What Lies Beneath - Recently Updated Pages

Sources and Links

lamontequinn — Fri, 25 Apr 2008 14:09:54 CDT

http://oceanworld.tamu.edu/resources/oceanography-book/groundwaterremediation.html - Describes various remediation methods

http://www.purdue.edu/envirosoft/groundwater/src/geo.htm - Describes the basics of hydrogeology

http://www.aquatechnologies.com/info_groundwater_remediation.htm - Describes various remediation methods

http://water.usgs.gov/wrri/05grants/2004CT31B.html - Describes CAEREM project

http://www.ctiwr.uconn.edu/Proposals/2004CT31B_Bagtzolgou_20031021.pdf - Expanded paper on the CAEREM project

http://www.pipeflowcalculations.com/reynolds/index.htm - Reynolds Number calculation

http://www.efm.leeds.ac.uk/CIVE/CIVE1400/Section4/laminar_turbulent.htm - Describes laminar and turbulent flow

http://coewww.rutgers.edu/~shinbrot/Marwan/JBear.html - Applet demonstrating advection with rotating cylinders

http://www.fractalog.com - excellent resource for a multitude of topics concerning Chaos and Complexity Theory

Cephalopods Like Fractals, Too

lamontequinn — Fri, 25 Apr 2008 14:08:43 CDT

One often pictures fractals as consisting of pretty pictures generated by computer programs, but they are quite prevalent in nature. A notable example can be found in the fossils of ancient cephalopods, specifically nautiloids and ammonoids. Nautoloids and ammonoids are the ancient ancestors of modern squids, octopi, and the nautilus. The ancient organisms looked like modern squids and octopi with shells, some elongated and some coiled like a snail. These shells had internal chambers that the organism filled with gas for buoyancy. Each chamber is separated by a wall, or septa. The contact line between the septa and the inner shell wall is called a suture line. The structure of the suture line determines how well the organism can resist water pressure and adjust its buoyancy. The evolution of suture lines follows an increasingly fractal-like pattern from straight sutures to highly undulated sutures. In complex sutures, the dips and folds in the undulations are called lobes and saddles, respectively.

Paleontologists (Daniel et al. 1997) have found that simple sutures, as in Permian (290 – 248 million years ago) nautiloids and ammonoids, are very resistant to high pressures, but are poor for buoyancy regulation. As a result, such organisms moved slowly. Conversely, the more complex suture lines of Cretaceous (144 – 66 million years ago) organisms have less pressure resistance along with excellent buoyancy control. These findings indicate that the evolution of Cephalopods proceeded from high-pressure deep water to low-pressure shallow water over millions of years, with increasing complexity in suture lines to compensate. Daniel, T.L., B.S. Helmuth, W.B. Saunders, and P.D. Ward. 1997. Septal complexity in ammonoid cephalopods increased mechanical risk and limited depth. Paleobiology 23(4):470-481.

Chaotic Advection

lamontequinn — Wed, 16 Apr 2008 16:25:05 CDT

The field of Chaotic Advection concerns itself with fluid flow, mixing, and turbulence. The two kinds of flows that we are concerned with here are laminar and turbulent flows. Laminar flow is characterized by steady particle motion in which fluid flows in parallel layers with little to no disruptions between the layers. This type of flow has relatively low velocities. Groundwater bears the most resemblance to this kind of flow. Contrary to laminar flow is turbulent flow, in which particles move erraticly in the general direction of the flow. Turbulent flow is more commonly observed in nature, such as in rivers, bodies of water, and wind currents. The problem with laminar flow is that particles mix poorly, and mixing is accomplished rather slowly by Brownian movement and molecular diffusion. Turbulence, in reference to the mixing of groundwater, is not particularly ideal either, for it can result in cellular damage to the organisms required for bioremediation.

Differentiating between these types of flows requires an understanding of viscosity and the Reynolds Number. Viscosity measures a particular fluid’s resistance to flow through a certain boundary. The point at which a fluid flows smoothly through its particular boundary, having relatively little frictional forces acting on it, would be a laminar flow, because fluid flows are viscous. Conversely, the point where a fluid has many frictional forces impeding its flow results in a turbulent flow. The concept of viscosity uses the assumption that in any type of flow there are different velocities present that cause a certain level of shear stress which occurs between the layers of the flow. This measure of shear stress is the viscosity of the flow.

