Drag Calculations for Vehicles in Very Long Tubes From Turbulent Flow Theory

1981 ◽  
Vol 103 (2) ◽  
pp. 361-366 ◽  
Author(s):  
I. Sud ◽  
J. B. Chaddock
Keyword(s):  
Fluid Flow ◽  
Turbulent Flow ◽  
Numerical Solution ◽  
High Speed ◽  
Limited Sample ◽  
Fully Developed Flow ◽  
Similarity Hypothesis ◽  
Annular Gap ◽  
Flow Techniques ◽  
Good Agreement

Fundamental turbulent flow techniques are used to examine the annular fluid flow occurring in an idealized model of a high speed ground transportation system. The model consists of a smooth cylindrical train moving in an infinitely long tunnel, creating an annular gap with one wall in motion. The developing, and the fully developed, flow regions are separately analyzed by using fundamental relations of turbulent flow and Von Karman’s similarity hypothesis. The relevant equations are developed and numerical solution procedures presented. Limited sample calculations show good agreement with existing empirical and experimental results.

Simulation and Analysis of Rigid/Foil Electrolytic In-Process Dressing (ELID) Systems for Grinding

2004 ◽  
Vol 126 (3) ◽  
pp. 565-570 ◽  
Author(s):  
Zhenqi Zhu ◽  
Xiaohua Wang ◽  
Siva Thangam
Keyword(s):  
Fluid Flow ◽  
High Speed ◽  
Governing Equations ◽  
Supply Rate ◽  
Mean Velocity ◽  
Unidirectional Flow ◽  
High Speed Grinding ◽  
The Mean ◽  
Machine Systems ◽  
Good Agreement

The fluid flow problem in a traditional electrolytic in-process dressing (ELID) system is analyzed and solved numerically. The predicted mean velocity profiles in the dressing zone show flow patterns that are in good agreement with the mean velocity distributions for plane laminar/turbulent Couette flows observed in the experiments. The computational results reveal that insufficient electrolyte supply rate is the cause of the failure of the traditional ELID system for high-speed grinding. Results also show that to obtain effective high-speed ELID grinding, a consistent high inlet electrolyte velocity or supply rate is required. For the foil ELID system, governing equations describing the fluid flow in the dressing zone and the foil elastic deformation are formulated. Analytical solution based on unidirectional flow model for the problem is presented and effects of wheel surface speed and foil tension on the performance of the dressing system are discussed. It is shown that the foil ELID system has the potential to be effective for high-speed grinding with low electrolyte supply rates. The results will be useful to the development of new machine systems and processes for high-speed grinding.

Tip region of a hydraulic fracture driven by a laminar-to-turbulent fluid flow

2016 ◽  
Vol 797 ◽  
Author(s):  
E. V. Dontsov
Keyword(s):  
Fluid Flow ◽  
Turbulent Flow ◽  
Numerical Solution ◽  
Hydraulic Fracture ◽  
Asymptotic Solutions ◽  
Turbulent Regime ◽  
Zone Size ◽  
Turbulent Fluid Flow ◽  
Fully Developed Turbulent Flow ◽  
Steady Propagation

The focus of this study is to analyse the tip region of a hydraulic fracture, for which a fluid flow inside the crack transitions from the laminar to the turbulent regime away from the tip. To tackle the problem, a phenomenological formula for flow in pipes has been adapted to describe flow in a fracture through the concept of a hydraulic diameter. The selected model is able to capture laminar, turbulent and transition regimes of the flow. The near-tip region of a hydraulic fracture is analysed by focusing on steady propagation of a semi-infinite hydraulic fracture with leak-off, for which the aforementioned phenomenological formula for the fluid flow is utilized. First, the distance from the tip within which a laminar solution applies is estimated. Then, expressions for asymptotic solutions that are associated with fully developed turbulent flow inside the semi-infinite hydraulic fracture are derived. Finally, the laminar zone size and the asymptotic solutions are compared with the numerical solution, where the latter captures all regimes of the fluid flow.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Axisymmetric flow near the critical point on the moving boundary

2010 ◽  
Vol 7 ◽  
pp. 182-190
Author(s):  
I.Sh. Nasibullayev ◽  
E.Sh. Nasibullaeva
Keyword(s):  
Fluid Flow ◽  
Finite Difference ◽  
Boundary Conditions ◽  
Numerical Solution ◽  
Axial Velocity ◽  
Moving Boundary ◽  
Axisymmetric Flow ◽  
Boundary Motion ◽  
Newton Raphson ◽  
Raphson Method

In this paper the investigation of the axisymmetric flow of a liquid with a boundary perpendicular to the flow is considered. Analytical equations are derived for the radial and axial velocity and pressure components of fluid flow in a pipe of finite length with a movable right boundary, and boundary conditions on the moving boundary are also defined. A numerical solution of the problem on a finite-difference grid by the iterative Newton-Raphson method for various velocities of the boundary motion is obtained.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

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