Numerical Analysis of the Turbulent Flow Field Applied to Thermal Spallation Drilling

2004 ◽  
Author(s):  
Angela O. Nieckele ◽  
Luis Fernando Figueira da Silva ◽  
Joa˜o Carlos R. Pla´cido
Keyword(s):  
Reynolds Number ◽  
Numerical Analysis ◽  
Flow Field ◽  
Gas Phase ◽  
Accurate Determination ◽  
Rock Surface ◽  
Drilling Technique ◽  
High Reynolds ◽  
Drilling Conditions ◽  
Volume Method

Thermal spallation is a possible drilling technique which consists of using hot supersonic jets as heat source to perforate hard rocks at high rates. This work presents a numerical analysis of a typical spallation drilling configuration, by the finite volume method. The time-averaged conservation equations of mass, momentum and energy are solved to determine the turbulent compressible gas phase flow field. Turbulence is predicted by the classical high Reynolds number κ-ε model, as well as with a low Reynolds number κ-ε model. The influence of the jet Reynolds number is investigated. Special attention is given to the rock surface temperature, since its accurate determination is required to predict spallation rates under field-drilling conditions.

scholarly journals Mixing and chemical reactions in a turbulent liquid mixing layer

1986 ◽  
Vol 170 ◽  
pp. 83-112 ◽  
Author(s):  
M. M. Koochesfahani ◽  
P. E. Dimotakis
Keyword(s):  
Reynolds Number ◽  
Gas Phase ◽  
Turbulent Mixing ◽  
High Speed ◽  
High Reynolds Number ◽  
Schmidt Number ◽  
Mixing Layer ◽  
Entrainment Ratio ◽  
High Reynolds ◽  
Mixed Fluid

An experimental investigation of entrainment and mixing in reacting and non-reacting turbulent mixing layers at large Schmidt number is presented. In non-reacting cases, a passive scalar is used to measure the probability density function (p.d.f.) of the composition field. Chemically reacting experiments employ a diffusion-limited acid–base reaction to directly measure the extent of molecular mixing. The measurements make use of laser-induced fluorescence diagnostics and high-speed, real-time digital image-acquisition techniques.Our results show that the vortical structures in the mixing layer initially roll-up with a large excess of fluid from the high-speed stream entrapped in the cores. During the mixing transition, not only does the amount of mixed fluid increase, but its composition also changes. It is found that the range of compositions of the mixed fluid, above the mixing transition and also throughout the transition region, is essentially uniform across the entire transverse extent of the layer. Our measurements indicate that the probability of finding unmixed fluid in the centre of the layer, above the mixing transition, can be as high as 0.45. In addition, the mean concentration of mixed fluid across the layer is found to be approximately constant at a value corresponding to the entrainment ratio. Comparisons with gas-phase data show that the normalized amount of chemical product formed in the liquid layer, at high Reynolds number, is 50% less than the corresponding quantity measured in the gas-phase case. We therefore conclude that Schmidt number plays a role in turbulent mixing of high-Reynolds-number flows.

Force on a Small Particle Attached to a Plane Wall in a Hiemenz Straining Flow

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
A. B. Maynard ◽  
J. S. Marshall
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Reynolds Numbers ◽  
Lower Surface ◽  
Ring Structure ◽  
Plane Wall ◽  
Small Reynolds Numbers ◽  
Particle Force ◽  
Volume Method ◽  
Excellent Accuracy

The force acting on a spherical particle fixed to a wall and immersed in an axisymmetric straining flow is examined for small Reynolds numbers. The steady, incompressible flow field is computed using an axisymmetric finite-volume method over conditions spanning five decades in the Reynolds number. The flow is characterized by the formation of a vortex ring structure in the wedge region formed between the particle lower surface and the plane wall. A power law expression for the dimensionless particle force is obtained as a function of the Reynolds number, which is found to hold with excellent accuracy for Reynolds numbers below about 0.1.

Reynolds Number–Strouhal Number Relationship for Cylindrical Bluff Body with Variation of Aspect Ratio in High Reynolds Number

2014 ◽  
Vol 69 (3) ◽  
Author(s):  
Nor Azwadi Che Sidik ◽  
Tey Wah Yen
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Strouhal Number ◽  
Bluff Body ◽  
Flow Parameters ◽  
Ansys Cfx ◽  
Sst Model ◽  
Model Equations ◽  
High Reynolds ◽  
Volume Method

The effect between Reynolds number and bluff body aspect ratio to the flow parameters such as Strouhal number and drag coefficient are studied. The range of Reynolds number applied is within 10000 and 200000 while three aspect ratio (Ar) where Ar = 1.0, 1.5 and 2.0 are implemented. Finite volume method with the aid of ANSYS CFX codes is deployed using the turbulence SST model. Equations of Re-St relationship for Ar 1.0 and 1.5 are then hypothesized as well in this paper for the range of 10000<Re<100000.

