scholarly journals Numerical and Experimental Study of the Flow Field Structure Evolution in the Circular Recess of Oil Cavity

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Feng Shen ◽  
Conglian Chen ◽  
Zhaomiao Liu
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Great Influence ◽  
Flow Region ◽  
Field Structure ◽  
Numerical Control ◽  
Navier Stokes ◽  
Structure Evolution ◽  
Finite Volume Approach

The laminar radial flow in the oil cavity of heavy-duty computer numerical control (CNC) machines is very complicated and has not been fully explored. Navier-Stokes equations have been applied through the whole flow region using finite volume approach to explore this complicated flow phenomenon, including the influences of the clearance height (h), inlet nozzle Reynolds number (Re), and geometrical aspect ratio (e) on flow behaviors. A fluid dynamic experiment has been conducted to study the flow structure by using particle image velocimetry (PIV). Numerical simulation results have been compared with the experimental results, finding a good agreement with the studied cases. The results suggest that there are complex vortices in the oil cavity. Flow field structure of the oil cavity largely depends onh, Re, ande. Re andehave a great influence on the size and amount of vortices, andhhas slight effects on the size of the vortices. The lengths of primary, secondary, and tertiary isolated vortices have a linear relationship withh. The lengths of the primary and secondary isolated vortices increase linearly with ascendingeaseis small. But when Re andeare large enough, the size of the three vortices decreases.

CFD in the Loop: Ensemble Kalman Filtering With Underwater Mobile Sensor Networks

2014 ◽  
Author(s):  
Axel Hackbarth ◽  
Edwin Kreuzer ◽  
Thorben Schröder
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Navier Stokes ◽  
Mobile Sensor ◽  
Dynamic Simulations ◽  
Navier Stokes Equations ◽  
Time Flow ◽  
Strong Current ◽  
Predictive Controller

In marine environments, sparse in-situ measurements can be used for the estimation of the fluid dynamic field. To make best use of a mobile sensor network in an environment whose dynamics can be described by the Navier-Stokes equations, we developed a framework for data assimilation with motion-constrained underwater vehicles, that takes the physical field properties into account while sampling. Our algorithm uses an ensemble Kalman filter that propagates hundreds of slightly varied coarse fluid dynamic simulations through time. Flow and scalar measurements from the mobile sensors are integrated into all ensemble members. We implemented a model predictive controller to calculate covariance minimizing paths from the estimated flow field and motion primitives of the vehicles, which are affected by a strong current. Thereby, we were able to indirectly track dynamically changing wall temperatures through measurements of flow field variables.

scholarly journals Numerical and Analytical Study of Fluid Dynamic Forces in Seals and Bearings

1988 ◽  
Vol 110 (3) ◽  
pp. 315-325 ◽  
Author(s):  
L. T. Tam ◽  
A. J. Przekwas ◽  
A. Muszynska ◽  
R. C. Hendricks ◽  
M. J. Braun ◽  
...  
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Circumferential Velocity ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Lumped Model ◽  
Destabilizing Factors ◽  
Recirculation Zones

A numerical model based on a transformed, conservative form of the three-dimensional Navier-Stokes equations and an analytical model based on “lumped” fluid parameters are presented and compared with studies of modeled rotor/bearing/seal systems. The rotor destabilizing factors are related to the rotative character of the flow field. It is shown that these destabilizing factors can be reduced through a descrease in the fluid average circumferential velocity. However, the rotative character of the flow field is a complex three-dimensional system with bifurcated secondary flow patterns that significantly alter the fluid circumferential velocity. By transforming the Navier-Stokes equations to those for a rotating observer and using the numerical code PHOENICS-84 with a nonorthogonal body fitted grid, several numerical experiments were carried out to demonstrate the character of this complex flow field. In general, fluid injection and/or preswirl of the flow field opposing the shaft rotation significantly intensified these secondary recirculation zones and thus reduced the average circumferential velocity, while injection or preswirl in the direction of rotation significantly weakened these zones. A decrease in average circumferential velocity was related to an increase in the strength of the recirculation zones and thereby promoted stability. The influence of the axial flow was analyzed. The lumped model of fluid dynamic force based on the average circumferential velocity ratio (as opposed to the bearing/seal coefficient model) well described the obtained results for relatively large but limited ranges of parameters. This lumped model is extremely useful in rotor/bearing/seal system dynamic analysis and should be widely recommended. Fluid dynamic forces and leakage rates were calculated and compared with seal data where the working fluid was bromotrifluoromethane (CBrF3). The radial and tangential force predictions were in reasonable agreement with selected experimental data. Nonsynchronous perturbation provided meaningful information for system lumped parameter identification from numerical experiment data.

