Cascades, curtains and water channels

Cascades, curtains and water channels

Flow design, fall edge, water path and coordination with architecture

In waterfall, curtain and waterway fountains, the form of the display is made from the path of water movement and the way it contacts the surfaces. Water can break off a regular edge, move over a textured wall, descend between multiple levels, or flow along an urban axis.

This family of fountains has a great capacity to connect with architecture. The wall, stairs, edge of the pond and path of the area can be part of the fountain itself. This link requires careful coordination between architectural design, structure, sealing and facilities.

The quality of the result depends on the details that are less visible in the initial image of the design: the uniformity of water distribution, edge alignment, surface quality, collection capacity and the possibility of cleaning.

12–1. Knowing the types of flow

To make the right choice, the desired form of water movement must first be determined.

The term "water curtain" is used in the market for several different structures. Therefore, in the map and contract, the brand name should be completed with cross section, behavior description and visual sample.

In GSO products, wall and base water curtain, multi-level gutters and steel gutters are introduced in separate groups. Source: GSO water curtain ^[66], Source: GSO spillways ^[67], Source: GSO waterways ^[68]

12–2. Choosing the type of fountain based on the desired experience

The choice should start with the desired space experience.

A relatively quiet layer on the wall can be suitable for close-up viewing. A stepped waterfall can turn the level difference of the area into a part of the landscape. The open curtain creates a visual and moving border and the waterway makes the movement of water visible along the path.

The main design questions are:

• From which direction and at what distance can the water be seen?

• How much volume is compatible with the use of the environment?

• Is the track exposed to wind or ventilation air flow?

• Is the contact of people with water foreseen?

• How does the surface look when turned off?

• How will the edges, walls and pond be cleaned?

Silent view is very important. A wall that's only beautiful when the water is flowing may reveal sediment, seams, or messy equipment when it's stopped.

Figure note from the source manuscript

Figure 1–12: A set of three or four real photos from the GSO archive, including a free curtain, a multilevel spillway, a water wall, and a waterway. Suggested Caption: "Path geometry and surface contact shape the flow's visual character." Enter the type of each image separately.

12–3. falling edge; The point of curtain formation

In Azad Cascade, the quality of the trailing edge plays a key role. Improper alignment, deformation, contamination, or edge discontinuity can cause thickness variation, streaking, or irregular water separation.

The edge details must be consistent with the desired behavior:

For the separation of water from the surface, the shape of the edge and the space under the flow are important.

To continue moving on the wall, the connection of the outlet to the surface and the distribution of water on it must be checked.

A single implementation detail does not necessarily produce both behaviors.

The long length also increases the sensitivity of the performance. Edge alignment should be checked in the installed state and under working load; Alignment of the part before installation is not enough.

In measuring weirs, the shape of the edge, the conditions of approaching the flow and ventilation under the water layer have an effect on the performance. The USBR manual specifies these conditions for the application of overflow relationships; Its relations should not be generalized to any decorative watershed without adjusting the geometry and validity range. Source: USBR rectangular overflow guide ^[69]

12–4. Distribution chamber and flow uniformity

Water entering from a pipe behind a wide outlet does not necessarily create a uniform flow. Inlet location, local velocity, turbulence and pressure drop along the chamber can affect the output.

The distribution chamber must be designed for the desired width and flow rate. Depending on the structure, solutions such as multiple inputs, relaxation space, distribution pages or setting branches can be explored.

The goal is to achieve optimal output across the width. This goal should be tested in different working flows; A curtain may be uniform at a high flow rate, but turn into several streaks as the flow rate decreases.

Access to the inside of the chamber is also necessary. A narrow and long outlet that cannot be cleaned will be vulnerable to the accumulation of particles and sediment.

Figure note from the source manuscript

Figure 2-12: Schematic cross-section of the distribution chamber, inlet, calming section, outlet edge, and water landing path. Suggested caption: "Uniformity begins with proper water distribution before departure." The shape and dimensions of the components in the image are educational and non-prescriptive.

12–5. The required flow rate and the concept of flow rate per unit width

For a linear weir, the total discharge can be expressed from the following equation:

Q = b × q

In this regard:

• Q: total discharge;

• b: effective width of the outlet;

• q: required flow rate per unit width.

The value of q depends on the type of output, the height of the fall, the desired shape of the curtain and the installation conditions. This value should be derived from the manufacturer's information or sample testing.

