Convection in Underground Oil Caverns: The Role of Double Diffusion

2007 ◽  
Author(s):  
H. J. S. Fernando ◽  
C. Y. Ching ◽  
Z. Zhao ◽  
S. Pol ◽  
S. W. Webb
Keyword(s):  
Double Diffusion ◽  
Experimental Program ◽  
Bottom Surface ◽  
Compositional Gradient ◽  
Geothermal Heating ◽  
The Us ◽  
Strategic Petroleum Reserve ◽  
Side Walls ◽  
Salt Caverns ◽  
Double Diffusive

The US Strategic Petroleum Reserve (SPR) stores oil in large underground salt caverns. This oil has compositional and thermal gradients induced by geothermal heating from both the bottom surface and side walls. Temperature layering has been recorded in SPR oil caverns, which is hypothesized to be predominantly due to double-diffusive layering that occurs when a stable compositional gradient is heated from below. Initial results of a laboratory experimental program aimed at studying dynamics of such double-diffusive layers in the context of SPR are described in this paper. Of particular interest are the thickness of convecting layers, layer evolution (migration/merging) and conditions for the formation/non-formation of double-diffusive layers.

scholarly journals The Influence of Soil Parameters on the Impulse and Airblast Overpressure Loading above Surface-Laid and Shallow-Buried Explosives

2011 ◽  
Vol 18 (6) ◽  
pp. 857-874 ◽  
Author(s):  
John Q. Ehrgott Jr. ◽  
Stephen A. Akers ◽  
Jon E. Windham ◽  
Denis D. Rickman ◽  
Kent T. Danielson
Keyword(s):  
Research Effort ◽  
Silty Sand ◽  
Experimental Program ◽  
Bottom Surface ◽  
Soil Parameters ◽  
First Year ◽  
Near Surface ◽  
Us Army ◽  
Military Vehicles ◽  
The Us

The dynamic airblast, fragmentation, and soil ejecta loading environments produced by the detonation of surface-laid and shallow-buried mines are major threats to lightweight military vehicles. During the past several years, the US Army has focused considerable attention on developing improved methods for predicting the below-vehicle environment from these threats for use by vehicle/armor analysts; thereby, improving the survivability of these platforms. The US Army Engineer Research and Development Center recently completed the first year of a three-year effort to experimentally and numerically quantify the blast and fragment loading environments on vehicles due to surface and subsurface mine and IED detonations. As part of this research effort, a series of experiments was conducted to quantify the effects of soil parameters on the aboveground blast environments produced by the detonation of aboveground bottom-surface-tangent, buried top-surface-tangent, and shallow-buried 2.3-kg (5-lb) Composition C4 charges. The experiments were conducted using three different well characterized soils; 10.8% air-filled-voids (AFV) silty sand, 5.4% AFV clay, and 29.8% AFV poorly graded sand. The combined aboveground loads due to airblast and soil debris were measured by an impulse measurement device. The near-surface airblast overpressure was quantified by a series of side-on measurements above the charges at one elevation and three radial distances. This paper summarizes and compares the results of the experimental program with emphasis on defining the effect of soil parameters on the aboveground blast environment.

scholarly journals Double-Diffusive Intrusions in a Stable Salinity Gradient “Heated from Below”

2008 ◽  
Vol 38 (10) ◽  
pp. 2271-2282 ◽  
Author(s):  
Julian Simeonov ◽  
Melvin E. Stern
Keyword(s):  
Salinity Gradient ◽  
Domain Size ◽  
Double Diffusion ◽  
The Arctic ◽  
Small Scale ◽  
Uniform Density ◽  
Equilibrium Solutions ◽  
Lateral Velocity ◽  
Gravity Acceleration ◽  
Double Diffusive

Abstract Two-dimensional direct numerical simulations (DNS) are used to investigate the growth and nonlinear equilibration of spatially periodic double-diffusive intrusion for negative vertical temperature Tz < 0 and salinity Sz < 0 gradients, which are initially stable to small-scale double diffusion. The horizontal temperature Tx and salinity Sx gradients are assumed to be uniform, density compensated, and unbounded. The weakly sloping intrusion is represented as a mean lateral flow in a square computational box tilted with a slope equal to that of the fastest-growing linear theory mode; the vertical (η) domain size of the box L*η is a multiple of the fastest-growing wavelength. Solutions for the fastest-growing wavelength show that the intrusion growth is disrupted by salt fingers that develop when the rotation of the isotherms and isohalines by the intrusion shear results in temperature and salinity inversions; the thick inversion regions are separated by a thin interface supporting diffusive convection. These equilibrium solutions were always unstable to longer vertical wavelengths arising because of the merging of the inversion layers. The DNS predicts the following testable results for the maximum lateral velocity U* max = 0.13NSL*η, the lateral heat flux F* = 0.008ρCP(Sx/Sz)1/2(NS/KT)1/4NSL*η2.5(βSz/α), and the interface thickness hρ = 0.12L*η, where NS = , g is the gravity acceleration, ρ is the density, β/α is the haline contraction/heat expansion coefficient, and CP is the specific heat capacity. The results are compared with observations in the Arctic Ocean.

