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1.5.3. Object Submerged in Fluid
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Let's start by discussing how pressure in a fluid changes with depth. Who can tell me the relationship?
Isn't it related to the weight of the fluid above?
Exactly! The pressure at a certain depth 'z' in a fluid is given by P = ρgz. Remember, ρ is the fluid's density, and g is the acceleration due to gravity. We can use the acronym 'P = ρgz' to recall this relationship.
How does this apply to submerged objects?
Great question! Submerged objects experience pressure changes depending on their depth, affecting the forces acting on them. As we learn, the net force on an object is tied to this pressure distribution.
So pressure is highest at the bottom?
Correct! This results in a net upward buoyant force that can be calculated.
In summary, pressure in a static fluid increases with depth according to P = ρgz, and this is essential for analyzing submerged objects.
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Next, let's discuss buoyancy. Does anyone know what buoyant force is?
It’s the upward force that counters the weight of an object in fluid.
Great answer! The buoyant force is equal to the weight of the fluid displaced by the object. We often use Archimedes' principle to describe it. Remember, 'buoyancy = fluid weight displaced'.
How do we determine if an object will float or sink?
This depends on the relative densities of the object and fluid and the position of the center of gravity versus the center of buoyancy. If the center of gravity is below the center of buoyancy, the object is stable.
Could you summarize how we assess the stability?
Sure! Remember BM (buoyancy) to CG (center of gravity) relationships. BM must be above CG for stable equilibrium.
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Let's apply what we've learned to solve some example problems. First, consider a square gate in a tank. What would you need to calculate the force on it?
We need to know the pressure at different depths.
Exactly! Using P = ρgz, you can find the pressure at the hinge point and the center of the gate.
After that, how do we find the total force?
Good follow-up! The total force is the average pressure times the area, and remember where this force acts—it’s not at the top or bottom, but often at a third of the way up from the base.
I see! So we calculate moments around the hinge to find the necessary applied force for equilibrium.
Precisely! In summary, we can apply pressure calculations and force analysis to find necessary equilibrium conditions for submerged objects.
Overview
Short Summary
This section discusses the principles of hydrostatics applied to objects submerged in fluid, focusing on pressure distribution, buoyancy, and equilibrium conditions.
Medium Summary
In this section, we explore how objects submerged in fluid experience pressure variations, the forces acting on them, and the concept of buoyancy. Through examples and problem-solving approaches, it illustrates how to determine the forces acting on submerged objects and their equilibrium conditions.
Detailed Summary
Detailed Summary
This section of the Fluid Mechanics course delves into the essential principles of hydrostatics as they apply to submerged objects within a fluid. It emphasizes the concepts of pressure distribution, buoyant forces, and equilibrium conditions.
Key Points Covered:
- Hydrostatic Pressure distribution: The relationship between fluid pressure and vertical depth in fluids at rest is established, represented as P = ρgh.
- Buoyant Forces: The section highlights the impact of buoyancy on floating bodies and establishes criteria for stability, such as comparing the distances between the centers of gravity and buoyancy.
- Manual Calculations: Several examples illustrate problem-solving techniques to compute the forces on submerged surfaces, including the calculation methods for triangular pressure distributions and equilibrium conditions.
- Applications of Fluid Statics in Engineering: Specific real-world applications, such as calculating forces on gates in fluid tanks, are discussed as part of the learning objectives, reinforcing theoretical concepts through practical examples.
Reference YouTube Videos
Audio Book
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Create a free accountNow let us come to a manometer problems. So there is a inclined manometer shown in the figure below. Reservoir is large. That is the, its surface maybe assumed to be remain as a fixed elevations. A is connected to a gas pipeline. The deflection is noted on the inclined gas tube. This is what the inclined gas tube is 100 millimeters the theta the angle of inclined manometers theta equal to 30 degrees and manometric fluid as oil with a specific gravity of 0.86.
Detailed Explanation
In this chunk, we discuss the concept of an object submerged in a fluid and the equilibrium it must maintain. When an object is submerged, it experiences both horizontal and vertical forces due to the fluid surrounding it. These forces vary with the depth of the fluid and the shape of the object. For an object to maintain its position, the sum of all moments about any point, such as a hinge, must be zero. This condition ensures that the object does not rotate.
Examples & Analogies
Imagine trying to balance a seesaw. If you put too much weight on one side, it will tip over. Similarly, an object submerged in water must have its forces balanced to avoid tilting. Just as you move weights on a seesaw to achieve balance, we adjust the position or shape of the submerged object to maintain equilibrium in the fluid.
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Create a free accountThis is the hinge locations, the but what is the basic concept of this submerged object. If you look it that there will be horizontal force will be act from these sides. Also horizontal force will go into act from this side. But those will be cancelled out, the same amount of horizontal force will act from this side. Also same amount will act from this side.
Detailed Explanation
When analyzing submerged objects, it is crucial to identify the forces acting upon it. The horizontal forces acting on opposing sides of the submerged object will cancel each other out. However, the vertical forces acting on the submerged surfaces will affect the position of the object. This requires careful calculation to find the resultant vertical force and its point of application. The moments about the hinge must also be considered to achieve equilibrium.
Examples & Analogies
Think of a balloon underwater. It experiences equal pressures from all sides; the upward buoyant force balances the downward gravitational force. Just as the balloon must find a point where it floats without sinking or rising, submerged objects must achieve a balance of forces to stay still in their positions.
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Create a free accountNow let us we compute it what will be the vertical force in the AB part. It is a very simple is the pressure distributions is uniform here and we know rho g into A will be the force component. That what will come it.
Similarly, in plate BC, we have to calculate the force acting at this section considering the vertical pressures.
Detailed Explanation
To maintain equilibrium, we calculate the vertical forces acting on different sections of the submerged object. For example, if we consider one part of the plate, the force can be determined by multiplying the density of the fluid (rho), acceleration due to gravity (g), and the area of the plate (A). Summing the moments around the hinge and setting it to zero allows us to solve for any unknowns related to the position and shape of the object.
Examples & Analogies
Imagine holding a long board on your palm. If you want to keep it level, you'll need to apply force at the ends of the board. The pressure of your palm against gravity acts as a balancing force, much like how forces on a submerged object must balance for it to stay in place.
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Key concepts
Core takeaways and short definitions to help you quickly recall the key ideas from this section.
- Pressure Distribution:
Pressure in a fluid at rest increases with depth, influencing the forces on submerged objects.
- Buoyancy:
The upward force that enables objects to float, dependent on the volume of fluid displaced.
- Equilibrium:
A state where the sum of forces and moments acting on an object is zero, leading to stability.
Examples
Memory aids
Imagine a diver going deeper in the ocean, feeling the pressure weight heavier as they descend; that's hydrostatic pressure acting on them, while the buoyant force helps them float back up.
B.P.E - Buoyancy, Pressure, Equilibrium: Remember these three essentials for fluid mechanics!