The Reynolds number is the main determinant used in establishing whether a flow is laminar or turbulent. It calculates the ratio of the inertial forces to the viscous forces of a fluid flow. The Reynolds number is a non-dimensional number because it has no units of measurement. The difference between flows can be classified by certain ranges of the number. An Re less than 2000 results in a laminar flow, which means that there are enough viscous forces acting on the flow to cancel out the effects of the inertial forces. An Re between 2000 and 4000 results in a transitional flow, which has the properties of a laminar flow, but it exhibits slight instabilities, as seen in more pronounced turbulent flows. An Re greater than 4000 constitutes a turbulent flow, which means that the inertial forces acting on the flow are significantly greater than the viscous forces (Zoran Savovic).

Groundwater Remediation

lamontequinn — Wed, 16 Apr 2008 16:22:50 CDT

Typically, groundwater is relatively clean and safe to drink, having been filtered by the soil, sand, gravel, and rock that it percolated through on its way down to the water table. This is part of a process known as natural attenuation, which may also involve microorganism break-down of substances. Unfortunately, it is still rather easy to contaminate groundwater and difficult to clean. Sources of contaminants may come from agricultural runoff, industrial/chemical waste, environmental sources, domestic sources, and so on. Aquifers that are confined by an aquiclude generally do not become contaminated easily, but many aquifers lie uncovered without any impermeable layer on top. Contaminants may linger for years in some areas. The process of decontaminating groundwater is known as remediation.

Common methods of remediation consist of pumping water out of the water table, treating it, and injecting it back into the ground or another natural water source. Contaminant plumes can also be contained and removed by manipulating the flow of groundwater through pumps. By injecting clean water into the ground, pressure is created which directs the plume to a certain area for containment or pump for removal. This procedure, however, can be costly and time-consuming. Other approaches to remediation involve air sparging, whereby air is pumped into the water table, generating bubbles that flush out contaminants and enhance the growth of organisms that can break down the contaminants naturally.

In-situ oxidation involves pumping an oxidizing agent, such as hydrogen peroxide, which will oxidize a contaminant plume, producing, for the most part, carbon dioxide and water. Another method involves digging a trench and filling it with reactive materials, such as iron filings, activated carbon, or peat, that filter the groundwater as it flows through. This method, known as a permeable reactive barrier, is effective only for shallow aquifers.

Phytoremediation involves the use of plants and trees that are good at absorbing metals (e.g. Pb, U, Cd), metal-like elements (e.g. As, Se), hydrocarbons, and other toxins. The plants are positioned so that their roots grow directly into the water table. Once they have absorbed large amounts of contaminants, they are removed and disposed of. As with the trench barrier described above, this method is limited only to shallow aquifers.

Biodegradation involves using microorganisms to synthesize and break down organic contaminants. The process usually results in carbon dioxide and methane products. Bioremediation is effective for removing hydrocarbons, and it often occurs naturally when bacterial levels are high and contaminant levels are low. Some bacteria do not require oxygen for contaminant break-down. Bacterial growth can be enhanced by injecting nutrients, carbon compounds, and oxygen (if necessary).

Sources:
oceanworld.tamu.edu
www.aquatechnologies.com

Chaos Theory and its Applications to Remediation

lamontequinn — Mon, 18 Feb 2008 15:47:56 CST

The field of Chaos, or more specifically Chaotic Advection, offers promising results for improving remediation efforts. A developing project (as proposed by A. C. Bagtzoglou, P. Oates, and E. Loehmann), known as Chaotic Advection Enhanced Remediation (CAEREM), proposes that by installing a series of oscillating wells into an aquifer, chaotic mixing can be induced in an effort to increase mixing in the aquifer. This chaotic groundwater flow would result in an increase in natural attenuation. The purpose of the mixing is to distribute microbial nutrients and electron acceptors to stimulate the growth of microbes that can process and eliminate contaminants in an effort to enhance bioremediation. Should they be approved, genetically modified organisms can be introduced as well for improved results. Such methods can be applied to shallow, deep, and confined aquifers, so long as the contaminants involved can be synthesized by the organisms utilized.