scholarly journals Double-Diffusive Interleaving: Properties of the Steady-State Solution

2015 ◽  
Vol 45 (3) ◽  
pp. 813-835 ◽  
Author(s):  
Yuehua Li ◽  
Trevor J. McDougall
Keyword(s):  
Steady State ◽  
Double Diffusion ◽  
Intermediate Stage ◽  
Steady State Solution ◽  
Finite Amplitude ◽  
Linear Instability ◽  
Vertical Diffusion ◽  
Prandtl Numbers ◽  
Pass Through ◽  
Double Diffusive

AbstractDouble-diffusive interleaving is examined as it progresses from a linear instability toward finite amplitude. When the basic stratification is in the “finger” sense, the initial series of finger interfaces is unstable and one grows in strength at the expense of the others. At an intermediate stage of its development, the interleaving motions pass through a stage when every second interface in the vertical is stable to double diffusion. At a later time this interface turns into a “diffusive” double-diffusive interface. This study takes the fluxes of heat and salt across both the finger and diffusive interfaces to be given by the laboratory flux laws, and the authors ask whether a steady state is possible. It is found that the fluxes across the diffusive interfaces must be many times stronger relative to the corresponding fluxes across the finger interfaces than is indicated from existing flux expressions derived from laboratory experiments. The total effect of the interleaving motion on the vertical fluxes of heat and of salt are calculated for the steady-state solutions. It is found that both the fluxes of heat and salt are upgradient, corresponding to a negative vertical diffusion coefficient for all heat, salt, and density. For moderate to large Prandtl numbers, these negative effective diapycnal diffusivities of heat and salt are approximately equal so that the interleaving process acts to counteract some of the usual turbulent diapycnal diffusivity due to breaking internal waves.

scholarly journals Strengthening of Composite Steel-Concrete Beams Openings by Adopting Different Reinforcement Methods

2019 ◽  
pp. 1-17
Author(s):  
Mohamed H. Makhlouf ◽  
Hala M. Refat
Keyword(s):  
Numerical Study ◽  
Concrete Slab ◽  
Low Cost ◽  
Composite Beams ◽  
Experimental Program ◽  
Bottom Surface ◽  
Steel Beam ◽  
Web Openings ◽  
Line Load ◽  
Steel Composite

This paper presents an experimental and numerical study carried out to investigate the flexural and shear behavior of concrete-steel composite beams with circular web openings strengthened using two different techniques around openings. The experimental program conducted on nine simply supported beams which were constructed with different variables. One steel beam and eight concrete-steel composite beams were experimentally tested. The tested beams are of 1500 mm length and BFI cross section of steel beam but composite beams were BFI steel section connected with concrete slab had 300 mm width and 70 mm depth, while this connection is done by headed stud shear connector. The tested specimens subjected to positive bending were loaded by one or two line load across the width of the concrete slab. The main parameters were the type of beams, web openings effect, location of web openings, strengthening techniques around openings externally CFRP strips and vertical steel links using steel plates placed on the top and bottom surface of beams anchored with fine threads, and number of CFRP strips layers. The effect of these parameters on the failure of modes, ultimate load, first cracking load and deflection were investigated. Moreover, a finite element models were developed by ANSYS (version 14) to simulate all the tested specimens, experimental test results were compared with FE results obtained. The experimental results showed that both strengthening systems applied in this research were remarkably increased the beam strength, and the capacity retrieve of beams without openings. This study approved that steel links technique gave more prominent simplicity of use and low cost. FEM models were in good agreement with the corresponding experimental ones. However, the calculated ultimate loads were slightly higher than the experimental ultimate loads up to 10%.

Transient Double-Diffusive Salinity in a Horizontal Fluid Layer

1989 ◽  
Vol 203 (5) ◽  
pp. 295-300
Author(s):  
I A Tag ◽  
M A Hassab
Keyword(s):  
Fluid Layer ◽  
Horizontal Layer ◽  
Bottom Surface ◽  
Linear Amplification ◽  
Salinity Gradients ◽  
Size Stability ◽  
Horizontal Fluid Layer ◽  
Stability Results ◽  
Wave Size ◽  
Double Diffusive

The transient double-diffusive stability problem for a horizontal layer of salty water bounded by two rigid isothermal surfaces was examined using both the frozen-time technique leading to an eigenvalue problem and the linear amplification theory leading to an initial value problem. Initially, the layer was subjected to zero temperature and salinity gradients. At the time t = 0, uniform step increases in both temperature and salinity were imposed at the bottom surface while the top surface is impermeable to the diffusion of salt. In the early developing stages scaling lengths based on thermal and mass boundary layer thicknesses were taken into consideration. Several parameters were considered in the analysis, namely, the thermal and solute Grashof numbers, Prandtl number, Schmidt number, time and wave size. Stability results based on the frozen-time technique and the linear amplification theory were compared in order to check the validity of the frozen-time technique within the range of the system parameters considered.

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