Guy on Simulink

Simulink & Model-Based Design

Watering my Plants with Simscape Fluids 1

Posted by Guy Rouleau,

Here is a picture of my backyard:

My Backyard

As you can see, I like to grow a few plants. And those plants need water.

During the last long weekend of July 4th, I decided to install a watering system for those plants.

When I looked at what was available at the hardware store, I saw two options: 1/4 in hoses and 1/2 in hoses. Not being too sure which one I should pick, I decided to do some simulation first.

Sanity Check

To begin, I did a bit of googling to find out that the typical household pressure is usually between 40 and 60 PSI. Based on experience, I know that filling a 1 gallon watering container takes about 6 seconds, so I decided to simulate that first, to ensure my simulation was in the correct order of magnitude. Good news, it is:

Test model

The Real System

Having good confidence that my simulation would be realistic, I drew my setup using a series of Hydraulic Pipeline LP, where LP stands for Low Pressure.

Watering System

On the house, that would look like the following, where I drew a yellow line for a main hose, and green lines for smaller sections going directly to each plant.

Watering System

In each block, I specified the radius and length of each section:

Hose dimension

Along with the elevation, to include the effect of gravity:

Hose Elevation

My first simulation with all the system made of 1/4 in pipes showed that I would get only 2.2 GPM of water coming out of the faucet... this means that it would take forever to water my plants, and that the last one farthest from the faucet would get no water.

To improve things, I thought about making the main line with a 1/2 in hose, and then tap into it using short 1/4 in hoses to reach each pot. This time, I got 10 GPM at the faucet, which is more acceptable. However, there was one problem. The first plant as receiving a lot more water than the last one.

Final Setup

Adjustable Nozzles

To fix that, I will need to add adjustable nozzles to restrict the flow on the closest plants.

Nozzles

To simulate those, I added an orifice to the end of each hose. By leaving the last nozzle fully opened and making the orifices smaller as I was getting closer to the faucet, I could get a roughly equal flow rate on all nozzles, and keep the flow rate out of the faucet close to 10 GPM.

Final System

Final Result

With confidence, I drove to the hardware store, bought everything I needed, installed the system, and now I can sit back and look at my plants being watered!

Now it's your turn

Share with us how Simulink helps your summer vacation by leaving a comment below.

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