The CAEREM model proposes that a system of three oscillating wells would be used to induce chaotic mixing. Without removing or adding any water to the aquifer, one of the wells is assigned a random pump magnitude and a random direction, either withdrawing or injecting. The other wells are assigned the opposite flow direction and the pump magnitude assigned to the first well is randomly divided to the remaining two to balance the action of the first well, whether it be withdrawal or injection. In this way, chaotic conditions are maximized and induced to mix the nutrient plume into the contaminant plume.

The oscillating well experimental model designed for CAEREM has proven to successfully create good mixing. Further laboratory experiments have demonstrated that chaotic mixing on the cell growth of the biological oxidation organism Saccharomyces Cerevisiae enhances and speeds up the growth of the organism. The experiment was conducted using two cylinders that rotated in different directions and speeds. While it has been demonstrated that chaotic advection stimulates biodegradation, it has not been shown to serve as the perfect solution to remediation. Rather, CAEREM should be combined with the common procedures of pumping and treating to improve remediation rates.

Sources:
water.usgs.gov

Darcy's Law

lamontequinn — Mon, 18 Feb 2008 15:31:56 CST

Integral to hydrogeology is the need to describe and measure the flow of water underground. In Dijon, France, French scientist/engineer Henry Darcy (1803 - 1858) was involved in obtaining freshwater for the city. He worked on a project that drilled wells and eventually he developed a public works system. Darcy became interested in water movement and as a result began the first study of how water moves.

Darcy set up an experiment in which he tilted a sand-filled tube at an angle and poured water through it, observing the water flow, the water height, and the cross-sectional area of the pipe. He wanted to know how the fast the water was moving and what it was a function of. From this experiment was developed Darcy's Law, which states that the discharge rate (q) is proportional to the gradient in hydraulic head and the hydraulic conductivity:
h2 = height 2 (head 2)
h1 = height 1 (head 1)
L = distance between h2 and h1
K = Hydraulic Conductivity
A = cross-sectional area of pipe
The greater the head distance, the greater the discharge rate. Q is inversely proportional to L; as L gets bigger, friction increases while Q decreases.

Darcy's Law is crucial to hydrogeology, for modern hydrogeology is built on what he researched.

Determining K

lamontequinn — Mon, 18 Feb 2008 15:31:09 CST

Determining K is a valuable tool required in the field. The field test, also known as the aquifer test, can be performed using one of two methods, the slug test and the pumping test.

Prior to initiating the pumping test, a step drawdown test is performed to determine at what rate pumping should be performed. Once the rate is determined, a pump is dropped down an observation well and water is pumped out at a constant rate. Water is typically pumped continuously for 72 hours, because the graph mapping the water table level during pumping begins to level off during the 72 hours, which is a desired effect for measurement. The goal of the test is to measure the response of the aquifer as a method of determining K. The test requires more than one observation well, however, and is more expensive and time-consuming than the slug test, yet more accurate and encompassing.

In the slug test, an amount of water, called a "slug," is added or removed from the well. Adding a slug created a mound in the water table and the rate at which the mound levels is measured, since it equals the rate of flow. Alternately, removing a slug is done by quickly drawing a slug of water out of the well and measuring the rate of refill. While the slug test is cheaper and faster, it is less accurate and measures a far smaller area than the pump test.

Hydraulic Conductivity (K) & Transmissivity (T)

lamontequinn — Mon, 18 Feb 2008 15:16:50 CST

Hydraulic Conductivity, or K, represents a measure of the ability for flow through a porous media. K is highest for gravels (0.1 to 1 cm/sec), high for sands (0.1 to 0.01 cm/sec), moderate for silts (0.001 to 0.0001 cm/sec), and lowest for clays (0.000001 to 0.00000001 cm/sec). K may also vary depending on how well or how poorly sediments and rock particles are sorted.

Transmissivity (T) measures the ability of an aquifer to transmit water. It measures the amount of water that can be transmitted horizontally through the fully saturated thickness of the aquifer under a gradient of 1. It is commonly measured in gallons per day per foot (gal/day/ft) and can be expressed as:
b = saturation thickness of aquifer in feet
K = gal/day/ft* ---> * = feet squared

Home

lamontequinn — Mon, 18 Feb 2008 14:32:01 CST

Has the thought of flowing water ever excited you? Have you ever wondered why life can be so chaotic? Then this site is for you! Step inside, and take a look at the wonders of Chaos Theory and Groundwater Remediation!!