Numerical analysis of exhaust jet secondary combustion in hypersonic flow field

2018 ◽  
Vol 32 (12n13) ◽  
pp. 1840045
Author(s):  
Tian-Peng Yang ◽  
Jiang-Feng Wang ◽  
Fa-Ming Zhao ◽  
Xiao-Feng Fan ◽  
Yu-Han Wang
Keyword(s):  
Flow Field ◽  
Hypersonic Flow ◽  
Flight Control ◽  
Stokes Equations ◽  
Field Structure ◽  
Control Surface ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Secondary Combustion ◽  
Exhaust Jet

The interaction effect between jet and control surface in supersonic and hypersonic flow is one of the key problems for advanced flight control system. The flow properties of exhaust jet secondary combustion in a hypersonic compression ramp flow field were studied numerically by solving the Navier–Stokes equations with multi-species and combustion reaction effects. The analysis was focused on the flow field structure and the force amplification factor under different jet conditions. Numerical results show that a series of different secondary combustion makes the flow field structure change regularly, and the temperature increases rapidly near the jet exit.

Computational Analysis of Two-Phase Mixing Inside a Twin-Fluid, Fuel-Flexible Atomizer

2017 ◽  
Author(s):  
Nathan J. Vardaman ◽  
Ajay K. Agrawal
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Fuel Injector ◽  
Cfd Model ◽  
Two Phase ◽  
Phase Mixing ◽  
Phase Mixture

We have developed a twin-fluid atomizer for combustion that creates a two-phase mixture of fuel and atomizing air upstream of the injector exit where a high-pressure region is established. The static pressure decreases rapidly as the fuel-air mixture exits from the injector, which causes air bubbles in the mixture to expand and breakup the surrounding liquid. This type of fuel injector can effectively atomize various biofuels including highly viscous straight vegetable oil and glycerol. While the combustion benefits have been demonstrated in our prior studies, an understanding of the underlying flow field and mechanism of the two-phase mixture formation process within the injector remains elusive. In this study, a computational fluid dynamic (CFD) model is developed to investigate the two-phase mixing and how it is affected by the operating conditions, particularly the atomizing air to liquid ratio (ALR) by mass. The axisymmetric isothermal CFD model, based on the mixture model for two-phase flows and Reynolds averaged Navier-Stokes equations, utilizes air and water as the working fluids. Both fluids are treated as incompressible, with constant fluid properties. The analysis reveals the flow field within the injector and successfully replicates the upstream penetration of the atomizing air into the liquid supply tube observed experimentally. The penetration depth increases with increase in the ALR, which again agrees with the experimental results.

Three-dimensional pressure- and shear-driven flow phenomena in a circular recess of a hydrostatic rotary table

2013 ◽  
Vol 228 (6) ◽  
pp. 989-1004
Author(s):  
Feng Shen ◽  
Cong-Lian Chen ◽  
Zhao-Miao Liu
Keyword(s):  
Reynolds Number ◽  
Vector Fields ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Region ◽  
Numerical Control ◽  
Navier Stokes ◽  
Rotary Table ◽  
Flow Phenomena ◽  
Flow States

The three-dimensional pressure- and shear-driven flow phenomena in a circular recess of hydrostatic rotary table in heavy-duty computer numerical control machines is very complicated and has not been fully explored. Navier–Stokes equations have been applied through the whole flow region using a finite volume approach to explore this complicated flow phenomena, including the influences of feeding Reynolds number ( Rei), sliding Reynolds number ( Res) and the recess geometry on flow behaviors. A test rig based on a particle image velocimetry was built to compare experimental and numerical results, finding a good agreement for stationary cases. The results show that the flow patterns in the recess are very complex and four three-dimensional vortices exist at Rei = 448 and Res = 74.6. Four flow states are defined according to the structure of the vortices. Different sectional profiles of the streamlines and velocity vector fields are examined to reveal the mechanism of pressure- and shear-driven flow interactions. The results of influences of recess geometry on flow states and pressure patterns are intended to contribute to represent a database in view of the hydrostatic rotary table theoretical modeling.

scholarly journals A low—storage Runge—Kutta OpenFOAM solver for compressible low—Mach number flows: aeroacoustic and thermo—fluid dynamic applications

2019 ◽  
Vol 128 ◽  
pp. 10001
Author(s):  
Valerio D’Alessandro ◽  
Matteo Falone ◽  
Luca Giammichele ◽  
Sergio Montelpare
Keyword(s):  
Sound Propagation ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Time Integration ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Central Schemes ◽  
Thermal Boundary Conditions ◽  
Finite Volume Approach ◽  
The Impact

A solver for compressible Navier–Stokes equations is presented in this paper. Low-storage RungeKutta schemes were adopted for time integration; on the other hand the finite volume approach available within OpenFOAM library has been adopted for space discretization. Kurganov-Noelle-Petrova approach was used for convective terms, while central schemes for diffusive ones. The aforementioned techniques were selected and tested in order to allow the possibility of solving a broad range of physical phenomena with particular emphasis to aeroacoustic and thermo-fluid dynamic problems. Indeed, that standard OpenFOAM solution techniques produce an unacceptable dissipation for acoustic phenomena computations. Non–reflective boundary treatment was also considered to avoid spurious numerical reflections. The reliability and the robustness of the solver is proved by computing several benchmarks. Lastly, the impact of the thermal boundary conditions on the sound propagation was analyzed.

