Our class BSEN 3310, Hydraulic Transport in Biosystems, has given us many opportunities to learn about how fluids such as air and water are used and behave in the environment. My favorite lab, the hydrostatic pressure lab, allowed us to use the Edibon Hydrostatic pressure system to view, on a small scale, how fluids put pressure on submerged surfaces. This was my favorite lab because it interested me the most and it also applied to a specific aspect of fluid mechanics that has always interested me. The picture above, taken from the FoxHavenJournal.com, shows a real life application of exactly what we did in lab. My lab report for this activity can be viewed by clicking the button below.
The real world application for this lab stems from the ability to take a small scale system and apply it to a large scale system. The physics and equations can be used in the field, just as they are in the lab. One thing that is very interesting to me is water resource management and conservation. Like the pond seen above, many times we have to build dams to stop water flow so it can be used as irrigation, a livestock water source, or it may be endangering a town or building downstream. No matter what the reason, the lab we did performed applies to this situation.
The first thing you have to figure out about is where your pressure will be affecting the dam. This is the key factor because the location of the center of pressure will be the main source of all the water that is being stopped by the dam. The equation used in the lab to find the center of pressure is
yp = yc + Ixx,c/(yc*A)
where yp is the height of the center of pressure from the free surface and Ixx,c is the second moment of inertia of the submerged body. yc is the height of the centroid of the surface and A is the area of the surface. As engineers, we have to know the center of pressure because we must calculate the moments in the system to be sure our forces will be strong enough to hold our dam in place. As we learned in statics, if even one force is off, the entire system can fail and could lead to disaster.
Another equation that we need to use when building our dam is the equation to find the velocity of the water that would be coming into our system. By finding the velocity, we can determine the volumetric flow rate as well as the total energy coming into our system. To find velocity, we will use the energy equation
The first thing you have to figure out about is where your pressure will be affecting the dam. This is the key factor because the location of the center of pressure will be the main source of all the water that is being stopped by the dam. The equation used in the lab to find the center of pressure is
yp = yc + Ixx,c/(yc*A)
where yp is the height of the center of pressure from the free surface and Ixx,c is the second moment of inertia of the submerged body. yc is the height of the centroid of the surface and A is the area of the surface. As engineers, we have to know the center of pressure because we must calculate the moments in the system to be sure our forces will be strong enough to hold our dam in place. As we learned in statics, if even one force is off, the entire system can fail and could lead to disaster.
Another equation that we need to use when building our dam is the equation to find the velocity of the water that would be coming into our system. By finding the velocity, we can determine the volumetric flow rate as well as the total energy coming into our system. To find velocity, we will use the energy equation
We can use this equation to find velocity because other variables in out system will be known.
One important aspect of designing water system in the environment, especially when it is being used for agricultural or wildlife reasons, is keeping it full. It is not infrequent for droughts to occur in any ecosystem and this can be detrimental to any farmer or wild life manager who counts on the water from the pond or lake. One way to keep the pond full would be to drill a well and install a pump. Pumps can be a great back up for any system that has to hold water, however, it is important to know what size pump you need. Pumps can come in just about any size and can have a very wide range of power. One thing that is very important is efficiency. Without the pumps efficiency, there is now way to know how much usable energy we will not be able to judge what size pump we need.
There is one thing that we must consider when we decide what pump we are going to get. We cannot just count on Bernoulli's equation to tell us exactly how much energy is needed for a system because it does not take into account the head loss by the fluid. Head loss is the amount of energy lost by the fluid due to friction inside the pipe and also any losses that occur during the bends and connectors of the pipe. The head loss equation is
One important aspect of designing water system in the environment, especially when it is being used for agricultural or wildlife reasons, is keeping it full. It is not infrequent for droughts to occur in any ecosystem and this can be detrimental to any farmer or wild life manager who counts on the water from the pond or lake. One way to keep the pond full would be to drill a well and install a pump. Pumps can be a great back up for any system that has to hold water, however, it is important to know what size pump you need. Pumps can come in just about any size and can have a very wide range of power. One thing that is very important is efficiency. Without the pumps efficiency, there is now way to know how much usable energy we will not be able to judge what size pump we need.
There is one thing that we must consider when we decide what pump we are going to get. We cannot just count on Bernoulli's equation to tell us exactly how much energy is needed for a system because it does not take into account the head loss by the fluid. Head loss is the amount of energy lost by the fluid due to friction inside the pipe and also any losses that occur during the bends and connectors of the pipe. The head loss equation is
Hear hL is the head loss by the fluid, f is the friction factor of the fluid and pipe system, L is the length of the pipe and D is the diameter. The V is the average velocity of the fluid and K is the loss coefficient for each bend and joint within the pipe. Once we establish our head loss, we can then determine what size pump we need to use to keep water in our system.
The final aspect of our pond or lake system we need to take into account is where the water is going to go when the pond needs to drain. We must install an underflow gate that will serve as a control for the height of the water in the lake. When the water starts to get too high, the underflow gate can be triggered to open and it will allow the pond or lake system to drain. Once the water has drained a required amount, the gate will close again and the water will begin to again fill the pond. The volumetric flow rate of fluid leaving a sluice gate can be found by using the equation
The final aspect of our pond or lake system we need to take into account is where the water is going to go when the pond needs to drain. We must install an underflow gate that will serve as a control for the height of the water in the lake. When the water starts to get too high, the underflow gate can be triggered to open and it will allow the pond or lake system to drain. Once the water has drained a required amount, the gate will close again and the water will begin to again fill the pond. The volumetric flow rate of fluid leaving a sluice gate can be found by using the equation
where Q is the volumetric flow rate, b and a are the width and height of the gate opening, g is the force due to gravity, and y is the depth of the opening below the fluid surface.
Taking all the matters into account is a tedious yet extremely important job for all engineers. These laws of fluid transport are key in completing many different projects we take on as engineers. Thanks to my experiences and time in my Hydraulic Transport in Biosystems class, I now feel confident that I can create one of these systems for whatever purpose it is needed.
Taking all the matters into account is a tedious yet extremely important job for all engineers. These laws of fluid transport are key in completing many different projects we take on as engineers. Thanks to my experiences and time in my Hydraulic Transport in Biosystems class, I now feel confident that I can create one of these systems for whatever purpose it is needed.