Groundwater is everywhere, whether you like it or not, and so is Chaos Theory. From the placid drip of the faucet to the cacophany of the Stock Market, Chaos has its applications almost anywhere you can imagine.

Chaos is more than just pretty fractals, such as the famous Mandelbrot set or numerous other computer-generated fractals. Of the many applications of Chaos, one of the most well-known is chaotic advection, or to put it simply, chaotic mixing. A growing problem today is the continued contamination of groundwater resources, whether by human or natural means. Chaotic advection applications offer new perspectives on how to enhance groundwater remediation faster, more efficiently, and more economically.

What is Groundwater?

lamontequinn — Fri, 15 Feb 2008 14:08:52 CST

Sure the Earth's surface is 75% water, but most of it is undrinkable saltwater. Of all the water on Earth, 99% is saltwater, leaving only a slim 1% freshwater. Even though this 1% seems as though there should be some kind of water crisis, it is still quite a large amount of water. Of that 1%, 96% of it occurs as groundwater, with the rest stored in lakes, rivers, glaciers, ice sheets, and the atmosphere. Groundwater is clearly strategic for modern civilization, for nearly half of the United States' drinking water comes from below the Earth's surface.

The common misconception concerning groundwater is that it is comparable to an underground lake or river. Rather, groundwater occurs in the pores of porous and permeable rocks such as sandstone and rock fractures, similar to water in a sponge. Underground lakes and rivers are associated with cave systems. The flow of water underground is different compared to that of a river or stream. The entire natural system of water flow is best represented in the Hydrologic, or Water Cycle, as seen here:
Groundwater is recharged by the constant flow of water as illustrated in the Hydrologic Cycle. Precipitation and water from lakes and streams are absorbed into the earth and percolate downward where water accumulates as groundwater. As the water travels through the earth, it is filtered in the process.

Sources:
www.purdue.edu

Groundwater Zone Characteristics

lamontequinn — Fri, 15 Feb 2008 13:15:24 CST

The ground itself is divided into different zones based on water content. The unsaturated zone, also known as the vadose zone, consists of downward-flowing water, water that adheres to soil (soil moisture) and rock by capillary action and hydrogen bonding, and air spaces. The saturated zone is the zone in which the name “groundwater” is applied, referring to the complete saturation of pore spaces and fractures in the rock by water in a zone known as the water table. Arguably, any water that is in the ground can be called groundwater, but for our purposes we will refer to any water at and below the water table as groundwater. Water that adheres by capillary action is located just above the water table in a zone called the capillary fringe. At approximately 3000-4000 ft. below ground, there is rarely any water. Even further, at 12000-13000 ft., there is no groundwater. All groundwater is confined primarily to the upper mile of the crust.

The body of rock that contains exploitable resources of groundwater is known as an aquifer. An aquifer may be unconfined and open to downward water flow or it may be confined by a body of nonporous rock or clay known as a confining layer or an aquiclude.

Common aquifers may consist of sandstone or limestone. Limestone bedrock is prone to developing underground cave systems, lakes, and rivers as a result of weathering by water action. In some cases an underground cave may collapse, leading to devastating sinkholes on the surface. All of these features are a result of the simple action of water flow. This seeming simplicity, however, often results in chaotic behavior.

Porosity Vs. Permeability

lamontequinn — Fri, 15 Feb 2008 13:13:47 CST

The ground widely varies in its porosity and permeability. It is important not to confuse porosity with permeability. Porosity relates to the total number of empty spaces in the rock. Secondary porosity is not the original porosity of the rock body, and it results when the rock experiences stress and pressure, such as fractures and cracks. Porosity can be expressed as n = Volume of voids / Total Volume. Just because a material may have high porosity does not mean, however, that it has high permeability. For example, clays have high porosities, up to 70 - 80%, yet they have very low permeability. Sand or gravel, on the other hand, have lower porosities but higher permeabilities.

