Deep Water and Shallow Water Relations - 1.3 | 25. Wave Energy and Wave Power | Hydraulic Engineering - Vol 3
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1.3 - Deep Water and Shallow Water Relations

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Interactive Audio Lesson

Listen to a student-teacher conversation explaining the topic in a relatable way.

Wave Energy Flux

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0:00
Teacher
Teacher

Today, we are diving into the concept of wave energy flux, which is the rate at which energy is transmitted by the waves in a specific direction. Can anyone tell me what this might look like mathematically?

Student 1
Student 1

I think it involves some kind of formula?

Teacher
Teacher

Exactly! It's represented as wave power, which can be calculated as 'e' multiplied by the group velocity 'CG'. Remember, 'e' is derived from wave energy. A good way to remember this formula is to think of 'Power = Energy times Velocity'.

Student 2
Student 2

What does 'CG' stand for exactly?

Teacher
Teacher

Great question! 'CG' stands for the group velocity. In deep water, this is half the phase speed, 'C0'. So, it's vital to understand these relationships.

Student 3
Student 3

Why is it important to study wave power in both deep and shallow water?

Teacher
Teacher

Studying it helps us predict how waves will behave when they approach shorelines, which is critical for coastal engineering and safety!

Student 1
Student 1

Got it! So, energy flux is key in these calculations!

Teacher
Teacher

Exactly! Remember this: Energy flux = Power per unit wave crest contributes to how we understand beach erosion and wave energy harvesting.

Conservation of Wave Power

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Teacher
Teacher

Moving on, let’s discuss the principle of conservation of wave power. Why do you think it’s essential to understand this concept?

Student 2
Student 2

It sounds like it helps us keep track of how wave heights change, right?

Teacher
Teacher

Absolutely! As waves move from deep to shallow water, their power remains constant if we assume no energy loss. The formula we often see is that the energy in deep water, 'gamma * H0^2 / 8' relates to energy in shallower water, 'gamma * H^2 / 8'.

Student 4
Student 4

What do 'H0' and 'H' stand for again?

Teacher
Teacher

'H0' is the wave height in deep water, while 'H' is the wave height at any given depth. Key to solving wave dynamics!

Student 3
Student 3

And why is it called conservation?

Teacher
Teacher

Because the total energy doesn't change; it’s redistributed as the wave transitions to shallower depths.

Student 1
Student 1

I see! So, we can use these relationships in practical applications, like coastal management.

Teacher
Teacher

Exactly! Understanding conservation helps engineers design better coastal structures.

Shoaling Coefficient

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Teacher
Teacher

Let’s dive into the shoaling coefficient, which helps us determine how waves change size in shallower water.

Student 4
Student 4

How does it relate to the previous concepts we've discussed?

Teacher
Teacher

Great observation! The shoaling coefficient, denoted as 'Ks', shows the ratio of wave heights at different depths. We often express it as 'H/H0 = √(C0/C) * (1/2n)'.

Student 2
Student 2

What does 'C0' and 'C' refer to in this equation?

Teacher
Teacher

'C0' is the speed in deep water, while 'C' is the wave speed in shallower water. This gives us a mathematical relationship to analyze wave behavior.

Student 3
Student 3

Is there a situation where we wouldn't use this coefficient?

Teacher
Teacher

Yes! It assumes a regular ocean bottom without fluctuations. So, it's ideal for theoretical calculations.

Student 1
Student 1

Got it! This coefficient is crucial for predicting wave effects on beaches.

Teacher
Teacher

Indeed! It's fundamental for coastal management and engineering!

Mass Transport and Wave Dynamics

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Teacher
Teacher

Today, we’ll touch upon the concept of mass transport in wave dynamics. How might mass transport relate to wave energy?

Student 3
Student 3

If waves carry energy, then can they also carry mass or water?

Teacher
Teacher

Exactly! The movement of water particles during wave motion transports mass, which affects coastal systems.

Student 4
Student 4

Is the mass transport affected by wave height?

Teacher
Teacher

Yes, it is! Higher, steeper waves result in more significant mass transport than longer, more gradual waves.

Student 2
Student 2

Is there a formula for calculating mass transport speed?

Teacher
Teacher

Yes, there's a formula involving wave height and the wave length, but understanding the concept is more critical than memorizing equations.

Student 1
Student 1

This makes sense, as stormy weather would create more turbulent energy and mass flow!

Teacher
Teacher

Exactly! Understanding this concept is key for predicting coastal erosion and sediment transport.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section discusses wave power and energy flux in relation to deep and shallow water wave dynamics.

Standard

The section explains wave power, the calculations of energy flux across a wave front, and how wave characteristics change as they transition from deep to shallow water. It emphasizes the conservation of wave power and introduces the shoaling coefficient as a key factor in calculating wave heights at various depths.

Detailed

In this section, we explore the fundamental concepts of wave energy flux and wave power. Wave energy flux is defined as the rate of energy transmitted in the direction of wave propagation per unit wave crest. It is mathematically represented as the product of energy 'e' and group velocity 'CG'. The relations for deep and shallow water are distinguished, noting that in deep water, the group velocity is half the phase speed. The conservation of wave power is a crucial principle, which states that as waves travel from deeper waters to shallower depths, their energy and height change according to a specified relationship. The section introduces the shoaling coefficient, a critical factor in predicting wave height transformation at various depths. By applying these concepts, one can better understand the behavior of waves in response to changing water conditions, crucial for maritime engineering and coastal management.

