The hydraulic conductivity comes into play only when quantitative discharge calculations are made. It is also worth noting that flow nets are dimensionless. how to draw a flow net The flow nets of Figures 5.2 and 5.3 are equally valid whether the regions of flow are considered to be a few meters square or thousands of meters square.
The method consists of filling the flow area with stream and equipotential lines, which are everywhere perpendicular to each other, making a curvilinear grid. A Flow bookkeeping net is a graphical representation of flow of water through a soil mass. It is a curvilinear net formed by the combination of flow lines and equipotential lines.
After completing part of a flow net it is usually possible to tell whether or not the final diagram will be correct. This line must now be redrawn in its corrected position and the procedure repeated again, amending the first flow line if necessary, until a satisfactory net is obtained. There is another type of flow net that is extremely difficult to construct by graphical means. For flow problems that involve both saturated and unsaturated flow, steady-state flow nets are usually derived by numerical simulation. This means that the soil is unsaturated at the surface, although if outflow to the drain is to take place, it must be saturated at depth.
The flowlines and equipotential lines form a continuous net over the full saturated-unsaturated region. They intersect at right angles throughout the system. As the how to draw a flow net pressure head decrease, so does the hydraulic conductivity, and increased hydraulic gradients are required to deliver the same discharge through a given flow tube.
The qualitative flow net in Figure 5.13 has been developed for a soil whose unsaturated characteristic curves are those shown on the inset graphs. Figure 5.14 is the equivalent free-surface flow net to the saturated-unsaturated flow net shown in Figure 5.14. A glance at the two diagrams confirms that our decision to specify CARES Act the water table as a flowline is quite a good approximation for this particular flow system. The outflow boundary ED is still known as a seepage face. We will encounter seepage faces in a practical sense when we examine hillslope hydrology (Section 6.5) and when we consider seepage through earth dams (Section 10.2).
In homogeneous, isotropic media, the distribution of hydraulic head depends only on the configuration of the boundary https://simple-accounting.org/ conditions. The qualitative nature of the flow net is independent of the hydraulic conductivity of the media.
This phenomenon can be observed in the flow tubes in the upper left-hand corner of the flow net in Figure 5.13, where the gradients increase toward the surface. Construction of a flownet is often used for solving groundwater flow problems where the geometry makes analytical solutions impractical. The method is often used in civil engineering, hydrogeology bookkeeping or soil mechanics as a first check for problems of flow under hydraulic structures like dams or sheet pile walls. As such, a grid obtained by drawing a series of equipotential lines is called a flownet. The flownet is an important tool in analysing two-dimensional irrotational flow problems. Flow net technique is a graphical representation method.