Educational example

Let's assume that in the test of a specific outlet, for the desired shape of the water, the flow rate is 1.5 liters per second per meter of width. For an effective width of 4 meters:

Q = 4 × 1.5 = 6 liters per second

Convert to cubic meters per hour:

6 x 3.6 = 21.6 cubic meters per hour

The number 1.5 in this example is not the general design coefficient of the water curtain. Using it for other output, without data or testing, will not be reliable.

Also, more flow does not always produce better results; It may increase the thickness, noise or splash more than desired.

12–6. Pump selection based on actual flow rate and head

After determining the flow rate, the required head must be calculated in the same flow rate.

For a typical circuit that conveys water from a lower reservoir to an upper weir, the check includes the following components:

Total head = base level difference + path drop + output hydraulic requirement

Path loss includes the effect of pipes, fittings, valves and equipment located in the circuit. The output hydraulic requirement should also be determined according to the manufacturer's definition or calculation so that no component is used twice.

The OASE guide also considers the transfer height and path friction loss in the total head when choosing a waterfall pump. Source: OASE total head calculation guide ^[70]

Continuing the educational example

Let's assume for a flow rate of 21.6 cubic meters per hour:

• Base level difference: 2.4 meters;

• Calculated path drop: 1.1 meters;

• Additional output requirement, outside the two previous components: 0.5 meters.

Then:

Total head = 2.4 + 1.1 + 0.5 = 4 meters

The pump must provide the desired flow in this head in its performance curve. Selection based on the "maximum flow" or "maximum height" listed on the specification alone is not sufficient; These two values ​​usually do not occur at the same operating point.

12–7. multi-story waterfalls; Continuous path and parallel branches

In a waterfall where water flows from one level to the next and has no side inlets or outlets, the steady flow through the stages is the same, regardless of losses.

If 6 liters per second passes through three consecutive floors, the flow rate of the pump will not be 18 liters per second due to the presence of three floors. The same water goes down.

But if three independent catchments are fed from one collector and each needs 6 liters per second:

Total simultaneous flow = 6 + 6 + 6 = 18 liters per second

In the continuous path, each stage must have the capacity to pass the flow and receive the spray of the previous stage. In parallel branches, it is important to distribute and adjust the flow of the branches.

Intermediate basins may also be filled first during startup; Therefore, the time for the flow to reach the bottom and the volume of circulating water should be checked.

12–8. Waterway design and flow in open channel

The waterway can be shallow and calm or have turbulence and local drops. The width, depth, slope, roughness and end conditions of the path determine the behavior of the flow.

The continuity relationship for checking the average speed is as follows:

Q = A × v

in which:

• Q: flow rate, cubic meters per second;

• A: cross-sectional area of wet flow, square meters;

• v: average speed, m/s.

Educational example

If a flow rate of 0.006 m3/s passes through a rectangular section with a width of 0.4 m and an actual water depth of 0.06 m:

A = 0.4 × 0.06 = 0.024 square meters

v = 0.006 ÷ 0.024 = 0.25 m/s

This calculation shows the velocity for the assumed depth; It does not prove that the same depth will be established in the actual slope and conditions. Determining the depth and capacity requires checking the flow in the open channel.

In bends, narrows, the place of passing under the track and the end of the waterway, the possibility of increasing the level, turbulence and overflow should be checked. The height of the wall should not be chosen just equal to the calculation depth of the water.

12–9. blue wall; The role of surface and materials

In the water wall, the water has continuous contact with the surface. The texture, seam, contamination and difference in the wettability of the surface parts can cause the formation of streaks or dry areas.

The selection of materials should be accompanied by water testing. The appearance of a stone or coating in a dry state does not indicate its final result in water flow.

Important items include:

• uniformity of water distribution on top of the wall;

• The shape of the seams and the place where the parts are connected;

• The possibility of descaling without damaging the surface;

• compatibility of materials, glue, sealant and sealing;

• access to high places;

• Collecting water at the bottom of the wall.

A very rough surface can break the movement of water and increase splashing. A smooth surface may also show distribution defects and contamination more clearly. The selection should be made with a sample of the same material and actual details.

12–10. Spray, sound and air flow control

After exiting, the water does not just move along a geometric line. Layer shape, exit velocity, fall height, impact with the bottom surface and air flow affect the extent of wetting.

The dimensions of the receiving basin should not be determined only from the view of the waterfall. Normal conditions and effective modes such as flow rate change, wind or ventilation turning on should be checked.

The sound of water also depends on the volume of the flow, the height of the fall, the shape of the impact and the surrounding environment. A decent outdoor sound may be distracting in a lobby with hard surfaces.

