2 2 Drawing a Flow Net for a Homogeneous Isotropic System Graphical Construction of Groundwater Flow Nets

draw flow nets

Consider the flow in a two-dimension region in a homogeneous, anisotropic medium with principal hydraulic conductivities Kx and Kz. Remember to ensure that your flow lines do not intersect, as that would indicate multiple flow directions at a single point, which is physically not possible. Always account for geological features like faults or fractures, as they can dramatically influence groundwater flow patterns in your flow net.

3 Flow Nets by Numerical Simulation

On the other hand, divergence happens when flow lines spread apart, indicating an increase in flow velocity. These areas of convergence and divergence are crucial in understanding the behavior of fluid flow within the system. To draw the equipotential lines, start at the boundaries of the flow system and work your way towards the center. Use a ruler or straightedge to ensure that the lines are straight and perpendicular to the flow lines. The equipotential lines should extend from one boundary to another, maintaining continuity throughout the flow system.

Box 5 – Drawing Flow Nets for Anisotropic Systems

Typically, a numerical groundwater model computes hydraulic head for a grid (or an array) of points and, unlike a graphically constructed flow net, this gives flexibility to how equipotential lines are drawn. A flow path tracking model enables one to draw a flow path starting from any location. Such flexibilities mean that numerically calculated equipotential lines and flow lines do not necessarily form shapes of constant aspect ratio, and flow tubes do not necessarily carry the same volumetric flow rate. Nonetheless, these computer-generated equipotential lines and flow lines form a bona fide flow net, because they satisfy the groundwater flow equation.

Steps for Drawing a Flow Net Using Pencil and Paper

In this case, it is determined that 18 head drops create curvilinear squares. So, the contour interval is determined by dividing the total head drop of 10 m by 18 to obtain a value of 0.56 m head drop between each pair of equipotential lines. This establishes the values of the contour lines and knowing that they must meet the water table at the elevation equal to their values further constrains the position of the lines.

3 Drawing a Flow Net for Flow Beneath an Impermeable Dam

draw flow nets

Alternatively, digital drawing tools can also be used to achieve accuracy and ease in drawing the equipotential lines. Once you have determined the number and spacing of the equipotential lines, it’s time to draw them. This means that the equipotential lines intersect the flow lines at right angles. Before we start drawing the flow lines, it is essential to determine the number and spacing of these lines.

A homogeneous and isotropic groundwater system is one in which the hydraulic conductivity is the same at every location and does not vary for different directions of flow. Hydraulic conductivity is a measure of the ease with which water can pass through a material and is discussed in another Groundwater Project book (Woessner and Poeter, 2020). The groundwater flow equation is based on Darcy’s Law and conservation of mass. The groundwater flow equation is derived and discussed in another Groundwater Project book (Woessner and Poeter, 2020).

The uplift pressure at any point within the soil mass can be found using the undermentioned formula. The flow needs to be doubled to account for drainage from both sides of the drain, so approximately 2.4 liters per minute. Either transform results in an acceptable isotropic geometry for the system as shown in Figure Box 5-2. Figure Box 5-1 – Hydraulic conductivity ellipse (a) in general orientation and (b) with major and minor axes aligned with the rectangular (x–y) coordinate system. Harr (1962) discusses the practical aspects of Dupuit-Forchheimer theory in some detail. Kirkham (1967) examines the paradoxes in the theory and provides some revealing explanations.

A flow net is a graphical representation of the flow of fluids through porous media, such as soil or rock. It consists of a network of flow lines and equipotential lines that help visualize and analyze the flow patterns and characteristics within a given system. Figure 9 – Creating shapes with a constant aspect ratio is a requirement when drawing a flow net.

Begin by selecting a starting point on one of the boundaries of the flow system. The starting point should be chosen strategically to ensure that the flow lines cover the entire system. Flow lines represent the path of flow along draw flow nets which the water will seep through the soil. When Equation Box 5-3 is applied to an anisotropic system, an equivalent hydraulic conductivity is used to account for the differing values in the horizontal and vertical direction.

Posted: August 2, 2024 8:03 am


According to Agung Rai

“The concept of taksu is important to the Balinese, in fact to any artist. I do not think one can simply plan to paint a beautiful painting, a perfect painting.”

The issue of taksu is also one of honesty, for the artist and the viewer. An artist will follow his heart or instinct, and will not care what other people think. A painting that has a magic does not need to be elaborated upon, the painting alone speaks.

A work of art that is difficult to describe in words has to be seen with the eyes and a heart that is open and not influenced by the name of the painter. In this honesty, there is a purity in the connection between the viewer and the viewed.

