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Air transfer analysis

AIR/W is a powerful finite element software product for modeling air transfer in mine waste and other porous media. AIR/W can be used to model a range of scenarios, from simple single phase air transfer problems to complex coupled air-water systems. Add AIR3D to analyze 3D air transfer using the same comprehensive set of material models and boundary conditions.

The true power of AIR/W and AIR3D is unlocked when it is coupled with TEMP/W to model forced-convection heat flow and density-dependent air flow. This type of analysis is important for studying mine closure, acid rock drainage, or gas transfer.

Key Features

Density Dependent Air Flow

AIR/W can be integrated with TEMP/W to model air transfer via free convection. Density-driven air transfer is often a dominant mechanism in systems subjected to seasonal ground temperature variations. Integration of AIR3D and TEMP3D is also available.


Estimate Material Properties

The air conductivity function can be generated based on the dry-soil air conductivity, a user-selected volumetric water content function, and basic soil properties, such as soil classification or grain size distribution.   


Forced-Convection Heat Transfer

Combine AIR/W or AIR3D with TEMP/W or TEMP3D to model forced-convection heat transfer. This process often governs the thermal regime in coarse-grain materials such as waste rock piles, rip-rap, and layered embankments.


Single or Dual Phase Flow

Air transfer analyses can be conducted using a single phase material model that only considers pressure and gravity-driven air flow. Alternatively, a dual phase material model can be used by coupling air flow and water transfer.

AIR/W and AIR3D can model almost any problem involving air transfer through porous media

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Passive Cooling

Goering (2000) investigated passive cooling within an embankment constructed of unconventional and highly porous material as a means of preserving permafrost. The objective of this example is to simulate similar convective cell behavior in AIR/W and TEMP/W as observed by Goering.

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Pore-Air Entrapment During Infiltration

This example illustrates the effect of pore-air entrapment during infiltration into an unsaturated soil given a range of material properties, for both open and closed systems.

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Tempe Cell Simulation

This example illustrates the ability of SEEP/W and AIR/W to simulate the results of a Tempe cell laboratory analysis for determining the volumetric water content function of a soil.

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Verification - Heated Closed System

The change in pressure of a constant volume of dry air subject to an increase in temperature is simulated in this verification example. The temperature increase is simulated by TEMP/W while the air pressure response is simulated by AIR/W.

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AIR/W's intuitive modeling workflow

Create an AIR/W analysis and set up the problem workspace. Choose analysis type, including steady-state or transient, and define initial pore-air pressure and air flow conditions, convergence criteria, and time duration and increments.

Draw the regions in your domain using CAD-like drawing tools, including drawing polygon and circular regions, coordinate import, copy-paste geometric items, length and angle feedback, region splitting and merging, and direct keyboard entry of coordinates, lengths, and angles. Alternatively, import AutoCAD DWG or DXF files directly into GeoStudio to create your domain geometry.

Define the material properties for your analysis, assign them to regions on the domain. Define the air conductivity function, along with the volumetric water content and hydraulic conductivity functions for the coupled SEEP/W analysis, if necessary. Define the initial air pressure and air flow conditions for transient scenarios using results from other AIR/W (or SEEP/W) analyses or defined spatial functions.

Define air and hydraulic (if coupled with SEEP/W) boundary conditions to simulate air pressure, air flow, total head, pressure head and more. Time-varying conditions can also be modeled.

Open Draw Mesh Properties to refine the mesh drawn on the entire domain, or along specific geometric regions, lines or boundaries.

When your problem is completely defined, start the analysis process in the Solve Manager window. The Solve Manager displays the solution progress, allowing you to cancel or stop/restart if necessary. While the solution is in progress, you can look at preliminary results in the Results window.

When the Solver is finished, the air pressure contours are displayed, with air vectors shown on the domain. You can display other contours using the Draw Contours window, including material properties, air flow, and gradients. Contour legends and properties can also be modified. Labels can be added to contour lines in Results View.

Interactively select any node or gauss region to view result information, including pore-air pressure, air flux, air content, material properties, and more. Display plots of computed results over the x- or y-direction or create time-varying plots of results in transient analyses, such as air density, air flux, cumulative air flux, air content, and more. Generate reports of the definition and results, and export into other applications such as Microsoft Excel for further analysis.

The power of integration

AIR/W offers simple but powerful analytical capabilities when used in combination with other GeoStudio products.


Couple AIR/W with SEEP/W

Coupled air-water systems can be modeled with SEEP/W and AIR/W. The two systems are coupled via the matric suction, which is the difference between the pore-air and pore-water pressures. A change to the air pressure will cause a change in the water pressure and vice versa. This type of analysis can be useful for modelling mine closure cover systems or water/air movement in acid generating waste rock.  

TEMP/W results in AIR/W

TEMP/W can use the air fluxes from AIR/W to model forced-convection heat transfer. TEMP/W can also be integrated with AIR/W to model density-dependent air flow.