基于空气动力学的极地重载甲板运输船烟囱的改进设计

本文针对某甲板运输船排烟易进入上建的问题,通过空气动力学计算对该问题的原因进行了探究和分析,结果表明钝型上建后部分产生的涡流将排烟向下吸,进而随空调入口进到船舶上建,通过提高排烟高度可以使烟气远离钝形上建后部分形成的涡流区,从而有效避免此类问题的发生。

Effects of circumferential configuration concerning splitter blade on the aerodynamic performance in a transonic axial fan

For a certain type of transonic axial fan, the flow field of a fan rotor with splitter blade was computed by numerical simulation, and the shape of the rotor was modified. The effects of different circumferential distributions concerning the splitter cascades upon the aerodynamic performance were investigated. The studies show that the optimum splitter cascade is not very close to the suction side of main blade. The load between the main blade and the splitter blade can be soundly distributed in terms of the adjustment of circumferential position of the splitter blade. The best aerodynamic performance can be successfully obtained according to the optimum shape of the expanding fluid channel reasonably formed by the splitter blade and the main blade.

Numerical simulation of aerodynamic interactions among helicopter rotor,fuselage,engine and body of revolution

Numerical simulations of helicopter aerodynamic interactions among the main rotor,fuselage,engine inlets/outlets and slung loads of specific geometries have been conducted by very few researchers.In this work,the steady-state compressible Reynolds-averaged navier-stokes equations are solved to study the aerodynamic interactions among helicopter rotor,fuselage,engine and body of revolution in three cases,namely MI-171V5,ROBIN and UH-60A.In the first case,the downwash flow provided by the rotor of the uniform actuator disc model induces a significant deflection of the airflow velocity.The vortex-shaped distribution and evolution are discussed in detail.The engine can effectively change the overall flow field.The asymmetry of the flow field is observed by using the non-uniform actuator disc model.Qualitative analysis of ROBIN and quantitative computation of UH-60A show a consistent accuracy of the rotating reference frame model for rotor.The blade tip vortex motion of UH-60A is simulated and its radial position prediction is compared to empirical formulas.While performing flow of UH-60A in hover,both the fuselage normal force and rotor lift decrease because of the impact of the body of revolution.

Numerical aerodynamic analysis of bluff bodies at a high Reynolds number with three-dimensional CFD modeling

This paper focuses on numerical simulations of bluff body aerodynamics with three-dimensional CFD(computational fluid dynamics) modeling,where a computational scheme for fluid-structure interactions is implemented.The choice of an appropriate turbulence model for the computational modeling of bluff body aerodynamics using both two-dimensional and three-dimensional CFD numerical simulations is also considered.An efficient mesh control method which employs the mesh deformation technique is proposed to achieve better simulation results.Several long-span deck sections are chosen as examples which were stationary and pitching at a high Reynolds number.With the proposed CFD method and turbulence models,the force coefficients and flutter derivatives thus obtained are compared with the experimental measurement results and computed values completely from commercial software.Finally,a discussion on the effects of oscillation amplitude on the flutter instability of a bluff body is carried out with extended numerical simulations.These numerical analysis results demonstrate that the proposed three-dimensional CFD method,with proper turbulence modeling,has good accuracy and significant benefits for aerodynamic analysis and computational FSI studies of bluff bodies.

Impact of Stagger Angle Nonuniformity on Turbine Aerodynamic Performance

The assembling error may lead to variation in stagger angles,which would affect the aerodynamic performance of the turbine.To investigate this underlying effect,two parallel numerical experiments on two turbines with the same profile,but uniform and nonuniform vane stagger angle respectively,were conducted in both steady and unsteady methods.The results indicate that certain changes in the detailed flow field of the turbine occur when the stagger angles are nonuniform,further,the blade loading distribution of the vane and rotor become markedly different from that in uniform vane stagger angle situation.Then these consequences caused by nonuniformity mentioned above enhance the unsteadiness of the flow,finally,the aerodynamic performance changes dramatically.It also shows that,compared with steady simulation,the unsteady numerical simulation is necessary in this investigation.

Numerical Simulation of the Tip Aerodynamics and Acoustics Test

The application of an efficient flow control system on helicopter rotor blades may lead to improved aerodynamic performance. Recently, our invention of Rod Vortex Generators(RVGs) has been analyzed for helicopter rotor blades in hover with success. As a step forward, the study has been extended to forward flight conditions. For this reason, a validation of the numerical modelling for a reference helicopter rotor(without flow control) is needed. The article presents a study of the flow-field of the AH-1G helicopter rotor in low-, medium- and high-speed forward flight. The CFD code FLOWer from DLR has proven to be a suitable tool for the aerodynamic analysis of the two-bladed rotor without any artificial wake modelling. It solves the URANS equations with LEA(Linear Explicit Algebraic stress) k-ω model using the chimera overlapping grids technique. Validation of the numerical model uses comparison with the detailed flight test data gathered by Cross J. L. and Watts M. E. during the Tip Aerodynamics and Acoustics Test(TAAT) conducted at NASA in 1981. Satisfactory agreements for all speed regimes and a presence of significant flow separation in high-speed forward flight suggest a possible benefit from the future implementation of RVGs. The numerical results based on the URANS approach are presented not only for a popular, low-speed case commonly used in rotorcraft community for CFD codes validation but preferably for medium- and high-speed test conditions that have not been published to date.

Streamwise Vortex Interaction with a Horseshoe Vortex

How control in turbomachinery is very difficult because of the complexity of its fully 3-D flow structure. The authors propose to introduce streamwise vortices into the control of internal flows. A simple configuration of vortices was investigated in order to better understand the flow control methods by means of streamwise vortices. The research presented here concerns streamwise vortex interaction with a horseshoe vortex. The effects of such an interaction are significantly dependent on the relative location of the streamwise vortex in respect to the leading edge of the profile. The streamwise vortex is induced by an air jet. The horseshoe vortex is generated by the leading edge of a symmetric profile. Such a configuration gives possibility to investigate the interaction of these two vortices alone. The presented analysis is based on numerical simulations by means of N-S compressible solver with a two-equation turbulence model.