As a through discussion of Balinese and Indonesian arts is beyond the scope of this catalogue, the reader is referred to the books listed in the bibliography. The following descriptions of painters styles are intended as a brief introduction to the paintings in the catalogue, which were selected using several criteria. Each is what Agung Rai considers to be an exceptional work by a particular artist, is a singular example of a given period, school or style, and contributes to a broader understanding of the development of Balinese and Indonesian paintng. The Pita Maha artist society was established in 1936 by Cokorda Gde Agung Sukawati, a royal patron of the arts in Ubud, and two European artists, the Dutch painter Rudolf Bonnet, and Walter Spies, a German. The society’s stated purpose was to support artists and craftsmen work in various media and style, who were encouraged to experiment with Western materials and theories of anatomy, and perspective.
The society sought to ensure high quality works from its members, and exhibitions of the finest works were held in Indonesia and abroad. The society ceased to be active after the onset of World War II. Paintings by several Pita Maha members are included in the catalogue, among them; Ida Bagus Made noted especially for his paintings of Balinese religious and mystical themes; and Anak Agung Gde Raka Turas, whose underwater seascapes have been an inspiration for many younger painters.

Painters from the village of Batuan, south of Ubud, have been known since the 1930s for their dense, immensely detailed paintings of Balinese ceremonies, daily life, and increasingly, “modern” Bali. In the past the artists used tempera paints; since the introduction of Western artists materials, watercolors and acrylics have become popular. The paintings are produced by applying many thin layers of paint to a shaded ink drawing. The palette tends to be dark, and the composition crowded, with innumerable details and a somewhat flattened perspective. Batuan painters represented in the catalogue are Ida Bagus Widja, whose paintings of Balinese scenes encompass the sacred as well as the mundane; and I Wayan Bendi whose paintings of the collision of Balinese and Western cultures abound in entertaining, sharply observed vignettes.

In the early 1960s,Arie Smit, a Dutch-born painter, began inviting he children of Penestanan, Ubud, to come and experiment with bright oil paints in his Ubud studio. The eventually developed the Young Artists style, distinguished by the used of brilliant colors, a graphic quality in which shadow and perspective play little part, and focus on scenes and activities from every day life in Bali. I Ketut Tagen is the only Young Artist in the catalogue; he explores new ways of rendering scenes of Balinese life while remaining grounded in the Young Artists strong sense of color and design.

The painters called “academic artists” from Bali and other parts of Indonesia are, in fact, a diverse group almost all of whom share the experience of having received training at Indonesian or foreign institutes of fine arts. A number of artists who come of age before Indonesian independence was declared in 1945 never had formal instruction at art academies, but studied painting on their own. Many of them eventually become instructors at Indonesian institutions. A number of younger academic artists in the catalogue studied with the older painters whose work appears here as well. In Bali the role of the art academy is relatively minor, while in Java academic paintings is more highly developed than any indigenous or traditional styles. The academic painters have mastered Western techniques, and have studied the different modern art movements in the West; their works is often influenced by surrealism, pointillism, cubism, or abstract expressionism. Painters in Indonesia are trying to establish a clear nation of what “modern Indonesian art” is, and turn to Indonesian cultural themes for subject matter. The range of styles is extensive Among the artists are Affandi, a West Javanese whose expressionistic renderings of Balinese scenes are internationally known; Dullah, a Central Javanese recognized for his realist paintings; Nyoman Gunarsa, a Balinese who creates distinctively Balinese expressionist paintings with traditional shadow puppet motifs; Made Wianta, whose abstract pointillism sets him apart from other Indonesian painters.

Since the late 1920s, Bali has attracted Western artists as short and long term residents. Most were formally trained at European academies, and their paintings reflect many Western artistic traditions. Some of these artists have played instrumental roles in the development of Balinese painting over the years, through their support and encouragement of local artist. The contributions of Rudolf Bonnet and Arie Smit have already been mentioned. Among other European artists whose particular visions of Bali continue to be admired are Willem Gerrad Hofker, whose paintings of Balinese in traditional dress are skillfully rendered studies of drapery, light and shadow; Carel Lodewijk Dake, Jr., whose moody paintings of temples capture the atmosphere of Balinese sacred spaces; and Adrien Jean Le Mayeur, known for his languid portraits of Balinese women.

Agung Rai feels that

Art is very private matter. It depends on what is displayed, and the spiritual connection between the work and the person looking at it. People have their own opinions, they may or may not agree with my perceptions.

He would like to encourage visitors to learn about Balinese and Indonesian art, ant to allow themselves to establish the “purity in the connection” that he describes. He hopes that his collection will de considered a resource to be actively studied, rather than simply passively appreciated, and that it will be enjoyed by artists, scholars, visitors, students, and schoolchildren from Indonesia as well as from abroad.

Abby C. Ruddick, Phd
“SELECTED PAINTINGS FROM THE COLLECTION OF THE AGUNG RAI FINE ART GALLERY”


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