Papers by Keyword: Numerical Computation

Abstract: The jet noise reduction of chevron nozzles was investigated on high bypass ratio turbofan engine separated exhaust system using both computational predictions and scale model experiments. Six different exhaust nozzles are designed including one baseline nozzle and five different chevron nozzles. The jet noise experiments were carried out in the anechoic chamber. Tam and Auriault’s jet noise prediction theory and MGBK theory were used to predict the noise spectra of different exhaust nozzles. The results show that the far-field noise spectra as well as the noise reduction benefits of chevrons are predicted correctly by the two theories although some discrepancies occur at the high frequency range, and Tam and Auriault’s jet noise theory can give relatively more accurate prediction results. chevron nozzles reduce jet noise at the low frequencies, but increase it at high frequencies.

Abstract: The conservation principle of energy and the mass center movement theorem of rigid body and the moment of momentum theorem relative to the center of mass were used to study the dynamic problems of the eccentric cylinder on the inclined plane. The mass center velocity and the acceleration of the cylinder and the normal pressure and the friction force of the cylinder acting on the inclined plane and etc are given. An example is introduced to show the variations of the physical variants, and the numerical results agree with the theoretical analyses.

Abstract: The theory, model and algorithm of three products heavy medium cyclone flow field were researched, and the heavy medium cyclone flow field was simulated based on aerodynamic. Through the researches, the numerical discrete algorithm of heavy medium cyclone flow field was deduced, the calculation algorithms of heavy medium cyclone flow field were given, the washed coal particle trace, intermediate coal particle trace, gangue particle trace in three products heavy medium cyclone, and the separation rules based on aerodynamic and flow field characteristics of three products heavy medium cyclone were obtained.

Abstract: For gas drilling, hole cleaning is a particularly critical problem. When the spiral centralizer is used in the down hole assembly of gas drilling, it will produce a powerful rotational flow which will be bond to have the influence of different level on the hole cleaning. For this matter, this paper has established a three-dimensional fluid dynamics model in the basis of gas-solid two-phase turbulent theory and got its numerical solution by using the finite volume method, therefore making a quantitative evaluation about the ability of cutting-carrying and lifting of the spiral centralizer. The results have shown that the spiral centralizer has the function of cutting-carrying and lifting; part of the rock debris pellet concentrates in the bottom of the blade, above less instead. The numerical calculation method has some guiding significance for spiral centralizer design in gas drilling.

Abstract: The theory, model and algorithm of three products heavy medium cyclone flow field were researched, and the heavy medium cyclone flow field was simulated. Through the researches, the numerical discrete algorithm of heavy medium cyclone flow field was deduced, the calculation algorithms of heavy medium cyclone flow field were given, the flow trace in three products heavy medium cyclone, and the separation rules and flow field characteristics of three products heavy medium cyclone were obtained.

Abstract: We have studied the approach for dynamic micromagnetic equilibrium conditions (Brown’s equations) in terms of nucleation theory provide micromagnetic solutions for linearized forms of the equilibrium equations. We focus on the case of ferromagnetic resonance here described for a ferromagnetic sphere with uniform magnetization and with no losses. With the linear approximation we have derived uniform and symmetric resonance mode to the micromagnetic equations describing the dynamic properties of the near single-domain states by ignoring the magnetostatic potential gradient in symmetric case. Moreover, using numerical integration solution to calculate exchange and magnetic energy, both resonance modes are proved to be effective approximate solution of Brown’s equations in the nanometer range.

Abstract: Modeling structures response to external blast loads is studied in this paper. A new model is developed based on the experimental data in literature UFC (unified facilities criteria) 3-340-2. The new model differs from the model which is available in LS-DYNA as take into account new abacuses for reflecting coefficients, leading to more precise load especially at great incidence.

Abstract: An analysis is made of the compression wave generated when a high-speed train enters a tunnel with hood. The purpose of the hood is to reduce as much as practicable the maximum gradient of the compression wave. In this paper the numerical computation simulates the pressure change in the tunnel,analysises regularity of the the initial compression wave and the pressure gradient wave,compares the mitigation effect of the two hoods which have different cross section on the pressure gradient.The following conclusions have been drawn from the research: The amplitude of the first compression wave is not significantly reduced with hood,however,the amplitude of the pressure gradient is significantly reduced with hood.And the mitigation effect of the enlarged-transect hood is better than the equal-transect one.

Abstract: In order to study heat transfer process in APU compartment of passenger plane and to perform structure thermal analysis, temperature field of APU compartment has been calculated by numerical computation. The computation model of flow and heat transfer process in APU compartment are setup by commercial CFD software Fluent, Realizable k-ε turbulent model and S2S thermal radiation model are used, and the flow field, temperature and heat flow information are acquired. Radiation heat transfer is the major heat transfer process in APU compartment; APU fireproofing cover and heat insulation hood of exhaust pipe function work as radiation heat shielding screens; and cooling air in the APU fireproofing cover plays an important part in decreasing the temperature of the fireproofing cover; the injection cooling air in the exhaust pipe reduced the wall temperature effectively. The results provide reference to optimization design.

Abstract: The airfoil NACA 4412 commonly employed in wind turbines is modified by attaching a Gurney flap with length of 2% chord at its trailing edge and its remodeled form as well. The SIMPLE algorithm of finite volume method and software FLUENT are respectively used to carry out numerical computation of aerodynamic performances of above-mentioned three airfoils (including the un-modified one), so that their aerodynamic characteristics, pressure distribution on their surface, and streamline around them are obtained for different angles of attack. It is shown by the computation result that the modified airfoils will result in such a strong downwash effect that the pressure distribution on airfoil surface is remarkably altered, the lift coefficient and as well as the slope of lift-drag characteristic curve are increased, and meantime the airfoil stalling is greatly postponed.