Audio Book

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Wave Energy Flux and Wave Power

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So, now we have studied wave energy it is very obvious that we study wave power wave energy flux is the rate at which energy is transmitted in the direction of wave propagation across a vertical plane perpendicular to the direction of wave advance and extending down the entire. So, the average energy flux per unit wave crest with transmitted across the plane perpendicular to the wave advances is wave power. And it is given as e into CG. This is important CG is group velocity and e is the energy that we just derived. So, the power is given as e into CG or in if you want to write it in terms of celerity. It is e bar n into CG.

Detailed Explanation

Wave energy flux refers to how much energy is moving through a specific area over a certain time period as waves travel. Imagine waves moving through the ocean; they carry energy along with them. This energy flux helps to calculate wave power, which is the total energy transmitted by the wave per unit length of wave crest. The relationship can be expressed mathematically as 'Power = Energy (e) x Group Velocity (CG)'. In simpler terms, if you know how much energy is in the waves and how fast the waves are moving (their group velocity), you can determine the power of the waves.

Examples & Analogies

Think of wave energy flux like a river flowing. If the river (wave energy) flows faster (higher group velocity), more water (energy) reaches a certain point (area) in less time, creating a larger volume at that location (higher power).

Deep Water vs. Shallow Water Conditions

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For deep water you know that CG was half c not. n = half so, power is going to be half into C not for shallow water it will e into CG because CG is C only if you assume that the wave propagates from deep water towards the shore...

Detailed Explanation

In deep water, the group velocity (CG) is half the wave speed (C0). This relationship is crucial when analyzing how waves behave differently in deep water compared to shallow water. When waves transition from deep to shallow water, their speed and energy characteristics change. For shallow water, the group velocity equals the wave speed. Therefore, when analyzing wave power from deep to shallow water, the equations consider these differences to conserve wave power.

Examples & Analogies

Imagine riding a bike on a smooth road versus riding on a sandy beach. On the smooth road (deep water), you move fast and smoothly due to less resistance, while on sand (shallow water), your speed decreases due to increased resistance. Similarly, waves behave differently in deep and shallow conditions because of these opposing forces.

Conservation of Wave Power

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Because you see this if there is no loss, it is average energy flux per unit wave crest rate. And if we apply the conservation of wave power. So, you see this is any depth...

Detailed Explanation

Wave power conservation means that as waves move from one depth to another, the total energy transmitted by the wave remains constant, assuming no energy is lost. This principle allows us to equate the power at deep water conditions with that of shallow water conditions using specific formulas that account for wave height and speed at both depths.

Examples & Analogies

Think of a water balloon. If you push the water from one end to another without any leaks, the amount of water (energy) stays the same even if you change the shape of the balloon (depth). Similarly, the power of the waves remains the same despite changing conditions as they move towards shore.

Shoaling and Wave Height Transformation

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So, in deep water, it will be gamma h not squared by 8 h not indicates the wave height in deep water... obtained relationship between the water velocities and only kinematics...

Detailed Explanation

Shoaling refers to the phenomenon where wave heights increase as waves approach shallower waters. The wave height transformation is quantified using a shoaling coefficient (Ks), which relates the deep water wave height (h0) to the height at any shallower depth (h). This transformation allows us to calculate how waves will behave as they move from deep to shallow water.

Examples & Analogies

Picture a car going downhill into a valley; as it descends, it speeds up (waves increase in height) before reaching flatter ground. In a similar way, waves grow taller and more powerful as they enter shallower water.

Mass Transport in Waves

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So, the mass transport velocity is given by phi h by L whole squared into C by 2 cos h2kd + z divided by sin h squared kd...

Detailed Explanation

Mass transport during wave motion refers to the actual movement of particles or water in the direction of wave travel. As waves pass, water particles follow an orbital motion, resulting in a net forward displacement. The mass transport speed will vary based on the wave height and steepness, with higher waves causing greater transport, while longer waves lead to less transport.

Examples & Analogies

Consider a group of kids on a merry-go-round (wave motion). When they push harder (larger wave height), they move forward more quickly when the merry-go-round spins. If they are moving slowly (long period waves), their forward motion is minimal. Thus, the wave characteristics dictate how fast the mass moves.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Wave Energy Flux: The rate of energy transmitted per unit wave crest.

  • Wave Power: A calculation involving group velocity and energy.

  • Shoaling Coefficient: A ratio that helps determine wave heights at different depths.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • In a coastal engineering setting, calculating how wave energy changes from deep to shallow water can help in designing effective structures to minimize erosion.

  • The shoaling coefficient can be used to predict the increase in wave height as waves approach the shore, which is crucial for surfer safety and beach management.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • Wave height rises as it nears the shore, energy conserved, we understand more.

📖 Fascinating Stories

  • Imagine a wave traveling from the deep sea, as it comes close, it swells with glee. Coastal builders watching with care, knowing energy’s value is everywhere.

🧠 Other Memory Gems

  • For remembering wave power: 'Energize Group Calmly' (E = Energy, G = Group velocity, P = Power).

🎯 Super Acronyms

SES (Shoaling, Energy conservation, Speed) to remember the key aspects of wave dynamics.

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: Wave Energy Flux

    Definition:

    The rate at which energy is transmitted in the direction of wave propagation per unit wave crest.

  • Term: Wave Power

    Definition:

    The average energy flux transmitted across a vertical plane perpendicular to the direction of wave advance.

  • Term: Group Velocity (CG)

    Definition:

    The velocity at which the overall shape of the wave's amplitudes (envelope) propagates through space.

  • Term: Shoaling Coefficient (Ks)

    Definition:

    A dimensionless number that describes how wave height changes as waves approach shallow water.

  • Term: Mass Transport

    Definition:

    Movement of water associated with wave motion that carries mass in the direction of the wave's progress.