AIR-WATER INTERFACIAL AREA AND CAPILLARY PRESSURE: POROUS-MEDIUM EXTURE EFFECTS AND AN EMPIRICAL FUNCTION
1School of Environment, Beijing Normal University, Key Laboratory of Water and Sediment Sciences of Ministry of Education, Beijing, 100875, China.
Journal of Hydrologic Engineering
|October 29, 2013
Summary
The air-water interfacial area increases with capillary pressure in natural porous media, with maximums dependent on residual water saturation. Sorting affects the rate of change, and a coupled equation reasonably simulates the observed data.
Area of Science:
- Porous media physics
- Soil science
- Environmental engineering
Background:
- Understanding air-water interfacial area is crucial for modeling unsaturated flow in porous media.
- Capillary pressure governs fluid distribution and interfacial phenomena in soils and rocks.
- Previous studies have explored these relationships, but higher water-content conditions require further investigation.
Purpose of the Study:
- To investigate the relationship between air-water interfacial area and capillary pressure in natural porous media at higher water contents.
- To determine how porous medium properties, such as sorting, influence this relationship.
- To develop a quantitative model for predicting air-water interfacial area based on capillary pressure.
Main Methods:
- Experimental investigation of four natural porous media under varying water content conditions.
- Measurement of air-water interfacial area and capillary pressure.
- Analysis of the influence of pore-size distribution and sorting on the observed relationships.
- Coupling empirical and established equations (van Genuchten) to model the data.
Main Results:
- Air-water interfacial area increases with increasing capillary pressure, correlating with decreasing water saturation.
- Maximum air-water interfacial areas are limited by residual water saturation, which varies with conditions.
- Better-sorted media show a higher rate of change in interfacial area with capillary pressure compared to poorly-sorted media.
- The coupled empirical and van Genuchten model accurately simulated the experimental data.
Conclusions:
- The relationship between air-water interfacial area and capillary pressure is well-defined in natural porous media.
- Porous medium characteristics, particularly sorting, significantly impact the dynamics of interfacial area.
- A combined modeling approach provides a reliable method for predicting interfacial area under varying capillary pressures.
More Related Videos
Related Concept Videos
01:19Capillarity in Fluid
1.6K
Capillarity describes the movement of liquid in small spaces without external forces acting on it. The capillarity is driven by surface tension and adhesive interactions between the liquid and surrounding solid surfaces. This effect is often seen in narrow tubes, porous materials, and fine particles.
Surface tension is crucial to capillarity. It results from cohesive forces between liquid molecules at the liquid-air boundary, forming a skin that resists external forces. When the capillary tube...
Surface tension is crucial to capillarity. It results from cohesive forces between liquid molecules at the liquid-air boundary, forming a skin that resists external forces. When the capillary tube...
1.6K
01:02Fluid Pressure over Flat Plate of Variable Width
1.7K
When a flat plate is submerged in a fluid, the fluid exerts pressure on the plate. This pressure can lead to many different phenomena, including drag and buoyancy. To understand the behavior of the fluid over a flat plate of variable width, it is essential to analyze the distribution of the pressure exerted.
The pressure distribution on the plate can be calculated by determining the force that acts on a differential area strip of the plate. Thus, the magnitude of the force is equal to the...
The pressure distribution on the plate can be calculated by determining the force that acts on a differential area strip of the plate. Thus, the magnitude of the force is equal to the...
1.7K
01:14Pressure of Fluids
13.1K
There are many examples of pressure in fluids in everyday life, such as in relation to blood (high or low blood pressure) and in relation to weather (high- and low-pressure weather systems). A given force can have a significantly different effect, depending on the area over which the force is exerted. For instance, a force applied to an area of 1 mm2 has a pressure that is 100 times greater than the same force applied to an area of 1 cm2. That's why a sharp needle is able to poke through...
13.1K
02:57Surface Tension, Capillary Action, and Viscosity
28.7K
Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
28.7K
01:28Capillary Exchange
12.4K
The cardiovascular system's chief role is to disseminate gases, nutrients, waste, and other substances to the body's cells. Small molecules like gases, lipids, and lipid-soluble substances directly diffuse through capillary wall endothelial cell membranes. Glucose, amino acids, and ions, including sodium, potassium, calcium, and chloride, use transporters for facilitated diffusion via membrane-specific channels. Glucose, ions, and bigger molecules may also pass through intercellular...
12.4K
01:14Fluid Pressure
1.3K
In mechanical engineering, fluid pressure plays a critical role in designing systems that utilize liquid flow, such as hydraulic systems, pumps, and valves. When designing these systems, engineers must ensure they can withstand the forces created by fluid pressure to avoid damage or failure.
According to Pascal's law, a fluid at rest will generate equal pressure in all directions. This pressure is measured as a force per unit area, and its magnitude depends on the fluid's specific...
According to Pascal's law, a fluid at rest will generate equal pressure in all directions. This pressure is measured as a force per unit area, and its magnitude depends on the fluid's specific...
1.3K