Development of a CFD Simulation Method for Extreme Wave and Structure Interactions

2005 ◽  
Author(s):  
Chi Yang ◽  
Rainald Lo¨hner ◽  
Solomon C. Yim
Keyword(s):  
Cfd Simulation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Simulation Method ◽  
Computer Code ◽  
Dam Break ◽  
Navier Stokes ◽  
Extreme Waves ◽  
Cfd Method ◽  
Incompressible Euler

A robust Volume of Fluid (VOF) technique is presented together with an incompressible Euler/Navier Stokes solver operating on adaptive, unstructured grids to simulate the interactions of extreme waves and three-dimensional structures. The incompressible Euler/Navier Stokes equations are solved using projection schemes and a finite element method. The classic dam-break problem has been used to validate the computer code developed based on the method described above. The numerical simulations of a three dimensional dam-break wave interacting with a single cylinder and a cylinder array have been carried out. Computational results have demonstrated that the present CFD method is capable of simulating the interactions of extreme waves and three-dimensional structures, which are of great importance for the comprehension of many natural phenomena in marine, coastal and marine engineering.

Effect of Blade Numbers on Pressure Drop of Axial Cyclone Separators by CFD

2011 ◽  
Vol 55-57 ◽  
pp. 343-347 ◽  
Author(s):  
Yi Gang Luan ◽  
Hai Ou Sun
Keyword(s):  
Pressure Drop ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Three Dimensional Model ◽  
Navier Stokes Equations ◽  
Pressure Drops ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Resistance Performance

In this article, computational fluid dynamics(CFD) method is used to predict the effect of blade numbers on the pressure drop of axial cyclone separators. A three-dimensional model is built to acquire the resistance of axial cyclone separators with different blade numbers. The flow field inside cyclone separators is calculated using 3D Reynolds-averaged Navier-Stokes equations. And turbulence model is used to simulate the Reynold stress. Also pressure drop of cyclone separators with different blade numbers is expressed as a function of different inlet velocities. At the same inlet velocity with increasing the blade numbers, pressure drops of cyclones reduce greatly. And changing the blade number of cyclone separator is an effective method to improve its resistance performance.

scholarly journals Relaxation and breakup of a cylindrical liquid column

1970 ◽  
Vol 39 (2) ◽  
pp. 57-64 ◽  
Author(s):  
Mohammad Ali ◽  
Akira Umemura
Keyword(s):  
Surface Tension ◽  
Stokes Equations ◽  
Capillary Wave ◽  
Three Dimensional ◽  
Surface Tension Force ◽  
Surface Force ◽  
Computer Code ◽  
Vof Method ◽  
Liquid Column ◽  
Navier Stokes

Instability of capillary wave and breakup of a square cylindrical liquid column during its relaxation have been investigated numerically by simulating three-dimensional Navier-Stokes equations. For this investigation a computer code based on volume-of-fluid (VOF) method has been developed and validated with published experimental results. The result shows that the agreement of numerical simulation is quite well with the experimental data. The code is then used to study the capillary wave and breakup phenomena of the liquid column. The investigation shows the underlying physics during relaxation of the square cylindrical liquid column, illustrates the formation and propagation of capillary wave, and breakup processes. The breakup behavior for the present configuration of the liquid column shows some significant differences from those predicted by conventional jet atomization theories. The formation of capillary wave is initiated by the surface tension on the sharp edge of the square end of the cylinder and the propagation of the wave occurs due to the effect of surface tension force on the motion of the fluid. The propagation of capillary wave to the end of liquid column causes a disturbance in the system and makes the waves unstable which initiates the breakup of the liquid column. The characteristics of the capillary wave show that the amplitude of the swell grows faster than the neck of the wave and that of the tip wave grows much faster than the other waves. The velocity of the liquid particle is dominated by the pressure in the liquid column. Keywords: Instability; Continuum surface force; Liquid disintegration; Capillary wave; Surface tension; VOF method doi:10.3329/jme.v39i2.1847 Journal of Mechanical Engineering, Vol. ME39, No. 2, Dec. 2008 57-64

Flow Studies in Canine Artery Bifurcations Using a Numerical Simulation Method

1992 ◽  
Vol 114 (4) ◽  
pp. 504-511 ◽  
Author(s):  
X. Y. Xu ◽  
M. W. Collins ◽  
C. J. H. Jones
Keyword(s):  
Newtonian Fluid ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Simulation Method ◽  
Velocity Profiles ◽  
Navier Stokes ◽  
Element Mesh ◽  
Finite Volume Approach

Three-dimensional flows through canine femoral bifurcation models were predicted under physiological flow conditions by solving numerically the time-dependent threedimensional Navier-stokes equations. In the calculations, two models were assumed for the blood, those of (a) a Newtonian fluid, and (b) a non-Newtonian fluid obeying the power law. The blood vessel wall was assumed to be rigid this being the only approximation to the prediction model. The numerical procedure utilized a finite volume approach on a finite element mesh to discretize the equations, and the code used (ASTEC) incorporated the SIMPLE velocity-pressure algorithm in performing the calculations. The predicted velocity profiles were in good qualitative agreement with the in vivo measurements recently obtained by Jones et al. [1]. The non-Newtonian effects on the bifurcation flow field were also investigated, and no great differences in velocity profiles were observed. This indicated that the non-Newtonian characteristics of the blood might not be an important factor in determining the general flow patterns for these bifurcations, but could have local significance. Current work involves modeling wall distensibility in an empirically valid manner. Predictions accommodating these will permit a true quantitative comparison with experiment.