Numerical Analysis of Inner Flow Field for Disk MRF Brake

2011 ◽  
Vol 181-182 ◽  
pp. 251-256
Author(s):  
Cheng Ye Liu ◽  
Feng Yan Yi ◽  
Ke Jun Jiang
Keyword(s):  
Numerical Analysis ◽  
Flow Field ◽  
Velocity Distribution ◽  
Theoretical Data ◽  
Numerical Data ◽  
Axial Direction ◽  
Analysis Data ◽  
Brake Torque ◽  
Set Up ◽  
Volume Method

According to structure of disk MRF brake computational model of inner flow field for MRF was set up at simplified condition when MRF was regarded as Bingham model. Velocity distribution in inner flow field had been analyzed at different brake velocities and magnetic intensity using finite volume method (FVM), and brake torque and power had also been received at the same condition by integral method. Numerical analysis data were compared with theoretical data. Result showed that velocity distribution of inner flow field was not linear at axial direction, and that brake torque of disk MRF brake was constant approximately, and that numerical data and theoretic data were identical and it can provide reference for design.

Experimental Investigation of the Fluid Motion in a Cylinder Driven by a Flat-Plate Impeller

2006 ◽  
Vol 129 (6) ◽  
pp. 737-746 ◽  
Author(s):  
Douglas Bohl
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Reverse Flow ◽  
Fluid Motion ◽  
Reynolds Numbers ◽  
Cylinder Wall ◽  
Water Mixture ◽  
Recirculating Flow ◽  
Blade Tip ◽  
High Reynolds

The flow field in a cylindrical container driven by a flat-bladed impeller was investigated using particle image velocimetry (PIV). A range of Reynolds numbers (0.005–7200), based on the container radius rw, were investigated using four Newtonian fluids: water (Re=7200,6800), 85/15 glycerin/water mixture (Re=108), pure glycerin (Re=8), and corn syrup (Re=0.02,0.005). Two impellers with a radius of 0.43rw and 0.95rw were used to drive the flow. The 0.43rw impeller was shown to generate a vortex near the tip of the blades. The peak magnitude of the vortices and the size of the vortices in the radial direction decreased with increasing Reynolds number. Additionally, the vortex generated at the high Reynolds number was unsteady with a trailing shear layer that periodically shed vorticity into the flow field. The structure of the flow in the region between the blade and the cylinder wall showed a Reynolds number dependence, though the two lowest Reynolds number (0.02 and 8) flows investigated had quantitatively similar flow structures. These cases were found to have a closed region of reverse flow between the blade tip and the cylinder wall. No recirculating flow was indicated for the Re=108 and 7200 cases. These data indicate that there may be a critical condition below which there is little dependence in the flow structure on the Reynolds number.

scholarly journals A numerical solution to the flow between eccentric rotating cylinders with a slotted sleeve

1999 ◽  
Vol 41 (1) ◽  
pp. 129-152 ◽  
Author(s):  
L. D. Hird ◽  
P. F. Siew ◽  
S. Wang
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Reynolds Numbers ◽  
Main Body ◽  
Rotating Cylinders ◽  
Rotational Rate ◽  
Through Flow ◽  
Large Eccentricity ◽  
Flow Through ◽  
Volume Method

AbstractThe flow between two eccentric rotating cylinders with a slotted sleeve placed around the inner cylinder is determined numerically using an exponentially fitted finite-volume method. The flow field is determined for various Reynolds numbers, eccentricities and rotational speeds for the cases when the cylinders rotate in the same sense and rotate in opposite senses. The flow field developed when both cylinders rotate in the same sense is characterised, for sufficiently large eccentricity and rotational rate, by two counter-rotating eddies. Only one eddy is observed when the cylinders rotate in opposite senses. The presence of these eddies restricts the flow through the slotted sleeve in the former case but encourages through flow in the latter. For both cases, the eccentricity affects the location of the eddies, while changing the relative rotational rate only affects the eddy location for the case when the cylinders rotate in opposite directions. The change in Reynolds number has little effect on the flow field for the problems considered here. The vorticity generated by the slotted sleeve is convected into the main body of the flow field. No inviscid core within the main body of the flow field is observed for the range of Reynolds number considered.

Sign in / Sign up

Export Citation Format

Share Document