For sensitive projects, prototyping should also cover splash and sound evaluation. The test is not complete just by observing the shape of the curtain.

In the interior, the direction of the air vents and the flow caused by the opening of the doors should also be in harmony with the location of the curtain.

12–11. Decorative curtain, display curtain and writing fountain

These three functions must be separated from each other in the project specifications:

Some systems can combine several functions. For example, the Aquatique Show, in its Aqua Graphic introduction, talks about independent outputs for creating shapes and text, as well as the ability to combine with image displays. Source: Aqua Graphic digital curtain ^[71]

On the screen, water texture, ambient light, projector location, viewing angle and content should be checked as a set. A transparent decorative curtain, without testing, is not considered a suitable platform for displaying images. Source: Aquatique Show Blue Curtain Guide ^[72]

Guided blinds also have a different structure. In Crystal Fountains' NRC product, Mylar threads are used to guide the movement of the droplets; Therefore, this product should not be described as the same as the free and integrated layer of water. Source: NRC rain curtain ^[73]

Figure note from the source manuscript

Figure 12–3: Three separate images titled "Decorative Curtain," "Projection on Water," and "Shaping with Controlled Outputs." Real or schematic images are clearly distinguished from each other. Suggested Caption: "Appearance doesn't necessarily equate to technology and performance."

12–12. Receiving basin, tank and return water

The collection system must receive the falling water and return it to the circuit without undesirable overflow.

In determining the capacity of the tank, only the volume inside it during stable operation is not important. Water in culverts, headwater ponds, and drainable waterways may also return to the reservoir after stopping.

For example, the water volume of a rectangular path 12 meters long, 0.4 meters wide and 0.06 meters deep is equal to:

V = 12 × 0.4 × 0.06 = 0.288 cubic meters = 288 liters

This amount is the water balance of the same route. The contribution that reaches the tank after stopping will depend on the slope, obstacles and level of the outlet. Basins and pipes should be checked separately.

Also, the drop in the tank level during startup and the possibility of water returning from the pump route should be determined. The choice of control or mechanical solution depends on the actual arrangement of the circuit.

12–13. Sealing, connection to building and water quality

In these fountains, the contact path of the water with the architecture is long. Water penetration from a seam can move behind the coating, and the location of the appearance of moisture is different from the location of the defect.

Sealing should be continuous at the place of change of materials, connection of gutter to the wall, penetration of pipe, movement joint and bottom basin. The exposed surface alone is not a substitute for an engineered waterproofing layer.

Test of hidden parts should be done and recorded before covering. For installation on the facade or above the usable space, the consequences of leakage and the access route for repair should also be considered.

In addition to appearance, water quality is a part of exploitation. In the Guide to Decorative Fountains, the CDC discusses the formation of suspended water particles and the importance of controlling sediment, biofilm, and water conditions. The cleaning, monitoring and disinfection program should be developed according to the system. Source: Management of CDC decorative fountains ^[74]

12–14. Lighting, cleaning and maintaining quality

Light can highlight a drop edge, wall texture, or waterway. The location of the light must ensure both the quality of vision and the possibility of service.

In a transparent curtain, the background and light angle are very important. In a textured wall, oblique light can reveal ridges, but also show more surface deposits and imperfections.

To maintain quality, the maintenance program should include:

• Cleaning the distribution chamber and outlets;

• checking the level and health of the edge;

• Cleaning the sediment with a method compatible with the materials;

• Pond and waterway cleaning;

• Checking the filter, water level and leakage;

• Comparison of the waveform with the state recorded during delivery.

For controlled curtains, performance testing of outputs is also required. A faulty output may distort part of the text or blue image.

Figure note from the source manuscript

Figure 4–12: A close-up of the weir edge and uniform flow distribution, along with a service access image of the same equipment. Suggested subtitle: "The quality of the edge and the possibility of cleaning play a role in the durability of the desired shape of the water."

12–15. Project testing and delivery

Acceptance should be done based on the desired water behavior and specific conditions.

For a quiet curtain, continuity may be the main criterion; For a natural waterfall, turbulence is part of the design. Therefore, the phrase "adequate water quality" should become an observable and testable result.

Cascade, curtain and waterway fountains are directly linked with architecture. Careful design of the waterway, construction details and maintenance conditions will maintain this connection over time.

In Chapter 13, combined water and fire fountains are explored; From the demonstration purpose and arrangement of equipment to coordination of control, environmental restrictions and specialized requirements of implementation and operation.