Experimental and Numerical Analysis of Compressor Inlet Volutes

1997 ◽  
Author(s):  
V. Michelassi ◽  
M. Giachi
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Computer Code ◽  
Navier Stokes ◽  
Complex Flow ◽  
Flow Distortion ◽  
Navier Stokes Equations ◽  
Flow Angle ◽  
Compressor Impeller ◽  
Compressor Inlet

A typical compressor inlet volute is studied by using both experimental and numerical approaches. The highly distorted and complex flow pattern is measured in two typical configurations. Measurements include velocity, flow angle, Mach number and losses. The same geometries are analyzed by using a computer code which solves the three-dimensional Navier-Stokes equations. Turbulence effects are modeled by a two-equation turbulence model. The set of measurements shows the flow distortion induced by the volute, and also highlights how this distortion can be controlled or largely reduced by small modifications to the geometry. The computational results indicate an overall good agreement with the measurements and allow reproducing the changes in the pattern induced by the changes in volute geometry. Both the measurements and computations prove the importance of the optimal design of this component which controls the uniformity of the flow approaching the compressor impeller.

Viscous Simulation Method for Unsteady Flows Past Multicomponent Configurations

1992 ◽  
Vol 114 (2) ◽  
pp. 161-169 ◽  
Author(s):  
Kamran Fouladi ◽  
Oktay Baysal
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Simulation Method ◽  
Parent Body ◽  
Navier Stokes ◽  
Reynolds Stresses ◽  
Navier Stokes Equations ◽  
Time Period ◽  
Cavity Opening ◽  
Averaging Time

An algorithm is developed to obtain numerical simulations of flows about complex configurations composed of multiple and nonsimilar components with arbitrary geometries. The algorithm uses a hybridization of the domain decomposition techniques for grid generation and to reduce the computer memory requirement. Three-dimensional Reynolds-averaged, unsteady, compressible, and full Navier-Stokes equations are solved on each of the subdomains by a fully vectorized, finite-volume, upwind-biased, approximately factored, and multigrid method. The effect of Reynolds stresses is incorporated through an algebraic turbulence model with several modifications for interference flows. The algorithm is applied to simulate supersonic flows past an ogive-nose-cylinder near or inside a cavity. The cylinder is attached to an offset L-shaped sting when placed above the cavity opening. The unsteady nature of these flowfields and the interaction of the cavity shear layer with the cylinder are simulated. These cases illustrate two significantly different and important interference characteristics for an internally carried store separating from its parent body. Unsteadiness of the cavity flow has a more pronounced effect on the normal forces acting on the cylinder when the cylinder is placed inside the cavity. The time averaged surface pressures compare favorably with the wind tunnel data, despite the averaging time period for the computations being three orders of magnitude smaller than that of the experimental measurements.

scholarly journals The dam-break problem for viscous fluids in the high-capillary-number limit

2009 ◽  
Vol 624 ◽  
pp. 1-22 ◽  
Author(s):  
C. ANCEY ◽  
S. COCHARD ◽  
N. ANDREINI
Keyword(s):  
Capillary Number ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Similarity Solutions ◽  
Dam Break ◽  
Navier Stokes ◽  
Flow Depth ◽  
Visualization System ◽  
Depth Profiles ◽  
Front Position

Experiments were undertaken to investigate dam-break flows where a finite volume of highly viscous fluid (glucose with viscosity μ ≈ 350 Pa s) maintained behind a lock gate was released into a horizontal or inclined flume. The resulting sequence of flow-depth profiles was tracked using a three-dimensional visualization system. In the low-Reynolds-number and high-capillary-number limits, analytical solutions can be obtained from the Navier–Stokes equations using lubrication theory and matched asymptotic expansions. At shallow slopes, similarity solutions can also be worked out. While the variation in the front position scaled with time as predicted by theory for both horizontal and sloping flumes, there was a systematic delay in the front position observed. Moreover, taking a closer look at the experimental flow-depth profiles shows that they were similar, but they noticeably deviated from the theoretical similarity form for horizontal planes. For sloping beds, the flow-depth profile is correctly predicted provided that different scalings are used at shallow and large slopes.

