Properties of open channel shape pre.pptx

about open channel shape

1. WHAT IS OPEN CHANNEL FLOW ? The flow of liquid which is open to atmosphere is called open channel flow. An open channel is a waterway, maybe canal, rivers, types of channel system in which a liquid flows with a free surface. A channel is open or closed as long as its surface is exposed to constant pressure

2. PROPERTIES OF OPEN CHANNEL SHAPE 1. Cross-sectional Area (A) This refers to the total area of the cross-section of the open channel that is normal to the direction of flow. A ffects the velocity, depth, and discharge (volume of water flowing per unit of time) of the flow.

3. PROPERTIES OF OPEN CHANNEL SHAPE 2. Wetted Perimeter (P) This is the length of the distance along the channel cross section that is in contact with the flowing water. T he wetted perimeter can impact the flow of frictional resistance and channel efficiency

4. PROPERTIES OF OPEN CHANNEL SHAPE 3.Hydraulic Radius (R) It is the ratio of the cross-sectional area to the wetted perimeter (R = A/P). It is a measure of the efficiency of the open channel in carrying water and is used in hydraulic calculations to determine the channel's ability to convey flow with minimal energy losses. The hydraulic radius can also impact the flow of velocity, flow capacity, channel efficiency, flow stability.

5. PROPERTIES OF OPEN CHANNEL SHAPE 4. Width (B) This is the horizontal distance between the channel walls or banks, typically measured perpendicular to the direction of flow. It is an important parameter that affects the flow characteristics of the channel, such as velocity distribution and turbulence.

6. PROPERTIES OF OPEN CHANNEL SHAPE 5. Depth (D) This is the vertical distance from the channel bottom to the water surface. It is a key parameter in determining the hydraulic characteristics of the channel, including flow rate, velocity, and energy losses.

7. PROPERTIES OF OPEN CHANNEL SHAPE 6. Shape: The shape of the open channel cross-section can vary widely, ranging from simple geometric shapes like rectangles, trapezoids, and triangles, to more complex shapes with curved sides. The shape of the open channel can significantly influence its hydraulic behavior, such as flow resistance, energy losses, and sediment transport. Rectangular

8. PROPERTIES OF OPEN CHANNEL SHAPE 7. Slope (S) This is the vertical drop in elevation per unit horizontal distance along the channel, also known as the channel gradient. Slope is a critical parameter that determines the velocity of the water flow and affects the channel's ability to carry water and sediment. Slope of an open channel should is carefully designed or managed to achieve the desired flow characteristics and to avoid issues such as erosion, sedimentation, and flooding .

9. PROPERTIES OF OPEN CHANNEL SHAPE 8. Roughness The roughness of the channel walls and bottom, also known as the Manning's roughness coefficient, is an important property of the open channel shape. It affects the frictional resistance and energy losses in the channel and is typically estimated based on the type of material, condition of the channel, and presence of vegetation or other obstructions. A higher Manning's roughness coefficient (n) represents a rougher channel, indicating higher resistance to flow, while a lower Manning's roughness coefficient represents a smoother channel, indicating lower resistance to flow.

10. GEOMETRIC PROPERTIES cross sectional area,  A hydraulic radius,  R top width,  T wetted perimeter,  P hydraulic depth,  D the section factor,  Z

11. S emicircular form is the most efficient ideal cross-sectional form, having ‘best conveyance characteristics’ with minimum wetted perimeter and maximum hydraulic radius. The most efficient section must have a minimum wetted perimeter and hence minimum resistance to flow. Compared to other cross-sections, the semicircular section has the lowest wetted perimeter, and is, therefore, the section of the highest efficiency, but, due to practical limitations in maintaining the section, trapezoidal channels are usually employed.