shedid Mohamed Fatouh 《International Journal of Automotive Technology》2018,19(2):233-243
Nanofluids, the fluid suspensions of nanomaterial, became a promising fluid that is invoked when heat transfer increase is required. Using of nanofluids as a coolant in the engine radiators is a crucial topic for the thermal engines manufactrers due to the expected enhancement in the cooling process. In this study, Two nanofluids (Al2O3/water and CuO/water) flowing in a flat tube of radiator are investigated numerically to evaluate thermal and flow performance. The resizing process for the radiator is performed by using nanofluid instead of water flow. A significant reduction in the radiator volume is achieved due to marked improvement in the heat transfer performance while, the required pumping power after this reduction in the volume is increased over that needed for base fluid. The normalized heat transfer (heat transfer to the pumping power) is found to be a function of both Reynolds number and nanofluid concentration ratio while the ratio of the normalized heat transfer is found to be dependent only on the nanofluid concentration ratio. These dependencies are formulated as general correlations. 相似文献
415.
Eunjae Lee Hojin Jung Seibum Choi 《International Journal of Automotive Technology》2018,19(4):669-676
As for the tire analysis, lateral tire force is a fundamental factor that describes the stability of vehicle handling. Attempts to analyze the vehicle stability have been made based on various objective test methods and some specific factors such as yaw, lateral acceleration and roll angle. However, the problem to identify which axle is lack of the tire grip at a certain situation still remains. Since indoor tire force measurement system cannot represent a real road and vehicle conditions, tire force measurement through a real vehicle test is inevitable. Due to the high price of the tire force measurement device, tire force estimator can be an alternative toward cost reduction and device failure. In this paper, nonlinear planar full car model combined with tire model is proposed. Then, using discrete-time extended Kalman-Bucy filter (EKBF), individual tire lateral force are estimated with modified relaxation length model. 相似文献
416.
The objective of this paper is to optimize the parameters of pellet drying and preheating process in grate. A mathematical
model of drying and preheating is developed, and is verified by the experiments. Further, the operating parameters of wind
temperature, wind speed, grate speed and bed depth etc. are investigated through the orthogonal method using the simulation
results. And a relationship of drying, preheating effects and operating parameters is achieved. The results show that the
optimization effect can be achieved in the given range when air velocity is about 3.0 m/s and temperature is about 300, 500,
800, and 1 100 °C in the updraft drying zone, downdraft drying zone, preheating I zone, and preheating II zone respectively.
The work is help for saving energy and reducing emissions in pellet induration. 相似文献
417.
Rolling force and temperature field are important parameters in the hot rolling process of plate steel. Most researchers use
ANSYS/LS-DYNA and MSC.Marc to simulate the hot rolling process, however, software DEFORM-3D is not used widely in this field.
Therefore, in this study, the commercially available finite element analysis software DEFORM-3D is used to simulate the distribution
of rolling force, stress-effective, strain-effective and temperature field during the hot rolling process of plate steel with
the size of 0.220m×2.070m×1.904m. Both the simulated rolling force and temperature of the multi-pass are compared with the
measured results. It is shown that the simulated values by the finite element method are approximate to the measured values
in the hot rolling of plate steel. So the simulation can provide an important reference and optimization to make rolling process
and parameters in steel factory. 相似文献
418.
Giorgio Contento Guido Lupieri Marco Venturi Tiziana Ciuffardi 《Journal of Marine Science and Technology》2011,16(2):181-201
The present study is aimed at determining the confidence limits of design wave parameters derived from numerical modeling—for
both extremes and operational conditions—over the Central and Western Mediterranean Sea. The paper presents the methodology
and results of an extensive validation activity conducted on a chain of medium-resolution third-generation wave models used
for hindcast purposes. The stringent requirements of state-of-the-art coastal and offshore engineering applications over this
area make the adoption of medium- or high-resolution hindcast wave and wind models almost mandatory because of the complex
coastal geometry, bathymetry, and orography that in turn lead to large variations of the design wave parameters even within
small regions. The chains of nested meteorological and wave models used in this hindcast study belong to the ETA and WaveWatch III
families, respectively. In this study the wind and wave numerical models have been run over the past 20 years, with increasing
resolutions of the wave models from 0.2° up to 0.04°. The results presented herein have 0.1° resolution for both wind and
wave models. The wave data obtained are compared with available measurements from 14 wave buoys in coastal zones in the Central
and Western Mediterranean Sea. 相似文献
419.
The experimental procedure to predict the full-scale performance of the CRP-POD propulsion system is studied. In the CRP-POD
system, the RPM ratio of the two propellers is not mechanically fixed, in contrast with conventional CRP systems. Therefore
the existing procedure for conventional CRP systems is not appropriate for evaluating the performance of each propeller. In
this paper, the characteristics of the CRP-POD system, designed for a 9,600 TEU class container carrier, are studied experimentally.
Based on this study, a procedure for propulsive performance prediction for CRP-POD propulsion ships is suggested. 相似文献
420.