Permeability is the ability of water to move through a media. Related to permeability is Specific Yield, which describesthe amount of water that will be released due to drainage. It is noted as Sy (with y being a subscript), is expressed as a percentage, and refers to unconfined aquifers. Clays have a low Sy (0 - 5%) while coarse gravel has a high Sy (12 - 26%). Sy is always lower than porosity because it is never quite possible to remove all of the water from an aquifer.

Governing Equations

lamontequinn — Wed, 16 Jan 2008 16:07:51 CST

Navier-Stokes equations are essential in describing the motion of fluids because they apply Newton’s second law to fluid motion. The equations use the viscous forces acting on a fluid, such as friction or gravity, to exhibit rates of change present in fluid motion. These equations give the fluid’s velocity, but not the position of particular fluid particles, in a solution called a velocity field. More often than not, there are not solutions to these equations because of their nonlinearity. This nonlinearity allows any type of flow, whether turbulent or laminar, to be modeled using the differential equations. In particular, it is believed by many scientists that the Navier-Stokes equations are able to properly model turbulent flows. The particular equation most closely associated with Newton’s second law is:

The left side of the equation describes acceleration of the flow. It is the pressure gradient that occurs from normal stresses within a particular fluid force, as well as a gradient surface force that describes viscosity for the incompressible force. "f" represents other forces acting on the fluid such as gravity. The following equation describes the incompressible flow assumption for Newtonian fluids, such as water:

The Navier-Stokes equations can be used in three different coordinate systems to describe the motion of fluids. These equations will prove to be useful because of the role they play in analyzing the many forces acting on a fluid. In particular, Navier-Stokes equations can be used to describe chaotic mixing in groundwater remediation.

Calculations in the CAEREM project

lamontequinn — Wed, 12 Dec 2007 16:54:14 CST

In the experimental phase of the CAEREM project, an index is being developed to describe the effects of the oscillating wells with regards to how well their initial chaotic mixing. In order to understand the degree to which the wells are instigating mixing, the average particle distances are calculated. The speculation of the experiment is that, as the particles mix, the average inter-particle distance between the contaminant and nutrient plumes (Dgr in the following equation) should decrease. The equation used to calculate the particle motion is:

The average inter-particle distance (Dg) of a particular plume, whether it be contaminants or nutrients, with particle coordinates xg and yg, is found by using this equation to calculate the average distance from each particle to every other particle and then dividing by the total number of particles. The average inter-particle distance (Dg) can be calculated using the same method for the coordinates xr and yr. The CAEREM project speculates that as the particles mix with one another, the three average inter-particle distances of Dg, Dr, and Dgr will converge to the same value while there is still an erratic oscillation occurring. When Dg and Dr approach the same value as Dgr, there is believed to be small-scale convergence occurring. In order to determine whether or not the system has mixed, another variable of average inter-particle distance must be introduced: Dg+r. As Dg+r and Dgr approach zero, mixing has occurred. To calculate the mixing percentage, the CAEREM project uses the equation:

This equation shows the percentage of contaminants and nutrients that were mixed by using the CAEREM project. By using this index and the previous equation, the experimental project can analyze how effective chaotic mixing is in the context of groundwater remediation. If a great percentage of mixing occurs while the system is operating chaotically, then the CAEREM project will prove to be extremely useful in future groundwater remediation projects.

Source:
"Chaotic Advection Enhanced Remediation" by Amvrossios C. Bagtzoglou

Videos

lamontequinn — Sat, 08 Dec 2007 14:47:38 CST

Computer Generated Fractals

lamontequinn — Sat, 08 Dec 2007 14:39:00 CST

On an unrelated note, here are some fractals I created using a program called ChaosPro 3.2:

Assumption Image created using ChaosPro 3.2	Diamond in the Rough Image created using ChaosPro 3.2
Seraphim Image created using ChaosPro 3.2	The Selfish Gene Image created using ChaosPro 3.2
Sanctuary Fortress Image created using ChaosPro 3.2	Wasteland Image created using ChaosPro 3.2
Runaway Train Image created using ChaosPro 3.2	Petal Dance Image created using ChaosPro 3.2

ABC

lamontequinn — Tue, 04 Dec 2007 13:34:37 CST

There is no abstract available for this page revision.