The inlet flow structure of a conceptual open-nose supersonic drone

2021 ◽  
pp. 095441002098304
Author(s):  
Eiman B Saheby ◽  
Xing Shen ◽  
Anthony P Hays ◽  
Zhang Jun
Keyword(s):  
Flow Structure ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Computational Fluid Dynamic Simulation ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Aerodynamic Efficiency ◽  
Performance Effects

This study describes the aerodynamic efficiency of a forebody–inlet configuration and computational investigation of a drone system, capable of sustainable supersonic cruising at Mach 1.60. Because the whole drone configuration is formed around the induction system and the design is highly interrelated to the flow structure of forebody and inlet efficiency, analysis of this section and understanding its flow pattern is necessary before any progress in design phases. The compression surface is designed analytically using oblique shock patterns, which results in a low drag forebody. To study the concept, two inlet–forebody geometries are considered for Computational Fluid Dynamic simulation using ANSYS Fluent code. The supersonic and subsonic performance, effects of angle of attack, sideslip, and duct geometries on the propulsive efficiency of the concept are studied by solving the three-dimensional Navier–Stokes equations in structured cell domains. Comparing the results with the available data from other sources indicates that the aerodynamic efficiency of the concept is acceptable at supersonic and transonic regimes.

On the Flow Fields of Inertial Impactors

1974 ◽  
Vol 96 (4) ◽  
pp. 394-400 ◽  
Author(s):  
V. A. Marple ◽  
B. Y. H. Liu ◽  
K. T. Whitby
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Relaxation Method ◽  
Water Model ◽  
Navier Stokes ◽  
Visualization Technique ◽  
Navier Stokes Equations ◽  
Theoretical Results ◽  
Plate Distance ◽  
Good Agreement

The flow field in an inertial impactor was studied experimentally with a water model by means of a flow visualization technique. The influence of such parameters as Reynolds number and jet-to-plate distance on the flow field was determined. The Navier-Stokes equations describing the laminar flow field in the impactor were solved numerically by means of a finite difference relaxation method. The theoretical results were found to be in good agreement with the empirical observations made with the water model.

Numerical Simulation of Flowfield around High Speed Trains Passing by each other at the same Speed

2011 ◽  
Vol 97-98 ◽  
pp. 698-701
Author(s):  
Ming Lu Zhang ◽  
Yi Ren Yang ◽  
Li Lu ◽  
Chen Guang Fan
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Flow Field ◽  
Point Source ◽  
High Speed ◽  
Stokes Equations ◽  
Field Structure ◽  
Vehicle Speed ◽  
Mesh Method ◽  
High Speed Trains

Large eddy simulation (LES) was made to solve the flow around two simplified CRH2 high speed trains passing by each other at the same speed base on the finite volume method and dynamic layering mesh method and three dimensional incompressible Navier-Stokes equations. Wind tunnel experimental method of resting train with relative flowing air and dynamic mesh method of moving train were compared. The results of numerical simulation show that the flow field structure around train is completely different between wind tunnel experiment and factual running. Two opposite moving couple of point source and point sink constitute the whole flow field structure during the high speed trains passing by each other. All of streamlines originate from point source (nose) and finish with the closer point sink (tail). The flow field structure around train is similar with different vehicle speed.

Fluid flow over and through a regular bundle of rigid fibres

2016 ◽  
Vol 792 ◽  
pp. 5-35 ◽  
Author(s):  
Giuseppe A. Zampogna ◽  
Alessandro Bottaro
Keyword(s):  
Porous Medium ◽  
Fluid Flow ◽  
Flow Field ◽  
Stokes Equations ◽  
Transversely Isotropic ◽  
Navier Stokes ◽  
Leading Order ◽  
Macroscopic Scale ◽  
Navier Stokes Equations ◽  
Homogenized Model

The interaction between a fluid flow and a transversely isotropic porous medium is described. A homogenized model is used to treat the flow field in the porous region, and different interface conditions, needed to match solutions at the boundary between the pure fluid and the porous regions, are evaluated. Two problems in different flow regimes (laminar and turbulent) are considered to validate the system, which includes inertia in the leading-order equations for the permeability tensor through a Oseen approximation. The components of the permeability, which characterize microscopically the porous medium and determine the flow field at the macroscopic scale, are reasonably well estimated by the theory, both in the laminar and the turbulent case. This is demonstrated by comparing the model’s results to both experimental measurements and direct numerical simulations of the Navier–Stokes equations which resolve the flow also through the pores of the medium.

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