Unsteady CFD Simulation for High Speed Centrifugal Compressor Operating Near Surge

2014 ◽  
Author(s):  
Ibrahim Shahin ◽  
Mohamed Gadala ◽  
Mohamed Alqaradawi ◽  
Osama Badr
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Cfd Simulation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Computational Domain ◽  
Transient Pressure ◽  
Actual Case

Centrifugal compressor surge and stall are an instabilities flow and system phenomenon, which can lead to a loss of engine power, large pressure transients and, in some cases, failure of the compressor and bearing system. Three-dimensional, compressible, unsteady Navier-Stokes equations are solved, using the sliding mesh at the interface between the moving and stationary parts. The investigated computational domain is composed of inlet pipe, inlet bell, impeller followed by a diffuser. The impeller side cavities are included in the computational domain, to make the simulation more close to the actual case. The present article focuses on the unsteady pressure and velocity results within the impeller and diffuser, at an operating condition close to the surge of the compressor. The computational data compares favorably with the measured data, from literature, for the same compressor and operational point. The pressure fluctuation results are analyzed for the surge and design operating conditions. Through the acquisition of both velocity and transient pressure data, the time evaluation of the unsteady flow during surge is revealed.

Numerical Investigation of Self-Driven Fan Performance With Tip-Jet

2017 ◽  
Author(s):  
Lei Li ◽  
GuoPing Huang ◽  
Jie Chen ◽  
JinChun Wang
Keyword(s):  
Stokes Equations ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Suction Surface ◽  
Navier Stokes Equations ◽  
Momentum Coefficient ◽  
Aerodynamic Properties ◽  
Flow Phenomena ◽  
Cfd Method

Tip-jet rotor system has unique potential value in the area of vertical take-off and landing (VTOL) or short take-off and landing (STOL) concept aircraft. The main objective of the current work is to investigate the aerodynamic properties of a self-driven fan with tip-jet (SDF_TJ) in hover by numerical experiments. In order to obtain the detailed flow phenomena of SDF_TJ, CFD method is performed, which is conducted by solving three-dimensional Reynolds-averaged Navier-Stokes equations using the shear stress transport turbulence model. For the purpose of investigation, the analysis of SDF_TJ performances with different nozzle configurations have been carried out. Current results indicate the conformal tip-jet not only provide the reaction torque, but also augment the fan lift via entraining the main flow above the suction surface of blade. The rotation speed of fan is mainly determined by bleed air parameters and nozzle area, so as to torque self-balance. The total torque produced by jets contains rotor required torque and penalty torque induced by Coriolis force. The blade lift coefficient and the ratio with jet momentum coefficient are influenced by the distance from the nozzle downstream edge to blade trailing. As the lift of SDF_TJ is larger than the thrust generated by jets alone, which could benefit the take-off and landing capability of VTOL concept aircraft.

3D Volume-of-Fluid (VOF) Based Simulation of Water Impact Problem Using Navier-Stokes Computations

2015 ◽  
Author(s):  
Van-Tu Nguyen ◽  
Warn-Gyu Park
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
Volume Of Fluid ◽  
Water Entry ◽  
Surface Flow ◽  
Dam Break ◽  
Navier Stokes ◽  
Water Impact ◽  
Impact Problem

In this paper, a three-dimensional (3D) numerical investigation of dam-break and water entry problems with emphasis on the water impact loading is presented. Flow fields of incompressible viscous fluids are solved using unsteady Navier-Stokes equations (NS). Pseudo-time derivatives are introduced into the equations to improve computational efficiency. The interface between two phases is tracked using a volume-of-fluid (VOF) interface tracking algorithm developed in a generalized curvilinear coordinate system. The accuracy and capability of the numerical model for free surface flow simulations are demonstrated by using experiments of the dam-break flow over a horizontal dry bed. The water impact problem has been analyzed by free falling water entry of a hemisphere and a cone. Comparisons between the obtained solutions, the experimental data and the results of other numerical simulations in the literature are presented exhibiting good agreement.

Numerical Simulation and Experiment Research on Aerodynamic Characteristics of a Multi-Blade Centrifugal Fan

2011 ◽  
Vol 317-319 ◽  
pp. 2157-2161
Author(s):  
Yong Chao Zhang ◽  
Qing Guang Chen ◽  
Yong Jian Zhang ◽  
Xiang Xing Jia
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Internal Flow ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Computational Domain ◽  
Centrifugal Fan ◽  
Cfd Method

The full flow field model of a widely used multi-blade centrifugal fan was built, and unstructured grids were used to discrete the computational domain. The moving reference frame is adopted to transfer data between the interfaces of the rotating field and the stationary field. Pressure boundary conditions are specified to the inlet and the outlet. The SIMPLE algorithm in conjunction with the RNG k-ε turbulent model was used to solve the three-dimensional Navier-Stokes equations. The steady and unsteady numerical simulations of the inner flow in the fan at different working conditions were presented using the CFD method. The numerical simulation results were validated by contrasting to the experiment results. The results displayed the characteristics of the velocity field, pressure field, pressure fluctuation at two monitoring points in the centrifugal fan. The results can provide basis for optimizing the fan design and the internal flow, and have important value of engineering applications in the increase of the overall performance in operation.

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